is knife blading a crank worth the risk of grenading?
>>13951716
People do that?
>>13951716
Do it. At home in your garage. Make your DD a rev machine. Super lightweight flywheel and all that stuff too.
And don't worry about getting the balance perfect on the crank. At such high RPM's, the vibrations just cancel eachother out and you won't even notice.
If you're in a race car, maybe. Like, a racecar so plastered with sponsors that you can afford an explosion here or there.
>>13951764
It's a thing hotrodders do when they have spare parts and want to experiment.
I have 7 4.6 4v motors and I'm planning on doing this in the future.
>>13951716
if it's done properly yeah
>>13951774
Troll, don't listen to this guy, it will destroy your engine with your stock engine mounts. It's true that the balance isn't important IF you get rid of the stock engine and trans mounts and replace them with custom made flex mounts, I like to weld 3 valve springs between 2 plates on each side and use that for engine mounts, that way the engine can move enough to counterbalance the imbalanced rotating assembly.
>>13951810
what's the best approach to knife blading a crank yourself so that there's little weight imbalance?
>>13951865
Step 1: Become a professional machinist
>>13951865
Lathe and a caliper?
>>13951865
Heh. I have an idea.
Use a marker to mark each future blade.
Sharpen it down until the marker cover isn't showing anymore.
Do it a set amount of times on each blade, should be good f@m. DESU.
>>13951875
how do i achieve step 1 without going to metalworking school?
>>13951877
cheapest metal lathe looks to be like $5k. danm...
i've talked to a few engine builders and they dont knife edge cranks.
it's dumb
just buy a lightweight crank.
>knife edged crank
>not dry sump
Once again /o/ demonstrates that it hates power and loves engine destroying jury rigging.
>>13951923
>>13951913
you guys are bums. like you'd rather take the easy route rather than venture into something new and daring. something that pushes your intimacy with your car and your repertoire of knowledge.
>>13951716
I had no idea that was even a thing lol, no that is not worth it, thats what someone would do to a car they want to blow the engine up in.
>>13951810
Shut up heartbreaker. You drive a single cab 90's toyota. You don't know shit about making engine mounts.
>>13951932
>something new and daring
yeah this isn't new. Stop with the "you don't want to do proven-bad-thing because you're a pussy!" bullshit. There's more to it than just knife-edging a crank.
>>13951716
It's better to just cut the counterweights off completely. That way you have a super lightweight crank.
>>13951940
clearly there isn't because someone did it and got more power out of it. don't be such a weenie. how would you even blow your crank? if you sharpened each counterweight you'd still have even balance, and not only that but less weight. any deviation can be fixed with a fine chuck.
>>13951956
Just getting rid of the counterweights entirely would have even balance and it would be lighter.
Checkmate athiest.
>>13951956
>more power
out of what, and how much did they spend on machining?
>>13951923
/thread
>>13951716
This shit looks just downright stupid. It's seriously some of the most niggerrigged shit I've ever saw.
>>13951965
you need counterweights to prevent flexing. it's just that knife edging doesn't fully remove the protection but gives better oil distribution without the need of a pump adding weight to your vehicle. less weight same dry sump results. now THAT'S checkmate.
>>13951971
out of the fact that a bladed crank would allow a higher redline while still being weighted. also it wouldn't cost anything since you'd tool it yourself if you were a real auto enthusiast.
>>13952003
>you need counterweights to prevent flexing
The counterwieghts are sized for the mass of the connecting rods. Unless your knife edging corresponds to an equal reduction in mass of the connecting rods you're unbalancing the engine significantly.
>it's just that knife edging doesn't fully remove the protection
Knife edging unbalances the rotating assembly.
>gives better oil distribution
No.
>without the need of a pump
LOL NO.
> less weight same dry sump results.
HAHAHAHAHA NO.
You seriously think doing this eliminates the need for an oil pump? Seriously?
>out of the fact that a bladed crank would allow a higher redline
No.
Not only will unbalancing the crank tend to make an engine that doesn't want to rev. Crank weight is not the limiting factor in setting a higher redline like, ever.
The valvetrain, rod:stroke ratio, rod/pin strength, and head flow limits are what ultimately set the limit for an engines redline.
>>13952003
how many engines have u built anon?
>>13952074
if you think rotating mass isn't a critical factor for what limits the redline of an engine then you're mentally disabled.
>>13951810
No shit, faggot. No one here would even frikin' try that.
>>13951971
tfw I haven't gotten an answer to this question.
tfw I won't because they were pretending to be retarded.
>>13951716
>risk of it grenading
There's no risk so long as its balanced. Intact if you took it to a reputable machine shop you would probably get it back with better balance than the factory.
That said the minor reduction in windage isn't really needed. On top tier race vehicles where every 0.1% matters sure.
You're better off just getting it re-balanced and going dry sump
>>13951971
You're not likely to see a power increase, most of the time redline is dictated by valve float, and knife edging only comes into play well over stock rpm.
>>13952088
>rotating mass is a critical factor for what limits the redline of an engine
In the realm of auto engines, engine layout, bore / stroke and valvetrain are far more important factors for rip'ms than the assemblies rotating mass.
A single cam pushrod stroker V6 can't spin fast for shit
A DOHC square inline 6, however, would rev it's tits off
Cutting down a crank as per OP won't increase a given engines rev limit, but it would allow it to get to it's limit in a shorter time frame.
>>13952140
if i want to be a zero point one percenter?
>>13952003
>out of the fact that a bladed crank would allow a higher redline while still being weighted. also it wouldn't cost anything since you'd tool it yourself if you were a real auto enthusiast.
How's high school going?
So, I'm a qualified mechanic. I don't build a lot of engines, but I've built a few. There is no fucking way I'd try and knife-edge a crank myself.
I work for a mechanic. He's a qualified mechanical engineer also, has built many, many engines, and there's no way he'd knife-edge a crank himself.
If you fuck it up, your engine is destroyed.
Leaving out the fact that the cost to benefit balance makes knife-edging not worth considering in about 99.8% of situations, including most purpose built race engines (You don't see 1,000hp speedway motors with knife-edged cranks - and I've seen the inside of those) the idea that you can just jig up a wood lathe and knife-edge a crank without consequences is pretty naive.
Since you're a real automotive enthusiast, how did you plan on balancing the crank afterwards? Balance has much more to do with max RPM than reciprocating weight does
What do i have to do to make my 2.0 liter 12 valve inline 4 rev higher?
>>13952351
whoa whoa we wow
>>13952211
you say you're mechanic yet you can't lathe for shit. top kek why are you even replying.
>cost to benefit balance
yeah because getting a dry sump is a higher cost to benefit balance.
>how did you plan on balancing the crank afterwards
by putting it in a balancer how else? what kind of question is this?
>>13952438
mechanic!=machinist
>>13952185
Wow! No kidding! The MAN B&W 32/44 I work on can flow almost 2000cfm per valve on a four valve head! It has a similar rod ratio to a SBC, and the valvetrain is both light weight and low friction so that should mean it will rev hard and high with a high redline!
I wonder why it won't go any higher than 890RPM though..... it wouldn't be the rotating mass. After all, that has negligible impact on redline.
You monstrous fool. You absolute, utter fool.
>>13952641
Where's your proof!
>>13952664
Any commercial vessel with a MAN B&W 32/44.......
>>13952670
Or if you can find it, the performance specifications for the MV Madang Coast (PNG). The vessel I work in the bowels on.
>>13952641
> it wouldn't be the rotating mass
no it'll be everything else. rotating mass would be low down on things that will be stopping it revving
>>13952701
Not quite, would you like to try again?
Remember, F=MA.
Entertain me and the First Officer, what else is stopping this machine from spinning faster?
>>13952701
>protip: the pistons are literally as big as your mom
Oh yeah, how fast do you think your mom can go up and down each second before she blow up? Basically how many Hertz can your mom be reciprocated at a stroke of several feet? 80? 100?
>>13951810
did you develop the fiat cinquecento?
>>13952749
Wow man. I laughed at the post you are quoting as I thought the idea of engine mounts sprung with valvesprings was very funny.
I had never heard of this Fiat before. I am no longer laughing.
Sprung engine mounts with tiny, tiny little springs in a commercially available car.
Why would you do that?
>>13952775
fiat 4 stroke engine 2 cylinder
fiat balances them pretty good but they still shake a lot on deceleration
>>13952927
>posting some Briggs & Stratton tier shit
>>13952934
>posting some Briggs & Stratton tier shit
fiat put it several shitboxes in italy and poland
>>13952982
>KOUUUUUUUUUUUURRRRRWWAAAAAAAAAA
>>13951716
>he doesn't have a forged crank from the factory.
lel
>>13953006
Who doesnt have a forged crank?
>>13951810
>I like to weld 3 valve springs between 2 plates on each side and use that for engine mounts
>>13952701
C'mon lad, your audience is waning. We are off the coast of Port Moresby (shithole) and bored as hell. You've got four crew plus me waiting to read the magnificence you will no doubt scribe.
Another 15 until shift rotation...
>>13951810
No fucking shit it's a troll
>>13953225
>>13953225
Well, back to working on the MAN.
Fairly recent motor, and the engine management panel still runs on XP embedded..... Looks like Win 95 but!
>>13953006
>implying you would know the difference
lel
>>13953383
whoa buddy. did you read the whole post or miss the joke?
>>13953478
I....may have typed that only after reading the first sentence.
>>13952641
Once again, the limitation comes down to valvetrain and reciprocating mass. Not rotating mass.
It is not difficult to create and balance a crankshaft to spin at high rpm, even with significant mass. The difficulty comes from trying to control massive valves under massive string pressure and holding massive rods/pins together at high rpm.
The rotating mass of the crankshaft is almost never the limiting factor in engine rpm. It is the reciprocating mass of the piston/rods and pins and the valvetrain.
You're an idiot.
>>13952088
Mass is yes, but not crankshaft mass.
The real critical mass is recipricating mass, such as rod mass, piston mass, valve mass, lifter mass, spring mass/tension, etc.
Pretty much every crank in every car ever is capable of holding together on its own with a >2 FOS for rotational strength.
>>13952737
>>13952728
>>13953225
reciprocating mass=/=rotating mass
things like g forces due to piston or valve weight, the speed and acceleration of those components, cylinder head design, are also all things that are *not* rotating mass
I can't even tell who's trolling anymore.
OP delete this thread please it's giving me aids.
>>13953609
why would i delete it? there's a valid discussion here regarding the reasoning for blading your crank, and why it's valid/invalid. the discussion about reciprocating and rotating mass seems pretty legit but there's no reason to try and ignore that the speed at which you'll reach your redline isn't as significant as the redline itself, and that is definitely influenced by the crank's overall weight.
>>13951774
this
I recommend machining the stock cast flywheel if you want to rev to the moon
>>13953841
you mean like drill a few holes here and there to cut weight?
>>13953570
I sure am! So much so, MAN B&W certify me for Main Engine overhauls and crank regrinds. If you honestly think you can overcome the crankshaft mass issues that stops large frame ME's from spinning past 100 then you better let MAN know, I think they've got some money for you. Any dicknose could bolt a head with valvetrain from a MaK onto a low speed me with the same bore, and fuck me dead if you won't find it's still a low speed me.
This is why the sea life pays off. I'm so far away from you and your ilk.
>>13952728
Combustion speed.
>>13952185
>In the realm of auto engines
>>13952641
>MAN B&W 33/44
That's a boat engine, your example is irrelevant.
itt
>>13951999
This faggot has never seen a race engine. Kek.
>>13955190
It's an engine, you dope. Does the Otto cycle (Miller in these powerplants) change because you lifted it up and put it an a boat?
Stick to this website young lad. You are so far away from being paid to do more than change lube. You need to remove the blinders on your mind if you want to succeed in this field.
>>13951912
going to community college
>>13954532
Just because you're certified to hop around a big diesel and troubleshoot/swap parts doesn't mean you know shit about engine design. Your argument from authority fallacy is hilarious.
As has already been stated, the limitation in rotating rpm is NOT from crank mass unless the crank is of an utterly shit design/quality.
The limitation comes from reciprocating mass and it's interaction with the rod:stroke ratio as well as the reciprocating mass of the valves and their necessary actuation hardware.
Once again, crank mass is not the issue, reciprocating mass and the exponential g loading produced FAR exceed the critical failure point of a crank being able to hold itself together at speed.
tl;dr you're a fucking idiot.
>>13957389
>Once again, crank mass is not the issue,
When considering the rotational limits of an engine alone, it boils down to rotating inertia and friction losses being the limiting factors.
Why don't you try controlling a rotating mass of hundreds of thousands of kilograms at several thousands RPM (remember, we're completely and ignorantly omitting the reciprocating masses associated for theoretical purposes)
>protip; you can't. It is entirely impractical to input the sheer amount of energy required to spin up such a rotating mass to several thousands of RPM before it's even outputted from the engine.
>>13957506
>When considering the rotational limits of an engine alone, it boils down to rotating inertia and friction losses being the limiting factors.
Wrong. It comes down to the limits imposed by reciprocating forces acting on materials of a limited strength.
>Why don't you try controlling a rotating mass of hundreds of thousands of kilograms at several thousands RPM (remember, we're completely and ignorantly omitting the reciprocating masses associated for theoretical purposes)
You can't base your argument around ignoring the most important part of mass-based limitations on an engine.
Reciprocating mass (be it drivetrain or valvetrain) is the limiting factor in engine speed, these limits are reached long before a crank's rotational inertia tears itself apart. Trying to exclude the reciprocating forces (which ultimately are what impose the limits on engine speed) from the argument only goes to show that you are wrong and are grasping for straws.
>>13957814
>Wrong. It comes down to the limits imposed by reciprocating forces acting on materials of a limited strength.
You freaking guy, of course reciprocating engine limitations come from reciprocating forces, but whoever that anon was (you?) wanted reasons why *rotating mass alone* would become a limitation. It as even explicitly outlined that the rotating inertial limits were theoretical because that bitch anon specified that there was no reason rotating mass alone could present any physical challenges, or limitations.
>You can't base your argument around ignoring the most important part of mass-based limitations on an engine.
Again, Idk who you are, if you're the shipmate MAN engine mechanic, I was agreeing with you. If you're the anon hung up on rotating masses alone, then the hypothetical example of an engine with only rotating mass was for him.
>>13957840
You don't seem to have followed this thread very well.
>The thread is about knife edging a crank.
>Someone said that knife edging removes mass from the crank.
>He then went on to state that reducing mass from a crank allows for a higher redline and allows an engine to spin faster
>I corrected him in pointing out crank mass and indeed rotational mass in it's entirety is not responsible for the limitations of modern engines, it is the reciprocating mass.
>Thus the argument then became about how crank mass is supposedly a limiting factor in engine speed
>Boat grease monkey guy came in claiming incorrectly that crank mass is responsible for engine speed limitations
>I continued to correct him and others by indicating that it is not rotational mass but reciprocating mass that imposes the critical limits on engine speed.
>You came in and began arguing with me and then the linchpin of your argument is that I should ignore the critical stresses induced by reciprocating mass from the argument and focus only on the rotating mass of the crank, which itself does not limit engine speed in light of more significant stresses from the engines reciprocating mass.
No one is claiming rotational stresses aren't a stress factor. The argument was that reducing crank mass somehow would allow a higher engine speed, which simply is not correct. There are more much more significant limits at play than the mass of a crankshaft that limit the speed of an engine.
I hope you understand now.
>>13953403
You'll know the difference when it comes time to boost...
>>13957389
This more or less.
There are plenty of heavy and fast spinning parts that are balanced like water turbines in hydroelectric dams and energy storing flywheels.
The up and down motion of a piston engine is what limits its rpm, not how heavy a crankshaft is. That and valve train
>>13957389
Those other cunts aren't ol' marine fag here. I'm not superior to anyone, except the Third Mate and the greasers.
But you guys are way off the mark with your high school physics. I don't troubleshoot and part swap, I build these things in-situ. Bring in a crankshaft in four pieces and balance it in the housing. Or at least I did, until I found going to sea to be far more interesting.
If you think you can continue to increase the size of a rotating mass by a factor of tonnes without consequence, then you are either a complete genius for figuring it out or fucking retarded. You don't need to be the former to figure out you're the latter.
>>13958611
Take a water turbine, and stretch it riiiiight out over about forty feet, and make it asymmetrical. Try your calculation again.
Again, if you think you have this sussed that the crank mass is not what is holding back these motors then you need to get in touch with MAN, Wartsila, whoever the fuck you want to get paid by.
It's not hard to make a medium speed diesel. MAN do that. It is hard to make a low speed diesel a medium speed diesel. You could put 14/20 heads and valves on a 32/44 and it will still sit at 890. You could lighten the pistons by a factor of twenty and remove the entirety of the friction from the motor, and the mass of the larger crank on the 32/44 will keep the rev limit right where it is.
Tell me what do you think will happen if I exceed 890? I'll give you a hint - for the first few seconds, the bores will be fine. As will the pistons. Cams, valves, rockers, injectors, all of that will be a-ok for just a little while. Something else is going to give out in spectacular fashion. Want to take a stab in the dark?
This is gold stuff.
>>13959037
Are you telling us this particular engine is absolutely limited by its crankshaft and nothing else?
The crank is right on the limit of assplosion at 890rpm?
>>13959098
Damn skippy. Spin one faster and find out. Hell google search ship engine crank failure and have a good old belly laugh.
For a long time, manufacturers have shared block and bore between medium speed and low speed diesel. The pistons remain identical provided the injection system remains the same. In some older examples stroke remains the same, but in most cases the low speed utilities a cross-head connecting rod which indeed reduces the operating speed, but not by a factor of eight.
So if the piston friction coefficient remains the same, the effective stroke length remains the same but a much higher mass crankshaft and flywheel are installed the effective rpm limit drops by a factor of nine.
It's really not rocket science.
>>13959116
I should clear up quick - Low speed diesels are dictated by an upper rpm limit of 110 to 140 rpm. Medium speed is from this range to 990rpm. Most you will find turn at 900 for power generation. Propulsion is often significantly less than this. 32/44 peak torque is at 750. We have a Controllable Pitch propeller so that's the speed she lives at for most of her life unless we are in a hurry.
So going from 990rpm to 110rpm is a decrease by a factor of nine. This is not a constant.
>>13959037
>>13959116
>/o/ - ships
good job
you have an example of an engine that has zero application in motor cars
you sure showed us
>>13959141
This is the worst comeback hey. It's a fucking engine. It's an Otto (Miller) cycle engine. It doesn't matter if it's in a ship, a car or a plane.
Physics is physics, and you cunts aren't on it.
>>13959141
Actually hey, while it's a bit more relevant for your small brain;
Toyota 1HD-FTE = Yanmar 6LP-STP
Little bit of fuckery with the Bosch VE pump. The low power versions have the same Toyo rotating assembly.
Now you add Yanmar's forged and high mass crank and turn the boost and fuel up. Same every-fucking-thing-else.
Upper rpm limit drops by 550rpm.
It must have been ghosts hey?
>knife blade crank
>faster acceleration
>better lubrication
remind me why this is a bad thing
>>13951783
Sell me one?
>>13959037
Once again, rotational mass is nothing compared to the limitations imparted by reciprocating mass.
Engine speeds are not limited by the forces rotational mass. They are limited by reciprocating mass.
I don't understand how you cannot get this.
>>13960130
I've just read that and I can't figure it out either. What he's saying makes no sense to me.
I like to look at these threads and imagine what it'd look like to a real engineer.
Unless your car is overfilled on oil it's not going to make a difference. It should be designed for rotation.
>>13960130
>>13960134
If you weren't completely closed minded you could follow the bouncing ball with two examples I've given with engine numbers. Hell the 1HD - 6LP example you can prove yourself wrong with an hour of google.
But you won't silly billies.
More than half the crew are from PNG and even they think you are silly. And that's saying something.
They're from PNG.
I'm off to make early six figures to ensure 20,000kw works for another ten thousand hours.
Stay good, internet friendos.
>>13962065
I did, I just couldn't find anything that confirmed what you said and then decided I didn't care sufficiently to look further.
I can't see how rotating mass would do what you say. Yes it absorbs more power through inertia, yes things like crankshaft whip could limit the rpms, yes balance issues could too.
But rotating mass and nothing else? I just don't understand.
>>13962374
Why haven't you taken into account the extra F needed to drive the increased MA?
Where is this extra F coming from? Do you think it is free? If I make X amount of power from Y kg/kwh and I increase the power needed to turn the crankshaft by a factor of 1.5, where is this power going to come from? Do you think now I am using more power, adding more force both needed to turn the crank and thrust load forces on the bearing caps and girdle that the motor would;
Slow down
or
Speed up
or
Do nothing
If you picked B or C, try again.
Why can't a ten meter water turbine hold the same speed as a one meter water turbine with the same water flow and penstock height? Why can't a 140mm inducer turbocharger hold the same rpm as a 100mm moving the same amount of air at the same PR with the same amount of drive? According to your logic, it's not anything to do with the increase in mass. Which is quite funny.
What about the insane added rotational force from the crank that has been induced now? If Fc= M v2 / r where force(centripetal) = mass times the vector squared over the radius of the turn, and we add mass, what the fucking shit do you think will happen to Fc? Just how much centripetal load are you going to put on this motherfucker? Just how much extra load do you think it would take to slow down a rotating object?
>>13962471
>If I make X amount of power from Y kg/kwh and I increase the power needed to turn the crankshaft by a factor of 1.5, where is this power going to come from?
It will just take 1.5 times longer to accelerate no?
Why can't a 140mm inducer turbocharger hold the same rpm as a 100mm moving the same amount of air at the same PR with the same amount of drive?
because it has a different aero profile and tip speed can't go supersonic?
>Just how much centripetal load are you going to put on this motherfucker?
fair enough Fc will pull things out of balance on v-engines.
I'm just amazed that this engine won't rev any higher when lightened and balanced and fitted with race cams and that MAN sell an engine right on the limit of its crank integrity.
sounds shit to be honest, why don't you just LS1 swap it?
>>13962868
This is like asking a mechanic how to design an engine. He doesn't know anything other than specs and procedures.
>>13962868
Haha man, I would give a years pay just to hear enough LS1's strapped together to move a coastal trader. The noise would be insane.
The tip speed of a turbo can always go supersonic if you drive it hard enough. This happens with restricted strainers and is well documented. I've never driven one to surge, but that's just me. But come on man, the trim of the wheel is not the key deciding factor on it's maximum speed. It is the key factor on the formation of the wheel's compressor map, but not maxv.
Fc is Fc. V, inline, radial, not important. Fc is Fc. Big spinning weight - lots of Fc. Small spinning weight - less Fc.
Please understand this is not a manufacturer selling a product right on the limit because they are cheap cunts. But it is right on the limit to hold the power it is generating at the speed it is generating it.
The middle of the paddock Wartsila all the way up don't have camshafts. They don't have pushrods, or bridges, or rockers. Just hydraulic valves on the smaller ME's and pneumatic on the larger ME's. So now the only part of the conventional valvetrain remaining is the return spring and collet as well as the valve. Still only turns to 105, any faster and the crank will (not might) let go.
>>13962937
If you asked a mechanic to design an engine, you would never have another fucked up oil filter location. I'd pay for that.
I'm at sea for months on end with limited spare parts but a full workshop. I know specs, procedures and how to jury rig a ship engine. I'd be surprised if you could overhaul a lawnmower. Now fuck off.
I am playing with the idea of bullnosing my crank, welding/loctite the counter weight bolts, tear drop contouring the journal oil holes, replacing pressed in oil passage plugs with threaded plugs, WPC treating the bearings and more and of course new forged rods/pistons.
>>13962973
so why not just say centripetal force instead of rotating mass, if that's what you mean?
>>13962868
Woo up, just saw the whole 'it will just take 1.5 times longer to accelerate' thing.
No.
It will require 1.5 times more Force to turn it to the same speed. Do you have enough potential headroom in the motor to add more power to the same factor?
If not, it's going to......
Turn slower.
Fuck.
>>13962973
You still aren't any kind of expert to be telling anyone what limits an engine. Cars don't have glass crankshafts like these boat motors you work on. The crank is absolutely one of the last factors in terms of engine rpm when talking about car and truck engines.
>>13963024
What? One is a real, physical change. One is a not-really-real force that is a convenient way to express force over a vector.
Over-threshold Fc isn't the cause, it's the symptom. A symptom of too much M.
>OE spec automotive engines will float valves or damage the valvetrain if the rev limiter is disabled or removed
>arguing whether or not lightening the crank will increase RPMs
>somehow boat engines several orders of magnitude larger are comparable
/o/ everybody
>>13963046
Oh piss off with your dribble. A crank that holds fifteen thousand KiloNewtons isn't glass.
It doesn't matter how you feel about it youngster, it's not true.
Now you tell me something boy. What's the difference between an Otto cycle marine platform and an Otto cycle OTR platform or an Otto cycle auto platform.
Do the laws of physics change based on what metal shell it's in?
Now, off you trot.
>>13963055
Good thing you have the butt made of straws that you can keep grasping at.
>>13963055
What about a boat engine completely comparable? 1HD = 6LP. Scroll up, google fy, educate yourself.
Fuck I hope you are an apprentice.
>>13963067
I googled and honestly found nothing to confirm what you said. apparently the bottom end is stock. please spoonfeed me.
>>13963058
You don't get it do you. I'm not arguing the physics. An industrial boat engine is not something you can draw direct comparisons against a car engine with. The crankshaft of any typical automotive engine has no effect on it's maximum rpm until you start reaching out to Sprint cup and Formula 1 engines, and guess what? They're limited by their respective valvetrain designs. The scales are not remotely similar.
Suck my dick old man.
>>13963078
Crock of shit. More mass, more power needed for the same revolutions. Got the room to add more power? No worries. Don't? Speed decreases.
You suck my dick trolley boy. No effect until F1, do you read what you type? Have you ever opened a motor before?
I won't be sucking your cock laddie. I'll be earning low six figures doing what you cannot achieve.
Doesn't bother me if you feel like you've won an internet argument. One of us here should you choose to believe it is an internationally qualified player in the field.
Who the fuck knows what you do apart from steal useful oxygen I could be burning to make power.
>>13963077
You want to learn, you don't eat of the spoon. I've given you more than you need.
Get the 6LP workshop manual and run the part numbers for the crankshaft. That will point you in the right direction, if you could be bothered.
Or, you know, read a high school physics textbook. That too will point you in the right direction.
>>13963091
>More mass, more power needed for the same revolutions
Nobody is arguing this.
The argument presented is that an automotive engine's RPM is being limited mechanically via valve train far before physical weight or drag created of a given rotating component.
Autism: The Thread
>>13963110
That was your original argument. Got nothing against that. Otherwise things like rev kits and beehive springs wouldn't be as effective as they are.
Where you have gone wrong is you and others believe you can add and subtract mass without consequence. Further a few of you have no comprehension of the effects even small(ish) changes of mass have to these rotating objects and the resulting change in force needed to turn this object.
Isaac Newton has a few issues with that.
>>13963091
This thread isn't about anything you're saying though. OP wanted to know if making his crank lighter would make it break easier. It could do. Then it became a question of diminishing returns. A lighter crank doesn't make an appreciable difference in most engines. If I went and put a crank that was 5lbs lighter in my car, it wouldn't turn over any faster. It could, but wouldn't. The valves would float long before the drag and mass had any effect on my power or rpms.
>>13952185
>>13952641
>>13963132
Scroll up. There's the Jackal saying removing weight will not increase maxv. Crock of shit. Thought I'd throw in a bit of satire to make light of it. Spoonfulls of angry young kids later, we are where we are now.
Will you hit valve float first? Probably, or bend a pushrod or whatever.
You can't go swinging your nuts around with facts that aren't true. And you have taken offence to me telling that to you, and cunts started an argument.
>>13963157
You busterd
>>13963165
No. I'm not a busterd. I'm custard.
>>13951716
Why is /o/ always filled with idiots making such unintelligent assumptions?
I'm going to assume you would have this done by a professional. And with that, I would assume you would make a custom specified request with exact numbers, etc.. I wouldn't cut too much to risk a problem, even on a full track car. I would just make sure the machinist knows what they are doing and warranties their work. I would even recommend making sure the machinist is a skilled metal clergy, too. And make the fuck sure he balances the thing.
>>13963157
If everything else is perfect, a lighter crank will let it spin faster, 100%. Even on stock cars it will rev quicker, otherwise ricer sales of lightweight flywheels would be non-existent. However, it is of little concern when dealing with car engines until pushing to the extreme. Strength is of much greater concern, otherwise we should be making cranks out of graphite that are internally cooled.
>>13963176
>I would even recommend making sure the machinist is a skilled metal clergy, too
You mean understands the metallurgy of steel alloys?
>>13963193
Hey, he's on it! We've found one! Fuck yeah, onya champion. That's exactly right.
This man smiles upon you. There has been much frowning as he read this thread over my shoulder.
We bored....
knife edged cranks are normal.. pretty sure even some production cranks are knife edged. It's just harder to lighten a crank by knife edging than it is to do it by drilling it.
if you're using a lighter rod assembly you're going to be lightening your crank anyway. and if you're doing it at a shop with experience in knife edging there's nothing wrong with doing it. it's not always as extreme as op's picture.
The counter weights aren't where the strength of the crank is determined anyway. There's probably some power limit where you need the increased inertial torque of a heavy crank to keep if from rubberbanding, but I don't know if road cars can make that kind of power. I really don't know what goes into the engineering of crank weight. but I'm sure that knife edging plays less of a role than simply removing material in any configuration. the knife edging is just reducing windage. it's the amount of weight you're removing that will have, if any, effect on strength and i'm pretty sure it will be due to less inertial torque keeping it "stable".
>>13963215
No I think he means he blesses the crankshaft before milling
>>13963249
..Fuck.
>>13963042
>It will require 1.5 times more Force to turn it to the same speed. Do you have enough potential headroom in the motor to add more power to the same factor?
That's not how it works.
F=Ma
a=F/M
Force is the not determining factor for crank speed. Force determines crank ACCELERATION.
Power divided by friction and output loading determines maximum crank speed.
Once again, you're an idiot.
>>13963058
God, for an old man you are retarded.
Rotational mass will not determine your Rev limit. It will determine how fast you GET THERE.
You can spin something as fast as you want until centripetal force tears it apart, but the heavier that something is, the more energy it'll take to get it spinning that fast.
IE: HEAVIER WILL ACCELERATE IN REVOLUTIONS SLOWER.
That does not mean the limit is slower.
Rotational mass will effect the limit but not significantly enough (contrary to your belief)
Jesus fucking Christ stop drinking the salt water.
>>13963249
>>13963262
Sod off ya wanker! I've had about a gutful of your bollocks ya cunt
>>13963261
And without the required Force, how are you to accelerate it to the same speed?
Your equation is way off.
w=2Piexrpm/60 for maxv. Where did you get your shit from?
>>13963262
Third line down, your words are; the more energy it'll take to get it spinning that fast.
Cheers, that's a hole in one. It will take more energy. And if you don't have that energy it will????
Follow the bouncing ball laddie.
>>13963091
You haven't proven jack shit that you are who you say you are. Have you fucking forgotten where you are? You're posting anonymously on an anonymous image board, here anybody can say whatever the fuck they want about who or what they are, and it doesn't mean a goddamn thing because NO ONE FUCKING CARES. Here, the ONLY thing that matters is the content of what you post, and for all of the volume of your spewing you've not actually 'won' anything. You keep arrogantly demanding that, after you throw out some model names, that we should go and do the research ourselves; sorry, here, that's NOT how it works. If you make a claim, then YOU have to provide the data and evidence to prove your point. And no, your supposed 'experience' doesn't matter, because again, anyone can say anything here. I'm talking about external links to reputable sources.
Otherwise? Go fuck yourself, and stop shitting up the thread.
>>13963275
Man I laughed hard. A gut full of someone else's bollocks.
>>13963262
>You can spin something as fast as you want until centripetal force tears it apart
Thus you hit the rev limit, friend. Unless vibration kills it first, which 99/100 times is what happens. You could also design an engine that couldn't make enough power to turn over its own crankshaft. In that instance, the rotational mass is 100% what limits engine speed.
>>13963282
It will Rev according to the energy you have. But theoretically you can give it more energy. What I'm getting at is the cranks mass is not the deciding factor of rev limit.
>>13963297
Didn't read. I don't have to prove anything. The physicists who came before me have done that.
Off ya trot, don't get so worked up about things. If you put as much effort into learning so you aren't a dumb cunt as you do arcing up over the internet, you wouldn't be a dumb cunt.
>>13963297
What the desu did you just fucking desu about me, you little desu? I’ll have you know I graduated top of my desu in the Navy Desus, and I’ve been involved in numerous secret desus on Al-Desu, and I have over 300 confirmed desus. I am trained in desu warfare and I’m the top desu in the entire US armed desu. You are nothing to me but just another desu. I will desu you the fuck out with desu the likes of which has never been seen before on this desu, mark my fucking desu. You think you can get away with saying that desu to me over the desu? Think again, desu. As we speak I am contacting my secret network of desu across the USA and your desu is being traced right now so you better prepare for the spam, maggot. The spam that wipes out the pathetic little thing you call your desu. You’re fucking desu, kid. I can be desu, desu, and I can desu you in over desu ways, and that’s just with my bare desu. Not only am I extensively trained in unarmed desu, but I have access to the entire arsenal of the United States Desu and I will use it to its full extent to wipe your miserable desu off the face of the desu, you little desu. If only you could have known what unholy desu your little “desu” comment was about to bring down upon you, maybe you would have held your fucking desu. But you desu, you desu, and now you’re desu, you goddamn desu. I will shit desu all over you and you will drown in it. You’re fucking desu, kiddo.
>>13963282
>>13963305
The counterpoint I'm trying to make here:
You're saying the sole deciding factor is Crank mass (at least that's what I've gotten), which it's not.
>>13963305
>>13963305
And you are mostly correct. It is one of the deciding factors. It isn't the only one, nor is it the smallest one.
Keep it up, you are a diamond in the rough.
>>13963328
Nah champ, I'm not saying it's the sole deciding factor. But it most certainly is one. See >>13963331
Anyone else ITT like to jack off to Eurobeat
>>13963328
That was what I was getting too, but he pointed out that some said it has 0 effect under any circumstance, something to that effect. In smaller engines it is low on the list of things needed to spin the assembly faster, to be sure.
>>13963331
Fuck off with the patronizing. I already have my career.
>>13963349
Wasn't being patronizing. Now I am. Don't be so self important to think I would waste time on encouraging you into an already overloaded career.
How about you turn you brain on and look at something objectively instead of emotionally. I was complementing you as a diamond among mongoloids on this site.
>>13963091
>Crock of shit. More mass, more power needed for the same revolutions.
This is wrong.
With more mass, more TIME is needed to achieve the same revolutions.
Mass, power, and angular velocity do not interact as you claim.
accel=Force/mass
work=Force*displacement
work=Power*time
I'll give you a simple analogy:
Take a 2000lb car that has 200hp.
This car has a aerodynamics limited top speed of 150mph.
Take that same car and ass another 2000lbs of mass (ignoring friction increases)
What sort of top speed do you think this car has now? Half the top speed?
No. The car now has the same top speed but it takes TWICE as long to get there.
This is how power and mass interact.
Your assertion that additional mass of a crank requires more power to achieve a given crank speed is flatly wrong. What is actually the case is more mass of a crank increases the TIME it take for the crank to reach a given angular velocity.
Which basically translates to:
Heavier crank = slower revving up to speed.
>>13963363
Here's a far easier example. You have a balanced weight of one tonne and you drive it with a powerplant of one kilowatt to reach a speed of one meter a second. Add another 500kg to the weight, keep every other variable the same.
Do you honestly believe you will achieve the same speed?
>>13963362
I took your comment as patronizing.
Thank you and sorry at the same time.
>>13963262
>>the more energy it'll take to get it spinning that fast.
To correct your statement, it requires more NET energy to get spinning that fast; at a set amount of power input, it'll take longer to deliver that amount of kinetic energy to the shaft, but it won't prevent it from reaching that speed.
Really the limiting factor is the maximum force the crankshaft can absorb from the movement of the pistons and connecting rods, which vastly exceeds any forces exerted by the cranks' own mass.
And getting back to the ACTUAL TOPIC OF THE THREAD, that's probably the biggest reason you wouldn't want to knife edge an auto engine crankshaft, the loss of metal would weaken it and leave it more prone to failure.
>>13963157
>Scroll up. There's the Jackal saying removing weight will not increase maxv. Crock of shit.
It wont' because as has been said before car engines are limited by valvetrain reciprocating mass and rotating assembly reciprocating mass. Not by rotational inertia.
Sure you can spin a perfectly balanced and axially symetrical steel rod fast enough for it to fail and come apart, but that is irrelevant to the discussion. The discussion is about lighting a crank to increase maximum possible revs. And the fact remains there are far more significant factors limiting engine revs than rotational inertia of a crank. Meaning lightening a crank does not increase an engines maximum revs.
>>13963378
All g man, not a worry in the world. I now have the uninspiring job of cleaning the oily water separator. I hope everyone, even the silly billies, has a great day and stays safe.
>>13963395
Haha, I'm free! I'm free! No separators for me!
Fuck yeah, love to all.
>>13963389
It will increase the theoretical top speed that the engine can turn over at, that's what this guy is saying. He's not using the right words and may be doing so on purpose, but he isn't wrong. More power is needed to move more mass, this is a fact no matter how you slice or dice it. Heavier crank will be more parasitic than a light one.
>>13963282
>And without the required Force, how are you to accelerate it to the same speed?
Force does not determine maxV. Force determines maximum rate of acceleration.
Do you know what ion engines are? They are engines that emit ionized gas at extremely high velocity, the product is a very minuscule amount of FORCE (fractions of a newton, ~100milinewtons) output by the engine. These very low FORCE engine are capable of driving spacecraft and satellites to very high VELOCITY.
You apply even a small force to a given mass, even a significant amount of mass for enough time and it will eventually even reach a large fraction of c.
Mass does not limit velocity. Even angular velocity.
>>13963423
You seem pretty smart, what happens if you accelerate the perfectly balanced flywheel of 17 million tonnes to a speed of 20,000rpm?
>>13963437
You have a whole lot of potential work and also very high potential for death.
>>13963374
>You have a balanced weight of one tonne and you drive it with a powerplant of one kilowatt to reach a speed of one meter a second.
Fair enough.
But you failed to state how long it took for the weight to reach that velocity. The time variable is critical to this discussion as it is critical for quantifying acceleration. Acceleration is critical because we are talking about moving a mass up to a velocity.
>Add another 500kg to the weight, keep every other variable the same.
If you keep every other variable the same it will reach the same velocity but take 1.5 times as long to get there.
>Do you honestly believe you will achieve the same speed?
Yes it will. This is basic newtonian physics.
Apply any force to a mass and it will continue to accelerate, indefinitely as long as the force is applied until you get close relativistic speeds.
>>13963422
>It will increase the theoretical top speed that the engine can turn over at, that's what this guy is saying.
If he's stating that for a given power lower crank mass will allow a higher maximum angular velocity, that's fucking stupid.
We're talking about engines here. Engines are meant to output power. meaning they have a surpouss of power in order to drive whatever they're hooked to, be it a transmission to drive wheels, or a generator, or a propeller.
If an engine is literally using all of it's power to drive a crank mass to it's theoretical maxV it's not a useful fucking engine as it would not be able to output any power.
I thought this point would be painfully clear but I guess not.
The power output of any useful engine is SIGNIFICANTLY higher than that needed to drive the internal components of that engine at it;s operating speed.
What he is apparently talking about is akin to a rocket engine that has a 1:1 power to weight and is incapable of producing any work by lifting or accelerating a payload (or even it's own fuel fraction).
>>13963479
Popped my head back in to the control room.
This part is a-ok.
Now we go to part duo of our problem. This spinning mass is held in place by parasitic bearings. Let's say there are ten bearing shells spaced equally along the weight in five places. The faster it turns, the hotter the shell becomes and the more it swells into contact with the shaft.
Knowing what we know now, will it still reach the same speed? In a ideal situation with no loss my oath you are spot on. We could spin a planet at a million revolutions a minute with enough time with a whipper snipper if loss was not an unfortunate real thing. Same with the Ion engine example above, flying through vacuum imparts very little loss.
Even if it took fifty days to spin up the shaft the Company would love to use the lower output ME's for fuel savings. But the crank must be a certain size in relationship with the proepller shaft, pitch and size (load.) But we can't, as it takes a certain amount of force to turn this object a certain speed with a certain load. If we could spin our shafts with whippersnippers we would. If we could lighten the cranks, we would.
Now I'm getting into this boiler before they put me back on the separators.
>>13963437
>what happens if you accelerate the perfectly balanced flywheel of 17 million tonnes to a speed of 20,000rpm?
It flies apart due to structural stresses centered at the hub radiating outward exceeding the tensile strength of whatever material it's made from and kills everyone within a three mile radius. Essentially becoming a very large fragmentation bomb.
If it was made of impossibly strong unobtanium?
You would spend a very large amount of power to spin it up depending on it's rotational inertia (dictated by the radius, thickness, and how the mass is distributed throughout the disk)
Ignoring friction:
You could take a very very long time spinning it up by applying one newton meters of force
Or you could take a very short time by applying 1,000,000 newton meters of force (which would take 1/1,000,000th the time to accelerate it up to speed)
In both cases the total power input to the system to reach 20,000rpm would be the same.
>>13963534
A lighter crank won't spin itself apart until you spin it faster. It should have less force acting on it for a given speed than one that has twice the mass and an equivalent distribution. It can absolutely allow more rpms from an engine, but that's not what they're used for obviously.
Lighter cranks don't increase RPM. Only acceleration of RPM. It will increase HP marginally due to less inertial loss, but at the cost of strength (depending on material though you can be lighter and stronger of course)
This is basic physics and it's one of the reasons why drag racing engines use relatively heavy cranks despite still turning 10k+ rpm.
The limiting factor to RPM is valve train mass and strength.
>>13951716
>block off pcv vent hose. Have crankcase constantly under vacuum. Gain more horsepower as there wont be any crankcase windage anymore when the crankcase is in constant vacuum.
I can't predict what the other unintended consequences will be but I would do this before I would try something like knife edging the crank.
>>13963537
Obviously the realities of engines mean there are things like bearing friction, cylinder friction, windage, etc. that further impart limits on the system.
Of these losses the only one of real note in our talk about crank mass has to do with bearing losses (rod end and main)
However we're talking about modern car engines here. Bearing friction will not increase/decrease substantially with the addition or subtraction of a few grams of metal to a crankshaft.
Lightning of a crank is never performed in order to increase an engines redline as the strength of the crank and the balance of the crank are far more critical to high rpm operation than it's total mass. Especially considering the relative lubricity of the bearings will not be effected by the amount of mass subtracted in a real world example.
What is more important in a performance context is the moment of inertia of the crank assembly. And what is done to reduce this is commonly a lightening and redistribution(more axially located, lower MoI) of flywheel mass.
>>13963616
>A lighter crank won't spin itself apart until you spin it faster.
A crank spinning itself apart is largely based on the balance of the crank assembly and the tensile strength of the material. A heavier crank with a higher MoI will be more prone to internal structural failure of the crank, but in the realistic context of the current discussion this limit is FAR beyond the limits of the other components of the engine (valvetrain, reciprocating rods/pistons/wrist pins/etc.), even for a very heavy crank.
>It can absolutely allow more rpms from an engine
The critical limit to engine speed is imposed by components that will fail long before the crank spins itself apart.
>>13963668
pcv doesn't keep the crankcase pressurized it relieves pressure due to blowby..
and whether or not something is in a vacuum has no effect on it's inertia or friction.
and knife edging is completely normal.
award for worst post goes to you
>>13963668
In reality blowby is a thing, and unless you have a very powerful (and parasitic) vacuum pump acting on the crankcase, you're going to have crankcase pressure.
Crankcase pressure is generated by blowby. Without crankcase ventilation the crankcase becomes pressurized.
A PCV system uses manifold vacuum to evacuate that crankcase pressure instead of letting the pressurized crankcase simply vent to atmosphere.
If you plugged a non-PCV engine's crankcase ventilation (atmosphere vent), you wouldn't have a vacuum, you'd have a dangerously pressurized crankcase which would spike draining oil pressure and start blowing out seals making an oily mess. Additionally you would also have significantly more pumping losses.
>>13963701
> so much god damn implying here.
I never spoke of inertia. Your post literally missed the entire point of my post.
Putting the crankcase under vacuum isn't a new concept. Like take this article from 1999 for example.
http://www.hotrod.com/how-to/engine/ccrp-9903-moroso-vacuum-pump-test/
Anon goes derp again.
>>13963624
>Implying counter-weights are a stressed part of the crank
lel
>>13963733
I didn't say counterweights I said lighter crank.
Try to keep up.
>>13963724
Yeah, the pcv system is not likely going to work under heavy engine load. You would need a pump in addition to continue drawing vacuum under heavy load. That's why the vent is there of course for heavy engine load when the pcv valve can't flow well enough to keep up.
>>13963733
Every part of a crank is stressed under high rpm loads.
Additionally the balance imparted by counterweights relieves stress from the crank.
Removing counter weights serves to imbalance the crank assembly and rely on material strength alone to counteract these imbalanced loads.
There is a reason crankshafts have counterweights.
>>13963731
That has nothing to due with windage, bud. So why would you post something irrelevant to the topic and then wonder why people think you're talking about windage...
>>13963755
You were posting in a thread about knife blading a crank (which means knife blading the counter weights, since that's what knife blading is) and provided no other context. How the fuck was I supposed to know that you only meant "lighter cranks" when you were generally referring to the topic at hand?
>>13963758
You don't remove the counterweights when knife-blading a crank, you just cut them on the leading edge and then rebalance the entire crank...
>>13963668
>Have crankcase constantly under vacuum
You would choke the engine and suck air/fuel past the rings and your engine would be a shit. All it would do is lose power immediately.Knife edging is to reduce turbulence and drag within the crank case and prevent oil foaming, it just has an added benefit of removing weight. OP doesn't even really know why you would do it and therefore should not be considering it.
>>13963765
It isn't irrelevant. The main reason people knife edge a crank is to attempt to reduce windage in the crankcase. Anything else to do with inertia is just an added benefit.
>>13963779
yes i do stop pretending you're better than me by wiki'ing it you shitbag.
>>13963756
>Yeah, the pcv system is not likely going to work under heavy engine load.
A PCV can and does work under heavy engine load. If not enough flow is allowed to properly evacuate the system, simply a larger orifice is needed.
The problems arise when you have a high performance forced induction engine. PCV only works when there is manifold vacuum which is not the case with a turbo/supercharged engine under boost.
Typically OEM's put the PCV outlet before the turbo/supercharger to always maintain vacuum but this has the issue of leaving an oily mess in your intake tract.
On high performance engines a PCV is usually just eliminated and a simple atmospheric vent is added. A PCV is largely for emissions anyway (instead of oil vapor and combustion blowby getting vented to atmosphere it gets sucked back through the engine and the catalyst to satisfy the tree huggers).
Vacuum pumps are a thing, but largely unnecessary. So long as your crankcase ventilation is sufficient to flow enough air to vent blowby and prevent crankcase pressure from building, a pump is unnecessary (and dirty) complexity.
>>13963689
>>13963578
>>13963534
>>13963479
Youre smart. Please stick around and educate these idiots.
>>13963799
What the fuck are you talking about..
I know that. I literally just fucking said that.
So why are you talking about crankcase vacuum in a thread about windage? It's irrelevant.
>>13963812
>A PCV can and does work under heavy engine load. If not enough flow is allowed to properly evacuate the system, simply a larger orifice is needed.
Google a pcv system. A pcv system will need a vent in addition to the valve. Even in NA applications.
>>13963858
crank case vacuum reduces windage losses as you're pulling oil droplets off the crank webs
>>13951716
>risk of grenading
I have a knife-edged crank in my DD. I hit 7,500rpm on a daily basis and am making 3x more power than the crank handled when stock. No issues. Just don't have some moron do it and you'll be fine.
>>13963775
>You were posting in a thread about knife blading a crank
The topic shifted from knife edging to crank weight in general and how it / if it affects RPM.
Some hot head came in talking about light cranks increase RPM and then got blown the fuck out by basic physics.
>>13963858
>That has nothing to due with windage, bud. So why would you post something irrelevant to the topic and then wonder why people think you're talking about windage...
>Doesn't seem to realize that the gasses in the crankcase and the oil contribute to windage.
Are you fucking kidding? You can't correlate how messing around with the pcv system will impact windage...
Lol and wow...
>>13963884
Maybe.. marginally, but that's not the reason you use crank pumps.
>>13963911
no but we were talking about crank vac in regrards to windage. yes it helps pull oil from the top end back down and reduces blowby thus allowing lighter, less power robbing piston rings
>>13963899
Windage is not the primary reason for using crankcase pumps, dude. But, windage is the primary reason for knife edging.
I'm done arguing with someone this retarded.
If you're getting your crank rebalanced and lightened there is literally not a single problem with knife edging it instead of drilling it. Period.
So yes, bringing crank vaccuum into a discussion about cranks and windage is irrelevant. That's all there is too it.
>>13963926
>it helps pull oil from the top end back down
uhh no
that's gravity and it's unaffected by vacuum or else our atmosphere will literally rip apart.
>>13963928
Oh god, if you're just going to play shifting around the goalpost logic fuck you bro.
>>13963872
I know what a PCV system is.
The PCV vents to the intake manifold. The "vent" you speak of is actually a crankcase intake that pulls in fresh ambient air into the crankcase.
Crankcase pressure is never bled to the atmosphere in a properly functioning PCV. Air is pulled in through a breather, flows through the crankcase and is vented to the manifold.
The "Positive" portion of PCV comes from the vacuum generated at the manifold.
>>13963810
But I am better by virtue of not having to come on 4chan and ask if it's a good idea or not. Clearly I understand it better than you, no need to wiki it or anything.
>>13963951
shut the fuck up all you're doing is reading all the material people with IQs past single digit wrote and parroted. the only virtue you have is that you're a plagiarist with no modesty.
>>13963948
Cool, well in an NA vehicle there's little manifold vacuum to assist in drawing in crankscase gasses under heavy loads like at WOT and that's when maximum crankcase gasses are being produced. The excess is often vented through the vent under heavy load such as WOT under these conditions. You're absolutely right though that a larger orifice would help in that situation.
>Crankcase vacuum
People still drive N/A cars? Lol.
>>13964001
>he boosts his crankcase instead of his manifold
>>13964001
>People still drive N/A cars? Lol.
Protip: Forced induction cs still produce manifold vacuum and thus crankcase vacuum.
In fact most OEM's place partial PCV vent before the turbo/supercharger to have vacuum ALL the time by harnessing the vacuum created between the turbo/supercharger and the air filter.
With this setup, crankcase vacuum can actually increase with load.
>>13964025
why would you have a vacuum at the turbo inlet unless you have a restrictive intake?
>>13964046
>why would you have a vacuum at the turbo inlet
>>13964025
a pre compressor pcv system will never be able to keep up with the crankcase pressure of a turbo car. but im sure it helps with emissions. not power though.
>>13964046
Any time you have suction (turbo/supercharger) and a restriction (air filter) you have negative gauge pressure.
>>13964057
This vacuum isn't as significant as manifold vacuum at idle but it does increase with load.
Pic related is a subaru setup. In this instance at low load, manifold vacuum is produced. Air is drawn in from the pre-turbo intake and fed to the crankcase and to the intake manifold.
Under high load (boost) the valve closes off the pressurized manifold and uses intake vacuum to evacuate crankcase pressure.
Between blowby pressure and intake vacuum, the system works Especially since pressure is being evacuated both from the heads oil galleys and from the crankcase.
The downside is oil buildup in your intake. This is typically solved with a catch can between the intake piping and the crankcase/heads
Having a PVC system at all helps immensely with emissions.
>>13964057
>>13964089
Pic related is the system under load (boost)
>mfw this thread has been highly educational.
thank you based anon.
>>13964055
>>13964057
I mean big vacuum, not 1 or 2 psi
>>13964118
Psi is a measure of pressure, not vacuum.
The pressure differential is not critical so long as a differential exists, the flow is.
it wont hold vacuum under boost. it's impossible without a substantial pump. it will vent, absolutely, but it will not hold vacuum. and thus is forgone on aftermarket turbo cars as it adds no benefit over atmospheric vent other than emissions.
>>13964198
It doesn't have to maintain crankcase vacuum to do it;s job and be beneficial. As I said, any pressure differential counts.
>and thus is forgone on aftermarket turbo cars as it adds no benefit over atmospheric vent other than emissions
Wrong, Having a point of pressure differential absolutely does benefit crankcase ventilation.
The reason PCV systems like this are eliminated for performance modifications is to eliminate a source of unmetered air.
In an open loop system system, load is calculated based on MAF readings. With a PCV setup like this, unmetered air is introduced to the intake charge via the PCV vent which makes calculating air mass inconsistent and unreliable thus affecting fueling. And when you're trying to push a motor to the ragged edge, the last theing you want is to not know exactly how much air mass you're pulling.
You cannot put a PCV system like this before the MAF because it will deposit oil all over it and render it ineffective.
That is the reason systems like this are either modified or disabled for performance.
>>13964269
>The reason PCV systems like this are eliminated for performance modifications is to eliminate a source of unmetered air.
and because crankcase vapours aren't exactly high octane
>>13964269
>It doesn't have to maintain crankcase vacuum to do it;s job and be beneficial
Actually, it does. That's the whole point. If there is positive pressure it won't be doing anything unless the vacuum is substantially high (greater force than atmosphere). Which is why atmospheric vent is adequate unless for emissions.
a pump will work but pumps are expensive.
>>13964341
>and because crankcase vapours aren't exactly high octane
Compared to the volume of air entering the combustion chamber, PCV ventilation is a non-issue.
>>13964341
>Actually, it does. That's the whole point.
That's not how fluid dynamics works.
>If there is positive pressure it won't be doing anything unless the vacuum is substantially high (greater force than atmosphere).
Any pressure differential is sufficient to promote flow (and thus ventilation of the crankcase).
A prime example. Do you think a turbocharged car is ONLY receiving the benefits of it's turbocharger when the turbo is actually producing positive gauge pressure?
Absolutly not. A turbocharged car is reciving VE% benefits from the turbocharger even under manifold vacuum wherehby the turbocharger is reducing manifold vacuum and thus increasing VE%.
This is directly analogous to the PCV example. Even if the pressure differential created by the intake isn't enough to create a true vacuum in the crankcase, the existence of that pressure differential is sufficient to promote flow and evacuate the crankcase.
If you suck on a straw inserted into an inflated Capri Sun you are promoting flow into your mouth even if you're not sucking hard enough to create a vacuum within the Capri Sun. Pressure differentials are all relative.
>>13964773
meant for:
>>13964303
too
>>13964773
You have to have vacuum to see power benefits, though.
If there's no vacuum it's not doing anything.
Lowering the net positive pressure by 5 inches is not going to give you any gains. There has to be net vacuum.
>>13964842
>You have to have vacuum to see power benefits, though.
>If there's no vacuum it's not doing anything.
This is wrong.
>Lowering the net positive pressure by 5 inches is not going to give you any gains. There has to be net vacuum.
You don't seem to understand what you're saying.
The term "vacuum" is a relative term. There is still positive absolute pressure. when we say "vacuum" in this context we are referring to gauge pressure vacuum, not absolute vacuum.
On the absolute pressure scale EVERYTHING is positive pressure all the way down to 0 absolute pressure.
In your example of 5 psi reduction. Take ambient pressure (14.7psi absolute, 0psi gauge). If our intake produces an absolute pressure reduction of 5 psi (9.7psi absolute, 19.7in Hg) then we've just effectively reduced our windage resistance by 1/3rd which is not insignificant.
Lets take it a bit farther, lets say the blowby pressurizes our crankcase by ~5psi (~20psi absolute, ~5psi gauge) then our intake provides a 5 psi reduction in pressure. We've still effectively reduced the density of air, and thus windage resistance inside the crankcase by 1/4th.
tl;dr what you are referring to as "vacuum" isn't an actual vacuum. There is no magical benefit when air pressure is reduced below 0psi gauge pressure. Because 0psi gauge pressure is still 14.7 psi absolute pressure. And drag and windage still exists in the same proportions below 14.7psi absolute pressure as it does above.
There's a reason rockets can accelerate to 17,000mph within the atmosphere so long as they are high enough (low enough pressure) whereas they would vaporize moving that fast at sea level.
>>13962471
Is this a load of shite or am I going senile? This makes no sense.
>>13965375
I don't know anon, I cant be fucked to read that guys posts anymore. I just glazed over them and picked out the blatantly wrong things that I cared to explain. Maybe I'll try to read it and make sense of it tomorrow when I give any fucks.
For now I'm going to bed. Goodnight.
>>13965383
sleep tite pupper
>>13963342
yes
bump for more ship wanker
>>13967143
>ship wanker
OP here. i get that this isn't the most economic approach to gaining performance, but i was just wondering if it had any benefits at all. i wasn't aware it would escalate to this level. wew.
