Questions that don't deserve their own thread!
I'll start off.
I'm going to try and build a set of 3-1 headers for my V6 as there aren't any proper aftermarket parts and the stock manifolds are fucked beyond belief.
I calculated the ideal diameter of the primaries however, and the calculation tells me that they need to be smaller than the exhaust ports. To me, it seems ill-advised to do so, but the math tells me something else. Wat do?
>>14874260
I've got to replace my rear driver side tire due to a nail in it. Is it better to get two new tires instead of one? My co-workers say I'm much better off replacing both rear tires. They said something about the balance of the car will be off or some shit like that. Is it true?
>>14874260
How did you go about these calculations?
>>14874448
>not just getting your tire patched
so you blew the sidewall or it's a giant hole right? There's a reason you're not paying less that $20 to get your tire patched from a single nail RIGHT?!
>replace both or balance will be off
this is somewhat true but after a rotation will be negligible; if you're buying a new tire just get the same tread pattern. Tread pattern matching is more of a concern
>if all tires wore at even speeds we wouldn't have tire rotations
>disregard if you have AWD, you "have" to get both
>>14874260
they should alway be bigger than the port, you fucked up somewhere unless you got some seriously big ass ports
>>14874448
>>14874596
Agree with this guy. The difference is negligible, only a few mm's. Wouldn't worry about it.
>>14874513
Various sources; books, Web articles. They all amount to more or less the same size and length.
>>14874717
I don't think I fucked up, there isn't much to fuck up anyway. Additionally, I don't think I have oversized ports or anything...
Regardless, it seemed counter-intuitive which is why I'm asking.
just make em bigger than the ports
>>14874596
No it's not blown out, it's a slow leak above the side wall. Dealer told me that it's non-repairable and that I have to get a new tire. Though this could be the dealership getting some shekels out of me. Obviously haven't taken it out since i'm afraid that it will just deflate instantly.
Probably should get it patched though. Better than paying $150.
>>14874836
>Various sources; books, Web articles. They all amount to more or less the same size and length
Don't sweat it. You will likely never get it pitch-perfect. Anything is better than stock manifolds in most cases.
I'm going from a 125 to an R1 soon, what amount of dead will I achieve?
>>14874892
What I mean is: Just make am big enough for the exhaust ports and you'll be fine. Even equal lengths aren't essential.
>>14874903
nah mate you always make intake manifolds faces smaller than the port and exhaust manifolds larger
>>14874878
You could try and get a quote from a different dealer/shop. Take a few clear pictures of the damage and have them look at what they can do. Worst case scenario you could get a better quote than $150. Good luck!
>>14874869
I suppose I'll look into my calculations again, perhaps I mis-measured my ports...
>>14874908
Just don't make em smaller, is what I'm saying.
>>14874925
no worries mate we all fuck up, post pics of the finished article on here and good luck :)
>>14874892
Like I said, the stock ones are absolutely fucked, pic related. If I could get my custom ones to be within a margin of 5% of ideal sizing and equal lengths is good enough, I've been told.
>>14874903
You seem to know your shit by the way. I thought the tuned length of the primaries were the most important factor to achieve the scavenging effect. Ideal lengths, however, often approach 30-40 inches: not something I can fit in my setup.
Now, I recall reading somewhere that dividing the optimal length by 2 / 4 / 6 / 8 / etc. can yield similar (but lesser) results because the waves will just bounce more than once, still dragging/scavenging out the exhaust gasses. Any truth to this? It's been a while I read this and I can't seem to find my source.
can someone explain to me how turbos without blowoff valves work? why dont all turbocharged cars have blowoff valves? what happens when you go to shift and let go off the throttle fast?
>>14874997
Most applications of turbo's are limited to fairly small ones, aimed at obtaining fuel economy. These small turbo's run on a relatively low pressure. In other words, the turbo doesn't spin very fast, nor does it produce heavy loads of boost. As such, the compressor isn't put under loads big enough able to harm the compressor wheel, bearings, etc.
Now, for most powerful applications turbo's are put under higher levels of boost, making the compressor spinning faster, under heavier loads. When the driver stops accelerating the engine, the pressure built by the exhaust gasses also stops, thus forming something called "compressor surge", which can sort of 'pull' on the compressor wheel with higher levels of force as compared to economy applications that, in this case, can damage the compressor wheel, bearings and other parts of the turbo.
Apart from this practical application of a BOV to relieve the turbo from stress, increasing longevity, the lag caused by the compressor surge is decreased significantly, perhaps even nullified ensuring more power due to a more responsive engine.
>>14875041
I notice I forgot to mention that the compressor surge 'pulling' on the compressor wheel does so in the opposite direction of it's current momentum as result of the vacuum.
Additionally, by 'heavier loads', I mean a larger, often denser volume of air.
Hope that clears things up. If not, ask more questions.
I never fully understood this, but in order to have lower RPMs while in fourth or fifth gear, does that mean I have to shift from the lower gears at high RPMs?
>>14875092
Not sure what you're asking here. Can you state your question differently?
>>14875109
Let's say, hypothetically, my 5-speed car's top speed is 100 mph. I want to cruise at 80mph in 5th gear in as low RPMs as possible.
If I shift from 1-2-3-4 at 3500 rpm, does that result in needing higher RPMs to sustain 80 mph in 5th? Is it different if I shift from 1-2-3-4 at 5000 rpm instead?
Basically, if I am planning to be cruising near my car's top speed, should I be shifting at higher RPMs than normal to prepare for this?
>>14875332
it doesnt matter
you go to higher RPMs if you want to reach the speed faster because your engine will produce more power at higher RPMs
shifting at 3,5k RPMs and 5k RPMs is exactly the same speed wise the only difference being shifting at higher RPMs will reach that speed faster and consume more fuel
this is just talking about your example, engines have different power bands etc.
someone correct me if im wrong
>>14875065
no, i get all of that i shouldve just asked "why some turbos have BOV and some dont" to which you wouldve just answered it depends on the size and pressure the turbo is pushing
>>14875332
Bare with me, this is going tot take a little while to type out. Check back in 10-15 minutes.
I need a car this summer, so I decided on buying a tj wrangler.
Any wrangler owners want to give tips, tricks, and overall buying experience on them?
>>14875408
Well, now you have a deeper understanding. Can't be any harm in that right?
>>14875408
>>14875417
Thanks gents, the reason I ask is because my shitbox's top speed is indeed 96mph. Speedo only goes to 85
>>14875431
im trying to say i already understood everything you explained just didnt put 2 and 2 together for some reason, i feel bad for wasting your time typing all that out
thanks anyway
>>14874956
As far as I know, this is usually done with smaller engines, to add a charging effect to the cylinders.
For fan exhausts on bigger engines (like yours), you actually want to eliminate the resonance effect as much as possible. The safest way to do so is to make the inner cross section of the collector pipe larger than the combined cross sections of the exhaust pipes. This way, the pressure behind the collector is lower, which helps moving the gasses. See >>14874940 for an example (it's from a 328i straight-six). The bottom one is the original.
>>14875332
Here we go. I think I see what you're getting it and if so, boy you've got it messed up. No worries though.
First off: Your gears are fixed. It doesn't matter how, when, or to what you shift, it'll always end up at the appropriate speed. In other words, depending on your engine RPM and selected gear, a certain speed output is attached.
Example of my car: 6400 RPM in 5th gear always equals a road speed of 150mph, regardless of how I shifted through the gears.
Further explanation of how this works:
From engine speed to wheels, there's a couple of factors impacting your road speed. These are:
- Engine speed
- Selected gear and its ratio
- Final drive ratio
- Size of wheels and tyres.
Now, let's take my car for example again, and let's say my current engine speed is 6400 RPM. This means my engine is making 6400 full turns per minute. Keep this in mind.
Next, my tyres are sized 215/45 R17. This means the diameter of just my rim is 17". The R17 of my tyres represents this figure. The 215/45 means the following: My tyres are 215mm wide, while their height are 45% of that 215mm, which amounts to 96,75mm. Converted to inches, that's 3,8 inches. Since there's tyre all around the wheel, we multiply this by two (7,6 inch) and add the rim diameter (17), arriving at 24,6 as the total diameter of my rims and tyres.
To arrive at the circumference of my tyres, we multiply this total diameter of 24,6 by pi (3,14) which is 45,86 inches.
Now we can state that if my engine was linked directly to my wheels, for every full revolution my engine makes, my car would travel 45,86 inches.
Because my engine is running at a speed of 6400 RPM, we multiply the earlier obtained 45,86 by 6400 to obtain the amount of inches traveled in a minute: 293504
Converting inches per minute to miles per hour yields the following value: 278 mph. Pretty ridiculous if you'd ask me.
cont...
>>14875484
what the fuck lmao
>>14875484
are your numbers squared ?
I think you might have missed something
>>14875556
Typing the second piece, I realize I might just have done exactly that.
Bare with me though guys, I've had very little sleep past few weeks. Is any of this making a point yet?
Are camshafts reasonably easy to install?
I have a 2006 Mustang GT and want to install Ford racing hot rod camshafts. I've installed axlebacks and an o/r x pipe in my car and a couple other things so I have some experience with wrenching. My cousin usually always helps me out as well.
>>14875460
What exactly is the purpose of eliminating the resonance effect on bigger engines? I don't quite grasp why this would be negative after certain engine sizes.
>>14875596
I did the exact cam swap on mine. Gonna need a torque wrench, chain wedge, new gaskets preferably and two new cam bolts because they are one time use only. They recommend a valve depresser but I didn't use one just have to remove cam caps slowly. Also some sealant for the area where the front chain cover bolts to the block.
>>14875587
Yes, it makes sense. I appreciate the effort Anon and am curious to see the second part anyways.
>>14875596
Cams are a tad bit more difficult than an axle-back. How experienced is your cousin?
Switching cams involves removing everything that's in the way of the valve covers (intake, manifold, possibly injectors, coilpacks) and everything that's in the way of the drive belt / chain.
The belt needs to be removed and replaced, unless you've done so very recently (like a month or so). In case of a chain, it can be re-used, but it still needs to come off.
Then the valve covers, cam journals, cam gears and finally, the cams can be removed. It's not something easily done by someone with no prior experience if you don't know what you're doing, haven't got the proper tools, etc.
I haven't followed a single class on cars/engines however, and I've been able to rebuild my entire engine from scratch because I had access to workplace manuals, proper tools and a smart dad willing to help.
Best of luck!
>>14875604
More revs, son! That equals to more torques with proper engine mapping.
>>14875632
Alright, I'll stop with the exact math here however, because the outcome will be incorrect, no use in that. The principles behind the math are still valid though.
Anyway, that concludes the impact of engine speed and wheels & tyres on road speed. Next: the gearbox.
Now, because a top speed of 278mph is utterly useless on practically every car, including mine, gears are put in place to accommodate the best fit for the car.
Additionally, because internal combustion engines only have a relatively limited operating range (in RPMs), it would be great if we could keep the engine in this range while accelerating by adding gears.
The first type of gear talked about here is the final drive, and is litterally placed as the final gear in the gearbox. This means it affects the ratios of every single gear before it. Put differently, if a final drive gear is swapped for a different one, the final top speed of the engine is affected, as well as all the gears leading up to that top speed.
The second type of gear talked about is the gear we talk about when discussing 'being in 4th gear', or any other gear for that manner. These gears, 1 through 5 in my case all have different ratios to accommodate further acceleration at the particular road speed the car is at, coming out of the previous gear.
So, the first gear being the highest ratio (1,78 to 1 in my case) offers my car a top speed of approx. 30mph in that specific gear. When I'm at 30mph, my engine will be running around 6000RPM, nearing the end of it's operating range. If we want to go faster, we have to have a smaller ratio: second gear. Physically, the second gear is a bit smaller, offering a higher output speed than first gear. ( I take it you know how gears work right? )
Again, we need these different gears because it's impossible to achieve top speed in first gear, just as it's (near) impossible, and at least very impractical to accelerate starting in the highest gear.
cont..
>>14875738
Still doesn't exacly explain why you wouldn't want to use the resonance to pull out the exhaust gasses. Wouldn't it be beneficial anyway, as it helps evacuating the exhaust gasses from the engine, reducing friction, thus producing power?
>>14875768
You get the pull by producing low pressure behind the collector pipe.
>>14875768
>>14875781
I mean, you can also try to achieve this resonance effect, but I wouldnt know how to calculate that...
>>14875746
what the hell are you talking about dude
>>14875746
.. Cont'd
Now, hopefully you'll see that only these gears can be exchanged for one another by accelerating the engine and switching gears while driving. Since the range of your engine is limited (in my case max. 6500RPM), and the final drive ratio and wheel circumference are constant, the only way to achieve higher road speeds is to rev up the engine, and switch up gears when the upper limit of the engine is reached. Although the gears can be freely exchanged while driving, their ratios are fixed aswell.
If you'd like to further your knowledge of the subject, you can play with calculators on the internet, converting transmission parameters (engine speed, gear ratios, final drive ratio, tyre circumference) to see some results of the system of gears at work here.
In short, the amount of revs in a particular gear are linked/fixed to that particular road speed you're driving at that moment. No matter when you shift, how you shift, the result will be the same because the system of gears is a fixed one.
Simply put*:
Engine speed * current gear ratio * final drive ratio * tyre circumference = road speed
*: This is just a simple illustration, which is inaccurate. Otherwise I would've continued math examples. Real transmission calculators do offer a proper answer however.
If two different transmissions have the same spline count and size, can they use the same clutch?
>>14875803
There's some formulas in books and articles that can calculate the dimensions based on engine speed, volume, engine efficiency, valve opening height, opening degrees, centerline degree and closing degree.
Assuming you know the volume that'll be pushed out when opening the exhaust valve, diameter can be calculated. Assuming you know diameter, plus when, for how long and how much the exhaust valves open the supposed ideal length of the primaries can be calculated. If done correctly, the 'waves' travel through the primary tube and arrive back at the valve opening when it opens, dragging the gasses out.
Naturally, it can be calculated. Companies designing headers do it, and so can everyone else, provided they have the proper information and formulae.
Apart from that, I'll look for collectors that are bigger in exit diameter than total entrance diameter (of all pipes). Many thanks!
>>14875829
Total diameter and thickness of the clutch, as well as placement/dimensions of the gripping surface are important aswell. The clutch has to line up with the flywheel, and as such has to be right.
Why would you want to use a different clutch than suggested anyway?
>>14875867
Okay, well, my clutch is starting to slip in my Lexus IS300. Now, I had plans to swap out the stock transmission (W55) for a R154. I haven't saved up enough for a R154, so I was thinking I could buy a really good aftermarket clutch for the W55, and reuse that clutch whenever I get that R154.
>>14875887
Depends entirely if all the parameters are met by the other tranny. You could try if all of the following are identical:
Spline count
Spline size
Clutch diameter
Clutch grip plate positioning and dimensions
Clutch thickness
And probably some other stuff, like spring pressure and such.
My advice? Don't do it. Depending on how far you're away from being able to afford the new setup, just be gentle with the slipping clutch and ride it out.
Of course, this depends completely if you need your car daily, if you have other ways of traveling, etc. Perhaps you can find a buyer for your current tranny and new clutch to be able to afford the R154?
Thanks for the info and advice.
I have been travailing by bicycle for close to ten years now
it can teach allot about gears and conservation of momentum
you can feel the power band of each gear with your legs
but there is a problem with the crank
flat plane two cylinder with no counter weights
without pedal clips and an oval chain ring you only have a power stroke every 190 ish deg (two stroke effectively)
so you have to feel the moment when pressure comes off the pedals to find the right cadence and force for each gear
any faster and you will spin the rear wheel faster than the sprocket can push it
any slower and you bog on the up-shift
I now have a subconscious habit that allows seamless gear changes
even sometimes stopping my legs for a fraction of a second to synchronize when things are not ideal
Someone in my area is selling a set of KW V3s for ~$1000, saying that one of them needs a rebuild because he "dropped a wheel" with it on.
Are they worth getting and then paying for the rebuild? Are they even rebuildable? And what is dropping a wheel anyway?
I'm still trying to learn. Thanks guys.
>>14876304
No clue what dropping a wheel is, but whether they're rebuildable depends on how fucked they are. Him telling you they are is not a way to know.
What you could do is visit him, check them out, ask him if you can have a professional look at them and figure out whether they're worth the trouble like that.
If there's no way you can do any of this, you should probably walk away. Perhaps a sad conclusion, but spending that much on possibly useless rims is even more sad.
I've got a set of off-road lights that need new reflectors. I think I can replace them with KC's, does anyone have a set I can compare pix/measurements with? The reflector/lens assembly is 5.5" diameter overall, the lens itself is 5".
If a ball joint I installed had a grease nipple on it, am I supposed to put grease in it? Cause I didn't.
Anybody know where to find a supercharger for a chevy 4.3l v6
Wanting to put one on a s10.
