Exhaust science and technology. Also a few questions.

[canadianae92]

Okay I have a broken ankle and have been home for a while reading a lot on exhaust and intakes, anyways I'd like some information on what would be best for my car and I'd like to see if I understand exhaust and intakes properly.
So the goal of aftermarket exhaust are to eliminate the pressure inside the exhausts and as the rpms increase the pressure increases, so when the engine is running at high rpms and it has a high exhaust pressure this means the exhaust will be more packed in and be moving slower and kind of choking the engine witch makes you lose power right?
So then that would mean we would want to eliminate pressure all together right? if not, why not?
As for intake, the best setup would be to have a better flowing intake manifold and piping that gets to cold air right? but of course to a limit, to use all the air you can get you'd need bigger cams and a aftermarket ecu, so if all you get is a after market filter to replace the air box you wont get much gains I guess, the intake path looks pretty smooth from the factory on the corolla gt-s's besides the small suction tube that sucks air into the air box so you cant really get WAY more air from an intake system unless your engine can actually intake it I guess.
So from how I see it the power gains from exhausts and intake mods are limited to what is actually done to the engine and they are more of a way of the engine breathing and exhailing.

So what would be the best Intake and exhaust setup for my car, my plans for now are to finish the body work get an intake and exhaust system, and so on.

1. So what stops people from getting 5" exhaust systems?
2. What would be the best piping size for a 16v 4AGE engine that maximizes power at the top end while maintaining torque through the rev range?
3. What type of header is this http://www.cardomain.com/ride/2140866/3 it's a header I got off a GT-S in the junkyard it looks to be freeflowing besides the sharp bends downward and the bend back to the collector, is it a good design, one guy mentioned it could be the pacesetter header?
4. before I was think about a 3" exhaust with hks hi-power muffler, but I'm thinking that might be to big, is it?
5.Whats a better muffler, Apex'i WS Sport, Apex'i N1, HKS Hi-power, or any other you can think of?
6. The exhaust setup I want is a straight through pipe to the muffler from the header with no resonators or cats, is this a bad idea?
7. Also looking at lots of the exhaust systems sold for AE86s/AE92s/Celicas etc are about 60mm piping and 90mm tip for n/a and for turbo cars its like 75 mm piping, why the difference?
Btw my car is a 1991 Corolla GT-S
Any help is appreciated

[Scubbs]

Here is an article on some basic exhaust theory, which may be of some help for question #1. http://www.geocities.com/MotorCity/7...usttheory.html

[canadianae92]

Originally Posted by Scubbs

Here is an article on some basic exhaust theory, which may be of some help for question #1. http://www.geocities.com/MotorCity/7...usttheory.html

Thanks, so I guess that means the only thing limiting the size of exhaust I get is ground clearence and noise. Good info that pretty much answered 1, 2 and 7 and partially answered a few others.

[saigons son]

another reason not to get too large of an inlet(exhaust size) is because u lose torque w. too much flow. most people only get a 3 in. for turbo setups

[canadianae92]

From what I read on that site more flow is better as the dude said "theres no such thing as back pressure". A car shouldn't have a bigger exhaust because its turbo, but from what I read it sounds like with more horse power the bigger you should have to keep it free flowing if the exhaust is to big the exhaust gases will cool down and become heavyer so its harder to push out and so you lose power.
I think I'd probably go with like a 2inch exhaust for my car because it'll be a while before I'm making enouh power to fill 3inches of piping.
Edit: I also identified the header I got as the pacesetters header

[epyon22]

pacesetter stuff is pos no better than stock. you have limited options when it comes to ae92 exhaust i know there is an hks cat back and a 5zigen catback and also aKBD Header. the catbacks will run you around 500 and the headers give you decent performace for about 250$. remember with the 4age when you replace headers you have to wrap your distributor in some kind of heat sheild or somthing cause it will over heat the distributor because their wont be a heat sheild on the headers any more. and yeah you can have too big of an ehaust for daily drivign you really want to go middle of the road so that you can keep some torque and also get the power. i trust hks to give decent performance in this area unless you are going to make them your self.

[canadianae92]

I also trust hks I've heard good things about the hks sport exhaust, but the 5zigen catback I'm not sure about actually but it must be decent, the pacesetter headers will have to do for now I got them for $50 so can't really argue with that for the price it'll be okay unless it leaks bad what is the website for KBD, and thanks for the distributor tip, I heard that making a custom heatshield would be okay, would this do? or wrapping the header in heat wrap?

[epyon22]

i would think that wraping the distributor in heat wrap would be alot ez'er than making a custom heat sheild. and the kbd headers are sold on www.cyberauto.com they got a decent reveiw from the guy on www.ae92gts.com

[canadianae92]

I'd think making a heat shield would cut down the heat in the engine bay and keep the header hot.
Thanks

[epyon22]

oh... never heard that side to it ive always heard that it causes the distributor to over heat but i guess your side makes sense also

[canadianae92]

Well the stock heat shield works so, it should work, maybe I can somehow form the stock one to fit?

[saigons son]

you can get headers through TRD if u want toyota reliability

[canadianae92]

Maybe sometime down the road but I got headers for now

[4Aaron GE]

4: Probably is too big for what you're looking for.
5: I like American mufflers. They flow fairly well, and sound good.
6: Good resonators and cats don't impede flow. Personally, if you can afford it, get them both. At the very least get the cat - it's good for the environment. And emissions testing if you have it.