swappers, what did you do for exhaust? Options

[Fastbird]

Dr. Tweak is hooking us up with a 3" downpipe and custom 3" exhaust for the swap that he's doing.

[Bigmeanbulldog55]

LOL 4" thats utterly pointless....

Dang it man, I know no one uses 4inch pipe. And I want to know why. I don't want to here things like it's pointless, and that's it. If your going to respond to one of my posts, give me a reason. Don't act like a little turd and say "LOL 4" thats utterly pointless," without explaining yourself. Please, just explain yourself. It rude not to. Even if you don't think it's rude, I do. And for future referance, when replying to something I've said, please keep that in mind. You are a very knowledgable person, please share that knowledge along with your comments.

EDIT: I just want to add that part of the reason I am curious about this, is because of the fact that sometimes turbo guys will unhook the exhaust at the bottme of the downpipe when at the track. I know the WRX guys were saying that at least. They could have been BSing me. And I know you can get those electronic cut offs to dump your exhaust up by the motor. So I don't understand how having a huge exhaust wouldn't have the same affect. I don't know how to run the numbers to find out what size pipe the 3sgte needs for optimum flow.

This post has been edited by Bigmeanbulldog55: Mar 11, 2006 - 9:23 PM

[scothaniel]

Yeah, dont use 2.5" piping - thats like only good for around 400HP.

[lagos]

4inch exhaust are only a benefit on 6-8cyl turbocars. if u look at all the supra guys they all run 4in.

on a 4cyl car, 3in exhaust is plenty to allow no restrictions.

[playr158]

i run my turbo with an pretty much open downpipe (well right after the cat) makes spool time much faster..less restrictive

pure and simple you only exhale as much as you inhale...anything over 3" diameter on a 4cylinder motor is over kill because you simply don't move enough air..by the end of the pipe your exhaust is moving so slow that the newest exhaust is probably pushing out the rest of wat has slowed in the pipe

This post has been edited by playr158: Mar 11, 2006 - 11:34 PM

[jgreening]

LOL 4" thats utterly pointless....

Dang it man, I know no one uses 4inch pipe. And I want to know why. I don't want to here things like it's pointless, and that's it. If your going to respond to one of my posts, give me a reason. Don't act like a little turd and say "LOL 4" thats utterly pointless," without explaining yourself. Please, just explain yourself. It rude not to. Even if you don't think it's rude, I do. And for future referance, when replying to something I've said, please keep that in mind. You are a very knowledgable person, please share that knowledge along with your comments.

EDIT: I just want to add that part of the reason I am curious about this, is because of the fact that sometimes turbo guys will unhook the exhaust at the bottme of the downpipe when at the track. I know the WRX guys were saying that at least. They could have been BSing me. And I know you can get those electronic cut offs to dump your exhaust up by the motor. So I don't understand how having a huge exhaust wouldn't have the same affect. I don't know how to run the numbers to find out what size pipe the 3sgte needs for optimum flow.

A 4" exhaust is NOT utterly pointless - particularly on a FF or FR car where the piping runs the length of the car. However, if you are running less than 400whp, it would not be cost effective because you are not going to see much of a gain. Above that hp level, you are correct Bulldog, it will improve flow and increase horsepower - more the higher up you go. On a "high power" turbo application, the best exhaust is no exhaust since it creates no back pressure. Heck, I would actually be willing to wager that you would actually see gains from a 4" exhaust over a 3" exhaust at 300whp too - just something in the neighborhood of 1-3 hp. Like I said, not exactly worth the added expense.

[Kadett]

3" piping with the stock st205 muffler for now. When the money comes in again i will set my eyes on a nice Blitz muffler!

[jgreening]

anything over 3" diameter on a 4cylinder motor is over kill because you simply don't move enough air..by the end of the pipe your exhaust is moving so slow that the newest exhaust is probably pushing out the rest of wat has slowed in the pipe

I am too tired to type a long response but suffice it to say that this is incorrect.

[Patrissimo]

I did a 3 inch straight back from Down Pipe. No Cat.

Sounds really nice.

2.5 inches is a waste of money. Go all the way man!

[presure2]

LOL 4" thats utterly pointless....

dan, sometimes your posts are "utterly pointless"


do you wanna tell noshoes his exhaust is "utterly pointless"?

[lagos]

3in is plenty for 90% of 4cyl turbo cars that are in the 200-300 power range. 400+ is where you would probably want something as big as a 4in, and if u have that much power, you probably wouldnt be on here looking for exhaust advice...lol

[Supersprynt]

Doubt alot of ppl heard of no shoes 'round here.

[scothaniel]

anything over 3" diameter on a 4cylinder motor is over kill because you simply don't move enough air..by the end of the pipe your exhaust is moving so slow that the newest exhaust is probably pushing out the rest of wat has slowed in the pipe

I am too tired to type a long response but suffice it to say that this is incorrect.

Sorry, you'll have to type a long response now, cause I have to agree with his statement (depending on the size of the motor).

Oversizing the exhuast can hurt due to the density, weight and velocity of the air traviling through it. Smaller exhausts will maintain higher velocity, which keeps the temps higher (less dense, lighter). If the exhaust is too big, the velocity slows, temps decrease and the exhuast pulses collide.

The key is to have the correct size pipe - not too big, not too small. I have 2.5" on my wife's car, 3" on my car due to the orginal T04 60-1 ( seems to be good with the 20G L2 as well).

2.5" was fine on the 16G powered DSM without any problems, and we hit low 12's with that car.

[jgreening]

Oversizing the exhuast can hurt due to the density, weight and velocity of the air traviling through it. Smaller exhausts will maintain higher velocity, which keeps the temps higher (less dense, lighter). If the exhaust is too big, the velocity slows, temps decrease and the exhuast pulses collide.

The key is to have the correct size pipe - not too big, not too small.

Exactly correct, for N/A applications.

I have 2.5" on my wife's car, 3" on my car due to the orginal T04 60-1 ( seems to be good with the 20G L2 as well).

2.5" was fine on the 16G powered DSM without any problems, and we hit low 12's with that car.

I am glad you have had good results. However, this anecdotal evidence does not disprove that turbo applications improve as back pressure decreases.

I have never seen one serious tuner suggest that someone should use a smaller exhaust in a forced induction application. By this logic, a 2.5" exhaust could potentially be better than a 3' exhaust with a small turbo. That has been disproven as myth time and again by real world dyno testing. The well accepted rule of thumb is the bigger, the better (on FI applications). That said, as I typed above, there aren't many people on this board that will benefit from larger than 3" piping. I wouldn't even consider it if my goals were under 400whp.

[scothaniel]

The addition of the turbo doesn't effect the basic principles of exhaust flow - it only makes it more important since a poorly flowing exhaust will hinder the turbos ability to make boost.

Looking back at the previous posts:

with a turbo setup, the best exhaust is no exhaust.

Right, because a 6" long exhaust means the gases are instantly out of the way. No worry about pulses or scavaging or back pressure. Though no back pressure will hinder performance before the turbo spools up.

The next best thing to having no exhaust is having an MR2 - thier full exhaust is as long as our cat backs. That or an exhaust big enough to seem like there no exhuast - like a 12" diameter! I have no idea where anyone will find a muffler to fit it though.

Can you post some dyno graphs for 2.5" versus 3"? I spent a few minutes on google and only found debates on the DSM, 200/240, SRT, and Volvo clubs on the same subject! I guess this makes 6gc a real club!!!!!!

[playr158]

Oversizing the exhuast can hurt due to the density, weight and velocity of the air traviling through it.

sorry i should have been more clear..that was a long night..
4" is pretty utterly pointless on a motor thats not supporting the HP for it..like the above stated oversized pipe without enough power to move the air isn't helping at all...yea "noshoes" can run 4" cause his pipe is 3' long in a "2" and he has a pretty freakin nice HP #......a stock 3sgte in a 10' long celica with 4" i doubt would see any gains..so "noshoes" motor and setup really doesn't apply in a celica situation..

and j...even on an FI motor if your exhaust is too big and long the exhaust velocity will eventually have slowed by the end of the pipe..you'll have increased back pressure from having to actually push the spent and slowed gases out regardless of FI or NA

its about correct size for your correct horsepower and CFM...you have to keep restritctions to a minimum and velocity to a maximum

This post has been edited by playr158: Mar 12, 2006 - 4:04 PM

[NuclearHappineS]

about the 4" exhaust

one of the big supra shops, either titan or horsepower freaks (i think it's titan actually) sells a 4" supra catback ...

if u go to their webpage they'll provide their '1st hand' commentary on why/when you'd need it...

i think to4r also had a dyno run of most supra exhausts starting with the oldschool greddy SP and working up to the newer titanium/stainluss catbacks (so from 2.38" up to some 3" and maybe slightly over 3" catbacks) with dyno data for all of it...

as far as titan goes they saw something like a 40hp gain pulling off a 'high flow' air filter on a 600 hp car... their exhaust (4") was worth over 120hp or so on some 700+ hp car that came in with a 3" if i remember correctly...

i just want to say this though...exhaust has to do with area which is related to diameter squared

2^2 = 4
2.25^2=5.0625
2.5^2=6.25
3^2=9
3.5^2=12.25
4^2=16

so the next step up if u had a high hp 3sgte isn't a 4" yet...

[playr158]

alright thats a inline 6 supra.....not a 4cyl celica
so the obvious reasons why 4" works there is pretty clear..

but defenitly right on the area

This post has been edited by playr158: Mar 12, 2006 - 4:24 PM

[jgreening]

"noshoes" can run 4" cause his pipe is 3' long in a "2" and he has a pretty freakin nice HP #......a stock 3sgte in a 10' long celica with 4" i doubt would see any gains..so "noshoes" motor and setup really doesn't apply in a celica situation..

Actually, its even MORE applicable. Try this experiment. Blow as hard as you can through a regular straw. Now cut the straw down to 2 inches and blow as hard as you can. Tell me which one flows more air. A: the shorter one of course. Flow is increased when the pipe length is decreased. The benefits from a larger diameter exhaust are more apparent in cars requiring longer piping - not less. Noshoes actually recommended to me to go with a 4" exhaust for just these reasons. Since my goals were less than most of his customers, I stayed with 3".

Although this argument about exhaust gases cooling and slowing down has some logical appeal, I am just saying that I have never seen any evidence it is true in terms of real world experience or reading what recognized experts have posted in the past.

This post has been edited by jgreening: Mar 12, 2006 - 4:40 PM

[jgreening]

Can you post some dyno graphs for 2.5" versus 3"? I spent a few minutes on google and only found debates on the DSM, 200/240, SRT, and Volvo clubs on the same subject! I guess this makes 6gc a real club!!!!!!

I know for sure that ATS did testing to show that the KO downpipe (2.5") yielded lower gains than a 3" downpipe on the same exhaust with the tiny ct-26. It was about 5hp difference I believe and was for levels way under 300whp. I know a downpipe is not a full exhaust but the principles are the same. I have also seen comparison dynos of full exhausts on other forums which have shown similar results but I am not sure I could find them.