swappers, what did you do for exhaust? Options

[playr158]

we've already established shorter is better? thats what we all agree on....

"it is easy to get overeager on fitting large-diameter pipes into an exhaust system. "the larger the better" is not always the case....there is an exhaust gas velocity that ought NOT TO BE EXCEEDED, this velocity is approximately 250 ft/sec.....to size a tailpipe, you can adhere to this exhaust gas velocity or to simple the guildeline of selecting a tube diameter approx. 10% larger then the turbine outlet diameter."
corky bell

a 3sgte @ 15psi makes 321cfm ruffly
just to make sure i'm correct
i got it by....((122.04cid x 5000rpm x .5stroke x .90ve)/1728)x(14.7x15/14.7) = 321cfm

a 2.5" pipe can flow more then 600cfm(ruffly 293ft.sec) adiquetly
but we all know that a 3" exhaust does prove gains over a 2.5"
but at the point of 4" it would seem too large for a celica

This post has been edited by playr158: Mar 12, 2006 - 5:01 PM

[scothaniel]

Interesting post by Dave Buschar on the evo forums with Dyno numbers on an 04' Evo:

snip----

3. BR 2.5" axleback muffler. 267.1 whp, increase of 15 whp!

4. BR 2.5" downpipe. 270.4 whp, increase of 3.3 whp.

5. Super AFC with BR settings, 289.3 whp, increase of 19 whp.

This with the addition of a boost gauge and the mount for the boost gauge completes our Stage 0 and costs $995. Overall gains with this kit while remaining emmision legal with the stock cat and with a very quiet car was 52.2 whp and 29 ft. lbs of torque. HP per dollar spent is $19.06.

This package really puts the car into a great spot to do further upgrades from. Actually I was surprised by the next test:

We left the 2.5" downpipe on, added a 2.5" offroad pipe and the 3" catback with the Magnaflow muffler. The horsepower jumped to 313 whp and 292.9 ft lbs. For further comparison we ran an open exhaust system from the back of the offroad pipe, in other words no catback at all, the car only made 1 more whp. The open exhaust numbers were 314.4 whp.

We then went to the full 3" turbo back exhaust using the Magnaflow muffler and an offroad pipe. The car layed down 314.9 whp.

--- snip

[jgreening]

Out of curiosity Scott, what lessons do you take from that post? Somehow I suspect we may have different interpretations.

[scothaniel]

That 3" exhaust is better then 2.5"
I was wrong when I said that 2.5" is only good for 400 HP, now I'd say its fine for sub 300 HP range.

It does go along with velocity and cool-down expansion effect I mentioned earlier, since replacing the rear section with 3" gained a good amount of power and replacing the turbo back didn't make much a difference. Unfortunately the dyno graphs on his web site are for buschars kits - which includes more then just the exhaust changes. I'd like to see what the effect was on low/mid range torque with the larger DP.

This post has been edited by scothaniel: Mar 12, 2006 - 9:31 PM

[jgreening]

It does go along with velocity and cool-down expansion effect I mentioned earlier, since replacing the rear section with 3" gained a good amount of power and replacing the turbo back didn't make much a difference.

In this post, I am playing devil's advocate for purposes of discussion. Lets assume that there are no factors in these runs like improper cool down times, variations between runs, margin of error, etc. Under your theory, wouldn't the power have been less with the 3" downpipe since the exhaust gas velocity would have decreased? I recognize that it only made 2 more horsepower with the 3" downpipe but the fact that it didn't lose hp seems to contradict your theory. The big 16G is not exactly a large turbo.

[scothaniel]

Its a turbo that pushes over 500 CFM at 20 psi though, which is a lot more then a stock ct26 btw. 300+ HP. In fact, Buschar was almost able to hit the 400 mark with the stock evo 16GH turbo! A ct20b cant even touch that.

Like I said, I'd like to see the effect on low / mid range torque.

[CheesyLobster]

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

That would be if you are running a rectangular shaped exhaust. For area calculations it would be diameter * Pi (3.14159...) or volume=area * legnth of exhaust.

[NuclearHappineS]

That would be if you are running a rectangular shaped exhaust. smile.gif For area calculations it would be diameter * Pi (3.14159...) or volume=area * legnth of exhaust.

sorry but you're wrong ...and i was wrong too...

circumferance (sp?) = 2pi R = pi D
area = pi r^2 ... i just dropped pi because and forgot to halven D to get R

so 2" exhaust ~ 1*1
2.5" exhaust ~ 1.25*1.25
...etc .. .they all share pi so if you're looking for % difference it doesn't matter (Why i dropped it)

the guy who said that's an inline 6 ... forget that

my point WAS ... if you are making 700 hp or so (i don't care if it came from a single cylinder or 700cylinders) ...as long as it's a 4 stroke, then 700hp is going to be about 1050cfm of air no matter what type of motor (b4, I4,I6,v6,v8...etc) it came from...and if you are moving that kind of air i'd think about using more than a 3" exhaust.

[jgreening]

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

That would be if you are running a rectangular shaped exhaust. For area calculations it would be diameter * Pi (3.14159...) or volume=area * legnth of exhaust.

Actually, that would be a square (not a rectangular) shaped exhaust. Diameter * pi would be the circumfrance. To determine area of the exhaust, you use radius squared * pi. Therefore, the following would be the correct calculations to determine area of the cross section of the pipe:

2 inch piping = 3.14 sq. inches of area of cross section of pipe
2.25 = 3.97
2.5 = 4.91
3 = 7.07
3.5 = 9.62
4.0 = 12.56

EDIT: Nuke beat me.

This post has been edited by jgreening: Mar 13, 2006 - 5:18 PM

[Speedy2k]

Heh I see some people have forgot high school math

Do you guys know how to calculate the area of an oval (ellipse)?

Its useful when comparing oval mufflers to round ones. The bigger the volume; the quieter the muffler.

Lets say you have a

5" (height) x 8" (width) x 14" (body length) muffler - $128.42 MSRP
Oval Muffler

and a

6" (diameter) x 14" (body length) muffler - $127.47 MSRP
Round Muffler


Which of these would have the bigger volume?


Volume of Oval Muffler: 2.5 x 4 x 3.14 x 14 = 439.6 cubic inches

Volume of Round Muffler: 3 x 3 x 3.14 x 14 = 395.6 cubic inches

In this case the oval muffler has the larger volume for the same money! If you guys already knew this then take no offence

[playr158]

we need to work on pipe size before we get to the muffler part lol

so a 3sgte 5000 rpm at 15psi flows 321cfm (5.35 cf per second)

what is the pipe size that will keep the velocity of 321cfm exhaust gas around 400 ft/sec or so

This post has been edited by playr158: Mar 14, 2006 - 1:11 PM

[lagos]

i like my math better

3sgte + 3in exhaust = the right thing to do


hopefully ill be getting mine installed soon. going today to get an estimate.

[Speedy2k]

i like my math better

3sgte + 3in exhaust = the right thing to do


hopefully ill be getting mine installed soon. going today to get an estimate.

What downpipe and muffler are you getting?

[celicurr]

[playr158]

thats my scan!

(and it came from "maximum boost" by Corky Bell) to give credit where it be due

This post has been edited by playr158: Mar 14, 2006 - 3:00 PM

[jgreening]

That must be what HP level the stated pipe would "support". It surely does not reflect the ideal size to use since a single straight 2.5" exhaust is represented as 500 bhp.

[JFrost9]

This is going to seem completly random and all, but has anyone run a dual-exhaust on a 3sgte? Im sure its not recommended, i could see it more on a mr2, but i was just curious.

[lagos]

i like my math better

3sgte + 3in exhaust = the right thing to do


hopefully ill be getting mine installed soon. going today to get an estimate.

What downpipe and muffler are you getting?

i already have a 3in stainless DP on the car and ill be using a 3in magnaflow muffler.

looks like my exhaust will have to wait some more. went to get a quote today, lets just say that it was insane! i have another shop that is willing to give me a great deal, but the guy has almost no time to fit me in... sucks.

[Speedy2k]

How much was the quote? Mandrel bent? Stainless/aluminized?

[DG_Performance]

What happened to the topic ... you know that sentence at the top of the page that is supposed to be what all discussion under it is about HAHA
"swappers, what did you do for exhaust?" is no more!

We should rename the topic to "swappers... what do you think about different exhaust sizes?"