Another Stupid Exhaust Question

[4WDFrenzy]

Hey everyone, I have plans to change the exhaust on my GL-10 AGAIN! I was just wondering if anyone here thinks that 3" crush-bent exhaust would be too large of a diameter for the EA82T?

 

OKAY...............REPLY!

 

Patrick

[joostvdw]

you'll probably lose a lot of low-end with that large exhaust, I'm currently running a 2,5inch from the turbo back and I noticed a bit loss of torque, but not dramatically

 

so I think you're better off with 2,5 inch and 1 (or 2) free flowing mufflers

[Tosh]

so you mean something like this ?

 

 

3" DP

 

 

2.5" DP back

 

 

it really adds a lot to the low end I don't know if it takes much away but over 85 seems like its pushing the motor hard so I usually top out at about 75-80

[SOOBOUTLAW]

I believe the exhaust diameter should be consistant from the DP to the tailpipe to be most effective.

[4WDFrenzy]

Well the reason that I ask, is because I am currently running a 2-1/4" turbo-back exhaust system w/ custom bellmouth downpipe(crush bent piping), but I am running 11psi of boost and don't know if I am overrunning the capacity of my current exhaust setup. So do you guys think that 3" might be overdoing it a bit?

 

Oh yeah, I have a custom made exhaust manifold(one that will keep the exhaust pulses flowing toward the turbocharger) that will be going into the works as well, and possibly a turbo swap.

[86subaru]

did the same thing here on my 88 turbo a/t wagon, no cat 2-1/2 pipe back , + air box mod , but problem here is the exhaust bolts at the head are stripped , but getting it fixed at the dealer , i am sure they will see the cat-less pipe

[desertsubaru]

so you mean something like this ?

 

 

3" DP

 

 

2.5" DP back

 

 

it really adds a lot to the low end I don't know if it takes much away but over 85 seems like its pushing the motor hard so I usually top out at about 75-80

 

 

You top out at 80 mph with a turbo? My 86 gl 4x4 wagon with holley 5200 no emissions, cat and stock muffler likes to cruse at 75 in 5 ith gear. Had it up to one hundred at 5000 rpms on closed road and still had more. Ran out off road!

[WJM]

on a turbo car, the BIGGER, the BETTER when you are after the turbo. Sizing is not all that important infront of the turbo, but is more important.

 

with the TWE header and DP+2.5" back from the DP...130mph on stock boost (7psi) was obtained almost daily, and rather swiftly.

[[HTi]Johnson]

Yeah I always thought that you'd want bigger after the turbo, because the turbo is the thing that's causing back pressure, and everything after is just for convenience or sound sanity!

[Uberoo]

3" downpipe,then 2.5" the rest of the way.Alot of 2lt turbo saabs lose low end torque with a 3" all the way.some run 3-2.5"for a subi however try a 2 7/8" downpipe(mandrel) and then no bigger than 2.5 for the rest of the way back.

[Hodaka Rider]

From http://www.racetep.com (tuning turbos for a LONG time):

Exhaust System and Manifolds

 

We recommend a 2.5” all the way back, no cats. with a 3” inlet and outlet 6” round Walker Ultra-Flo muffler. This is not smog legal and therefore should only be done on cars that are only driven on the track. When driving on the highway always run your cat under the car. We offer High Flow replacement cats for under the car in both 2.5” and 3” diameters. We do not believe in 3” pipe systems for Street Starions. We don’t want to argue with everyone so I will say that… Yes we feel a 3” system will make more power on an extremely modified car running big turbos and big boost… But on a street car it will cause poor off boost driveability and laggy response. 2.5” is sufficient for all street systems up to the high 300 HP levels. We run 2.5” from the Turbo back through a 2.5” catalytic under the car and exit through a 3” muffler. This gives good response and sound while allowing a very free flow system. For now we supply the components to do your own.

 

This particular quote was from their Starion page, for a car with a 2.7L engine. I would think a 1.8L putting out WAY less than 300hp would be fine with a 2.25" to 2.5" system.

[ausubaru92]

Like WJM said,... The pipe size after the turbo isnt important like it is on a non turbo car. This is because the turbo chops up the exhaust pulses that would normally aid in extraction on a non turbo car.

 

I think 3" with crush bends will be fine

[Jpitty]

The exhaust size is important, I have owned a number of turbo charged cars. it isn't important for the same reason mind you, well sorta not. Ok heres the deal with a small exhaust is restrictive, obviously, hence causing the turbo to spin slower. turbo lag. The reason a smaller exhaust on an NA car seems better is it creates a vacuum and scavanges the cylinders sort of sucking out the burnt fumes, but that only really helps at low rpms at higher rpms its another story. An engine is an air pump. the goal is to get air in and out as quick and smooth as possible, Honestly it all really depends on the type of driving you do or want to do smaller for a more stop and go type city driving bigger for a more racing type of highway, my starion has three inch from the downpipe back and it never had a problem. my xt has 2 from the turbo back with custom headers and a blown 12a (starion turbo) so i have no clue if i'll need to go bigger yet, i do know its loud as hell.