RazorLab

iTrader: (8)

Ever wondered what just adding a test pipe to the otherwise stock exhaust system on a Evo 10 would gain?

Wonder no more.

2008 Evo 10

Mods:

Works Drop-in filter
Custom EcuFlash for track use
Stock downpipe and stock catback

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Just adding the test pipe (everything else stock in the exhaust system) gained:

+15whp / +17wtq peak.

Also gains in spool.



It also knocked a little up top as you can see. Adding the test pipe allowed the car to run approx 1psi more boost over the whole rev range and leaned it out .4 AFR

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I retuned it for the test pipe, richened it back up for safety (it's a track car) on 91 octane and added our boost assembly which allows more boost to be tuned in and it gained a total of:

+22 whp / +27 wtq peak over what it made before.




Data of boost curves:

Before test pipe and boost assembly:

3500 - 23psi
4000 - 23psi
4500 - 22.5psi
5000 - 21psi
5500 - 20.5psi
6000 - 20psi
6500 - 18.5psi
7000 - 17.5psi

After test pipe and boost assembly and tuned for them:

3500 - 24psi
4000 - 24.5psi
4500 - 24.3psi
5000 - 24psi
5500 - 24psi
6000 - 23.5psi
6500 - 22psi
7000 - 20.5psi

Massappeal

iTrader: (1)

Nice! I got great gains from my testpipe as well using stock catback still!

Jabjab

iTrader: (2)

how was the sound with just the test pipe with stock catback?

Rguy

iTrader: (6)

The stock cat is insanely restrictive eh?

I looked inside it while installing my catback and it looked downright horrid for flow.

SpeedI2acerX

iTrader: (2)

nice i have the same set-up but with a works stealth exhuast

RazorLab

iTrader: (8)

Barely louder than stock, I was impressed.

Massappeal

iTrader: (1)

I can't really tell much difference, its barely noticable. just slightly stinkier!

STi2EvoX

Razorlab, which particular test pipe was used? I am also curious about one thing... if the stock exhaust is 2.5 in, would using a 3 in test pipe not cause turbulence in the exhaust flow? I would tend to think that by having a smaller diameter open up to a larger diameter and then shrink back down to a smaller diameter again that it would hurt exhaust gas velocity when compared to a constant diameter, such as by using a 2.5 in test pipe.

I know that people back in the day used to gut their cats thinking that it would boost performance, but it actually caused a power loss because the exhaust gas would get caught in the large chamber of the gutted cat and circulate, creating back pressure and causing a reduction in exhaust gas velocity as a result.

Granted, the difference in diameter is much greater in a gutted cat, but if I planned on keeping the stock exhaust for stealth/noise factor, would it be beneficial to use a 2.5 in test pipe to match the diameter of the stock exhaust, or would the difference be negligable? Thanks for any info or advice. Oh, and nice work man; it seems like this boost pill is the shiznit!

HardRideCafe

Makes me wish I just kept my stock exhaust on with a test pipe.

jayevo23

now the gains be higher if it was a high flow cat?

STi2EvoX

^A test pipe will always gain much more power than even a high flow cat. I think running cats on an AWD car is stupid anyway because most emissions testing places don't have an AWD dyno, so all they can do is just plug into the OBD2 port (or CAN port in our case) and check for CELs. If you have a reflash, not only will you have huge gains in power but you will be able to disable certain CELs like the one you get from a test pipe. No check engine light, no problem. With a test pipe creating less backpressure, more, flow, and more boost from the turbo, I don't see why anyone would even run a cat on an EVO.

stokEd

iTrader: (3)

If I'm on the street I won't run a test pipe because of the smell, the noise, and the extra pollution. I'm curious how a good-quality high-flow cat would perform on the same setup. Those gains are pretty good though .

Clark_Kent

iTrader: (5)

Is this boost assembly you use available to the public for purchase?

RazorLab

iTrader: (8)

The vendor side will post more information about it shortly...

simons

iTrader: (1)

I thought when the inspection place does emissions, all they do is start the car while it's stationary and they put whatever measuring tool they use in the exhaust stream exiting the tail pipe. I can't see them needing a dyno for emissions testing.