I'm going to autocross the car and in stock class I can only add a cat-back exhaust. This may be the only modification I make to the powertrain. I am unwilling to give up any bottom end and would like to improve that if possible.

Does anyone have dyno results of a 2.5 or 3" cat-back on an otherwise stock Evo? I am curious if the car picks up any power and whether one size is better than the other.

I've seen plenty of 3" systems, but who makes a 2.5" system?

Thanks!

FYI the pic is at California Speedway.

 

Ultimate Racing makes a very nice 2.5" system. Good product, good service and nice price. I would highly recommend it. It is my belief that on an otherwise stock car, you won't see any gains going with a 3" catback over a 2.5". My thoughts are that you are attaching this to a 2.5" stock cat, having the extra room after that big of a bottle neck just isn't going to do anything.

 

unless you have a hi flow 3" cat...

 

i would say go with the 3" anyway. it would give you the option to run a larger downpipe in the future if you ever wanted to. Ultimate Racing is a good choice

 

3" is a waste of $ IMO, unless you're running a bigger turbo. Axel back and test pipe is all you need. Do some research

 

A lot of people here need to do some research... backpressure in and of itself is a myth... "not enough back pressure" is a shad tree mechanics tail of what happens when you go so big on the exhaust diameter that the flow loses too much velocity... reducing proper exhaust gas scavenging... In our case that is not going to happen with a 3" cat back exhaust. It would not be a waste... would you see a huge power improvement over a 2.5"? Maybe not... might be interesting to see what temps at the O2 housing look like on the two though.

 

I can't do anything with the cat since I will autocross the car in stock class. So, like I said, all I can do is replace the cat-back part of the exhaust. I am curious if a cat-back system in and of itself will really provide a benefit. I don't want to buy a system just to change the sound or the look.

 

"would you see a huge power improvement over a 2.5"? Maybe not... "

http://www.pruvenperformance.com/evoexhaust.html

Keep you cabbage for other mods (IMO)

 

Two words:

"Axel back"

Pruven http://www.pruvenperformance.com/evoexhaust.html
Works
...

Why pay $600 dollars for a cat back to see identical gains from a $260 dollar axel back

4-BNGR

P.S. you can always go with 3" DP in the future... sice you have to run a cat
3" cat is a waste of $ (IMO) unless coupled with a 3" DP - only because you've done a TURBO Upgrade...

 

I think most would agree with this basic path if the engine/ turbo combo is going to remain box stock;

Delete the muffler completely; Works and Buschur sell pipes for this. At the same time or closely thereafter add a Brain flash or a proven form of electronic management. Leave the stock intake intact.

We’ve decided to leave our Evo mostly stock and the homework indicates that with the Works Exhale AB, the Brain flash and everything else stock that we will not only have 300+ H.P., but a more drivable car with a relative economic investment in mods. (about $750). In the near future we plan on attending a dyno day and will post the numbers.

After that money is going to be invested in high performance street driving classes so we can learn how to drive the Evo to its best. Then and only then will we consider further power modifications.

Rick

 

I was hoping somebody would have dyno runs showing the difference between bone stock and cat-back only... but I guess not. Understandable, given that there are many effective mods out there that most peopel will opt for.

 

Hey, I noticed you were a local guy in SD. Give us a call if you need anything for your EVO and we will take care of you.

With our 3" catback you will see about 13whp.