I have been doing some research and on the recent evo purchase I have decided to do some mods to it.

It came with a downpipe and Koyo radiator so i am thinking it was once modded then returned to stock.

Tonight I am installing a turbo XS catback and it will still have a cat converter and I am looking for a drop in intake or cold air style.

My question is related to an issue of turbo magazine I had that featured the evo exhaust shootout. On the beginnning of the article they tested en evo that was equipped with an AEM because they said a stock ECU'd evo would lose power if you just went ahead and installed a cold air intake and exhaust.

Is this true?

 

If it was a crappy intake maybe it would screw up the MAF readings enough to be a problem but I don't think it would loose power on a stock tune. AEM certainly isn't needed at those level of mods.

The car probably would pick up a couple of horsepower with no tuning but it certainly would see more power if you had it tuned. Take a look into the Ecuflash forum for some in depth threads on flashing the stock ecu and the potential limits of the ecu.

 

After only being a member for several days, and a new Evo owner, maby I shouldn't be giving advice. But from my research, you're probably better off saving money and purchasing the AMS stage one kit. Everything you need to make the claimed 330hp. All of the beginning tuning stages are addressed. This is the route I will be taking once I am comfortable driving my car.

 

I would get a test pipe or high flow cat before an intake. A full 3 inch exhaust will unleash a lot of power where the intake is only a little. And if you have a 3 in downpipe going to a 2.5 in stock cat, then to a 3 in cat-back... you are still limited to 2.5 in based on the size of the stock cat. I'm just assuming the cat you have is stock.

 

I've replaced all my exhaust parts one at a time.

First was the down pipe and o2 housing, almost unnoticeable really car didn't sound any different the top end seemed only slightly better imho.

Secondly I got a HF cat from works which was again almost no noticeable power gains.

But when i put on the catback finally i felt that extra torque kick in on the bottom end of the power curve. So its my belief that the can is maybe even more restrictive than the cat.

 

I disagree... You should start from the back of the car and work forward or whatever else you do near the front is ultimately going to be restricted by the smaller pipes in the rear. If you would've went cat-back, then HF cat, then downpipe, then O2 housing you probably would've felt a small gain from each part.

Your entire exhaust is only has as good of flow as the smallest part in the system. By doing just a cat-back you'd be allowing exhaust gas to escape quicker once they got that far back in the pipes. But if you did just a downpipe, the exhaust gas would flow quicker through the downpipe... but then just slow back down at the cat and be pretty much the same as stock.

 

Yes I have the stock cat on but i just installed my Turbo XS catback on and wow....what a difference. My car with a downpipe only and exhaust housing had a difference compared to my stock yellow car.

The next step is to eliminate that cat and go with a helix high flow cat. i really don't want to get it any louder than it is but the the only drawback is that I feel the need to keep it floored the entire time because I love what little power that pea shooter is making