914 WRX needs Turbo exhaust Engine builder Experts Advice needed, more backpressure/heat in exhaust...what needs to be adjusted? Options

[budman5201]

Okay i have a question out there for the Engine builder or exhaust experts.....

I have a 914 with a WRX 2.0 turbo in it, it flys! I am basically making it into a very streetable quiet car. One of the first things i did during my build is put this aftermarket very shiny equal length chrome header on it and took off the stock heavy cast manifold for more power(never tuned or ran with stock).

I had the engine tuned with this header on it, so its perfectly tuned with it. Now.....I have the stock heavy manifold back on with all the heat reflectors,etc to keep the heat in the manfolds......its is Noticeably quieter than with the equal length, lower to the ground, crappy shiny header and... power seems almost just as great.

So....
New heaver manifold before turbo, smaller diameter exit than aftermarket so more backpressure.....do i need any changes on my fuel map? (i have programmable Link storm ecu.)

(I did get one backfire through exhaust....thats really why i am asking)

[Numbchux]

going back to stock exhaust, your turbo will spool slower. so you'll actually have a bit less air than your fuel trims are set for. So you'll run a bit rich. Not an issue for reliability, not at all. But, you're probably not getting as much power or mileage as it's capable. The biggest change is that if you're running the stock up-pipe (USDM, anyway), there's a cat between the engine and turbo, that really slows down the spool!

The issue is going the other way, if your turbo is spooling quicker, you're going to run lean. and that's when you risk detonation.