So I have an 03 evo and we recently pulled the turbo to put on an 02 housing. Turns out my exhaust manifold bolts were stuck into my 10.5 exhaust housing from the TME 6.5 turbo and we just swapped that with my 9.8 from my stock turbo.

My question is why does a 10.5 make more power than an 9.8? If my car is boosting 21 lbs at redline with a 9.8, how would a 10.5 make more power if the compressor side is already making max boost that I want?

I'm not a good mechanic so could someone explain please?



Also, i remember reading a while back when i first got my car that pulling the ebrake my while moving is a good way to mess up the drivetrain. Can anyone explain how the ACD in the 05s allows for ebrake pulling while the 03/04 cant?



Edit: Well, I searched for turbine housing instead of exhaust housing and it came up with some results. Is it correct to say that the 9.8 housing restricts exhaust gas flow and because of this a .7 cm upgrade in the size of the housing increases the flow and creates more horsepower? Are there bigger exhaust housings available for the stock compressor?

 

The 10.5 is a bigger exhaust housing. Why wouldnt it make more power? its very similar to having the option on aftermarket turbos to do bigger hotside becuase it makes more power and flows more. Hence why putting bigger exhaust on a stock turbo car makes more power. Or even an all motor car. More flow more horsepower. And explain to me why you would want to pull the ebrake while driving????

 

It just didn't add up in my head really, If the first restriction in flow in the exhaust system is right after the turbo, why do people add turbo back exhausts first? Wouldn't the right path of mods be exhaust housing, 02 housing, and then DP and catback? It seems most people go the other way around.

I think i was playing collin mcrae dirt with some friends and they kept telling me to pull the ebrake for hairpin turns and it popped in my head that 03/04s without the ACD can't do that and I couldn't remember why.