I brought my 05 Evo MR to the dealer, according to a "head-mechanic" I shoudln't change the exhaust (I have B&B + HKS downpipe), because the EVO comes with 2 steps exhaust.
according to him"With after market exhaust it will decrease the power instead of increase it."

 

no- the MR and regular evo,in fact all evo's 03,04, 05 have the same exhaust. i didn't change mine cause it's a pretty decent factory exhaust but in general, he has a slight point cause you will lose a little low end but gain much much more on the top end w/ exhaust.

 

thats just bull****.... the muffler has some stupid flap in it thats what i imagine he is refering too.... just for reference the head mechanic at my mitsu dealer destroyed my driveline and cut a hole in my bell housing... sooo head mechanics arent always right

 

incorrect. I got 25WHP from adding the Buschur turbo-back alone. With no engine management. When you get tuned, the power increase is substantial.

 

It is true that the EVO has a so called "2 step" exhaust but all it is, is a flap in the muffler to make a little back pressure to increase low end tourqe. But switching to aftermarket will make more power.

 

i suppose a cheap, doesnt really fit, not made for an evo aftermarket exhaust would decrease the power.

but i will have to say that most exhausts, from reputable companies, increase your power

 

I was under the impression that the flap was mostly to help emissions. By causing back pressure at idle and during cold starts to help light off the cat. It also helps keeps it quiet when not under load.

 

From the 03 handbook that came out before the 03's actually made it here. It said that "flap was to reduce noise at idle and open up under acceleration."

 

From what I have read I don't believe anyone has been unhappy after installing an exhaust, with maybe the exception of the sound level....

 

not true, I have dyno charts to prove it... oh and I drive a MR

 

not true at all! 1: theres a NINETY degree bend right before the muffler (lots of back pressure, lots of exhaust flow restriction) and as previously mentioned, there a flap inside the tubing, which opens and closes. I could list the more technical reasons, but just those two prove the point

 

Aftermarket exhuasts are better in every aspect except sound DB and low end torque, other wise it's an improvement everywhere else across the board.

 

Will I lose low end torque with any aftermarket cat back 2,5 and 3?

 

a little, but you will be HAPPY with what you get all around and especially up top! and nothing a little tuning cant take care of down low. Also the sound of a new exhasut makes you feel as if you have a new car again.

 

thats funny