Hey guys i have a question about back pressure. i'm running a 2.5 exh. with a 3.5 outlet. if i put the quiet core back in my car boosts more and i think runs faster, but at the same time more quiet. without the core boosts 10 ruff, with the core about 13 psi. need help guys, is more backpressure better for SC?

 

sc need back pressure. 2 1/4 piping has been known to give the sc 16 whp. are you running stock pulley? 10-13psi seems a little low

 

Yeah with an intake. injen

 

do a search for backpressure, there was this whole huge debate on why you DONT need back pressure, to an extent... despite what everyone thinks.

 

wrong, wrong, wrong, wrong. tell me how ANY cobalt needs backpressure. huge, very old myth. backpressure at any level does nothing but make the engine work harder to get the same results. engine working harder = less power.

there is ZERO benefit to increasing backpressure, it's all negative. backpressure = bad, end of discussion.

the reason why you're losing power/boost with your setup is that it's WAY too big. a 3.5" outlet is really slowing down your exhaust velocity. you want the velocity of the exhaust to be as high as possible. with your 2.5" inch exhaust that then opens to 3.5", what's happening is the air is moving quickly, then slowing down when it hits the bigger pipe.

the idea is to make the engine more efficient. the reason for getting an exhaust is to move the air out of the engine as quickly as possible. (unless you're a ricer and want to annoy your neighbors) i feel that 2 1/4" piping is too small on this car, regardless of what one or 2 dyno's have shown. 2.5" piping is the best bet for majority of 2.0 owners on this site.

 

So i should just go for the straight 2.5? thanks guys.

 

thats what i have work for me the car is still a tourqey beast and i gained a lot of top end by going with straight pipe

 

Um... no.
More boost is not necessarily a good thing, and doesn't mean faster. What your doing is choking the system. It's all about keeping your boost low, while pushing more flow into the motor.
Highly suggest you go with a 2.5.