Is it very restrictive???? the reason I ask is that I'm going fully catless with a helix downpipe, but for noise reasons I was going to mate it to the stock catback. I'm also running an up-pipe and Ecutek.

Will I lose much of the catless gains???? or is it like the airbox where it won't matter until I'm running big power???

TIA

 

If you're fully catless it wont make much of a difference

 

im fully catless and i felt a difference..it doesnt pull as hard because the stock catback piping is thinner than the downpipe. ive have many different catbacks and HKS gets the most power..i have a borla hush now for sound reasons and it sounds great, not loud until you step on it and the power is still there. ive also had a GReddy Evo2.

 

I sense a disagreement of opinion.

 

Imho, noticed a lot less restriction when I had just my Blitz Nur Spec axle back on a fully stock car. Boost came in quicker and the car was much more responsive.

 

Using the stock catback on a free-flowing exhaust will be somewhat restrictive. There will still be improvement from a good downpipe and midpipe system, even with a stock or quiet aftermarket catback. If you must have a restriction, it's best that it be as far away from the turbo as possible (like a catback). By then, some of the exhaust has lost velocity and cooled down.

My car has a stock turbo, downpipe, and midpipe (3rd cat) and was dyno tuned with that combination. After switching to a Strömung 3" dual tip catback, I was able to improve my ¼-mile E.T. by 2/10ths of a second with no other changes. I did notice, however, that my trap speed (which indicates horsepower) dropped by one mph, indicating that the power gain was in the mid-range. A visit to my tuner and a quick reflash regained the top end trap speed and resulted in yet another couple of tenths from my E.T. His opinion was that the new catback caused a top end lean condition because it a less restrictive exhaust may necessitate a slight richening of mixture at full-throttle, while at the same time require less ignition advance, IIRC.

While your results may vary, I'm convinced that a catback is important to a free-flowing exhaust system.

--
0==WW==0
"…axles of evil…" - george w. bush

 

TONS of restriction, at least my 05 was. It might not be a problem with the stock turbo, but I went through a PITA with a VF34, PDE Up, Madded Catted DP, 3CE, halfback and stock axleback. Long story short, picked up about 20whp and 18lb-ft on the gruppe-s dyno going from halfback and stock axleback to Borla "hush" catback.