I installed a HKS downpipe, HKS Res. midpipe and a R/B dual tip exhaust. It is constantly backfiring and popping. Is this normal for a straight through exhaust. As far as other mods I have every bolt on you can get on the car with a PFC. If I need to put a cat back on to stop the backfiring, how much horsepower will I lose with a high flow cat?

 

so do u have the pfc tunned for all your mods?

 

yes, when i bought the PFC I had it tuned. i put it on the dyno and the A/F reading are 10's so I could lean it out a bit to get it to 11.0 or 11.5 or so but the car has been in the shop for 5 months getting the turbo,rad, exhaust, brakes and Pfc installed. rebuilt ect. I just want to drive it for a little while before I take it back to the shop.

 

Of course you will lose power if you put on a high flow. Why do you think so many people run midpipes?

How bad is the popping? A little bit is perfectly normal.

 

how much hp will I lose? when I first warm it up and then start to drive it, it hardly pops at all then after driving it for awhile it begins to pop more. it doesn't pop so much when I drive it hard, just mainly stop and go traffic, around 2K-3K rpm.

 

You will still have the backfiring (popping) with a high-flo cat as well.

 

what causes it to back fire then? the down pipe?

 

Yes, removing the pre-cat will allow you to hear it. If you want it completely gone, put your pre-cat and main cat back on the car and then you can tune down the PFC during deceleration.

However, it's really too much trouble. Unless it's harming the car (and this isn't), I would leave it alone.

Make sure your O2 sensor, spark plugs, etc, have all been changed recently. That will help it out a little.

 

hell, with that free flowing of an exaust its gona pop...

my bro's fc, spits 2 foot flames out the back when he's Auto X'ing

 

OK THANKS ALOT GUYS.

 

no prob sexy