1. What's the difference between a Test Pipe and a High Flow Cat?

2. If the law doesn't apply, which would you recommend for performance gain?

3. Is there a large noticeable difference in the "rasp factor" between Test Pipes and High Flow Cats?

 

 

pics of gf or

 

1. Test pipe is a straight pipe with not cat. High Flow Cat is a cat designed to flow better than the stock.

2. As far as performance gain, well that depends on a lot of factors, main one is are you running turbo or are you naturally aspirated. If you're turbo you need the test pipe.

3. As far as rasp, that has other things to it than just the HFC or the TP. the type of exhaust you're running, weather you have headers, plenum spacer etc...if you search you'll see some guys eliminate rasp by switching to a HFC and some guys run TP with no rasp.

Best thing to do is search the exhaust you plan on running, read the thread and see if a HFC or TP's were used and if there is a rasp issue.

 

My car is naturally aspirated, with no other performance mods todate (but I will install plenum spacer in the coming months).

 

Do not be afraid of rasp. It will not hurt you. Be strong for Jesus.

 

Rasp comes with all test pipes.. I never seen test pipes that don't rasp.. To minimize the rasp as much as possible. Get resonated test pipes. I have them. Little rasp. Only when the rpms drop. But its not bad.. Test pipes are better then hfc basically because the cat restricts alot of hp. And hfc.. There is still a cat. Both are good. If your not worried about the law. Then you know you were lookin to hear the test pipes were better. And can we please see ur gf?? lol.

 

There.

 

Searching for your answer to your question (which are mostly common sense questions) will give you better answers. However, in the spirit of giving, here are your answers:

1. Test pipe is just a regular pipe without a catalytic converter and can come with or without a resonator. High flow cat is a catalytic converter which is much less restrictive than a regular catalytic converter on your car.

2. Test pipes will give you more performance gain than high flow cats. However, N/A-wise, the difference is very minimal. If you're FI, then you should opt for test pipes.

3. Rasp can be reduced with matching diameter pipes, with exhaust configuration, with resonators, etc. High flow cats can also give you rasp, but is frequent than test pipes. Resonated test pipes can reduce rasp, but doesn't always do so (search for other solutions). Keep in mind that with resonated test pipes, there are more welds to break (I've broken them 4 times) and the resonator itself can rattle (mine did until it broke on its own).

 

LOLLOLLOLLOLLOLLOLLOLLOLLOLLOLLOLLOLLOLLOLLOLLOLLOLLOL!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:icon21 ::ic on18:
that is freaking hilarious!!!!!!!!!!

 

your answers are in red

 

I have ? are the o2 sensor before or after the cat or on the cat itself? IF they are on the cat, do they have test pipes with o2 sensor threads already on them?

 

We have a total of 4 cats:
-one at each header (so 2 here)
-one at each cat (so another 2 here)