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Discussion Starter #1
I have searched and searched and wait....searched. I have not found one dyno or proof that test pipes add any hp/tq to our cars. Sounds wise, I like it but its a little bit raspy and have been considering putting my stock secondary cats it. Can anyone provide me with any sort of information on this?

Currently, I have my test pipes on but have been contemplating taking them off and putting my stock secondary cats on. I have read mixed reviews that they either add hp up top or lose hp and tq and only add sound. You can read my mods in my signature if that helps.

I would also like to add that since I have had my test pipes on, my car has been popping a lot. My car grumbles when I downshift, sounds good, but every so often, it has this loud pop sound. It doesn't sound good, and has me a bit worried. If anyone can shed light on this, I would greatly appreciate it.
 

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The loud pop and grumble sound is what causes the people behind you to be all:



TPs are for sound on this application and the occasional fire throwing.

I would also recommend against plasti-dipping your tires.
 

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I had the same issue then I got an oil change and the sound went back to normal. Weird huh.
 

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Discussion Starter #8

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Cats and downpipe are the only thing i haven't done to my exhaust and i ran 5-10hp lower on the dyno at last weekends tuning day than others with fully built exhausts including test pipes and downpipes.

Is it worth it for you? Only for noise. If you're running stock headers its not going to help the engine breathe any better.
 

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No, he did three separate pulls, one with CBE, one with CBE and TPs, and one with CBE, TPs and SRI.
I have a very hard time believing that gain, especially considering the car would have to be moved to a lift for install and then returned to the dyno, who is not to say the fan was not moved or maybe the hood was opened. There are many dyno tricks out there to get those kind of gains on any car.

To add further to that, Jay (SFR), has stated the secondaries are not restrictive and are the closest thing to high-flow cats you can get from the factory. He even recommended putting them back on if you are running headers and DPs.
 

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Discussion Starter #12
I have a very hard time believing that gain, especially considering the car would have to be moved to a lift for install and then returned to the dyno, who is not to say the fan was not moved or maybe the hood was opened. There are many dyno tricks out there to get those kind of gains on any car.

To add further to that, Jay (SFR), has stated the secondaries are not restrictive and are the closest thing to high-flow cats you can get from the factory. He even recommended putting them back on if you are running headers and DPs.
But are test pipes worth it with stock headers and stock downpipes?
 

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Discussion Starter #14
They won't yield any appreciable performance gain. So in short, no.
How about test pipes in correlation with a SFR canned tune?
 

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Glad I got the GDI. My test pipes rock
 

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I really think you're reading way too much into what a foot or 2 long of a pipe would actually do for you.

As everyone has said, it's mainly a sound changer and would only benefit you with an entire system in place; CBE, TP, DP, headers.

The tune itself does all the work for any gains you see now.
 

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Discussion Starter #19
I really think you're reading way too much into what a foot or 2 long of a pipe would actually do for you.

As everyone has said, it's mainly a sound changer and would only benefit you with an entire system in place; CBE, TP, DP, headers.

The tune itself does all the work for any gains you see now.
I have been under the impression that all they do is increase sound, that's it. People have claimed gains, but others have claimed losses. Also, doesn't jay recommend that you run with your secondary cats on with headers?

My main point is no one has proven if its a worthy mod. Yes it's a foot long pipe, but catalytic converts have always been seen as very restrictive. On a n/a car like our 3.8's, having some back pressure is necessary or we will bottom out.


Sent from AutoGuide.com App
 

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I have been under the impression that all they do is increase sound, that's it. People have claimed gains, but others have claimed losses. Also, doesn't jay recommend that you run with your secondary cats on with headers?

My main point is no one has proven if its a worthy mod. Yes it's a foot long pipe, but catalytic converts have always been seen as very restrictive. On a n/a car like our 3.8's, having some back pressure is necessary or we will bottom out.


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Can we PLEASE put this back pressure bullshit to bed?

Because why say something again that somebody else has already said better:

No Specific Make The myth of "back pressure" - CarForum.net - Car Forums, Automotive News and Community

Backpressure: The myth and why it's wrong

Exhaust Backpressure Study - Thrasher Engineered Performance 3800 & 3800SC Pontiac Grand Prix GTP & Buick Regal GS

If you don't like to read, here it is.

N/A engines benefit from scavenging so exhaust design is always a balance between largest pressure drop (maximum flow) to (attempt to) zero out back pressure, and highest velocity (minimum flow) to maintain scavenging and (attempt to) zero out mechanical pumping.

Turbo engines benefit from largest pressure drop only, because the turbine is always the largest restriction, and the turbulence caused by the turbocharger and positive manifold pressure all but eliminate any benefit to scavenging.
 
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