xtremerevolution Posted November 2, 2007 Report Share Posted November 2, 2007 would getting one for the L27 make much of a difference. Not sure who it was, but a guy I talked to at the last meet said I have all the backpressure I need from the exhaust manifold to the cat. Would getting a high flow cat improve performance much? It wouldn't be a very expensive mod at all, although I'd need to find a shop who would make me a new pipe for the oxygen sensor that goes after the cat so I don't have that as a bottleneck. I'd be looking for a 2.5" high flow cat, since my current one runs a 2" pipe and everything past that is a 2" pipe. There was a noticeable performance boost going from 2.0 to 2.5" after the cat. Quote Link to comment Share on other sites More sharing options...
digitaloutsider Posted November 2, 2007 Report Share Posted November 2, 2007 would getting one for the L27 make much of a difference. That engine is really nowhere near powerful enough to worry about exhaust restrictions. Stock is just fine. If you open the exhaust too much you're going to lose the ONLY thing the L27 has going for it, being torque. And it doesn't have much to lose. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted November 3, 2007 Author Report Share Posted November 3, 2007 would getting one for the L27 make much of a difference. That engine is really nowhere near powerful enough to worry about exhaust restrictions. Stock is just fine. If you open the exhaust too much you're going to lose the ONLY thing the L27 has going for it, being torque. And it doesn't have much to lose. It has more than an LQ1 and about the same as an L36. Considering most L36 powered cars are 200-300 pounds heavier than mine and the fact that the torque is all on the low end, I'd consider it a pretty fun car to drive. That being said, I wouldn't mind a few extra horses all around. I'm not worried about a restriction here. I'm not pushing for 500+ hp. I just want to know how much it will help, if any. As previously stated, going from a 2.0 to 2.5" exhaust after the cat immensely improved throttle response and made a noticeable difference in performance. If I can get another 5 crank HP from a high flow cat, it would be worth my while, even if I had to put in a resonator to keep the backpressure. Quote Link to comment Share on other sites More sharing options...
Andrew Posted November 3, 2007 Report Share Posted November 3, 2007 no, you will not see any gains. Quote Link to comment Share on other sites More sharing options...
MonteCarloDude Posted November 3, 2007 Report Share Posted November 3, 2007 no, you will not see any gains. argeed, at most my guess would be 1-1.5 hp at the crank. Quote Link to comment Share on other sites More sharing options...
CSI_MuNkY Posted November 3, 2007 Report Share Posted November 3, 2007 Not sure where your from, but if you have to do regular emissions tests you will fail the next one. My exhaust had a Magnaflow high flow cat on it when I got it. Of course I bought it with a gut feeling the cat was gonna fail me. I've heard many times that high flow cats are no good for passing e-tests. Last year I passed with flying colors, then I swapped the exhaust and failed misserably. I changed the cat and then passed again. After I did the exhaust swap I went to the track, ran a best of 15.6... Then after the e-test and new cat I went back and ran a 15.4. Go figure Stay stock Jamie Quote Link to comment Share on other sites More sharing options...
GOT2B GM Posted November 3, 2007 Report Share Posted November 3, 2007 I agree with Jamie. Im running a 14.8 @ 91 on my TGP with a brand new stock cat. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted November 3, 2007 Author Report Share Posted November 3, 2007 Alright, thanks guys. I'll keep the stock cat on. Quote Link to comment Share on other sites More sharing options...
pontiacmaniac94 Posted November 3, 2007 Report Share Posted November 3, 2007 well, i would just gut the cat itself. that is what i did with my 94 gp, it runs like a scalded cat now.....(no pun intended) the reason i gutted it out was because mine was clogged, so that might be why i noticed it running a lot better after i took it off. Quote Link to comment Share on other sites More sharing options...
Chancho Posted November 3, 2007 Report Share Posted November 3, 2007 yes that was most deffinatly the problem Quote Link to comment Share on other sites More sharing options...
boulevard Posted November 4, 2007 Report Share Posted November 4, 2007 Andre, I thought I told you before that when you ever need any thing for your car to please talk to me first. Theres a shop in La Grange that would do anything YOU want for a very fair price. I might be going there tomorrow since my car dosen't run as good as it once did plus I'm hearing a tin-ny sound coming from the exhaust. I can't pin point the location of it but when I step down on the exhaust tip, the sound goes away. Strange day today, seems like nothing has gone my way since todays meet. Quote Link to comment Share on other sites More sharing options...
mfewtrail Posted November 4, 2007 Report Share Posted November 4, 2007 I doubt you'd gain much of anything from swapping the cat unless your stock one is failing & clogged up. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted November 4, 2007 Author Report Share Posted November 4, 2007 I doubt you'd gain much of anything from swapping the cat unless your stock one is failing & clogged up. How do I know if my stock cat is clogged up or failing? The car currently has 162,000 miles on the original cat, and this was a California cat. Andre, I thought I told you before that when you ever need any thing for your car to please talk to me first. Theres a shop in La Grange that would do anything YOU want for a very fair price. I might be going there tomorrow since my car dosen't run as good as it once did plus I'm hearing a tin-ny sound coming from the exhaust. I can't pin point the location of it but when I step down on the exhaust tip, the sound goes away. Strange day today, seems like nothing has gone my way since todays meet. Last shop I tried told me they couldn't mess with the OBD 1.5 oxygen sensor after the cat, so they couldn't increase the size of that pipe. If these guys can install that oxygen sensor in a bigger pipe after the cat and fix the stupid angle on my muffler for a decent price, then I should go down there and have a chat with them. Thanks for reminding me. Quote Link to comment Share on other sites More sharing options...
mfewtrail Posted November 5, 2007 Report Share Posted November 5, 2007 How do I know if my stock cat is clogged up or failing? The car currently has 162,000 miles on the original cat, and this was a California cat. Your cat is still in good shape since your car is still making stock power or a bit more(shown by your trap speeds from the track results you posted). Quote Link to comment Share on other sites More sharing options...
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