I just changed my exhaust set up from a custom dual exhaust set up that was 2.25 inch piping all the way back from the cats to 2 hks canisters. Now i have a single exhaust set up that is 2.5 inch y-pipe that ends at 3' inch and continues 3'inch all the way back. My question is, would i have to retune my set up since i was running such a small diameter piping in my last set up to adjust to the new 3'inch diameter set up?



thanks, Chris

 

Is there any way you can check the AFR ... using datalogging or just get it up on a dyno?

I would just compare AFR before to after, and see if everything's still cool.

 

You're all N/A?


Your old setup was two 2.25 pipes. That's a total area of 7.948125.
The new one is 3". That's 7.065 area.

So you now have less overall diameter piping than you did before.

Being that you have a UTEC, a tune couldn't hurt....but it probably won't be huge. I would personally get it tuned.

 

Yes im completely n/a. All my mods are on my sig. i do have my last dyno somewhere in my room, so i guess i can go get it dyno'd and see if it might need a retune. But if you guys think that its such a little diffrence in diameter and i'll be wasting my time then i wont bother. My last dyno number where 266whp & 243tq. I think the tq could go up a bit but i dont think the whp would go much higher than that. I think the power in the curve might need a look at since theres my back pressure now to deal with.

 

question is, is it really worth retuning and spend 100-300 for a few more ponies and a bit more tq?hmmmm i might just do as wired said and redyno it and compare the a/f and tq curve. i have notice a slightly faster drop in gas then before!!! a little odd but it can be do to an exhaust leak that i have, one of the y-pipes flanges is not sealing right and left a little gap where the exhaust is leaking out. im going to fix that next week and hopefully that fixes that little problem.

 

Did you eliminate any additional cats by doing the exhaust swap? If not, you don't need a retune. Save your money. You won't gain much because your flow characteristics did not change enough to influence your EGTs which will directly effect your timing and knock tendencies.

Forget about checking the AFR. I can't see how exhaust would change that since your O2 sensor feedback dictates that, not your exhaust flow characteristics.

It would be cool to see before/after EGT readings to determine how the exhaust effected backpressure profile. A better flowing exhaust, if that is what you're after, will lower your EGTs and allow for more timing. Usually dropping cats will do that and a retune may be a good idea. That's where my original question came from.

 

well my dual set up did have 2 resonators. now with the single I have one. so im sure its flowing much better now and im sure theres more back pressure too.

 

Ok, sounds like you don't need a retune. The change you made is not significant enough to warrant a retune. I think you can put that money into something better, if it is burning a hole in your pocket The setup sounds nice.