[ZTWsquared]

Scourge,Jan 2 2009, 03:02 PM Wrote:Alright I've got some questions regarding exhaust sizes, sound, and performance. I want technical feedback and personal experience from people. I understand the basic principles of flow, backpressure, and scavenging but I'm looking for everyone else's thoughts.

The car: 07 ZX4 SES 2.0. So far all I've got is the Steeda SRI. I'll be doing the exhaust next and following it up with an Xcal, not sure who I'll go to for the tune yet. I'm going to go with MBRP but I’m not sure if I should go with the 2.25" or the 2.5".

My last car had a lot of mods and because of what I chose to mod, it was very loud (Short final drive, no cat or resonator, and all solid motor mounts). I grew to hate the sound on road trips, so much so that I always kept earplugs in the car (and I used them regularly). So needless to say, I'm a little concerned about the sound level of the exhaust.

So, 2.25 vs. 2.5. Performance gains/drawbacks (difference in low end/top end)? Sound difference between the two? I don't plan on getting a header, not going F/I with this car, once I've got the I/E/T the only engine mods that may be in the future are UDP and a lighter flywheel.

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MBRP should advise you on any difference in performance, but in terms of a normally aspirated engine I would be surprised if there was any noticeable difference - - in fact, for n/a bigger might not be better at all.

If you remember the sound from my car - - it has the 2.25" MBRP with stock intake and a 92 octane tune from the X-cal2 ... plus it retains the 2 stock cats ... I would think that anything that is bigger, or eliminates the second cat, would be louder - so perhaps you could use my car's sound as a base line.

With an intake and tune, but especially with no FI and with stock exhaust header, my vote is for the 2.25"