Nissan 370Z Forum - 2.5" or 3" for a TT

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Nissan 370Z Forum (http://www.the370z.com/)

- Forced Induction (http://www.the370z.com/forced-induction/)

- - 2.5" or 3" for a TT (http://www.the370z.com/forced-induction/12102-2-5-3-tt.html)

Zsteve

12-09-2009 09:30 PM

I had a 4 cyl turbo car, 2 actually, and when I chipped the car, it went from 200 hp/220 tq to 260 hp/300 tq and I went with a 3 inch TBE with highflow cats (200 cell). The exhaust note was quiet compared to my Z now, but of course it was a 4 cyl. But there has always been the 2.5 or 3 inch debate and some say the 3 inch will give you better high end but you might lose some on the low end. A 3 inch on our car will scream if its any indication from my 2.5 FI CBE but needed for the extra flow.

Black370ZTT

12-09-2009 09:30 PM

Well with the 3in with HFC on the TT it sounds great. Its a lot louder, more exotic like, not raspy.

A 2.5 probably could get to 500hp, but if you ever upgraded to like stage 2 and so on, it would be better having the 3in and if you got 3in now no need to upgrade later on, but thats just my thought.

kannibul

12-09-2009 09:40 PM

Quote:

Originally Posted by Minicobra1 (Post 315267)

My 2 cents, and I'm not a Turbo expert, but I know that on alot of smaller 4 cylinder motors such as my Turbo Mini Cooper, we went with a 3" exhaust because of the amount of boost we were running on the front end, which is 18psi.
I think all the Turbo aps for the 370z from Greddy, AAM, GTM, etc. are in the 6 to 9psi range, because of the hi-compression pistons in our motor. I know a lot of the experts out there recommend running 3" in anything that is pushing over 300whp. how much more power you could get out of the 3" is to be seen, IMO I think you could probably get to 500whp with a 2.5 exhaust that has good flow. There is a lot more to flow then just the diameter of the tubing, cats, resonators, mufflers, tubing bends all play a role. Bottom line is if you are going to be for sure boosting the car later on, you should probably talk with whoever is going to be supplying the kit and building it, most of them are designing the exhaust around that application.

That's kind of screwy since I'm approaching 300WHP without Forced Induction...

Less boost = less pipes. Also consider that 3" exhaust on a 4 banger is 3/4" per cylinder. For the Z, that'd be 2.25" per side...

NYBladeZ

12-09-2009 11:48 PM

Quote:

Originally Posted by Black370ZTT (Post 315400)

I could always sell the 2.5 cbe down the line I just want to make 500whp now and I'm wondering if it's better suited to have a 2.5 or 3in. right now it looks like we have a 50/50 split

2fast4thelaw

12-10-2009 08:44 AM

You wont have trouble making 500 RWHP with a 2.5" exhaust. A good free flowing 2.5" exhaust with HFCs will flow up to 550 RWHP. A 3" exhaust is unecessary unless you after the really big gains of 600RWHP and beyond.

G37Sam

12-10-2009 08:48 AM

Quote:

Originally Posted by 2fast4thelaw (Post 315819)

You wont have trouble making 500 RWHP with a 2.5" exhaust. A good free flowing 2.5" exhaust with HFCs will flow up to 550 RWHP.

:wtf2: :wtf2: :wtf2:

Where'd you get this data from? Yeah you probably could but you'd need to pushing like 15 psi with a stage 3 kit

Rob@Altered

12-10-2009 09:33 AM

A full 3" exhaust is really recommended for a TT kit around 500whp. You MIGHT be able to hit something close to the range you're looking for with only a 2.5" exhaust, but you're going to have to push the engine a little harder to make up for the loss of power from the smaller exhaust.

And in my honest opinion, the 500HP 370Z we had here sounded AMAZING! It was definitely louder than stock, but it wasn't raspy, or obnoxious by any means, and it didn't drone at all either.

Kastley85891

12-10-2009 10:22 AM

Or run 2.5in 100% E85 , less boost and a **** load more timing,, EGT's should be managable still....

again dropping dollars on a TT kit, do the 3 in , sure you can sell the current pipe easy enough

NYBladeZ

12-10-2009 11:26 AM

damn that crosses off the new Berk CBE

Sharif@Forged

12-10-2009 12:26 PM

Depending on the dyno, as you approach the 500whp mark you should definately consider an upgrade from the 2.5 inch exhausts. We've done many 2.75 inch exhausts in the 350Z world up past 650whp without any restrictions. Although 500whp is achievable with a 2.5 inch exhaust, it's not something I would recommend. The heat load on the engine will be significantly reduced if you run the larger exhaust, so you will see more power safely. :)

Daishi

12-10-2009 12:26 PM

Lets not forget that the 4cyl turbo applications are a single exhaust.. you went from 2.5 to 3" and your running the whole motor through 1 pipe whereas we have 3 cyl per 2.5" pipe..

2fast4thelaw

12-10-2009 07:18 PM

Quote:

Originally Posted by AAM_COMP (Post 315893)

It was these guy's when I was shopping for an exhaust system. I was going to buy their 2.5" Exhaust. They told me it would flow up to 550 rwhp with hfc's. I really wanted it but I couldnt wait the lead time on it as it was pre-production. I went with Stillen instead.

370Zsteve

12-10-2009 07:33 PM

Quote:

Originally Posted by Sharif@Forged (Post 316159)

There have been a hundred threads on the subject of exhaust flow/hp/torque but this is the first time I've seen someone mention heat load in the equation. Good show, Sharif! :tiphat:

Kastley85891

12-10-2009 08:15 PM

Quote:

Originally Posted by 370Zsteve (Post 316710)

There have been a hundred threads on the subject of exhaust flow/hp/torque but this is the first time I've seen someone mention heat load in the equation. Good show, Sharif! :tiphat:

See post on EGT a few up:tiphat: lol

NYBladeZ

12-10-2009 11:03 PM

thanks to the guys at AAM and Sharif from forged sharing their expertise, looks like I'm going to hold off any exhaust purchases until I jump for the TT

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