2.5" or 3" for a TT

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

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

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.

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

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.

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

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.

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

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.

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!

Kastley85891 · 12-10-2009, 08:15 PM

Quote:

Originally Posted by 370Zsteve

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!

See post on EGT a few up

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

12-09-2009, 09:30 PM	#16 (permalink)
Zsteve A True Z Fanatic Join Date: Sep 2009 Location: TX Posts: 3,298 Drives: the 2 balled club Rep Power: 21	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. __________________ 2010 LS3 C6 Silver coupe corvette

12-09-2009, 09:30 PM	#17 (permalink)
Black370ZTT Base Member Join Date: Nov 2009 Location: Maryland Age: 33 Posts: 47 Drives: A TT,Nothing special Rep Power: 15	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. __________________ AAM Twin Turbo Kit, 500hp/400TQ UPrev "America is all about speed. Big, nasty, bad a$$ speed." Roosevelt

12-10-2009, 08:44 AM	#20 (permalink)
2fast4thelaw Enthusiast Member Join Date: Feb 2009 Location: Denver Co Age: 49 Posts: 403 Drives: 09 370Z Sport/MT6 Rep Power: 16	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. __________________ To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be.

12-10-2009, 09:33 AM	#22 (permalink)
Rob@Altered Enthusiast Member Join Date: Jul 2009 Location: Gaithersburg Posts: 282 Drives: 350Z/370Z/GTR/G35 Rep Power: 368	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. __________________ Altered Atmosphere Motorsports RobS@alteredatmosphere.com

12-10-2009, 11:26 AM	#24 (permalink)
NYBladeZ A True Z Fanatic Join Date: Apr 2009 Location: New York Posts: 2,158 Drives: Lotus Exige S Rep Power: 20	damn that crosses off the new Berk CBE __________________ 2009 Carbon Fiber/Red 370z aka Trish: Sports Package, Meisterschaft full catback, Fast Intentions Longtube Headers, Injen Long Tube Intakes, UpRev Tune: Sold 2008 Lotus Exige S Club Racer aka Bella, always leaves me smiling

12-10-2009, 10:22 AM	#23 (permalink)
Kastley85891 A True Z Fanatic Join Date: Nov 2009 Location: ATX 370 - Sold Posts: 1,149 Drives: 2003 Wagon Rep Power: 17	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

12-10-2009, 12:26 PM	#25 (permalink)
Sharif@Forged The370Z.com Sponsor Join Date: Dec 2008 Location: Marietta, GA Posts: 840 Drives: 2009 GT-R, 2010 370Z Rep Power: 17	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. __________________ Sharif@Forgedperformance.com General Manager/Certified Tuner/NASA-PCA-BMWCAA Instructor JRZ RS1's Available NOW...PM me Cobb ProTuner, Uprev ECU Flash, FCON Vpro, Haltech, Motec Certified

12-10-2009, 12:26 PM	#26 (permalink)
Daishi Track Member Join Date: Jul 2009 Location: NJ Posts: 683 Drives: 09 370z 6Speed Rep Power: 16	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..

12-10-2009, 11:03 PM	#30 (permalink)
NYBladeZ A True Z Fanatic Join Date: Apr 2009 Location: New York Posts: 2,158 Drives: Lotus Exige S Rep Power: 20	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 __________________ 2009 Carbon Fiber/Red 370z aka Trish: Sports Package, Meisterschaft full catback, Fast Intentions Longtube Headers, Injen Long Tube Intakes, UpRev Tune: Sold 2008 Lotus Exige S Club Racer aka Bella, always leaves me smiling

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