2.5" or 3" for a TT
 

Yeah I know the quick answer is a 3" exhaust but there aren't many vendors out there producing them. My question is can 500whp still be reached with a 2.5" exhaust? I love the berk cbe but like most exhausts out there it's a 2.5" and there would be no point in getting it if I need to swap out to a 3" so I can make 500 at the wheels. Answers appreciated!

I'm not positive but I think 500 RWHP will be difficult with a 2.5" and if it is possible you'll probably still suffer at lower rpms a lot more and have a longer spool up time.

Greddy has a 2.75"
AAM has a 3"
GTM has a 3"

As more turbo kits hit the market we'll likely see more 3" exhausts hit the market.

I'd like to hear what Tony from F.I. has to say about this. He is a great, honest guy who really knows his sh*t, and I bet he would know and give an unbiased opinion. Now, F.I. created a 2.5" system (which I bought), so why would they do that if it is incompatible with a TT setup, especially since I assume that a lot of us guys wanna eventually go TT? Just my :twocents:

Actually not a lot of people want to go TT that are actually seriously considering it. The costs to do so, correctly, is in the 15K price range which is more than most will pony up.

There's a G37 that GTM tuned with an FI exhaust & test pipes, it's doable

He was hitting mid 400s whp I believe

A 3" surely is more recommended, I'm sure Tony can make a 3" exhaust for you if you needed it.. I've come to believe there's nothing that man can't do

Tony = God?

Tony had mentioned tackling a TT kit at some point. I think right now though he is still finishing up orders and his LTHs. I'm really interested to see what he'd fab up and I'm sure he'd custom make a 3" exhaust for a TT setup

:icon18: And give us guys who've already bought the 2.5" exhaust a huge discount on the 3". :tup:

Dude he probably would just for the repeat business!!:bowrofl:

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.

Get a set of catless DP's and you will prolly make your goal, the 3in TB would be nice but I ran 400 WHP on 26 psi with a 3 in catless DP and a stock catback on a different platform, TBH, tuning wise the little bit of exhaust restriction actually helped control the boost curve better up top.
Thats just my thought on it technically, personally I would just get a 3 in catless deal if I were dropping monies on a TT kit.

I remember when purchasing my AAM Comp 2.5 inch True Dual Exhaust that their webpage mentioned handling up to 500HP. I went and copied it here:

"This is the perfect exhaust for both NA (naturally aspirated / non-supercharged or turbocharged) applications and forced induction (supercharged or turbocharged) applications where the AAM Competition 370Z 2.5" True Dual Exhaust System has been proven up to 500hp."

Well the AAM TT kit just made 500RWHP with a 3" exhaust at 6-8psi. Soooo if you had a 2.5" and you bumped up the boost a little you might attain the 500RWHP mark then?

I'd think this would be less than ideal unless you had a built bottom end..

As much as I would like to agree with you (and I really would since I paid over $1800 for my F.I. 2.5" exhaust/HFCs), that may be a bit of a biased opinion. As I said before, I would like Tony ::cough cough:: to comment on what he thinks.

It wouldn't make sense to up the boost while keeping the same 2.5" exhaust diameter. Uping the boost will just create more backpressure and more heat to the engine. Plus, you get slower spool the turbo is pushing more into the engine but it's not exiting fast enough. I'm not saying that 500rwhp is not attainable with a 2.5 but at what cost? longevity maybe?

The question is, what will a 3" sound like. I know when i switched from my stock exhaust to 4into1 header, 3" downpipe with hfc and 3" magnaflow exhaust with a 12" res. It sounded like ***...but then again that was on my 4 banger supercharged cobalt and i made 300fwhp.

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.

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.

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...

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

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.

: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

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.

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

damn that crosses off the new Berk CBE

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. :)

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..

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.

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

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

I guess I will stick my neck out and be the only to say that my 2.25" has been working great with my HR-TT up to 470 WHp. For sure it has seen over 500WHp during development caused by boost creep before my internal wastegates were changed.

I've never noticed slow spool-up and EGT has never gone over 1300 at the manifold, but then again, how long do you plan to be in boost? At steady idle, the EGT will be around 750.

I've rode in a GTM VHR-TT with 3" pipes and I can say it was too loud for my taste, but I'm sure others will feel otherwise.

IMO, if max boost at any given pressure is what you are looking for, sure go to 3" ... but here in CA ... I can assure you that the CHP will also notice it.;)

BTW ... any existing CBE for a NA Z will work with the GTM TT kit, so you may as well try it out before you decide to go bigger.