best exhaust piping size for N/A?
 

I was reading through the forums a bit and am thinking of going to a single exhaust. 3" or possibly even 2.5". I feel like the exhaust I have right now, 2.5" true dual with x pipe and resonated test pipes may be a bit much for n/a and there is too much flow/not enough velocity. I know the stock cats are very restrictive so I would like to keep the test pipes in.

Just trying to get some opinions of what the best option would be?

right now current mods are:
2.5" true dual w/ x pipe and 2 resonators.
2.5" resonated TS1 test pipes.
440cc injectors
UTEC w/ map sensor
jwt pop charger w/ z tube.

in the future I am considering 11:1 pistons, rods, and jwt cams.


as far as exhaust considerations, these are what I am thinking:

Topspeed pro 1 w/ y pipe but using included silencers.

Custom single 3" to hks carbon muffler w/ resonator

custom 2.5" single to HKS carbon muffler w/ resonator.

any suggestions/ advice would be appreciated. Just trying to find the optimum setup for my goals. thansk in advance.

IMO, 2.5 true-dual is perfect for NA VQ35's. I have a Fast Intentions exhaust (2.5" piping with an X-Pipe), along with 2.5" resonated test pipes. I had great gains throughout ALL the RPM's (2000-7000 RPM's) with my current NA setup.

Normally 2.25-2.5 true dual is idea. I can't say for single since im not exactly sure.

just want to make sure I will have the right balance of flow with the setup i am pursuing. I know a lot of people use 2.5" true dual but I just want to make sure it will fit my needs correctly without sacrificing low end.

I talked to a muffler guy, one that has been in the business for over 40 years. This guy does some great work and will be doing my custom exhaust. He too said if you go with a true dual, that the maximum you should go with is 2.25 - 2.5".

For a single pipe, which I'll be going with, he recommends 3".

best flow and more power = single exit exhaust 2.75 to 3inch.( you may lose alittle down low but you will gain alot up top)

For NA, a 2" true dual would be ideal even with your high power/rev plans. 2.5" TD on these cars is overkill and probably hurts low to mid range power because the exhaust velocity is too low. The lack of exhaust velocity is why people report low/mid range suffering when adding high flow exhausts. The OEM single setup is nearly 2.5" ID. It's plenty large enough for these motors assuming you're NA. The most restrictive parts on the exhaust are the cats, manifolds, and then the muffler (in that order). 3" single is probably overkill. I had a 3" single on my 94 Z28 and 3" single are common place among the LS1 F-Body crowd. A 3" single can easily support 450whp and the LT1/LS1 motors move A LOT more air than the VQ does, even a VQ revving to 7200rpms. A 3" single would probably hurt low/mid range power and throttle response on your car. I'd stick with 2.5 and no more than 2.75".

I couldn't be happier with my Borla 2.25" dual with my magnaflow resonated X. But I have not had a chance to drive a car with the Stillen dual/X with 2.5" piping.

Hydrazine was very specific on what pipe sizes he experienced as ideal. Best way to get a really good/educated hands on opinion would be to search his posts. Luckily, he doesn't post that much and when he does, it's very educational.

He likes 2.25" and 2.5" piping. And 3" single exhaust depending on which cats and Y you are using.

these are the posts ive been reading. seems like daveB makes good points in all of his posts.

if the restrictive order is as such, then would an ideal setup be Dc headers, test pipes, stock y pipe and mid pipe, to an aftermarket muffler?

Like I said before, I have had great gains all around the RPM for NA. Even as low as 2000 RPM's, I have gained about 20 lb ft of torque. I don't see the 2.5 TD exhaust hurting me

In theory, I see what you're saying. But it doesn't seem to be the case for me. Not atleast for my setup.

whats is your setup?? im looking at getting a exhuast myself and im thinking bout going the same route you went but swap TS for FI HFC's

2.5" pipe works for torques increase.

Okay ignoring the above testimonials for now, why is 2.5" best for torque? In technical or dyno sheet terms?

Dave B has absolutely no clue as of what he is talking about. I've seen VQ30 maxima's make gains on a 3inch exhaust over a 2.5. At EVERY RPM. Same with Nissan KA24DE's, 3inch ehaust gain power at every RPM, and as much as 15whp at redline. And unlike DaveB, I have dyno graphs to back up what I say.

I've seen guys run single exhaust up to 3.5 with HUGE gains. Infact, I've been reading that single exhaust are actually better than true dual exhuast. When you have a dual exhaust, you need a properly placed X pipe to converge the exhaust gasses, and because of the 2 pipes, and the added drag, they don't seem to flow as well.

Got a post I can read about these VQ30 maximas running 3" na exhausts?