This is going to be hard to swallow for a lot of people here so I am STILL expecting denial, which is the most predictable response here.
This car has 3" headers merging into a single 3.5" exhaust. A 2.5" dual exhaust was tried which made less horsepower.
Even when the motor was stock with only an intake and dual 3" headers and 3.5" single it still made more power than stock. 279whp http://my350z.com/forum/na-builds/39...-roadster.html
It got to a 327whp with a stock motor and more boltons. http://my350z.com/forum/na-builds/47...ideo-pics.html

Since I am using stock headers which have only 2" collectors and test pipes that are 2.5" with divorced 3" singles I have more backpressure then that car BUT still make more power over stock or a 2.5" dual exhaust.
http://my350z.com/forum/na-builds/50...ml#post8821049

Then I'm really screwed, my Borla is only 2.25in duals, I think. Sounds great with that X-Pipe though

You mean bigger exhaust with headers and cams and a spacer and a 3" intake and so on to fill up the increased volume. Thennn it all makes sense but a bigger exhaust alone? Never.

I agree.. if you have all those other upgrades then it would make more power. But can't say for a stock car to go 3inch all the way will give you more power... =/

I beleive it and seen it many times on VQ35de's.

aj update you sig foo

Who here can name one stock Revup (350z or G35) with an intake, 2.5" headers with a dual 2.5" exhaust that made more power than this stock Revup with 3" headers, single 3.5" exhaust and an intake? http://my350z.com/forum/na-builds/39...-roadster.html

There are none even though there have been plenty of people with 2.5" headers and 2.5" exhaust + an intake on a stock motor.

I think the debate is FAR from over. What you're saying really doesn't make and sense and you're trying to apply way to many variables to argue your opinion as fact.

Go to the strip and get 5+ runs. Record density air conditions and correct ET/MPH for DA.

Put the stock exhaust on and go back to the strip and get 5+ runs. Record density air conditions and correct ET/MPH for DA.

Compare MPH results. If the car is consistently over 1mph faster with the 3" exhaust, then you validate your claim that the 3" exhaust is making more power.

Did they test a Revup an intake, 2.5" headers with a dual 2.5" exhaust on THIS dyno and compare the two? If not, your argument has NO basis.

Andrei, you need to read a little more and verbalize a little less - or at least try asking questions when you really are not sure... If you read a little more about exhaust theory and you will learn that piping size is just one variable. SGSash has posted some nice threads, so thanks for the links to those, I guess...

I knew about that LTH header design. I was all for it until I saw the price. If I had the cash, I'd have them right now. Quality looks on point and I don't doubt the gains. This header and exhaust design alone would would probably put the REVUP over the Non-REVUP with cams and bolt-ons and into HR territory.

So far as for our exhausts, bigger is better without a doubt to an extent. That's one of the reasons I went with the X02 over the HKS due to it's bigger piping diameter at a cheaper price.

The only thing I don't see in that build is a merge. I still haven't seen how merges such as x-pipes and h-pipes effect the VQ with a true dual. No factual dyno's to prove the myth over no merge vs x-pipes vs h-pipes.

Here's some more good info done by Motordyne themselves on exhaust testing. Pretty good read. http://my350z.com/forum/intake-exhau...ml#post7412469

H and X pipes help the scavenging effect to help promote higher exhaust gas velocities (which is what everyone really wants here).

One side will "pull" the exhuast from the other side and vice versa.

Of course we know the scavenging effects of merge pipes but the question is how they effect the VQ in relation to the distance from the engine to the merge. In other words, X and H pipes may even have no effects if put too far down stream or up stream. Still haven't seen a specific VQ x-pipe/h-pipe dyno.

Correct. When I put my X pipe on to my borla (that has no X or H), I tried to see where the best place would be (within reason). I researched where Motordyne put there Y merger and where Stillen puts there X pipes.

One thing I have noticed working on these cars

Yes you can get more horsepower out of breathing mods and the correct tuning
but you will always lose out on TQ if you go that route