I'm almost ready to have the exhaust put on my VQ swapped 510 & have decided single exhaust is the best option for me (duals just won't look right on a 510 & I want to maintain some sleeper look, though it won't sound like one).

Anyways, back on target. I'm wondering if it would make sense to construct the Y pipe asymmetrically so it Y's just to the passenger side of the driveshaft's centerline. The reasoning is because of how the cylinders are staggered, passenger side further forward if my memory serves me right. Lengthening the drivers side portion of the Y & shortening the passenger side (if done right) will make it so the exhaust travels an equal distance before merging. The OEM & aftermarket design seems to be effectively unequal.

I imagine this has already be considered & the benefits are minimal, but was curious what the consensus is?

 

go for it, let us know.

 

From what I understand on an even firing engine like the VQ it should not matter or matter very little. The reason you see an H-pipe on a V-eight engine and the reason they are effective is because of the odd firing order.

Hope this helps

 

I could, & may end up doing it anyways for fitment reasons, but the "problem" is I won't have a before & after dyno to know whether it was beneficial or not.

As far as the firing order thing vs. V8's go, I don't know much about V8's & their exhaust dynamics, but it seems with a "even firing" VQ35 that anything you can do to keep the exhaust more even helps insure that exhaust pulses from each side are less likely to interfere with eachother, especially at the Y when they merge. Some of this logic comes from my 4-banger days in which a good Tri-Y header does it's best to get the runner lengths the same at each point where things merge. Just like a good header for the VQ has equal runner lengths. I have a feeling that the somewhat uneven nature of the stock exhaust lengths on each side before they merge is responsible for the distinctive VQ exhaust note (same with V8's) & may help with the low end torque.

Now that I think about it, I think the only case an asymmetrical Y pipe would be of benefit is when the header runners are even before merging. I couldn't fit an aftermarket header on this swap & had to use modified stock headers, which are not equal length runners, so in my case a Y pipe that tries to maintain equal lengths probably won't do much for me since it is already dealing with uneven exhaust pulses.

My logic may sound like a bunch of crock to someone that knows exhaust dynamics, so hopefully an expert will chime in.

 

Nobody with a better understanding of exhaust dynamics?

 

The best exhaust will always be of equal lengths. That being said, it not always possible. Symmetrical would be what I would shoot for and more important. The even fire and odd fire engine types are not all that different when it comes to exhaust. The main thing you are looking for is to move the spent gas out quickly and effectively and make use of the remaining energy to move the next gas pulse.

The trend today is bigger is better, which is absolutely false. It sounds neat but doesn't do much for exhaust dynamics. Think velocity.

Study PV=nRT where
P absolute pressure of the gas
V volume of the gas,
n number of moles of gas
R univesal gas constant
T the absolute temperature

If you look at it from this stand point, you'll be able to determine what the gas pulse is doing as it leaves the exhaust port.

Header length has more to do with valve timing, overlap. The key is you want that exhaust pulse to leave the header at about the time the next one is getting ready to leave. The only problem is the engine turns at different speeds so you would have to lengthen and shorten the header with varying engine speed, kind of tough to do.

A discussion on H pipes will get you multiple pages of what folks believe. The truth was is that they help eliminate standing waves in the exhaust system, the end result being less resonance and some power gains. The X pipe did the same, but allowed for a smoother flow and better gains.

An old school trick for finding the standing wave was to use cheap paint on the exhaust pipes. With the engine warm, spray the paint on there and watch where it bubbles first. Today we can use an infrared gun to see the standing wave.