Black05

I'm finally about to do an exhaust mod.
Question is, what does the crossover pipe do?
Is it necessary?
What's the difference with that pipe compared to what I have now,the stock pipe?

TTZ06VETTE

I believe it evens out the exhaust pulses between engine banks

Seadawg

1.) As answered in the post above, it provides for greater engine efficiency by "balancing" the exhaust pulses.

2.) It is not absolutely necessary, but certainly desirable, thats why high performance cars have them.

3.) If you have a stock C6 exhaust system, I thought all of them had one, but maybe not. If you don't already have it, you should see a performance enhancement when it is installed with your new exhaust system. How much depends on many things, such as the style of new exhaust, other engine mods, tuning, etc.

cclive

The crossover allows each exhaust pulse to travel through both mufflers rather than being confined to only the one on that cylinder bank. It makes for better sound also, though slightly quieter than a system where the two sides of the system are completely isolated from eachother.

Gman in NC

The stock C6 exhaust does have a crossover. It's an 'H' pattern. A lot of aftermarket exhausts are 'X' pattern. Smoother I guess but I'm not sure what it does better.

RadarP3C

Yes, all stock C6's have a crossover pipe and I believe it's the H pipe through 2007 and changed to the X pipe from 2008 to the present.

Dave S

The crossover pipe in an exhaust system allows for balancing of the exhaust pulses & improved engine efficiency by virtue of more effective exhaust gas scavanging. All C6's to have crossover pipes of the "H" configuration. Aftermarket crossover pipes are usually of the "X" configuration, which is more effective since the exhaust flow is more direct. You'll also find that aftermarket headers such as American Racing also use the "X" pipe configuration for their hi-flo cats. As an aside, you'll also get much more of an exhaust "note" if you add an X-pile with aftermarket mufflers. Do you have to add an X-pipe? No....but why do the job half-way?

Chrisbert

Not Corvette, but same principles. Over on an F150 forum (my daily driver is my KR F150) there is a decent thread about exhaust systems:

http://www.f150online.com/forums/exh...ust-guide.html

LDB

None of the answers above are incorrect, but none mention what is causing the pulses that need to be evened out. With a V8, a cylinder fires every 90 degrees of crankshaft rotation, so that part is even firing. But the crankshaft only has 4 throws, not 8 throws, so you don’t have complete freedom to choose firing order. What you find if you scratch your head and think about it for a while is that on each bank, the firing sequence will be two intervals of 180 degrees of crank rotation between firing, one of 90 degrees, and one of 270 degrees. So the cylinder firing on each bank is not evenly spaced. The crossover pipe allows the exhaust system to partially compensate for that. When you get to the point that the 90 degree interval is firing on one bank, that’s also about the point where the 270 degree interval is occurring on the other bank, so the crossover pipe lets a bit of exhaust from the side that is firing on 90 degree interval at that instant cross over to the side that is on 270 degree interval at that instant.

Black05

Thank you all for the responses, although I have to admit that I didn't understand some of the technical stuff.
Looks like I'll be switching from H to X !

cclive

If you end up having a choice, go for the X, but don't let the X vs H make the decision for you on what system to buy. The difference will never be noticed.

cwing85b

I went with BB without X cross over. Very soon after I installed the X cross over simply because with out it I got a lot of exhaust "poping" when using compression to slow down. Some like the pop, I hate it. The X cross over eliminated all poping.

njfl

Same with me, but with the Corsa Xtreme. The X pipe definitely reduces the popping. It also quiets it down a little, but makes it sound a bit better on acceleration, but not too quiet as the Corsa Xtremes are pretty much a straight through pipe.

carl3989

I'm sure that your answer provides some insight. Perhaps you could recommend some type of glue that I could use to paste my poor head together. LOL

FortMorganAl

As LDB indicated, without a crossover the exhaust is uneven through each side. A crossover helps with that. But once the pressure is allowed to go from one side to the other, how it gets there is a trivial difference. You already have a crossover. Changing it seems a waste of money.

As a side note, changing pipe sizes is also a waste for most on a C6. You need a larger exhaust if you are going with FI or mods to get higher RPM but if you aren't doing that a larger exhaust pipe will tend to DECREASE performance. GM engineers created a pretty good design for the C6. A larger pipe size will decrease low end torque because it will reduce scavenging at low RPM.

LDB

How about this? Considering the whole engine, the 8 cylinders fire evenly, meaning bang, bang, bang, 8 times, evenly spaced, in a row. But if you just consider the 4 cylinders on the left bank of the V, or the 4 cylinders on the right bank, neither bank fires evenly. Each bank of 4 goes bang, pause, bang, bang, pause, bang, extra long pause, and repeat. Furthermore, it works out such that the short interval “bang, bang” on one side corresponds in time to the extra long pause on the other, so the crossover pipe lets some of the momentarily higher flow of exhaust from the short interval “bang, bang” cross over to the other side where there is momentarily lower flow because of that bank’s long pause. The earlier post tried to explain a bit more about why that is, namely degrees of crankshaft rotation between firing pulses related to a 4 throw, V8 crankshaft, but it sounds like it failed to do that clearly enough.

Tremelune

This was a handy post. I think this animation will help clarify. As you can see, each cylinder fires at a different moment, so the crossover allows each pulse to travel through both mufflers:

Red08

Cool!

jrose7004

That's fun to watch!