Yo...Tech heads...shhhhh...V8 question...

[VTEC_boi]

What exhuast option is best?

H-Pipe
X-Pipe
or side-pipes


Now...i don't really see how H and X will help...becuase it seems to me to just cause turbulence (i know it doesn't - but it just seems that way).

Explain? Fritz?

[fritz_269]

You remember all that stuff we've discussed about backpressure vs. delta-pressure and the idea of exhaust scavenging? See the sticky at the top of the forum if you don't...

Well, in your 4 cyl, you can scavenge between cylinders since they are right next to each other; but in a V8, the firing order jumps back and forth between banks (each side of four cylinders is a bank). If I have a dual exahust on a V8, each bank has a completely seperate exhaust route. By adding the crossover pipe, I now get that scavenging wave from one bank across to the other.

X pipes are generally considered a little better from a standpoint of turbulence, but H pipes work almost as well and are a LOT easier to route and install. They generally boost mid-range power significantly; but they may not affect the peak, high-RPM power much at all. Most people try to get them as close as possible to the collector to push the effect as high in the rpm band as possible.

But both the H- and X-pipes work (and they do work!) by allowing us to exhaust scavenge across banks.

[Crackerman]

In general x-pipes will almost always out perform h- pipes side pipes or even open headers. In carcraft a few months ago they dynoed a cutlass with open headers, x-pipe and h-pipe and no balance tube. The x-pipe had more peak horsepower and torque and more of each "under the curve" also.. Which equals extreme driveability and fun. With a balance pipe the exhaust note is much smoother and quieter. So you don't have to deal with head splitting resonance.

[Someguy]

As close to the collector as possible? Hmm... Well, I guess it depends on the legnth of the primary tubes of the headers. Usually the cross over ends up being some 4-5 feet down stream from the exhaust ports, which is pretty close to the collectors of a lot of headers.

Anyway, like fritz was saying, it acts basically like an extention to the purpose of headers. Instead of just scavenging from cylinder to cylinder, you can also scavenge from bank to bank.

Most V8s have a L-L-R-L-R-R-L-R-L-L... ect firing order, which is why they have a fairly unique exhaust note. But like Crackerman said, with out some sort of balancer pipe it would resonant like crazy.

[fritz_269]

Originally posted by Someguy
As close to the collector as possible? Hmm... Well, I guess it depends on the legnth of the primary tubes of the headers. Usually the cross over ends up being some 4-5 feet down stream from the exhaust ports, which is pretty close to the collectors of a lot of headers.

That's basically what I meant. In most V8 configs, you really can't get any sort of crossover pipe any closer to the engine than across the bottom of the tranny. If you have decent headers, then the collector is pretty much right there. If you have stock "shorty" iron headers from a target engine, under the tranny is still the closest you can get a crossover (although you'd be better off spending that money towards a new set of headers!)

Most V8s have a L-L-R-L-R-R-L-R-L-L... ect firing order, which is why they have a fairly unique exhaust note. But like Crackerman said, with out some sort of balancer pipe it would resonant like crazy.

As a random point of interest, Small Block Chevy order is 1-8-4-3-6-5-7-2, which would be L-R-L-L-R-R-R-L.

Just to make sure we're still on the same page here, is what you call a "balancer pipe" the same thing as a "crossover pipe"? I have stock dual exhausts on my '64 El Camino (without a crossover pipe) and have never had problems with it "resonating like crazy".

[VTEC_boi]

Ah...can u 'dive deeper' into explaining the physics behind why an H or X pipe works?

I heard a newer Saleen the other day, who has X-pipes (a friend from church..her boyfriend knows the guy i guess) and it sounded AWESOME


o yeah..I'm a 4-cyl. guy! I forgot

[Someguy]

Originally posted by fritz_269

As a random point of interest, Small Block Chevy order is 1-8-4-3-6-5-7-2, which would be L-R-L-L-R-R-R-L.

You should probably just ignore what I said before. Must of been day dreaming here at work. Lots of different manufactures have used different firing orders for V8s.

Just to make sure we're still on the same page here, is what you call a "balancer pipe" the same thing as a "crossover pipe"? I have stock dual exhausts on my '64 El Camino (without a crossover pipe) and have never had problems with it "resonating like crazy".

Yeah, although I'm kinda in left field today...

[fritz_269]

Originally posted by VTEC_boi
Ah...can u 'dive deeper' into explaining the physics behind why an H or X pipe works?

Read this thread (again) - particularly that first (long) post.
http://www.automotiveforums.com/vbulletin/t13199.html

Now, do you understand what exhaust scavenging is?

[Crackerman]

In your el camino if you don't have headers or a larger cam then stock, you probably wouldn't even notice the thrumming or deaffening drone that gives you a headache, usually aroud 2,000 to 3,000 rpm in a cruise with a slight load on the engine(up a hill) the car will usualy try to shake itself to death then. Cross over pipe is the same as a balance pipe or even an x-pipe. Usually try to install them as close to the collector as possible but still infront of the cats or mufflers if they are in the way. The tailshaft of the tranny or the first couple of inches of the driveshaft is probably the easiest place to mount them.