X-pipe

[bmergner]

still have not done my exhaust yet but iam getting there. had anyone did a x-pipe before and after? any sound difference or perf gains on the Mark VIII. i have 1995 with stock exhaust now and going to run true duals so i was thinking of adding a x-pipe. any input would be great.

 

[beerdog]

an x pipe or a Xpipe muffler is a must with a custom exhaust. The exhaust will flow better since you currently have a 3rd cat where the X-pipe will go. There are a bazzilion threads on this topic.

 

[chris2523]

or H pipe.
i think an H pipe has a deeper tone than an x pipe.

 

[KStromberg]

An x-pipe will scavenge the exhaust better. If there is any quantifiable gains, expect the gains on an x-pipe to be greater than that of an h. The h-pipe will have a more conservative sound.

http://www.carcraft.com/techarticles/exhaust_system_installation/index.html

 

[driller]

Consider the H-pipe best for pushrod or SOHC engines and the X-pipe better for more high revving DOHC engines.

 

[J]

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Can you do the temperature test before installing the X pipe? There IS an optimum placement for the X, putting them randomly in the system (before AND after) will definitely hinder performance.

 

[steve]

An x-pipe will scavenge the exhaust better. If there is any quantifiable gains, expect the gains on an x-pipe to be greater than that of an h. The h-pipe will have a more conservative sound.

http://www.carcraft.com/techarticles/exhaust_system_installation/index.html

the corvettes come with an H pipe, but the hole is tiny in the cross over pipe, i think it is more for pressure balancing then over all performance.

 

[BadSax]

I don't know if this is something I've asked in the past, or only thought about... but I just don't get the whole X pipe thing...

Might as well just have the non LSC system... in my mind, true duels means that each pipe carries only the exhaust flow from the side of the block it is attached to...

I know "everyone says" that the X pipe gives you more power, or whatever, but I don't understand why...

 

[J]

It's all about equalizing (balancing) the pressure between each bank (side) of the engine. As each cylinder fires it throws off the balance.

 

[george2]

I've always thought it was more about velocity. and the two flows working together to make a "vacuum" on the opposite bank.

 

[J]

I get what you're saying but there's definitely NO vacuum effect going on. If you had that effect, that would mean no back pressure and the engine wouldn't run.

 

[billcu]

It's not vacuum, it's scavenging.

An engine will run without back pressure, ever run an engine without exhaust manifolds?

 

[DLF]

I get what you're saying but there's definitely NO vacuum effect going on. If you had that effect, that would mean no back pressure and the engine wouldn't run.

It's not vacuum, it's scavenging.

An engine will run without back pressure, ever run an engine without exhaust manifolds?

Absolutely correct!

The false "back pressure" theory dates back to carbureted engines that couldn't automatically adjust the A/F ratio after exhaust upgrades.

HERE is an explanation.

 

[BadSax]

Ok, that was an interesting read, but didn't answer my X pipe question.

I understand the basics of how something flows, but are there really measurable gains by mixing the left and right exhaust flows?

I just can't help but think there is zero difference, or really that it would cause increased pressure, and not be helpful at all.

awaits answer

 

[DLF]

H vs. X is primarily an issue of sound, however, the X-Pipe will flow a bit better at higher RPM's. Either are better than no cross-over at all.

 

[steve]

I think they first used them in NASCAR, so you know the rednecks know how to make more power, that is were they will provide the most benefit. In a street car you won't get a SOTP gain but could measure the gain on a dyno or at the track and also when used with other exhaust modifications.
BTW they mostly benefit V8 engines due the the pulsing of the firing order of the cylenders.

It has been proven time and again that the X-pipe design is more efficient than the H-pipe. Various tests have shown that for multiple cylinder engines the X-pipe outperforms H-pipe exhaust systems, especially as rpm increases, providing both better torque and power. Unified exhaust pipes work most efficiently with multiple cylinders because of the scavenging effect. With exhaust X-pipes the almost seamless connection between the two exhaust pipes allows sequential firing cylinders to salvage any spent exhaust gases from the combustion chamber more efficiently and creates more room in the cylinder for a fresh intake of undiluted fuel and air. When you have two exhaust pipes, as the velocity in one header tube increases, the pressure in the adjacent tube is lowered causing the exhaust to be sucked out of that cylinder. X-pipes are simply better at doing the job, especially at higher speeds.

Ok, that was an interesting read, but didn't answer my X pipe question.

I understand the basics of how something flows, but are there really measurable gains by mixing the left and right exhaust flows?

I just can't help but think there is zero difference, or really that it would cause increased pressure, and not be helpful at all.

awaits answer

 

[J]

The false "back pressure" theory dates back to carbureted engines that couldn't automatically adjust the A/F ratio after exhaust upgrades.

You over analyzed what I wrote. I said if you had a vacuum effect there would be no back pressure and the engine wouldn't run. The exhaust isn't a vacuum, if it was, the engine wouldn't run.

I, of all people, OBBVIOUSLY know that an engine doesn't need back pressure to run. That still doesn't change the fact that if you don't have the right amount of pressures that the engine won't run right.

 

[J]

It's all about equalizing (balancing) the pressure between each bank (side) of the engine. As each cylinder fires it throws off the balance.

BTW they mostly benefit V8 engines due the the pulsing of the firing order of the cylenders.

Glad we are on the same page with that atleast.

 

[BadSax]

I dunno... I still think an X pipe is basically BS...

why would it matter where in the system the x pipe is placed?

 

[DLF]

If you had that effect, that would mean no back pressure and the engine wouldn't run.

You over analyzed what I wrote. I said if you had a vacuum effect there would be no back pressure and the engine wouldn't run. The exhaust isn't a vacuum, if it was, the engine wouldn't run.

I, of all people, OBBVIOUSLY know that an engine doesn't need back pressure to run. That still doesn't change the fact that if you don't have the right amount of pressures that the engine won't run right.

I don't think I misunderstood, you keep making statements that the engine wouldn't run under this or that condition, which simply aren't correct.

The value of properly tuned headers/exhaust is the scavenging effect (a slight vacuum) seen at the exhaust ports prior to the exhaust valve opening caused by the exhaust velocity of the other cylinders. If, in fact, you could have negative pressure in the exhaust system, the engine would run better due to more complete emptying/filling of the cylinders.

More reading HERE.