I would like some feed back regarding putting an x pipe right behind my 2 MagnaFlow cats. It's the only place there is any room and it is where both pipes are level side by side. I currently have a true dual exhaust system. Long tube headers 2.5" pipe, Magaflow cats and Flowmaster 44 mufflers. Pros and cons of doing this modification would be ? I priced different x-pipes on ebay and the MagnaFlow x-pipe is $100. Other brands same size are as it the as $35.

 

The function of an X- or H-pipe is generally not well understood. The first step to understanding is to realize exhaust flow is not a steady stream - it comes in pulses (I know, duh). The dynamics of pulsed flow is quite different than a steady stream, so that's why it matters.

Things like "reflected wave" and "speed of sound" are involved. When a pressure pulse moves through a pipe, it will move along until it comes to a break in the pipe - when that happens, the flow will continue, but a pressure wave is reflected back up the pipe. When that wave hits a wall or break, it is then reflected back down the pipe. The speed of the wave is determined by the speed of sound of the exhaust gases, which varies with gas density (which is affected by temperature, gas composition, etc.).

The key is to get the reflected wave to move back down the pipe when the next pressure pulse comes - this means it leaves a low pressure zone when it moves away, making it easier for the coming pulse to move. This is commonly called "savaging", and is a pretty good description.

So, the best location for the X-pipe is the distance from the header collector that makes for the best reflected wave timing. As you might already realize, no one location is ideal for all operating conditions (load, engine RPM, etc.).

But...

The cats can also produce a break in the flow path that reflects a pressure wave. So, it's a bit more difficult to get the X-pipe to be the primary reflected wave generator. And, the cats aren't in the "ideal" location in the pipe. You're basically giving the post-cat exhaust two paths to follow for the least restriction. (It will also affect exhaust tone to some extent.)

Bottom line: It's fine to put it behind the cats.

 

How do you feel about what brand of X pipe to use ? The weld quality is my thought. The union is pretty straight forward right ? Would you use a X pipe in my system or would you leave it as is ?

 

I have a Magnaflow 3" exhaust system in my '57, and the X-pipe quality is top notch. I can't speak for the others, as I haven't seen them.

I would say go ahead and install it, but you may not see a big change. I don't know much about the Flowmaster 44's, but from my other experiences with Flowmaster, they either don't flow that well, or don't sound that good. The X-pipe should help if either are the case for the 44's.

 

The Flowmaster 44's are wo cjamber and that is why the resonance but they flow well. If money was no object I would buy Billy Boat or Corsa. I was on a budget and paid for the entire exhaust system Hedman headers $500, Magnaflow cats $150, Flowmaster 44 $30 yes $30 off a guy in Fountain Hills AZ and the labor for the muffler shop to bend, cut and weld it in $300. I was qouted $120 to cut and weld the X pipe in so now it is a matter of what X pipe to buy ? As long as it wouldn't rob the engine of any power and if it can cut the noise in the cab down a little it sounds like a good thing to do.

 

Not much of a chance it'll rob power. Hard to say how much difference it'll make in exhaust tone.

 

My opinion is; you are wasting money And going to make the car slower due to the added weight if you put an X pipe behind the cats. Relocate the cats and get the x-pipe as close to the front as possible.

 

That is the wrong place for the X-pipe, for the reason explained in my first reply. Somewhere between 20"-30" downstream from the header collector, depending upon your RPM operating range, is the correct location. Putting the cats behind the X-pipe will reduce their efficiency due to heat loss.

 

The function of the cats are to collect soot from egr. They are not a performance enhancing. Want a power improvement, remove the cats. It makes no sense to me why you would put an x pipe behind the cat or aft of the cat in the exhaust stream. The purpose of the x pipe is to scavage exhaust gases from the cylinders in order for there to be cooler more dense air for combustion.

 

The cats don't "collect soot". They catalyze harmful exhaust gases to less harmful exhaust gases.

That being their function doesn't mean they don't have other effects. If you have to have cats (and every C4 driven on U.S. public highways/byways/streets have to have cats), then you let them do their thing and do what you can to minimize the other effects.

Ideally, the X-pipe would be in a straight, smooth pipe 20-30" from the collectors. But, we don't live in an ideal world. As I already stated, the cats would probably reduce the effects of the X-pipe, but that doesn't mean they would negate all of the favorable effects of the X-pipe.

Whether or not it is "worth it"? That's a case-by-case call.