I've seen a million discussions on the relative merits of "X" pipes and "H" pipes.

However, I have yet to see any meaningful discussion on the two different types of "X" pipes that are available.


For the purpose of this discussion, I will call one type a "HARD X" and the other type a "SIAMESE X".

Also, for the purpose of this discussion, I want to leave out any considerations of what fits a particular car and what doesn't. I want to address this as a strictly theoretical issue.


In a "Hard X", the pipes are designed in such a way that it appears that most of the exhaust coming from the driver's side of the engine crosses over to the other side, and exits the exhaust system on the passenger side of the car, and vice versa. As a way of visualizing, it looks somewhat like this:
X


In a "Siamese X", the pipes are designed in such a way that it appears that most of the exhaust stays on the same side of the system, with a fairly small amount actually crossing over to the other side.
As a way of visualizing, it looks somewhat like this:
)(


My thinking, which may be wrong, is that in a "Hard X", both the sonic pressure wave and the actual exhaust has a very good opportunity to travel back up the system on it's opposite side.

In a "Siamese X", it doesn't look like this would happen.


Can anyone with either some direct experience on this issue, or a better understanding of fluid dynamics than I have, shed some light on this?

As I said, I would tend to think that the "Siamese X" is a superior design, but I want to do a reality check before spending my money.

 

I highly doubt there is much difference. If any, I think the "Hard" x pipe would create a more even flow between the two pipes and the siamese would be more cluttered. But I dunno, I don't think there is going to be much difference at all between the two.

 

My local exhaust shop now makes all their "x" pipes
and bases the style of "x" on the fitment need of the
car. They are more of the siamesed style you described.

I have no idea what the performance differences would
be. I have a siamesed "parallel pipe" setup in my exhaust
and have no idea what it does relative to a true "x". The
true dual is a definate improvement to a single though.

 

I guess my thinking was that in a siamese type of pipe, which allows the exhaust flows from both sides to get parallel before the opening, only the "overpressure", for lack of a better word, would get across.

In an X type of pipe, the sound waves would, I assume, propagate equally all around when they come to the intersection, and it would appear that there is a good opportunity for some of that wave front to travel UP the other side. Same with some of the exhaust gas.


Of course, since I don't understand fluid dynamics all that well, even after trying to, I could be completely off base, which is why I'm doing a reality check.