Theo, a very interesting comparison of the H pipe and the X pipe. I was
surprised to see the H pipe come out ahead of the X pipe in the dyno
test, but of course with the same/same on the car, except the two
different exhaust, the dyno does not lie.
I would have expected the X pipe to be slightly ahead, but no.
Frank, I looked at the X pipe, but I could see no way to put it in. Of
course you could shorten the collectors , but that hurts the torque
curve. And Theo's suggestion of angling the collectors would help get
it in, Maybe. But why do this if the torque and HP are the same or
better with the H pipe.
I should also add, that when I hit the H pipe on a clearance issue, I
also hit the frame X member, so the H pipe is tucked up very well.
Exhaust systems are part science, part art, and you have to look at what
you are going to do with the car.
I was surprised to see an article on a single mnf brand of headers for a
Mustang 5.0L. They compared on the dyno of course, shorty, equal length
shorty, equal length, all in 1 5/8" diameter, and a equal length in 1
3/4" diameter. The surprise is that the larger diameter did not help
but 2-4 hp and torque, and the shorty headers were not off the mark but
the same amount.
Also going to larger diameter pipes after the headers will change the
torque and hp curves. I wanted a torque motor, so 2 1/4" diameter pipes
was the max for my 5.0L engine, with only 1:7 ratio roller rockers, and
stock cam. Of course the roller rockers change the valve opening, but
not the overlap, so again, helps a torque motor.
Only the dyno tells the True Story, not the claims posted on EBay of a
289 with 350 HP, or a 5.0 L with 400 HP. That is a pure figment of
someone's imagination.
The guys at CAT with Dyno Day know this to be true.
Larry
Theo Smit wrote:
>Steve, and Listers,
>
>Larry's exhaust is a (very nice) example of an H-pipe crossover. A popular
>modification on late-model Mustangs is to install an X-pipe crossover, so
>dubbed because the pipes have 45 degree elbows immediately aft of the header
>collectors, the pipes meet in the middle, and then have a 90 degree bend so
>that they again separate at 45 degrees (relative to the long axis of the
>car). This is supposed to give some slight performance benefit over H pipes,
>but obviously is hard to do on an installation as tight as the Tiger's, at
>least if you use production headers like Rick's or CAT's. If you were to do
>up a custom header set where the collector exits were already aimed at 45
>degrees inward, then you might save enough room front-to-back to get it all
>to fit in.
>
>http://www.ampperformance.com/store/bxpipe.htm
>http://www.mustang50magazine.com/techarticles/4376/index1.html
>
>Best regards,
>Theo
|