[Z Code 400]

Ccass wrote "And we have performed numberous dyno tests and have seen pretty much the opposite. Additionally, there are many 'real-world' results that support it. One that comes to mind is Member 'hotrod' Running open headers; 10.90 1/4 mile. Adding full exhaust (100lbs) 10.80's with higher mph. (straight thru mufflers were used)"

We always...always ran some sort of muffler, even if it was nothing more than an extended collector with an inverted cone and our cars always ran faster with some sort of 'mufflers' installed. I do not find the above numbers surprising.

I would like to see the same tests run with and without the X pipe to see where the true benefit lies...Robert

[Ccass]

Here is a post that just coincidentally was posted on another site about 30 minutes before my post. With that kind of horsepower, the 3" X is probably undersized. Still it appears to have netted a gain.

"I recently tested my 3" X pype vs. a 18" 3.5" extension on the header.
The header collector is 3.5" and necks down immediately to the 3 inch
pipe and on to the X. Open headers with extension vs. necked down X, the
X won with 10hp across the board. My engine makes about 580hp with 461,
87cc eheads, solid 260/270 cam. Just some info to chew on. The X is a
lot quieter than the open extensions as well."

[Jim Hand]

Z Code 400.
Robert, apparently you are unaware of the extensive exhaust system testing Tom and I have performed over the years! And the performance portions of the testing have been done where the real effects of exhaust components become immediately obvious - the drag strip! And with exclusive use of the track, we were able to make run after run in a short time in order to minimize any variables in track and weather conditions. In addition we have used very precise pressure and temperature measuring equipment to measure these characteristics at various points on the exhaust system. I can assure you that back pressure has a negative effect on performance, and that is regardless of all the advertisements you have
read to the contrary

Here is a summary of some of our testing:

http://www.pontiacstreetperformance....p/exhaust.html

Jim Hand

[Z Code 400]

Jim,

On the contrary, I am very aware of your testing and I applaud your contribution to the hobby. We did much of the same back-to-back testing on several of our race cars, to include verifying the results on the Dyno.

I do not doubt people who post a '10 HP gain' with the X pipe, but what I am trying to explain is I have watched that 'Dr. Gas' system installed on a 500 HP BBC and it didn't pick up any HP or TQ. Simple as that.

Advertisments??? No, the word of tuners like Yunick and Iskenderian is far from a simple advertisement. Mario Andretti stading newt to a magnaflow Cat-Back Exhaust System is advertising.

I certainly appreciate the link. Keep up the good work...Robert

[Z Code 400]

By the way, what I thought was resonance inherent to the Flowmaster crossflow design was not. The pipes were hung in a slight 'bind' and when I bent the fingers to allow the pipes to relax, the noise went totally away.

I just had Pypes 2.50" stainless tips installed and it had a mellowing effect on the exhaust note that surprised me...Robert