[Double Venom]

Excel,

I too thought "back pressure" was a bad thing, Heck it even just sounds like a bad thing! I wish I could get technical for you, but I can't so I wont even try. However I will give you my latest information.

When we started building our first DV"s, we of course wanted every pony that was built into the V-10 that we could get out.
Thusly we were using almost straight through exhausts.

Racing and showing with the Vipers, we have had numerous contacts with some very knowledgeable Viper engine engineers.

The scenario stays pretty much the same, bunch of guys standing around shooting the breeze, when two of these "engineers" mentioned our custom made exhaust. Being pretty darn proud of what we built, I went into great detail about the "Step-up" headers we hand made, a filler block if you will for the 02 sensor, so that it could read all 5 tubes within the recommended 10"s of the heads, etc.

These two guys looked at each other and asked if I had ever put it on a mobile Dyno? answering"YES", I bragged that we were getting more than 412 RWHP! This is almost 15 more HP than any stock Viper was getting at the rear wheels at the time! Both were quite impressed, then stated, close up the "bullitts" a little adding more "backpressure" and you will get another 10 to 20 HP.

End of this tirade, I did. I changed the exhaust centers to what we now use on all our cars-definately adding more back pressure than a straight through system.

New dyno numbers - jumped 15.? RWHP, now reaching over 427 RWHP and the torque took a humongeous jump too!

In my opinion "back-pressure", the right amount at least IS needed!

For what it's worth!
DV