[CobraEd]

I agree that the Top Fuel pipes would not be optimal for any street car, that was just an example of tuning for the particular application, but my point is that each system must be tuned for each car. Again, lets not confuse backpressure with proper scavenging, they are not the same thing, and backpressure by itself in pure terms is not a good thing.

For any particular car, given the proper "tuning" of the exhast for optimal pulse scavenging at the desired RPM, with the mixture optimized to the exhast, you want the least backpressure possible.

The reason why some backpressure is sometimes called "needed" or "good" is to compensate for an overall exhast system that is not tuned properly (header pipe diameter/length, collector diameter/length) or more commonly where the mixture is not correct (typically too lean)

If the newer Vipers have less aggressive camshafts, then rather than increase backpressure (a compromise) to work with less overlap and combustion chamber scavenging, the primary pipe length on the headers should have been made longer, and perhaps the diameter should have been made a little smaller. This is standard practice. But again, this is proper exhast tuning, not the adding of backpressure such as making a muffler more restrictive.

Ed I would have to believe, that had you reduced the primary diameter of your header pipes, or just removed the steps where you had them getting wider, and made the primary pipes a little longer instead of restricting your mufflers, you would have made WAY more power. The Viper guys knew that would mean reworking everything, and probable gave you a good compromis solution. If you are talking to them ask them about this. It would be interesting to see what they say.

Ed