[Fishin2Deep4U]

Originally Posted by Formulajones

There is no restriction with the transverse, provided you use a good transverse like the Pypes or dynomax 2 1/2" mandrel bent systems. With that said there are no gains to be found going dual mufflers all else being equal. I've been back and forth with that with no ET to be found on a mild 12 second car and in fact it's fine on an 11 second car.
There are Pypes Transverse systems used in the PS drags with those cars running deep into the 11's and high 10's, and the rules dictate a stock configuration exhaust and has to be 2 1/2" maximum. In fact that exhaust rule is still applied in the FAST class too, and plenty of those cars going even quicker.

If you really started pushing the HP pipe size would be more of a player.

I think where this stems from is the old stock type transverse systems from 50 years ago or the reproduction Gardner stuff. I tested that too and I can say without a doubt if you use a stock type transverse with crush bent 2 1/4" pipes and the stock type muffler from Gardner, it's a huge restriction. My bird was stuck at 14.0's at 98-99 mph with that system.

As soon as I replaced that with a Flowmaster Force II transverse system (2 1/2" mandrel bent) it immediately went 13.70 at 102 mph and a couple more passes was going 13.60's. Never touched a thing under the hood.
Granted the Flowmaster chamber muffers are pretty restrictive themselves, yet that system was worth a solid 30+ HP over the stock Gardner transverse setup.

I later installed a Pypes setup, still transverse, still 2 1/2", but the muffler design is worlds ahead of any chamber design. This system also has an "X" cross vs an "H"
I have the car now going bottom 13's in the heat consistently with a best of 12.79 at 106 mph. Still the same bone stock RAIII engine.

Very much appreciate the info.

I wonder if a case can be made for max HP for a given pipe size. I am not making big power at all. I am going to throw a set of heads on and would like to get to 500-550 and still have great street manners. The transaxle setup would be much better clearance wise even though I would most likely have to fab up the axle area pipes to clear the suspension and 315's.