Hey guys, I'm getting my dual exhaust today, what size piping do you guys recommend going from the race header to the mufflers? I was thinking just to go with 2 inch piping.........does bigger piping automatically mean more performance? I know some guys have up to 2.5 inch piping here.

 

if you are interested in max power for a N/A motor the optimum size is 1 7/8 primariers collecting into a 3" after the rear subframe. this keeps the gas volosity up and promotes scavenging. my car uses 2" inplace of the 1 7/8 because I couldn't find the smaller tube at the time. WARNING: this setup is very loud!!!!

 

SO you're saying to have an X setup then? Have the 2 pipes from the header collect, then Y back out again for a dual muffler setup?

Header
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X
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Mufflers

I was thinking just a true dual all the way.

Header
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Mufflers

What's the diff?

 

Hes talking about dual collecting into a single after the rear sub frame. This gives a little more top end power than duall all the way.

 

Wrong, that gives better low end than the true dual. More high end than a single outlet header, but less than a true dual system.


For the pipe size, the best way to do it is this: 2" pipes from the header for 48". Then flare it to 2 1/4 for half of the distance left to the mufflers, then for the last section use 2.5" to the mufflers. You will have the same low end power as 2" pipes all the way, with a little more peak power due to less restriction close to the end of the pipes. This is for mufflers with a 2.5" inlet. if it is something other, the last section of pipe should be the same size as the muffler inlet. Warning...this will be very loud. If youre concerned with noise you should get a pair of presilencers.

 

Most SCCA Improved Touring cars run a system like EProdRX7 explains. I'm guessing the SCCA E Productions cars do too by his signature. These cars are setup for max top end HP and geared to get it there (4.88 and 5.13 gears). If a true dual systems were giving more power they'd be used. Speedsource, which builds the quickest road racing IT NAs around uses a similar system. One of there team cars (at the ARRC) actually had a single 3" running well past the sub-frame when looking at the back of the car. Meaning the collector was closer to the header. If you're building an NA they're the people in the know.

Chris

 

Aha, another good recipe from the Guinness book of road racing.

 

One thing to not forget when getting custom exhaust work done. If the pipe bender is of the crush type the 2" pipe you are using will no longer be 2". Its easy to create a restriciton in the exhaust with that type of bender. If its a mandrel bender you should be OK.