I'll start with headers since thats where the exhaust system starts.
Headers. For the LS1, almost all headers have 1 3/4 inch primaries going into 3 inch
collectors. Tunded, Equal Length Headers are the best because the exaust pulses will
arrive in the collector at different times. This will reduce backpressure as much as
possible.
In order to not cause a kink in the system, the (2) 3" collectors need to merge into
a single 4" pipe (Y-pipe) or a dual 3" exhaust via an X-pipe (or duals w/an H-pipe).
This will provide a relatively restriction free flow for the exhaust gasses - the less
work the engine has to do pumping the exhaust through the pipes, the more HP goes to
the wheels.
The problem with a 4 inch exhaust is sound - I think it may be a bit loud.
The problem with a single 3 inch catback is it only supports about
400 flywheel horsepower before it starts robbing power like mad.
Comparisons:
Single 2.50 inch exhaust would give 31% decrease in flow vs a single 3 inch system.
Single 2.75 inch exhaust would give 16% decrease in flow vs a single 3 inch system.
Dual 2.00 inch exhaust would give about 11% decrease in flow vs a single 3 inch system.
Single 3.00 inch system - BASELINE
Dual 2.25 inch exhaust would give about 12% increase in flow vs a single 3 inch system.
Single 3.5 inch exhaust would give 36% increase in flow vs a single 3 inch system.
Dual 2.50 inch exhaust would give about 39% increase in flow vs a single 3 inch system.
Dual 2.75 inch exhaust would give about 68% increase in flow vs a single 3 inch system.
Single 4.00 inch exhaust would give 78% increase in flow vs a single 3 inch system.
Dual 3.00 inch exhaust would give 100% increase in flow vs a single 3 inch system.
What is the answer? Well, single 3 inch catbacks are popular and readily available, but
are unable to support the power levels that most people are achieving with moderate modifications.
In my opinion, it would be best to move up to either a single 3.5 inch catback or a dual 2.5 inch
system. I imagine the dual 2.5 inch would sound a little quieter than a single 3.5 inch.
Of course, I could be totally off in my guesstimation, but the numbers don't lie...a single 3 inch
isn't a whole lot of volume. Even a dual 2.25 exhaust flows over 10% better.
The only problem is: where do you put a dual exhaust system on our cars without killing the
clearance? If you have the answer, please email me: episode1@email.com
