will the 2.5 exhaust that everyone sell support 500whp,600whp or will i NEED 3 inch exhaust? what is the hp level where 3 inch exhaust is real needed. i have seen kits for the 2.5 that look nice and i plan on using flow master mufflers to complement the system. any input would be great.

 

My 2 1/2 is supporting my 409 RWHP about 500 crank HP no problem. Should have a little room to grow also.

 

You MAY find that with a 3" system you'll lose a little on the low end as you'll lose some effective exhaust scavenging. Engines need some back pressure to make the best power and exhaust efficiency. The 3" pipes will really shine at high rpm's. Whether you'll be driving the car to those levels often enough to justify 3" pipes only you can answer.

The 2 1/2" pipes will give somewhat better low end, and maybe mid-range as well. At the higher end when the engine is screaming it doesn't need help with exhaust velocity...that why you'll see drag racers running open headers. They're putting out such extreme horsepower that exhaust velocity and scavenging isn't an issue and they would blow mufflers clean off the car anyway.

Exhaust design is a science in itself...it's more than simply sticking a random size pipe and muffler on it and expect it to perform optimally. Manufacturers and aftermarket suppliers spend a lot of engineering time and effort designing their products.

As an example, back in WWII, the Pratt & Whitney R2800 engine used in the P47 Thunderbolt put out something like 2000 hp. The P&W engineers, after research, trial and error, squeezed several hundred more horsepower out of the engine by routing the exhaust properly and in a way to keep the pipes within the tight engine cowling.