What Pete said and Rossco929.Pete said:Also depends on the OEM exhaust headers. The current breed of sportbikes have exhaust headers designed for top-notch performance; it's the can that is used to bring things to within the parameters set by governing bodies like the EPA.
POSER!! Sorry I had to. I've been taking alot of poser heat lately and felt I should spread it around.Birdman said:Your ZX-6R's headers are probably fine. But it was a different story on the XX. Instead of calling the stock system a 4-into-1-into-2 they should call it a 4-into-campbell's soup can-into-2. Seriously!! The collector that the headers dumped into looked like a squashed soup can sitting sideways not lenghtways with four pipes coming in one side and two coming out the other. I'm sure that's real good for efficient gas flow. Switching to an Akra 4-into-1 and rejetting netted 12HP. Bash those numbers and I'll post the dyno printout to prove it! And no, I didn't need the extra power. I did it because I like the way it looks and I like the way it sounds. Now before the "poser" flames begin, take note that the emphasis is "I" like it. I did it for me. Not to impress anybody else!! Geez, that's a lot to say just to avoid flames, which will no doubt still happen. Well I say, bring it on.
Oh a slip on will probably get you within a couple HP of a full system on the newer bikes. Hell, you can vary that much with the air temperature difference between morning and afternoon.