![]() ![]() Typically, you can see a few hp gains from swapping out the exhaust due to either an increase in diameter, or in flow rate, allowing the engine to spit out its post combustion gas more effectively leaving less residual gas in the chamber (reduction in backpressure). The only thing the exhaust does is channel the flow of exhaust gases out in a controlled manner. It does not change the amount of fuel/air in the chambers, or the compression ratio. The exhaust pipe itself, merits no additional horsepower. Given that we have no access to those documents, let me try my best.Īdding an aftermarket exhaust does not change anything other than the exhaust itself, this seems like a simple statement but allow me to elaborate. There seems to be a lot of questionable logic and here-say thrown about when it comes to aftermarket exhausts, and i would love to hear one of the development engineers offer up their technical paper on it. Turbos are special considerations for exhaust flow. If you start throwing in larger injectors, turbo, and raise the compression ratio, THEN you will see improvements from an aftermarket exhaust with increased diameter and reduced backpressure, typically in order to keep pyro temps down and provide better heat dispersion. Tuning is not required due to the computers a/f adjustments, however, if you chose to tune, tune for a leaner mix with a longer fueling window and you may be able to benefit mildly from the reduced backpressure and pipe diameter to keep temps low(er), but its all negligible at best. In conclusion, you buy an exhaust for the sound. This of course, changes wildly when you introduce a turbo into the equation, but this is an NA engine so well leave it at that. Barometric pressure, elevation, and ambient temperature account for sizeable differences in dyno graphs more than an exhaust. You could fart into your intake and show a gain of 1-3hp. Truth is, most of the dyno graphs showing 1-3hp gains can be attributed far more likely to environmental changes (ie adding one of the cooling fans at the dyno at the intake) than anything occurring with the actual engine exhaust flow. ![]() There seems to be a lot of questionable logic and here-say thrown about when it comes to aftermarket exhausts, and I would love to hear one of the development engineers offer up their technical paper on it. Id say it does more harm then good getting a full system without proper tuning (plus its expensive getting a full system but we are pretty limited for slipon options!) - if you just want looks and noise then maybe just get a slip on? That being said many people dont run ECU flashes or fuel controllers and they feel their bike is ok - maybe im just being picky. I ran my S1R on this bike without a fuel controller for a while and it was ok but it had power inconsistencies and popped like crazy which made the torque and power curve all over the shop - I dont like the feeling my bike isnt 'just right' so I wouldnt do it for a long time. If your going a slip on option then a fuel controller or flash isnt really required as you arent getting increased airflow so you are just getting looks and a loud exhaust. Forgetting the obvious power you'd be missing out on, most aftermarket full systems are straight through so you are going to get a truck load of popping as most if not all stock bikes run lean for emissions requirements and you just make it worse by adding a full system as airflow is increased due to less resistance. A PC (or other fuel controller) that has been tuned/mapped for an exhaust or a ECU tune is nearly always recommended by exhaust suppliers but its not a necessity. ![]()
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