EVP Sidewinder SRX Thundercat/9000/King Cat ECU Programming with Maptuner X:
A note on Sidewinder/Thundercat exhausts: There are many others claiming that by putting their “magic” exhaust on that the boost pressure will increase by 2-3 lbs and wild horsepower gains are achieved. This is simply false. The ECU programming controls the boost electronically. When the programmed value is deviated from, (stock is 9.5-10lbs) there is a correction table which will actively move the boost back to the target value. Flow dividers or any other device after the turbine outlet does not change the fact that this table exists and will move the boost back to the target pressure. Anyone who is actually tuning this ECU knows this. If the wastegate flapper valve travel were limited (this is called locking the wastegate), this would allow the turbo to produce more boost, but the variables in turbo efficiency depending upon altitude or temperature would make this completely unworkable in addition to fighting the ecu boost correction and overboost limitations.
Without additional boost/fuel, it is impossible to make 30 more horsepower by just changing an exhaust. So why does the mixture lean out and where does the extra horsepower come from? The stock exhaust has a lot of back pressure. This resistance to flow contaminates the cylinders with gases from the previous combustion event which RICHENS the air fuel mixture because there is less available fresh air to burn. When you replace the factory exhaust with a free flowing one, now there is more fresh air to burn and the mixture LEANS out. The ECU does not run closed loop fueling, so it cannot compensate for this. Here is a video showing the stock tune with the EVP 2.5″ Bullet free flowing exhaust – it makes the exact same boost as with the stock muffler.