what is the truth about back pressure and the turbo does it really need some back pressure to make the turbo last or is this just BS. If back pressure is needed how much is needed?
I agree with this guy. Don't let people tell you that no exhaust is too big for a turbo diesel.Well the turbo does provide a good amount of drive pressure to the engine already. Now a turbo diesel is less sensitive to backpressure when compared to a gasser but not totally immune. Running an exhaust that is too big will cause eddies, or swirling masses of a fluid, in your exhaust and hurt performance. Now just exactly how big is too big, well that is relative to the amount of fuel you have going into your motor. On stock fuel frankly I would not go over 4" but if you add some fuel a 5" exhaust should be ok. Unless you are pushing around 1000rwhp or so a 6" exhaust is not going to help you. There is some debate over whether even a 5" exhaust is too big or not, in my experience I have noticed no increase in turbo lag or anything of that nature. My EGTs are around 200 degrees cooler at heavy throttle compared to my factory exhaust. Ok that was kinda a rant...sorry.