|
Mechanically it's caused by valve duration overlap. As you let off the throttle and the engine revs down, alittle exhaust gas gets sucked back into the combustion chamber. This "burble" is the change in exhaust pulse. Performance exhaust makes it louder and cars with valvetronic can be programmed to leave the exhaust cam timing alittle retarded longer. By product of the exhaust cam timing is more top end power.
|