Post by
jemil118 »
https://forums.nicoclub.com/jemil118-u1859.html
Wed Oct 23, 2002 3:22 pm
That would probably be a little hurtful on the engine...ever heard of valve over lap? It's a little complicated, and it only happens on high revving engines. Imagine the exhaust coming out of your car, not in one continuous stream, but in short bursts... The bursts(or pulses) vary in size, depending on the size of the engine or if it has been forced induced(is that a word). Anyway, the size of the exhaust system all depends on the size of the pulses. For example, you shouldn't put a three in. exhaust on a NA four banger. What happens is when the diameter of the pulses are smaller than the diameter of the piping, then the pulses don't exit the exhaust system properly, almost like they're bouncing back and forth inside the pipes. Now what happens when valve overlap occurs is the intake and the exhaust valves are open at the same time. The intake valve is just beginning to open and the exaust valve is about to close. Under normal circumstances the pulse that leaves the combustion chamber is almost sucked out by the pulse in front of it, because a vacuum has occured from the diameter of the piping being smaller than the diameter of the pulse. Now this only occurs at high rpms, and if the pulses aren't leaving the exaust system completely because they're"bouncing" back and forth, then when valve overlap occurs, then the exhaust pulses can be partially sucked into the combustion chamber. This'll cause a loss of rpms and even slight damage. The same thing can happen if you put dual exhaust on a four banger. You'd get two cylinders emptying into one 2 in. exhaust pipe. Now I'm sure that if you put 1 in diamter piping onto each side of the engine, then that could happen, but you would have to find a custom shop that is willing to bend some pipes for you...that would be a little expensive, and a little overkill
Whew...I'm outta breath