Maxima Forums - What's Back Pressure????

Backpressure is basically the ease the exhaust gas flows out. If you tried to blow into a small diameter straw, you would have a tougher time than blowing thru a large diameter straw, hence the "backpressure". In general, for cars, you want minimal backpressure for the exhaust by utilizing a free flowing exhaust system. Excessive backpressure will not allow the burnt fuel mixture to completely exit the combustion chamber and so a totally fresh charge of fuel and air cannot be sucked in. But...., (there always is a butt:laugh: ) a exhaust system that has too little backpressure is not good either. Bigger is not always better.
It's a fine line that has to be met. You need some backpressure to maintain the scavaging effect inside the cylinder when the intake and exhaust valve overlap. It starts to get kinda technical after that, so I'll end it here. I hope this helps.