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      10-21-2012, 12:54 PM   #10
donsaxena
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Drives: BMW 135i
Join Date: Sep 2012
Location: oklahoma city

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Quote:
Originally Posted by Stohlen
All motors need backpressure to some extent. Like everything in cars, you have to find the perfect balance. A smaller pipe is going to have poor flow, but high velocity flow. A bigger pipe is going to have good flow, but low velocity flow. A motor needs velocity to help evacuate the cylinders of exhaust gasses, it creates a suction like effect that pulls the exhaust out of the engine. This works to a lesser extent on turbo cars as well, and while it doesnt have as much of an effect, it is still an important part of the engines operation. Take the exhaust off of your car at the turbo (or from the cylinders on an NA motor) and if you can stand the noise, you'll find that your car isn't as chipper as it once was.

I can go into all the details of exhaust pulses and the velocity effect if you like, but I find most people dont really like reading a novel and just skip over it. Essentially in short, you need to keep up as much exhaust velocity as posible to help evacuate the cylinders and pull exhaust through the turbo (rather than pushing it through) while not claughing the pipes and significantly lowering exhaust flow potentials.
Very good explanation thank you
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