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Old 11-07-2006, 03:21 AM   #21
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Back in WW2, they tried just about everything, including using a */C type setup to suck exhaust gases out of the motor. I believe it'* called after-charging. The problem is that it creates a huge drag on the motor, and uses more power than it produces.

And by the way, if backpressure has no use what-so-ever, why do we lose torque if we go too big on the exhaust? Just like everything else in an engine, backpressure can be tuned to help the engine operate more efficiently.
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Old 11-07-2006, 04:12 AM   #22
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It'* not the backpressure, but a drop in CFM. The goal is to get everything out as quickly as possible in the exhaust, but going to too big a pipe slows down the velocity of the gasses to the point to where the engine is hampered. If you go to big, it has to expand, and that kills your CFM and power.

Backpressure by definition isn't a good thing ANYWHERE. Backpressure in our context is a wave created by a physical flow restriction. Think of it on the intake side of things, you want air flow as smooth and unrestrictive as possible for maximum power. Going to big doesn't create backpressure.

Faster CFM also promotes more exhaust scavenging between cylinders, e.g. the velocity somewhat "pulls" the exhaust out of the cyl that just fired.

We're saying the same things, but with different terminology.. (i think)
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Old 11-07-2006, 05:22 PM   #23
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Quote:
Originally Posted by BonneMeMN
We're saying the same things, but with different terminology.. (i think)
I believe you are now speaking my language...
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