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08:32:12 - 04/20/2024
V6 Dakotas
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Aiden
Dodge Dakota
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6/10/2003
16:21:34
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 Subject: back pressure... good?
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Message:
a guy was telling me that back pressure was horrible i was under the impression that in certain cases (small engines) that it is good for torque, is this true? if soo how does it work?
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Jon
Dodge Dakota
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6/10/2003
18:48:22
| RE: back pressure... good?
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Message:
All engines, big or small need back pressure to produce good power and torque. If you have too much back pressure you will have no power because the exhaust can't get out of the engine fast enough. On the other side of things if there is no back pressure you will lose low end power. It is a delicate balance to tune the exhaust just right to make maximum power. Thats why companies spend millions designing mufflers, headers, and pipes that are designed to work together as a system. You need to have a certain amount of pressure in the system to help the exhuast scavenge, which means that the exhaust in the pipes will create a vacuum in the exhaust manifolds when the exhaust valve is closed, when the valve opens that vacuum will help suck the new exhuast out of the cylinder and help pull in the new air/fuel mix at the same time, this ensures that no old exhaust is left in the cylinder when the valve closes. If you don't have back pressure the exhaust flows out too fast and can't create a vacuum to scavenge the cylinders. At high rpm's everything happens so fast that it doesn't make a difference, thats why dragsters can run open headers because they are turning 8,000rpm all the way down the track.
-Jon
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