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Old 02-24-2010, 09:48 AM   #1
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Default supercharger and back pressure

thought id post it here where it is not realy specificly related to bonnies.....with supercharged car is back pressure good or would it be better to have as little pressure as possibul ???
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Old 02-24-2010, 09:52 AM   #2
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You want some back pressure but not too much that it is restricting, now if you have a turbo then you can do anything to clear that exhaust out of there
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Old 02-24-2010, 09:55 AM   #3
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seei always thought it was the other way around cause with a turbo the more back pressure the more the turbo will go ...wont it ??
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Old 02-24-2010, 09:57 AM   #4
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the gases coming out of the heads make the turbo spool up, the more air you can get through the turbo the faster it will spin, at least thats how I understand it
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Old 02-24-2010, 10:05 AM   #5
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With a turbo its all about making the gas flow as fast as possible through the hot side (turbine side) of the turbo, the best way to do that is the remove ALL restriction from the discharge side of the turbo.

Heres a good example of a "Perfect turbo exhaust" Its huge, almost straight and less then 2 foot long.


Since turbos make pressure on the compressor side there is a ratio of pressure to the other side, basically the more boost you make the more pressure there is on the exhaust BEFORE the turbo, but after you still want as little a possible,


With supercharged cars, back pressure isn't a huge deal because you are mechanically forcing more air into the engine, if you have too much back pressure then you can get all the fresh air in that you may be able to.
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Old 02-24-2010, 11:09 AM   #6
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With a supercharger you dont really want more then 14psi. And that'* with a lot of flow. Air movement is they key. Pressure is heat and heat is not your friend.
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Old 02-24-2010, 11:15 AM   #7
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Some back pressure is needed. There is a balancing point. To explain it further,

I had a pulley and intake when the headers found their way onto my car. This instantly took away a lot of the low end torque the drivetrain had. I could still spin the tires, but I couldn't bake them anywhere near as badly off the line. Lots more top end though. To this day, my Bonneville retains about a 5 foot section of ti'* original 2.5" piping and a stock muffler.
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Old 02-24-2010, 12:04 PM   #8
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While I don't have a large grasp about forced induction. Just a little back pressure is wanted in any application. Without it the exhausts valves won't properly seat, and cause premature exhaust valve failure. Thats been something I have read and heard for 40 years. I think Bill'* way of going about it, an easy economical way to avoid this.

The GXP OEM exhaust utilizes "pulse technology" by Borla. It sends a pulse of back pressure back against an exhaust valve just as it closes. And when replacing your exhaust on such, considering we can't alter the intake flow of gas and minimally the air. Something to consider before you cut off the Borla'* and replace with something else. Though it won't affect performance adversely, every bit helps. I don't know that I want to pay the near $800 for the one piece OEM replacement when it burns out, but I certainly won't just cut it off for a better sound.
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Old 02-24-2010, 12:24 PM   #9
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Actually that piping and muffer are there because I hate loud and droning exhaust. If I could open it further w/o compromising those further I would. But full exhaust is behind the motor.
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Old 02-24-2010, 12:28 PM   #10
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......... WHAT???? I'm deeeeeeeeeaf!.
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