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Ed's Auto Parts - Mention MOTORGEN for a Discount!
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View Poll Results: Is back pressure a good thing?
No way Jose. 3 30.00%
Some, but with qualifications. 7 70.00%
Voters: 10. You may not vote on this poll

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Old 09-21-2009, 04:19 PM   #41
VettezukiVettezuki is offline
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The only ones I've ever seen is the 180 degree exhaust systems. But I think that was to due to having to run header tubes all over and under the engine.

As in they actually mechanically change length over the rpm range. For instance longer to shorter on intake.
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Old 09-21-2009, 04:21 PM   #42
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Crazy ass tangent.

We know that some (super fancy race) engines utilize variable length intake runners. Most modern super bikes use this technology. Has there ever been an engine with variable length exhaust?
I do not know about variable length, but I do know of late model ferrari and the corvette z06 have computer controled exhaust flaps to tune the velosity
at different rpms and load conditions.
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Old 09-21-2009, 04:22 PM   #43
BRUTAL64BRUTAL64 is offline
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As in they actually mechanically change length over the rpm range. For instance longer to shorter on intake.
No, haven't seen anything like that. There might be something to that. Instead of variable timing, variable exhaust length.
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Old 09-21-2009, 04:25 PM   #44
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I do not know about variable length, but I do know of late model ferrari and the corvette z06 have computer controled exhaust flaps to tune the velosity
at different rpms and load conditions.
That makes sense. Actually "resistance to flow" could be adjusted that way.
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Old 09-21-2009, 04:28 PM   #45
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I do not know about variable length, but I do know of late model ferrari and the corvette z06 have computer controled exhaust flaps to tune the velosity
at different rpms and load conditions.
Yah, on the Z06 it's worth 6HP. On a side note I don't think that OEM's take into account performance when they design an exhaust for new cars. I think it is more a factor of what will fit and emissions. That's why you can gain so much HP by upgrading the exhaust on some cars such as the 03/04 Cobras.
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Old 09-21-2009, 05:22 PM   #46
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Yah, on the Z06 it's worth 6HP. On a side note I don't think that OEM's take into account performance when they design an exhaust for new cars. I think it is more a factor of what will fit and emissions. That's why you can gain so much HP by upgrading the exhaust on some cars such as the 03/04 Cobras.
I'm goddmaned curious what my "BP" is now. . .

I know my exact motor with headers, but with a much less high flowing intake (LS1, I have an LS6) was making 432WHP in a C5 on an aggressive tune. I'm making 391 with stock headers and a very conservative tune (18 degrees total as I recall) in my C3.
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Old 09-21-2009, 05:35 PM   #47
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I'm goddmaned curious what my "BP" is now. . .

I know my exact motor with headers, but with a much less high flowing intake (LS1, I have an LS6) was making 432WHP in a C5 on an aggressive tune. I'm making 391 with stock headers and a very conservative tune (18 degrees total as I recall) in my C3.
I have a back pressure tester if you would like to borrow it.
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Old 09-21-2009, 05:44 PM   #48
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I have a back pressure tester if you would like to borrow it.
Please and thank you. Do you live close to your brother? Maybe I can just come out and use it on the spot?
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Old 09-21-2009, 05:52 PM   #49
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Please and thank you. Do you live close to your brother? Maybe I can just come out and use it on the spot?
Yes, within 5 miles. I can just leave it with my brother.
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