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guest
Dodge Dakota
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4/23/2005
21:07:52
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 Subject: RE: back pressure
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Message:
It all has to do with:
Bernoulli's principle
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N56629
Dodge Dakota
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4/24/2005
22:55:31
| RE: back pressure
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Message:
Thanks, hybrid, but no matter how many times you try to tell people that they are going to start babbling about 2 cycle engines or something they have read on the internet. The laws of physics mean absolutely nothing to them.
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Mann
Dodge Dakota
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4/25/2005
02:02:47
| RE: back pressure
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Message:
I'm going to step out on a limb here. This is the way I was taught and learned from a automotive school. That in an exaust you want just enough backpressure to keep a raw flame front from going across the valve seat. this will cut it like a blowtorch, Nominally 1PSI or probably even slightly lower would prevent this. Any more is a loss in efficency.
before I get flamed ,...
I've worked on several rebuilds that had burned valves, most had ignition timing way off. One was a nissan ricer that had a 2 1/2 collecter dumped into a Y pipe W/2 1/2 duals no mufflers no cats on a four banger. I stuffed shop rags into one of the pipes and the car actually ran better and gained low end tourque.
Anyway back to subject, Look at a top fueler running after dark, they have massive flame fronts passing the valve face. But they also get replaced at every 1/4 mile.
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reddakota360
Dodge Dakota
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4/25/2005
04:04:38
| RE: back pressure
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Message:
Im not sure about back pressure, but air flow makes a difference. My '99 dak RT went 89mph stock. A ram air hood and Moper Perf PCM got me 91. Then I added headers/dual exhausts, and dropped to 90. My mileage went up from 14.5 to 16. I increased the air flow, which started to "lean" out my engine. Then I added a 52mm TB, and dropped to 86mph, and my mileage jumped to 20. I had B&G flash my stock PCM to the M1 setting, but I'm only getting 89mph. Back to where I started! Now I have to get my truck dynoed, so B&G can get a better idea how to program the PCM. (This speed thing can be complicated!)
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