Is it bad......?
06-22-2009, 02:15 PM
#11
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http://www.veryuseful.com/mustang/te...Scavenging.pdf
halfway down page 3 it puts this pretty well into layman's terms. sometimes people see increased power with increased backpressure, but this most likely isn't directly a result of the increase in backpressure itself...
"If, in fact, power does increase with increased exhaust back pressure, it is most likely the air/fuel ratio and/or ignition timing that are no longer optimal for the altered state of engine tune."
halfway down page 3 it puts this pretty well into layman's terms. sometimes people see increased power with increased backpressure, but this most likely isn't directly a result of the increase in backpressure itself...
"If, in fact, power does increase with increased exhaust back pressure, it is most likely the air/fuel ratio and/or ignition timing that are no longer optimal for the altered state of engine tune."
06-22-2009, 08:00 PM
#12
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why the hell would your motor "need" backpressure? you want as little backpressure as possible in your exhaust, because all backpressure does is rob power from your motor having to work harder to expend exhaust gases. if an engine needed backpressure, then race cars wouldn't run open exhaust.
I wasn't thinking straightthanks for the article, it was helpful
06-22-2009, 10:17 PM
#13
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haha it's alright, i've heard this theory from a lot of people, i'm sure some cars have seen a loss in power when removing the mufflers but they don't consider that the tune is most likely no longer optimal for that setup... and that's the real cause for the decrease in power. i read a book several years ago about Smokey Yunick, and he did some testing on circle track cars and found spots under the car where there was either lower pressure or negative pressure (a result of the air flow around and under the car) and routed the exhaust so it dumped right into that low pressure area and saw increased performance from it.
06-22-2009, 11:56 PM
#14
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haha it's alright, i've heard this theory from a lot of people, i'm sure some cars have seen a loss in power when removing the mufflers but they don't consider that the tune is most likely no longer optimal for that setup... and that's the real cause for the decrease in power. i read a book several years ago about Smokey Yunick, and he did some testing on circle track cars and found spots under the car where there was either lower pressure or negative pressure (a result of the air flow around and under the car) and routed the exhaust so it dumped right into that low pressure area and saw increased performance from it.
06-23-2009, 06:06 AM
#16
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i think another thing that confuses people is the scavenging effect of the exhaust. when i dyno tuned my circle track car, we found the optimal exhaust setup to be open headers with about 14 inches of 3" diameter pipe at the end of the collector. and this was another piece of wisdom that we got from Smokey Yunick's book. even though it's primarily aimed at pushrod, carbureted small block Chevys, it's still a great read for anyone who's interested in the mechanics of your engine. the same general principles apply to pretty much any internal combustion engine (with fixed valve timing, of course).
06-23-2009, 10:04 PM
#18
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06-23-2009, 10:39 PM
#19
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yes the cats are still one....the sound is kind of raspy, more like a truck sound than anything, but i'll get a video up soon.
