losing horsepower?
04-12-2007, 12:11 AM
#2
2nd Gear Member
Join Date: Jul 2006
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Posts: 303
RE: losing horsepower?
I read this a while back, it was a response to a question about losing back pressure. It is as follows:
Despite persistent beliefs, backpressure is ALWAYS bad for power.
Now, I know you're thinking "Wait a minute Al, I've heard people say that motors need some backpressure to run properly". You might even have experienced it. For example, people sometimes see a power LOSS after removing their tailpipe.
Now, here's the kicker: This MYTH comes about because people think "oh, when I removed my tailpipe and my HP dropped, that's becasue I now have too little backpressure". That is an incorrect conclusion. The HP drop did not come from backpressure loss. It came becasue the resonant properties of the exhaust pipe changed. When you alter the shape, diameter, and length of an exhaust pipe you are changing two things: backpressure (resistance to flow) and the resonant characteristics of the pipe. They are two seperate things.
Backpressure is ALWAYS bad.
Resonance can be bad or it can be good, it depends on many circumstances and what your goals are. (This is why thin, long, headers are best for low-end HP whereas short, wide, headers are good for top-end HP).
QUOATED FROM: CrazyAl
Hope this helps
Despite persistent beliefs, backpressure is ALWAYS bad for power.
Now, I know you're thinking "Wait a minute Al, I've heard people say that motors need some backpressure to run properly". You might even have experienced it. For example, people sometimes see a power LOSS after removing their tailpipe.
Now, here's the kicker: This MYTH comes about because people think "oh, when I removed my tailpipe and my HP dropped, that's becasue I now have too little backpressure". That is an incorrect conclusion. The HP drop did not come from backpressure loss. It came becasue the resonant properties of the exhaust pipe changed. When you alter the shape, diameter, and length of an exhaust pipe you are changing two things: backpressure (resistance to flow) and the resonant characteristics of the pipe. They are two seperate things.
Backpressure is ALWAYS bad.
Resonance can be bad or it can be good, it depends on many circumstances and what your goals are. (This is why thin, long, headers are best for low-end HP whereas short, wide, headers are good for top-end HP).
QUOATED FROM: CrazyAl
Hope this helps
)
04-12-2007, 01:39 PM
#7
RE: losing horsepower?
no hes wrong, backpreasure is bad in any way shape or form, however, you want your exhaust gasses to flow out of the car with a certain velocity, try running a mile while breathing through a straw
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