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Hi all,
I talked to a very knowledgeable person about pipes today.
When you see a dyno chart you are in fact seeing maximum possible torque delivered at RPM. In just about all cases throttle openings at less than full throttle will not deliver peak torque for any given rpm.
So, the best indication that you can use the extra hp or torque is that you ride with the throttle wide open. In the words of this person, "you can bake a cake as big as you like but if you only eat one piece it does not matter". To which I responded, "standing in a high ceiling room makes you no taller", and he said, "but it allows you room to grow."
It was postulated elsewhere that the "stronger signal" of a less restrictive after market pipe would increase throttle response.
In further discussion he said that the different gas velocity exiting the exhaust valve (depending on how much air was let in at partial throttle opening) would bounce around in the pipe differently and it would be a crap shoot to determine when the negative pressure wave arrived at the exhaust valve. In short the "stronger signal" wouldn't mean much. It could make things better or worse but odds were about even; but the stronger signal would likely make things "more better" or "more worse" at a given opening/rpm.
He said it takes about 3 hours of dyno work (by Erion Racing no less) to get maps of partial throttle openings more or less correct but that the power commander III would do a passable job of it. And that's just the fueling end of it.
Moreover in cases of relatively small changes in throttle position, like accelerating out of a corner, improvements in response wouldn't matter much. You would need a very large amplitude change in throttle position to make improved response (if any) matter to any measurable extent. In a word it would only matter if you "nail it"
So, in the end, pipes are best for straightaway acceleration where the throttle can be pinned, and a wide open throttle is the best indication you could use a pipe. It's also a good indication that you are using your pipe.
For most of us they are of no use.
A~