Quote:
Originally Posted by Kurlon  Again, what makes one engineer's theory better than another's? Some of us are offering our opinion based on direct observation, measurement, and theory. I've been discussing motor theory with many engineers who are also guys that build crazy fast motors, and often times they have differing ideas yet they are all able to produce practical results... so which of them are wrong? If their ideas differ with Keith, does that make them or Keith wrong?
Unfortunately for you, thanks to my hand injury I've got nothing but time to pursue this, so half assed childish rebuffs won't detur me.  |
The exhaust valve closes. The air that left is still moving forward. A low pressure area forms behind this "chunk" of moving gas.
From the valve opening and closing we would wind up with positive and negative waves of pressure in the pipe. Look up four stroke exhaust tuning.
These pressure waves will have good and bad effect depending on when they arrive at the valve. The timing of this would be, in large part, due to the escape velocity of the gas. The escape velocity of the gas would depend on the pressure of the gas that is escaping the cylinder. This would be determined to a great degree by the amount of gas ingested by the motor, throttle position.
You would want that negative pressure wave to arrive at the exhaust valve just when the valve opens and to maintain itself through valve overlap.
You should be able to see that there's a lot of things effecting that pressure wave. They are not very commonly discussed but they are there.
Also, there is a possible bad affect too. The positive pressure wave could arrive at the exhaust valve when it's open.
There is so much going on there that's it just about impossible to arrange things to work all the time.
EXUP type valves are meant to deal with this.
The same harmonic system exists on the intake valve side. Honda attempted to get around this first with telescoping intakes on the NSR, I think and I think Yamaha has a simpler variable intake length scheme on the R bikes.
All I am saying is that reduced restriction is going to amplify these effects, good and bad.
I am also saying that at part throttle you're not making max torque. If your dyno chart says 50 ft lbs of torque at 5000 rpm it's only making that at WOT.
Why? The engine is ingesting and compressing less gas than it would be at WOT reducing BMEP (brake mean effective pressure) and thus, torque.
If you are not using the full amount of torque (riding at WOT) adding more does not do any good.
Throttle response may be increased or decreased depending on your throttle position, and RPM and how the pipe interacts just there.
If there was, theoretically, an increase in throttle response we would have to demand it to make use of it.
In a situation where we roll on the throttle I doubt that anyone here is doing it quickly enough so that we are going to ask for more response than the stock bike is capable of delivering when the bike is leaned over exiting a corner considering the type of hardware that people are using on this list.