Olav Aaen - clutch tuning handbook
04-05: To tune your clutches you have to know where the power band of your engine is.
04-06: When the engine has been modified, it is important that you know how the power curve has been changed to so that you can tune to the new power peak.
04-07: Any internal combustion engine is an air pump, and the amount of power you obtain is directly proportional to the weight of air and gas you can burn in a given time.
The density of the air has a direct effect on the power output. Air density is controlled by pressure, temperature and humidity. Pressure and temperature have the largest influence on your power.
04-08: Know your power curve and its limitations when you work on your clutch.
04-09: Your job as a clutch tuner is to the match the clutch to your engine curve and obtain the best possible performance of the conditions your vehicle is experiencing.
For the most part, I don't like cans for 2 reasons.
1] I can't take the noise from using them. Ive run many cans, either bought, borrowed or given to me. Always there is an ear stabbing sound between 62~6800 rpms at part throttle.
2] Many cans change the power peak rpm to a lower rpm. Only a rare handful have shown a "real" increase of a power peak change to a higher rpm by 100.
People can see published numbers by certain shops running the same dyno as everyone else. Their mufflers showing -1hp, or, same hp, or, +1, +2hp, ok fine...but then the same can's are brought to one of the types of Eddy current dynos and show a power peak rpm movement. Notice I did not say "Hp gain or loss".
i] That EC dyno showed a -250rpm movement in the power peak, or
ii]...a -100rpm movement in the power peak, or
iii]...a +100 rpm power peak movement.
i]Supposed to be 8000, went to 7750.
ii]Supposed to be 8000, went to 7900.
iii]Supposed to be 8000, went to 8100
I didn't say the word "horsepower." YOU immediately go to the word "horsepower" in your mind, because that's what you've been trained to do.
That word "horsepower" is for the people who know dynos. Since I dont know what they know, then i'll say "power peak rpm".
So I gets this phone call one day from a tech in this shop down in eastern Canada [not ontario] that has one of these eddy current dynos and he give me the power peak rpms of a list of cans. One popular can losing 250 rpms and pipe surging. One can losing 150 rpms. One can losing 100 rpms. Some cans original 7950 rpms, one can in particular gaining 100 rpms.
But the Johnnycan showed a power peak rpm movement of -250 rpm on Dan's EC dyno.
But Johhnycan company shows a HP gain on the Jonnycan's house dyno.
Now, i'm not trying to invoke anyone to show their current psychological condition of going on a rant about dynos.
Ski-Doo Muffler PT-2, [DETAILED] 850 turbo can...
www.dootalk.com
Its about this...
2 guys, Moe and Larry, have same sleds, bone stock except Moe has a Johnnycan muffler where it said on the Johnnycan website +X.X hp.
Both guys about the same rider weight with gear, run at the same elevation, bought gas from the same pump, same drive belt, same clutching....
But at the riding area, Moe is having difficult to get 8000 rpms.
Larry is 8000 and pulls like a freight train [Moe's words]
Only difference? Exhaust.
This is my answer to Moe
SKI-DOO MUFFLERS. This PT-1 video is a summary of main points to know when a Ski-Doo exhaust is modified, [MUFFLER/CAN] it may change the power peak rpms of your engine. A simple todo list at the end of it; how to prevent and/or correct a power peak rpm change.PT-2 video next, is detailed, covering many or all important points of WHY a muffler can change the power peak rpms. What's happening in the pipe regarding backpressure.
Short summary @ 7min long.
SKI-DOO MUFFLERS. This PT-2 video is DETAILED, why, how, what may happen when a Ski-Doo exhaust is modified, [MUFFLER/CAN] it may change the power peak rpms of your engine.
ADJUST THE PLAYBACK SPEED; You can speed up the video using youtube settings, playback settings 1.25, go.
I go into the theory and my own "bad, but-good" learning experience on why my engine could only run 6800 rpms in Cooke city at 7500~9500 feet. I changed out to 2 cans.
Borrowed stock = 8000.
Aftermarket can I owned & ran = 6800
Certain aftermarket = 8000.
Aftermarket can I owned & ran = 6800..what is happening?