Arctic Cat Forum banner

21 - 24 of 24 Posts

·
Administrator
Joined
·
19,791 Posts
Hey Al! Thank you for taking the time to post Jims info there...

This below is what I've strived to folks for a long time..... And is absolutely KEY when clutching a sled for "Real World operating Conditions"

"EngSpd RPM self-explanatory—this is RPM, and on engines with digital tachs, the readings have proven to be identical from dyno to sled. But analog sled tachometers are another story—vast differences can be seen from digital dyno RPM to analog sled tachometer readings. So it pays to have analog sled tachometers calibrated electronically (Aaen does this for a small fee) or with a digital tach like those sold by Stihl (less than $100) for tuning chainsaws. Those are perfectly accurate. But keep in mind that the peak HP RPM on our dyno tests is with pipe(s) extremely hot. And since the speed of sound increases with temperature, the HP peak in the field may be at lower RPM (trail riders on-off-on throttle) or at higher RPM (lake runners or mountain climbers who might spend minutes at WOT). Sled dragracers used to think that they achieved best acceleration by clutching to the “peak torque RPM” which often occurs 2-400 rpm lower than dyno test HP peak. But now we know that we clutch to a shifting HP peak—cool pipes on takeoff will make peak HP several hundred RPM lower than hot dyno test pipes, and finding that constantly changing peak HP RPM is critical in creating best acceleration."

Both, the rpm's vary, and like Jim points out, progressive shift rate helixes are key in clutch tuning....
 

·
Registered
Joined
·
1,631 Posts
Hey Al! Thank you for taking the time to post Jims info there...

This below is what I've strived to folks for a long time..... And is absolutely KEY when clutching a sled for "Real World operating Conditions"

"EngSpd RPM self-explanatory—this is RPM, and on engines with digital tachs, the readings have proven to be identical from dyno to sled. But analog sled tachometers are another story—vast differences can be seen from digital dyno RPM to analog sled tachometer readings. So it pays to have analog sled tachometers calibrated electronically (Aaen does this for a small fee) or with a digital tach like those sold by Stihl (less than $100) for tuning chainsaws. Those are perfectly accurate. But keep in mind that the peak HP RPM on our dyno tests is with pipe(s) extremely hot. And since the speed of sound increases with temperature, the HP peak in the field may be at lower RPM (trail riders on-off-on throttle) or at higher RPM (lake runners or mountain climbers who might spend minutes at WOT). Sled dragracers used to think that they achieved best acceleration by clutching to the “peak torque RPM” which often occurs 2-400 rpm lower than dyno test HP peak. But now we know that we clutch to a shifting HP peak—cool pipes on takeoff will make peak HP several hundred RPM lower than hot dyno test pipes, and finding that constantly changing peak HP RPM is critical in creating best acceleration."

Both, the rpm's vary, and like Jim points out, progressive shift rate helixes are key in clutch tuning....
Your Welcome and I agree on the pipe temps.
 

·
Registered
Joined
·
149 Posts
Discussion Starter #23
Very Interesting!

Thanx Al and everyone for the Interesting Replies. Ive got my little shop all geared up for some new projects. Appreciate the replies Mike
 

·
Registered
Joined
·
1,631 Posts
Thanx Al and everyone for the Interesting Replies. Ive got my little shop all geared up for some new projects. Appreciate the replies Mike
No Problem Mike. I will continue to add to this thread here and there so every one following this thread can keep up. Al
 
21 - 24 of 24 Posts
About this Discussion
23 Replies
8 Participants
Zrt1200
Arctic Cat Forum
Arctic Cat forum is a community to discuss Arctic Cat 400, 440, 500, 650, snowmobiles, sleds, ATV's and more. Join the fun!
Full Forum Listing
Top