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P Drive Clutching 2017 vs. 2018

toms

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Thanks for the info Tom. I'm curious, does the SAE numbers from the track dyno have any correction built in? Or are those uncorrected numbers for the ~4,000' your shop is at?

Thanks for sharing. Little disappointing considering there's 160+ at the crank. Assuming 165hp at the crank, and 60hp at the track, that's only 36% efficiency...

Yes it is corrected hp
Yes, it typically is 50% of engine hp
We have currently run over 35 tests or changes
We will systematically document primary secondary and gearing
 
J

JJ_0909

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Yes it is corrected hp
Yes, it typically is 50% of engine hp
We have currently run over 35 tests or changes
We will systematically document primary secondary and gearing


Just to add - Who cares about motor horsepower? It is academic if you can't get it to the ground.

This is one of the biggest things in snowmobile world I can't get over. If we could get even close to the automotive world (25% on the high end) it'd make your NA sled act a lot more like a turbo.

Tom doing testing in this "real world" scenario may not win any internet arguments but it actually may help us find some clutching that makes a stocker perform a lot more like a mod sled (as well as reducing belt temp!)
 

Matte Murder

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What’s your recommended set up for an 18 175? Ride mainly 4000-6000’ with a couple trips to 8000-10,000’.
 

BIG JOHN

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Good post/info Tom!!

Just adding info to help clarify (correct me if I'm wrong Tom) the ramp comparison was on 1 sled (2017 with a 170/350 spring) correct?

ramps
967 44 gr 4 gr tip
965 46 gr 5 gr tip
971 46 gr 5 gr tip (first 1/3rd profile more agg)

Same track/gear/helix/spring...

The track HP was achieved from the ADDED over all weight and tip weight of the 965/971 vs lighter 967...

The stock 2018 with a 170/400 spring would counter act the extra weight of the 965/971 and the track HP would be closer to 967s...

Basically the 850 can pull more weight = more track HP and with less belt slip = lower belt temps!!!

Now toss that blu/blu secondary spring and add more weight:face-icon-small-coo-BJ
 

kfa670

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This is solid info. My 18 175 makes a crap load of heat... Under trail riding conditions... And yeah my belt deflection is correct and this is a maybe 40mph trail not a 80 mph trail where the gearing is maxed out.

The pdrive on theory is a much more efficient clutch. How do we get rid of all this waste?

I always heard 50% efficiency was pretty good. 36% ouch. Do we have any side by side comparisons of Arctic and Polaris?
 
P
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A Floating secondary would be my first guess.

As the clutch goes through the shift the belt gets bent one way first and the other way at full shift out ( between Primary and secondary clutch). That may work fine on a 600 class sled , but not with 850 power. Thats why Yamaha always floats their secondary and you can watch it move as it shift's and the old Yamaha belt ( 20 years the same belt and a 1/3 of the cost of doo or Poo ) handles 300 HP no problem in my Apex and Rx1 turbo sleds. Secondly to have a wobbly clutch sheaf is ridicules -- can you say slip and grip 8000 times per minute without heating up - ridicules who comes up with that stuff. Ones that is fixed, proper clutching would just be icing on the Cake. I am ranting cause a few guys here with 18 are blowing belts as bad as the worst 17s did. So the updates did not work at all.
 

toms

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Here is another comparison of some clutch tests. Run # 25 is stock 2018 clutching on a 2017 sled. The others are prototype parts.
 

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  • 2018 clutching evaluations.pdf
    61.3 KB · Views: 210

toms

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Toms has officially entered the clutch kit market.
Here is a stock 2018 set up (red line; #25 dyno run) , vs. our new ramp profile (blue line; #103 dyno run.
This has been done with stock secondary set ups. Next week we will make our changes to that.
 

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  • St18 vs proto #6.pdf
    60.9 KB · Views: 204
A

ak

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Toms has officially entered the clutch kit market.
Here is a stock 2018 set up (red line; #25 dyno run) , vs. our new ramp profile (blue line; #103 dyno run.
This has been done with stock secondary set ups. Next week we will make our changes to that.

Good info and gains when will they be available? Work for lower elevations?
 

Blk88GT

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I'm not sure how I missed this, but THANK YOU for sharing this. I've spent a lot of time around a chassis dyno with wheeled vehicles, but never a sled dyno.

Very interesting information!
 
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