850 turbo 165 (stock clutch) vs Xpert 165 (iBackshift kit)

Dynamo^Joe

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Today we had some fun working for about 6 hours on the new 850 turbo sled. I been working on the clutching for a turbo for a few seasons now and wanted to see the fruits of it on the stock skidoo turbo 850 sled. Kinda had it about 90% setup already but wanted to vidya some of the last testing before I send kits out to test guys in snowmobile land.

James arrived, unloaded the sled and was excited to get started.
James) "This turbo sled goes real good Joe"
Joe) ok, if you think so. We'll see about that. I know they go but after you run your sled then drive Corey's sled, you may re-evaluate your conclusion.

The track is 660 and in the back where you can't see is a small circle track, kind of a mini-sno-x track. Just basically a bunch of bumps you can play with the throttle a bit and get into some fresh snow on the infield.

First I got James to slowly drive his sled around the track back and forth and then go into the crosser section in the back and giver a bit over the bumps. Then take Corey's xPert and follow the same course.
James was shocked at the engagement speed and how Corey's pulled off the bottom end.

Next test. Lets drive side by side up and down the race track and switch sleds each round and do this 4x because i want him to get the feel at part throttle speeds of both sleds. Then after James taking his for a rip again, then Corey's for a rip, he said "Make mine like Corey's"

DRAG TIME - Notice how I pulled up to James on the start, then hit reverse and I give him 1 full length start. My ski tips to his rear bumper. He's asking me "you sure about this" I said "im going to eat your lunch by the 200 foot mark". We did 4 races switching lanes, and he could pick the best line and give me the worst line, I wanted James to make the rules and give me 1 disadvantage. By 70 feet I reeled him in and going by at 100 and by 200 foot cone, the xPert made at least a 1 sled GAP between it and the turbo. And that's not my words, I was not looking back. I dont know how far I was ahead. That's James saying "at least a sled length gap between us"

Ok Sled in garage and start to put the clutch kit in. Instead of taking the muffler out, James massaged the shield to have a relief for the top shaft tool. Once he did that, we were on our way to installing.

First RIP
Stock 984 ramps
Engagement speed around 3400 the sheave touches the belt and 3500 sled starts to move
97 grams total arm weight (Pivot bolt, Popeye arms, 984 ramp, clicker assembly weighed on a scale_)
Clicker 3
Out for a drag run to 60mph, ran at 8000~8100 rpms. James ran 8200.
Back in shop and add 1.8g to the pivot bolt.
I could get 8000 on track spin and 7900 and pull like a b@stard.
James on sled could see 8100 on track spin and hookup 7900 and pull like a b@stard.

After doing 4 more runs alone, James come back and said "wow, i see what you mean by stock dont pull after 40mph and now it pulls smoothly till i let off"

Now, for someone to get uppity about me doing all of this at 900 ft elevation and in that snow and label this effort "flatlander". Ermm...i'll remind you that xPert has the same clutch kit as guys are running in Utah and Colorado at 12k feet. Just the pivot weight is lower as elevation increases.

Every clutch kit that you've ever read about of mine since 1999 has started at this garage and drag strip. you gotta start somewhere. Once I have something that feels good compared to stock at this site, then the "Test kits" go out all over God's creation. I get feedback and do something with that feedback to trim off and commission a kit.

Now James turbo sled can take me by a hood length to 3/4 length to the 100 ft mark and by 200 feet, he's gapped me 1 sled gap. Holy cow does that turbo sled rip now. HAHA.
850 turbo kit.jpg 850 turbo kit drag.jpg
VIDEO
850 turbo clutching stock then prelim clutch kit
James, the turbo owner and I, testing 800 trail kits years ago.
 

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XP860

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You the Man Joe! Thank you for all your hard work! Can’t wait to get my kit from you and make my T850 even better! ?
 

Dynamo^Joe

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Its like this

sea level
xpert 160hp (minus 5hp)
turbo 165hp

1000 ft asl
xpert 155hp (minus 10hp)
turbo 165hp

2000 ft asl
xpert 150hp (minus 15hp)
turbo 165hp

3000 ft asl
xpert 145hp (minus 20hp)
turbo 165hp

4000 ft asl
xpert 140hp (minus 25hp)
turbo 165hp

5000 ft asl
xpert 135hp (minus 30hp)
turbo 165hp

6000 ft asl
xpert 130hp (minus 35hp)
turbo 165hp

7000 ft asl
xpert 125hp (minus 40hp)
turbo 165hp

8000 ft asl
xpert 120hp (minus 45hp)
turbo 165hp
-----------------------line in the sand-------------------
9000 ft asl
xpert 112hp (minus 46hp)
turbo 158hp

10000 ft asl
xpert 108hp (minus 45hp)
turbo 153hp

11000 ft asl
xpert 103hp (minus 45hp)
turbo 148hp

12000 ft asl
xpert 97hp (minus 45hp)
turbo 143hp

Lets say both sleds left sea level and were able to drive up to 12000 feet in one day.
Every 1000 feet, the xPert will have to pull out around 0.9 grams to 1.1 grams pinweight to achieve 7950 rpms again. The Turbo will not till around 8000 feet.
By the time the turbo gets to 9000 feet, the operator has a choice. Either clicker up to 4 OR pull out 0.9~1.1 gram pivot bolt weight.
From 8000 feet and higher, then BOTH sleds will have to alter their pivot bolt weight and/or clicker position to maintain 7950 rpms on average until maximum elevation.

In an ideal world, What you see in the drag race video, that turbo should act with the same performance at 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000 and not have to chagne the clicker. If we were running that race at 1000 feet where I am and then helicoptered up to 7000 feet, according to BRP, the sled should have the same performance at 1000 feet where you watched the video.

Those are BRP hp claims on estimate.
I have a ROTAX aircraft engine manual that has a chart of power loss percentage per elevation and the "rate" at which the power loss changes at around 8000 feet, the hp loss is more than 5hp per 1000 feet after 8000 feet.
 

Dynamo^Joe

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Nov 26, 2007
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Thunder Bay, ont
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Sheave touches belt at 2900 and starts to pull sled at 30~3100 rpms.
My own 850 x 154 x 3.0 has 2300 (twenty three hundred) engagement speed.

2020 skidoo 850 turbo clutch tuning objective is to have 2700 and beat the 900ACE expedition at 2800 rpms.
This will help with crawling around in the trees searching for that line and then......send it full ketchup.
 

XP860

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Nov 28, 2007
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I have a New T850 with Joey’s New T850 Clutch Kit. I have been waiting to post my excitement about how good my sled is clutched now! I will also vouch for the speed Pat said in Joey’s post above. With Joey’s New Turbo Kit I also see 57-60 plus mph at elevation 6500-8000ft. I have 120 miles with stock clutching and just over 400miles with Joe’s new T850 clutch kit to compare! At home at 2200ft I see consistently at WOT across a field with about a foot of fresh and hard snow base beneath pulling 76-79mph. My Sled pulls so hard all the way through to max speed and backshifts like no other sled I’ve owed. My sled accelerates much faster from point A to B and recovers engine speed instantly back to peak RPM! This is also all done with clutch engagement of 2700rpm. (Stock was 4300rpm on my sled). My sled is now faster in every RPM range, pulls hard as hell!! On top of it all the belt Temps run 40-50’f cooler belt temps! I can honestly say STOCK clutching SUCKS Loud! Joey’s T850 kit is not just another blah blah clutch kit. Joey’s kit turns the T850 an animal.......Power by the Hour a good buddy told me! Thanks Joey! You Rock buddy!��
 
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