Bikemans stag 2 tune for turbos
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It’s new enough that I doubt very many have had it on the snow.
Stage 2 is a significant step up in power. Doesn’t seem to have quite as linear of a power curve as the stock tune tho.
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Are you running the stage 2?
I ran it for a couple rides last season before the snow went to crap
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Ok, What did you do for clutching? how many grams did you have to add to the pivot bolt? or did you go to a straight 42 degree helix?
I just used a pivot bolt that was 1 gram heavier.
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OK, very interesting, rule of thumb, 5HP = 1 gram of weight, Stage 2 is 20HP = 4 grams.
3 arms........
And pivot bolt weight is different than tip weight
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should be 4 grams per arm. no different from a N/A sled, go up in elevation from sea level to
8,000 feet and see how much power you lose and the grams of weight you have to remove.
At 10,000’ 4 more grams on pivot bolt would
definitely not work with stage 2 on this sled. Maybe drag racing on the road but not in the steep and deep.
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From Dynamo Joe.
One of my 850 turbo test guys has a bm tune.
Flyweight is a mirror of engine torque. More torque, more flyweight to maintain "rated rpms". If the engine is rated at 7950 rpms and now you add 10 pounds of torque at 7950 rpms, then you have to add more flyweight to keep from overrevving past rated rpms.
Stock (with iBackshift clutch tune)
984 ramps
Flyweight @ 102 grams
Primary spring @ 100-340
After going to bm tune stage 3 non ethanol w/diamond-s can. (with iBackshift clutch tune)
984 ramps
Flyweight @ 108 grams
Primary spring @ 100-260
Had to add 6 grams of flyweight and take the primary spring end force and lower it 80 pounds to keep the engine from overrevving.
its kind of a rule of thumb that for every 1 gram of flyweight you have to add, there is an addition of about the equivalent of 5hp.
This is easily proved, since for every 1000 ft elevation increase, there is 5hp loss. Every 1000 ft increase, an estimated 1 gram must be removed to maintain rated rpms.
Therefore; IF 1 gram = 200 rpms and 1 gram for 1000 feet and 5 hp per 1000 feet, THEN for every 5hp added, you need to add 1 gram.
5hp loss for every 1000 feet, I got that out of a Rotax 503 fan aircraft shop manual, so they are not my words, they are Rotax's words.
Going from 102 to 108g then that's like there was an addition of 5hp x 6 grams = 30hp increase. Then there is a rule of thumb of for every 30 pounds primary spring end force change, there is a hp change to match it. The calculation is a little bit more complicated because you have to factor the track speed to know what forces are being used by the spring, at-that-track-speed.
I would put my neck on the chopping block and safely say there's a 30hp+ gain to pull off that amount of flyweight gram increase and not put forth how much more hp there is based on primary spring change.
Yep. Good luck with that.
yep. Good luck with that. Keep in mind the turbo sled starts loosing power after 8,000’.
yep. Good luck with that. Keep in mind the turbo sled starts loosing power after 8,000’.
I
Yep. Good luck with that.
yep. Good luck with that. Keep in mind the turbo sled starts loosing power after 8,000’.
[/QUOTE]
Well here is what a ibackshift stock turbo vers a ibackshift clutched N/A 850 is in comparison...…. turbo rider is 250lbs with no gear and a 190lb rider on a N/A 850....
turbo vers N/A 850
And its not even close now with the stage 3 tune in it now...….
And if it looses power after 8000' it wont be that noticeable since you will be so far ahead of the N/A 850's or the stockers turbos....its a $hit eatin grin from the truck to the top of the mountain !!!
Oh ya belt tems are all in the 180ish zone wen flogging the crap out of it !!!
yep. Good luck with that. Keep in mind the turbo sled starts loosing power after 8,000’.
[/QUOTE]
Well here is what a ibackshift stock turbo vers a ibackshift clutched N/A 850 is in comparison...…. turbo rider is 250lbs with no gear and a 190lb rider on a N/A 850....
turbo vers N/A 850
And its not even close now with the stage 3 tune in it now...….
And if it looses power after 8000' it wont be that noticeable since you will be so far ahead of the N/A 850's or the stockers turbos....its a $hit eatin grin from the truck to the top of the mountain !!!
Oh ya belt tems are all in the 180ish zone wen flogging the crap out of it !!!
A chart in a Rotax Aircraft Engine Shop manual says 5hp loss for every 1000ft elevation increase. [Lazair Aircraft w/503 fan manual]
Ok then, according to BRP values, then...
@ sea level, 165hp
@ 8000 ft, 165hp
@ 9000 ft, 160hp
@ 10000 ft, 155hp
@ 11000 ft, 150hp
@ 12000 ft, 145hp
Since its a constant, then...
Stage 3, 95 octane is 30+hp
@ sea level, 195hp
@ 8000 ft, 195hp
@ 9000 ft, 190hp
@ 10000 ft, 185hp
@ 11000 ft, 180hp
@ 12000 ft, 175hp
...so what if it lost power? I'd still be happy with that at 12k feet.
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Joe, with your Ski Doo insiders, do they think Ski Doo will have their own tunes coming out this season? always better from the factory.
Heh, umm, not insider. I have a privilege with BRP still, so I get to ask some of the race techs questions directly. Far as I know right now, you have to be high-in-the-eye in the race department or in chassis development for the privilege to get a re-calibration. There might be 1 or 2 guys who'll get "something", and outside of that...nope.
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