Optimal RPM for 850T?

[NoSoup4U]

What is the optimal RPM for the 850T? Ski Doo manual says 7900 +/- 100 for all 850’s, but on Bikeman’s dyno they found peak HP at 7700 +/- 100 for the 850T.

 

[el__gato]

eTecs like to be lugged, thats what my dealer told me. if you consider they have diesel characteristics with DI and the ring support inserts, they are designed to make max HP under 8000 rpm

 

[caper11]

Does bikeman have the ability to do a 1min long dyno pull to see what the engine likes on a hot pipe?


My seat of the pants feel on my sled, it seems to work better at 8000/8100 observed on the tach. Dunno how accurate the tach is


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[Darrell262]

I saw same video and he does 3 runs. I would say 7700 to 7800 sounds like the sweet spot to me. Now how do u clutch to there? I have the 38mm bolt 9mm spacer plus 3mm and 2mm spacer which is as much as u can put on that bolt. And I get 7900 to 8k at clicker 1.

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[Darrell262]

Also I saw dyno of a 850 doo with the Polaris from same guy and the 850 doo non turbo likes 7900 to 8000 for best performance.

So how do I go about making my turbo lug down. I cant add any more weight on that bolt

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[1709]

you can go to a steeper helix, 41/45 will work good, or better yet 43/47 with a 180/303 secondary spring. with just the 38mm bolt.

 

[xpturbo600]

An Etec 850 is not designed after a diesel. It was engineered to more closely emulate 4 stroke grunt than prior models. Direct injection was applied from the boating division 2 stroke tech to reduce emissions, so the two stroke could remain in production as emissions were tightened in 2012, leading to the ETEC 800 and 600 engines. Those engines were the first to implement sealed mains if memory serves. In response to market demand for more power, Doo engineers applied common diesel oiling techniques in the crankshaft to improve oiling of the main bearings and improved the piston design because the initial intention was to release a turbo 850 from the factory. To meet that objective, the 800 class engine had shown common failures with pistons and crank bearings following the initial change to the etec. Those were corrected in the 850 design with an eye toward a turbo.

Regarding the optimal settings, don't worry about getting exact rpms unless you have dyno data for your sled. Each motor is slightly different and port timing/port efficiency determines the optimal rpm. Turbo motors typically like higher rpms than non turbo motors conditional on using the exact same cam profiles...meaning port design in a two stroke. I say this to clarify, you don't know where your optimum is and Doo sets the recommendation for the average sled. Plus the optimum varies slightly as terrain conditions change track load. So, get close and just ride it. Or, pay to find out the optimum for your sled. But, that is a lot of effort, time, and money for 1 to maybe 3 hp at peak. You likely won't notice that even if you got it. If you need more power, throw a tune on it or cut some weight.

 

[caper11]

you can go to a steeper helix, 41/45 will work good, or better yet 43/47 with a 180/303 secondary spring. with just the 38mm bolt.

Reverse angle on a factory doo turbo???

You will be leaving alot on the table.

 

[1709]

that`s what you think. does not surprise me that you would make a dump statement like that.

 

[caper11]

that`s what you think. does not surprise me that you would make a dump statement like that.

Lol, I’ve used both of those helixs on Boondocker G4 turbo I tuned. I know what that sled put down for numbers on my test hill, and I know what my 850t puts down for numbers on the same hill. To each his own but thats a helix I would not consider on my 850T.


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[Idahodoo]

I always use clicker 3 to tune using pivot bolt length + spacers to get the correct RPM Below is where I'm currently at Using This Clutch Kit

21.9g = 40mm pivot bolt + s4mm spacer = 98.3g [TURBO START HERE [CLICKER 3] FOR 8000 PULL DOWN TO 7900, HOLD AT 7950]

Runs great & RPMs are spot on, but may have to adjust after sled is broke in and get to ride in good snow.

 

[Dynamo^Joe]

Aaen) all testing is done at full throttle
I suggest my long track, deep lug customers make their objective of seeing something along the lines of..."hit throttle and see 8000, pull down to 7900 and float around 7950" if they can.
IF see 8100, THEN add a 1/2 gram.

 

[Darrell262]

I love 7800 rpm on my turbo. Pulls hard. Massive weight to get there clicker 3.

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[kanedog]

that`s what you think. does not surprise me that you would make a dump statement like that.

This thread belongs in the dump.