850 Engine thread (840cc)

[Motorbreath_]

Regardless the Polaris will get more of it to the ground and perform better without the need for a

Double Wobble Slipper Clutch System.

No need for a Teeter Totter rear suspension and flex edge tracks either.

I hope Polaris does well with this engine and all of the other little updates they did. I hated my old axys.. love my teeter totter though. I think the narrow front end and decent horsepower is what the old axys was missing.

 

[Snojet34]

injectors

I think I will wait for direct injection.

 

[sledhead_24_7]

So, the Pros always had a little problem with running hot when conditions were not adequate. That's why some of us opted for the standard RMK with 2 heat exchangers. Does this new engine's design help in this regard? Seems like I read somewhere about better heat dissipation. Also, has Polaris every had a standard 4 year warranty before?

Polaris had a 4 year warranty on their 08 Dragon 800 RMKs, not sure when they stopped offering it though.

 

[Golanda]

I like most of the changes but after the dragon engine fiasco I will never be a fan of a one ring piston. There is a reason for two.

 

[mtncat]

There have also been dyno #'s of well broke in 850 Doo's in the 170+ just as there were some 800 Poo's and Doo's in the 160+ so it really comes down to the day and the dyno, Cat needs to come back with a modern version of the 862 and raise the bar again for our sport

 

[RMK935VA]

I like most of the changes but after the dragon engine fiasco I will never be a fan of a one ring piston. There is a reason for two.

Polaris is using a much higher quality piston ring. The old rings were chromoly. The new single ring is better than the old two ring design. This information is from a very credible source. Lots of two stroke engines have successfully used a single ring piston design over the years.

 

[snobyrd]

There have also been dyno #'s of well broke in 850 Doo's in the 170+ just as there were some 800 Poo's and Doo's in the 160+ so it really comes down to the day and the dyno, Cat needs to come back with a modern version of the 862 and raise the bar again for our sport

Im my opinion, you dont race a dyno, i believe that polaris has much better power to the track hp than doo. Pol has been doing more with less hp. Back in 13 when pol was 3ird in hp, it would easily run with a doo in the powder, but i feel its due to clutching, attack angle, suspension and track desgin. Im estatic that pol finally has made a industry leading 2 stroke hp sled, along with ther other great attributes, this sled should be a ringer.
Class leading hp
Class leading weight
Class leading driveline efficiency.
I think theres gonna be lots of perma-grin going on

 

[AndrettiDog]

I think I will wait for direct injection.

You can get it from Doo, but I think you could be waiting for a long time from Polaris. What does it get you from Doo? They still have their issues too. Polaris is keeping the weight down and power up all while keeping the fleet EPA numbers on par. So why spend the money on the DI and pass it to us?

 

[dexter]

Current 800 h.o. Came with a 4 yr motor warranty on the 2016 snow check. This looks like a awesome motor but I am wondering where the added 8 lbs came from. Especially when they are advertising that the front shock springs lost 3 lbs. that’s 11 pounds of extra motor/ wiring/ mounts??

 

[JJ_0909]

You can get it from Doo, but I think you could be waiting for a long time from Polaris. What does it get you from Doo? They still have their issues too. Polaris is keeping the weight down and power up all while keeping the fleet EPA numbers on par. So why spend the money on the DI and pass it to us?

Cleaner idle? LOL

DI has been awesome on the marketing front, but that's about it. My 850 feels a little more refined but it burns just as much gas/oil, hasn't proven to be incredibly robust and is not offering any more absolute performance than non DI.

I'd rather see DI level technology in the clutches, that's where we are lacking in this era of stepper motors and advanced telemetry...

 

[goridedoo]

Current 800 h.o. Came with a 4 yr motor warranty on the 2016 snow check. This looks like a awesome motor but I am wondering where the added 8 lbs came from. Especially when they are advertising that the front shock springs lost 3 lbs. that’s 11 pounds of extra motor/ wiring/ mounts??

I believe the warranty was an option in 2016... not standard. And hopefully a chunk of that weight is in the can.

 

[aksledjunkie]

800 can was already almost 20# can't imagine the 850 can would be heavier!! Crazy if it is ha.

 

[Scott]

So, the Pros always had a little problem with running hot when conditions were not adequate. That's why some of us opted for the standard RMK with 2 heat exchangers. Does this new engine's design help in this regard? Seems like I read somewhere about better heat dissipation. Also, has Polaris every had a standard 4 year warranty before?

The AXYS has NOT had that issue. They have a cooler thermostat in them. It opens sooner.

My Pro RMK runs 125-135 most of the time.
Axys RMK runs 95-105 all day long.

 

[Sheetmetalfab]

I believe the warranty was an option in 2016... not standard. And hopefully a chunk of that weight is in the can.

My 16 sc has 4 year warranty.
1.5 years left.

No extra charge.

 

[mountainhorse]

The 850 Doo is a torque monster. It may only have 10 more Hp at the peak than an 800 but at 6500-7000 it's like 30 more. I hope the Polaris is the same.

There is no free lunch however.

The reason it is a torque monster is because it has an 80mm stroke (same as the 866cc '900 RMK')...

The 840cc 2019 Axys motor has a 74mm stroke... big difference as forces generated increase exponentially as you move further from center.

In terms of torque...at any given RPM... the Doo will most likely outshine the Patriot engine, unless P.I. has come up with some way to radically improve the combustion process that gets more force to the dome of the piston.

An 80mm stroke will induce more effect into the chassis and will make directional changes more difficult... it's just physics.

The 800 HO has a 70mm crank in it... and I'd bet that, for a smaller rider, end of the day, the shorter stroke will not fatigue you as much as the 840.



.

 

[sledcaddie]

cooling and warranty

So, this new engine has a 100 degree thermostat. Can the older Pros get a 100 degree thermostat? Ours normally run about 120 degrees, when they don't run hot. Also, is the 4 year warranty a snow check only option? Is the SKS (with chain case and double heat exchangers) offered on snow check? Thanks for any info.

 

[RMK-King]

So, this new engine has a 100 degree thermostat. Can the older Pros get a 100 degree thermostat? Ours normally run about 120 degrees, when they don't run hot. Also, is the 4 year warranty a snow check only option? Is the SKS (with chain case and double heat exchangers) offered on snow check? Thanks for any info.

The T-stat will not fit on the older Pros,the 850 has a external t-stat that could possibly be retrofitted to work. A lot of guys put a skidoo external T-stat bypass kit on the older Pros that worked well. Here is the link to that.
https://www.snowest.com/forum/showthread.php?t=367303

The free 4yr warrenty is snowcheck only. The SKS is available to be snowchecked.

 

[89sandman]

There have also been dyno #'s of well broke in 850 Doo's in the 170+ just as there were some 800 Poo's and Doo's in the 160+ so it really comes down to the day and the dyno, Cat needs to come back with a modern version of the 862 and raise the bar again for our sport

Your wish could be out being tested and refined as I type,

 

[kylant]

the only reason I bought an SKS is for the extra cooler, my old pro ran very hot. now with the new cooling system and cooler running '18, I see no need to get the SKS again

 

[diamonddave]

Bigger displacements:
To make a big oversquare engine like a true 900cc with a 74mm stroke... you are running 88mm pistons.
You need to have a good piston skirt length to bore ratio... which then stretches out the height of the cylinder, rod length and add rotational mass which would need to be compensated for with larger bob weights of the crank.

I guarantee that engineers in Roseau learned from the 866cc '900's of the past, with the big 80mm-stroke... and what does and does not work, from experience and the school of hard knocks... so they are most likely 'not missing the boat' for optimal powerplant dimensions for MOST of the mountain riders out there.


Lots to consider:
You still need to fit the engine in the sled, keep it compact, make it so that it works in synergy with the nimbleness of the chassis, has snappy throttle response with moderate compression on pump gas, and vibrates as little as possible, has a reasonable cost and can be mass produced with good QC...AND, will function well/durably in GREATLY varying altitudes/air-density/temps/abuse/fuel....Emissions considerations ta boot!.... All while giving the beancounters the confidence of putting a 4yr warranty on the sled.

I'm not sure if you all know just how difficult that is to pull off... a sled that will run strong from sea-level to 13,000 feet with only small clutch calibration changes... HMM.

Quite a feat.

I really hope that Polaris integrates all of these changes in the 840cc into a super potent 600cc package in the near future.






.

I believe that one of the things that is making these new evolutions of the CFi engines better each year.... the control system is getting that much better.

It would be nice to have closed-loop fuel system... but not practical on a mass produced two-stroke... So we have things like pipe temp, coolant temp, air temp, MAP, TPS, DET and now fuel pressure monitoring and on-the-fly automatic adjustment based on these variables... hundreds of times per second...brings the reliability up greatly.


My biggest hope for 2019 is that the engineers in Roseau were able to work with the accountants in Medina well enough to invest in a marked improvement in the quality and componentry of the electrical system on these beasts.... It really is needed to evolve this product.




.

Here are 2 of the best articulated, simple posts I have read on here in a long time. Nice job Eric. I would have had to write a novel to say the same thing. I hope everybody reads them at least twice.



Honestly, I don't necessarily think we need closed loop, would be nice but not needed. A much quicker reacting ECU and more fuel tables for the changing of conditions is really what is needed. If we believe PI, then it sounds like the road they're going down.


It's interesting they will be monitoring fuel temp/fuel pressure. I know I have preached not liking injector location placement, but I've also wondered what effects might be happening with the fuel prior to entering the motor with the fuel rail housing being heated from the motor?? Sounds like the Engineering group is doing their homework.

Let's just hope they have been allowed enough testing and development for this new Engine and control system to be a success.