Why DOO SKI-DOO motors blow up at such a low mileage?

[Rhodesie]

we are asking a lot of these engines. more power, higher rpm, lighter weight. still using the same 'ol cast pistons. the skirts collapse a few thou over the first 1500 miles. not sure about the others but the 800 polaris piston drops out of the cyl skirt a lot at bdc.

 

[Lem Lamb]

Just a 50/50 crap shoot !!!

Slight De-tune,,, drop the rmps below the 8.800 rpm """ish""" mark,,, stay away from the 9.200 down hill over revs and they will last a long long time...

Don't get me right or wrong,,, We like our 2-strokes lean and crisp coming off the bottom end for hole shots,,, other then that we lose alot of speed and power climbs...

Guess it depends on what a person wants...
Performance or longevity...
A person can get both if a person chooses too invest some coin...

2-stoke engines offer both worlds,,, Fast for fast or Slow for Tractor mode...

The old guy said:
360 hour service life if they've been working hard,,, in most cases something will need replacing ,,, this can be discovered on scheduled maintenance inspections...

If a person dosen't mind doing them...

It's part of the costs for high performance race engines...

Most of Todays sled engines fall into this catagory...

Cheers

Jt

 

[maxwell]

Good to see many people observing how important proper warm up is. In addition, lots of these issues are related to emissions. The oil injections are cranked down on all OEM motors to meet the emissions standards, and they don't want to crank them back up after for the production stuff - nobody wants to be the next Volkswankin' where they meet the targets at the test and then fail in the real world.

I've been watching these engines for years, and primarily the way they inject the fuel and oil separately plays a big part in motor longevity. The case oil injection only does so much to pick up the oil in the intake charge as it comes through. The top down fuel injection then also washes some of the oil from the cyliinder and the RAVE injectors. Not enough lube is getting to the bottom portion of the piston. The skirt wears and it either rocks in the cylinder until it breaks off or it loses compression. The Doo has a pretty low rod ratio so that contributes to the skirts breaking in any engine typically. This is not a Ski Doo bash, just an observation, all OEM's have similar issues.

Good preventative maintenance and never hurts to dump 2-3 capfuls of oil into a each tank of fuel (or a bit more) - just gives it a little more lube in the top end from the injector side. Change plugs 2-3 times a season is still cheaper than a top end.

not sure how much time you've spent around the skidoo turbo but its oil consumption rate is extremely high. No way that engines not getting enough oil lol. Maybe not to the correct spots. But it drinks it

 

[ABMax24]

I wonder how investors feel about Doos engines?

Oh look:

 

[lilduke]

Maybe there is something else going on in the industry?

 

[Caper11]

I’d say the price of oil is hitting their stocks. Look at the price at the pumps. These luxuries usually get back burnered if people cannot afford to run them.

The stock markets are way down as well.

 

[ABMax24]

Maybe there is something else going on in the industry?


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This is a thread about skidoo, we're going to have to ask you to keep your Polaris fanboiism out of this thread and stay on topic please. Lol

 

[Modman]

not sure how much time you've spent around the skidoo turbo but its oil consumption rate is extremely high. No way that engines not getting enough oil lol. Maybe not to the correct spots. But it drinks it

Ya, not a ton of time around them and not one us compare oil usage during fill up, everyone just tops up, I'll have to ask the boys, but ultimately deferring to you guys on that one. I haven't really seen one apart to see all the internals. Interesting.

Maybe it will be better longevity due to the added oiling or just more charge in the combustion chamber and more leaking past the rings. The way I understand the oiling system for the turbo is there is a small reservoir at the turbo drainback that has a pump and sends that oil to the RAVE's? Is there any priority oiling to the turbo?

 

[lilduke]

This is a thread about skidoo, we're going to have to ask you to keep your Polaris fanboiism out of this thread and stay on topic please. Lol

No Its any thing goes here last time i checked lol

 

[ABMax24]

Others have touched on design aspects of the 800 vs 850 ETEC, but I'll share my thoughts.

Background; 2-stroke engines utilize a total-loss lubrication method to lubricate the crankshaft bearings and piston. As 2-stroke engines don't operate on pressurized lubrication, traditional journal bearings are not permissible, necessitating ball and roller bearings for the crankshaft and rod bearings. Generally all or some portion of the fuel is injected through the crankcase in a 2-stroke engine, diluting and washing the oil film from the bearings and cylinder surfaces. Dilution of oil with fuel reduces the oils viscosity and reduces its lubricating effectiveness at best, at worst it washes the fuel completely from the surfaces allowing metal to metal contact and engine wear and possible engine seizure. Given that 2-strokes don't have an oil sump to collect and circulate oil, a continuous feed of oil is required to maintain lubrication in the engine, but this oil consumption must be kept to a minimum to meet emissions regulations.

The 800 ETEC was designed with a very key feature that I believe is a major cause of it's extended reliability. The 800 relies solely on direct injection to supply fuel to the combustion chamber of the engine. (BRP acquired the assets of OMC which was undergoing bankruptcy in early 2001, one of these assets was Evinrude, which held patents for 2-stroke direct injection). None of this fuel travels through the crankcase, almost guaranteeing fuel dilution will not occur, and with proper fuel injector nozzle design and injection timing minimizes fuel wash on the cylinder keeping the piston properly lubricated. The non-diluted oil film can also serve as "padding" for the piston as it rocks back and forth in the cylinder during every crank rotation, this oil film also acts to transfer heat to the cylinder walls which keeps the piston cooler. A piston that rocks less in the cylinder, and does so at lower temperatures suffers much less cyclic fatigue, which greatly improves piston life and reduces the chances of skirt breakage. The lack of fuel in the crankcase also ensures the crank bearings are well lubricated, and are much less prone to failure from oil starvation.

The 850 was designed as a more powerful version of the 800. Except with the future intention of adding boost. The 850 has smaller fuel injectors installed than the 800, necessitating adding fuel by another set of injectors, BRP decided to do this through auxiliary injectors in the throttle bodies. There are benefits of adding fuel this way, including better mixing of the air fuel mixture prior to combustion, for better emissions and performance at high rpm and high loads (Ford has even added secondary injectors to the 3.5 ecoboost for similar reasons). The 850 relies heavily on the auxiliary injectors above mid throttle to supply enough fuel to the engine. The downside of this is oil dilution in the crankcase and lower cylinder, greatly reduced oil viscosity in the bearings, and the decreasing the oil film strength on the piston. Inevitably decreasing the service life of the crank bearings and of the piston by removing the oil cushion for the rocking piston. Both of which have been seen as failure points on the 850.

BRP didn't design the 850 without knowledge of the oil dilution issues that throttle body injectors creates, BRP has created a very innovative 2 piece forged crankshaft, with well placed oil galleries to delivery oil to the lower rod bearings. On paper it looked good, from what I've seen though on the snow, and other failure reports I've read, crank failure is still more prevalent than the 800 ETEC.

 

[kingcat162]

An 800 etec that has boost injectors in the airbox will still last longer than an 850 doo

 

[SUMMIT TREE]

I wonder, do some guys run oil in the fuel tank on the 850’s and if so, do they seem to be the ones lasting longer?

 

[SUMMIT TREE]

How much oil are you putting in if so?

 

[ABMax24]

An 800 etec that has boost injectors in the airbox will still last longer than an 850 doo

I do know that at high boost the 800 does have rod issues, as in break the rod in half under full load issues.

 

[kingcat162]

I do know that at high boost the 800 does have rod issues, as in break the rod in half under full load issues.

The 800 etec swallows up 8lbs of boost all day long - I've got 8000kms on the chassis - I put a new crank in it at 5000kms just to be safe - 3000kms now of 8lbs - I'm running it till the rods leave the chatroom then she's gettin parted out

 

[ABMax24]

The 800 etec swallows up 8lbs of boost all day long - I've got 8000kms on the chassis - I put a new crank in it at 5000kms just to be safe - 3000kms now of 8lbs - I'm running it till the rods leave the chatroom then she's gettin parted out

Depends on the engine. Some went forever on 10lbs, some snapped the rods the first time they hit 5lbs.

I don't know if it's a metallurgy issue, a pre existing crack from manufacturing, or just undersized for boost. All I know is some break and the rest don't.

 

[shawnmcgr]

Just to cool the enthusiasm for 800 xm, my 16 needed a top end at 3400kms. Always warmed up, skidoo oil.

 

[kingcat162]

Just to cool the enthusiasm for 800 xm, my 16 needed a top end at 3400kms. Always warmed up, skidoo oil.

It's hit and miss with all of em I guess - I just talked to my buddy this morning - he's at 9700kms 850 doo with a 5lb silber last service on it was probably at 4500kms and that was putting new plugs in it

 

[M1ryguy]

My 800 went kaboom at 1000kms on 8lbs of boost, it was really cool getting to see what the inside of the motor looked like way back in frisby ridge.

 

[kingcat162]

My 800 went kaboom at 1000kms on 8lbs of boost, it was really cool getting to see what the inside of the motor looked like way back in frisby ridge.

They can be one of the trickiest sleds to get the mapping figured out - that would be my guess as to why she blew at a grander - I'm loving my aurora box - 12.5afrs at 8lbs - flat lined there - runnin off the 02 sensor - runnin flawlessly