Polaris Engine and surrounding information

[RKT]

I thought it may be helpful to post a little info on this engine and the large amount of "information" that surrounds this engine. I suspect it will not stay civil (it will on my part) but one can hope.

PLEASE take it as ONLY MY opinion (even though there are many other engine experts (including the manufacturers) who share this same opinion), but an opinion BACKED UP by REAL DATA (not theory or hear-say) and decades of experience

1) Rod Ratio is lacking: FACT: Polaris 800 CFI has the BEST rod ratio of any of the , modern, 800cc engines out there. The rod ratio is actually on the HIGHER end of the "acceptable" spectrum. Yes, there exists design guidelines for all engine builds.. and , again, the rod ratio of the CFI 800 is the best out there.

In short: There is absolutley no rod ratio issue. If there were, then Cat and Ski Doo would be suffering even worse. Again, opinion only , but opinion based on real data, text book design criteria, and experience.

2) There is a "Cold Shot" that causes engine failure: This is a good one and a huge gimmick.. Arctic Cat has had the SAME type as Polaris of coolant system for ever (no by pass loop) and has no issues .. the difference between Cat and Polaris is Polaris has a digital gauge so you can see the actual temps.. Cat has the same temps but no gauge.. Install a gauge on the Cat and ,SUDDENLY, it will have a Cold Shot problem as well... Only Ski Doo utilizes a by-pass loop and they only started doing this in 2000. For more details on why this is simply not an issue please check out this article:WHAT CAUSES and ENGINE to COLD SEIZE?

3) The cylinders, from Polaris, are sized wrong as delivered: This could be one of the biggest falsities of them all.. The simple fact is that the cylinders, when plated, are all plated to within .0005" of each other. This spec is a requirement and is inspected at the factory before installed on the block. RK Tek, as well as, many other Shops, have inspected a large number of these cylinders, ALL, I mean ALL, have fallen within the given spec.

Think about what kind of error it would take to have this SIMPLE inspection/operation "SLIP" by at a HUGE manufacturing facility like Polaris. Polaris has been doing this same manufacturing bore size inspection for over 50 years they are not suddenly going to quit checking cylinders or, worse yet, plate them to the wrong size.....

Not to mention.. it would be very hard for a diamond hone to NOT hone correctly.. It will always hone "round" , When the stones get worn, it will actually make the bore SMALLER not larger..

Think about what a major screw up this would be and how hard it would be for this to be "over-looked" THEN... couple that with the countless cylinders that have been measured (all in spec) and you can realize how rediculous this rumor really is..... Again, simply one person's opinion.

4) The cylinders are offset with respect to center-line of the crank.:

This is a rumor that has been surfacing for some time.. This one is 100% provable (and has been proved via video and, best yet, confirmation from Polaris direct)
In short, the Polaris cylinders are 100% pinned on centerline with the crank center-line.. There is no Offset..

Anyway, I hope this thread can stay purely informative and some information exchange can be had..

Nobody is trying to sell anybody anything... this is strictly and informative thread.

 

[RoffRider]

so what is wrong with this engine

 

[Pro-8250]

so what is wrong with this engine

I think Kelsey is just being Myth Busters. I appreciate his threads. If he said anything negative, even if it's true, he will get jumped all over by some. :argue:

 

[Oregonsledder]

I think Kelsey is just being Myth Busters. I appreciate his threads. If he said anything negative, even if it's true, he will get jumped all over by some. :argue:

Not by me!

 

[RKT]

I think Kelsey is just being Myth Busters. I appreciate his threads. If he said anything negative, even if it's true, he will get jumped all over by some. :argue:

Myth Busters.. LOL.. I like that....

Hopefully, this thread can stay on track and purely informative without the usual BS that ends up engulfing the forums and threads of this nature...

The truth is that there are many myths that surround this power-plant.. It would be nice to try and prove or disprove any or all of them.

I have offered my opinion and data to back up why I came to the conclusions that I did...

I only ask that any other contributors do the same..

Back it up with real life data to support any claims... No "hear-say" based on what they have "heard" or what somebody else "told" them.. But data based on personal experience.

If anybody has anything to contribute.. by all means, please do... just be prepared to have the supporting data ..that's all..

 

[wfieldin]

http://www.youtube.com/watch?v=4trn2lJxl00&sns=em

 

[ottawaair]

On another note, a member of another forum does a lot of repair work and research on this sled and motor. He has reached some interesting conclusions.
This one, i think could be a problem over time.

Basically, when you are running your sled, and shut it off for 5 to 20 minutes, or so, the engine heat rises to the top of the airbox, warming the air box and surrounding componants. This is why the defrost bag works as it does.

Well, the other thing being heated up is the air temp sensor.
So, when you fire up the sled, you know it already warmed up, so you hammer it.
Meanwhile, the IAT sensor is telling the ECU that it is 100 degrees outside, leaning the motor out until the sensor cools and starts reading the correct air temp.

Just a theory, but seems quite possible to me. Even logical.

Any thoughts. ??

 

[RoffRider]

Well, I for one, know this engine suffers from inferior pistons. cone shaped, out of round.
That seems to be the main factor in many of the failures. sure, other things go wrong too, but, pistons are by far the leading problem.
I have the data to support that from my own tear down and measurements.
Coupled with the fact that my engine had a severe vibration in the 3-4,000 rpm range, and with doing NOTHING other than changing out the pistons for better ones, the vibration is nearly non-existant.
I gained back some lost power, and the runs cooler with a better throttle response.

Thats my exrerience anyway. along with many other on the forums.

pistons arnt supposed to be straight, the top of the piston heats more than the skirts so if its straight they would need to make a small piston, but if they taper the piston with a small top, the bottom of the piston could be tight, while a cold piston would be loose at the crown, when hot it will expand and become round when hot...GM motors clack hard when cold because the pistons need to expand into the cylinders so the cold pistons are a little small, but when hot the piston slap goes away...pistons arnt supposed to be perfectly round either, the wrist pin entries have more material than the inake and exhaust skirt, so when expanded, they push out more than the skirts, so a very slight oval shap is better, with the pin entries have just a touch more clearance than the intake and exhaust skirts

 

[ottawaair]

Well, I for one, know this engine suffers from inferior pistons. cone shaped, out of round.
That seems to be the main factor in many of the failures. sure, other things go wrong too, but, pistons are by far the leading problem.
I have the data to support that from my own tear down and measurements.
Coupled with the fact that my engine had a severe vibration in the 3-4,000 rpm range, and with doing NOTHING other than changing out the pistons for better ones, the vibration is nearly non-existant.
I gained back some lost power, and the runs cooler with a better throttle response.

Thats my exrerience anyway. along with many other on the forums

 

[ottawaair]

sorry, i deleted that post on accident. Re-posted it.

 

[ottawaair]

pistons arnt supposed to be straight, the top of the piston heats more than the skirts so if its straight they would need to make a small piston, but if they taper the piston with a small top, the bottom of the piston could be tight, while a cold piston would be loose at the crown, when hot it will expand and become round when hot...GM motors clack hard when cold because the pistons need to expand into the cylinders so the cold pistons are a little small, but when hot the piston slap goes away...pistons arnt supposed to be perfectly round either, the wrist pin entries have more material than the inake and exhaust skirt, so when expanded, they push out more than the skirts, so a very slight oval shap is better, with the pin entries have just a touch more clearance than the intake and exhaust skirts

What are the correct tolerances for out of round and taper top to bottom. ??

We ain't makin this up just to argue.

I have my old pistons, and monoblock, that is cracked at the bottom.
I found that while replacing the pistons that are supposed to be cone and egg shaped. ??

something cracked that cylinder skirt, and its not because the stock piston fit so well.

 

[ottawaair]

i have however been inside yamaha motors with over 10,000 miles on the original pistons and rings. SRX's, Vmax's, Ant the pistons look as if they are nearly new.

Those are round also.......

 

[RoffRider]

What are the correct tolerances for out of round and taper top to bottom. ??

We ain't makin this up just to argue.

I have my old pistons, and monoblock, that is cracked at the bottom.
I found that while replacing the pistons that are supposed to be cone and egg shaped. ??

something cracked that cylinder skirt, and its not because the stock piston fit so well.

while i do not know what polaris makes their pistons to, i do know they shouldnt be perfectly round and straight, only slight tapers and oval shapes...if you ever seized a piston tell us where the score marks on the cylinder and piston are located

 

[RoffRider]

i have however been inside yamaha motors with over 10,000 miles on the original pistons and rings. SRX's, Vmax's, Ant the pistons look as if they are nearly new.

Those are round also.......

you cant compare an old 90's engine to a 2010+ engine those motors used carburetors and had a good oiling system, with much smaller cylinders and pistons, this gets rid of your vibration... this engine has to meet epa standards and doesnt have the best oiling system or injection system...with two cylinders that are 400 cc's each...

 

[ottawaair]

The score marks are usually on the exhaust side. Where the heat is.

Occasionally on the intake side.

Pretty much where the main contact points of the piston and cylinder are.

 

[Pro-8250]

THUMBS UP!

Myth Busters.. LOL.. I like that....

Hopefully, this thread can stay on track and purely informative without the usual BS that ends up engulfing the forums and threads of this nature...

The truth is that there are many myths that surround this power-plant.. It would be nice to try and prove or disprove any or all of them.

I have offered my opinion and data to back up why I came to the conclusions that I did...

I only ask that any other contributors do the same..

Back it up with real life data to support any claims... No "hear-say" based on what they have "heard" or what somebody else "told" them.. But data based on personal experience.

If anybody has anything to contribute.. by all means, please do... just be prepared to have the supporting data ..that's all..

Here is my real life data!


Stock 2011 Pro RMK 155". 3506 miles. One exhaust temp sensor.
Stock 2011 Pro RMK 163". 2147 miles. Zero problems.
Stock 2013 Pro RMK 155". 1507 miles. Zero problems.
Stock 2014 Pro RMK 155". 0 miles. On the way.

 

[ottawaair]

you cant compare an old 90's engine to a 2010+ engine those motors used carburetors and had a good oiling system, with much smaller cylinders and pistons, this gets rid of your vibration... this engine has to meet epa standards and doesnt have the best oiling system or injection system...with two cylinders that are 400 cc's each...

Ok, 1986 Honda CR 500... One huge piston, 500cc's worth.

Correct piston fitment, no broken skirts. hmmmm......

2010 and up cat motors... correct piston fitment. No broken skirts.

Since you have so much knowledge, but haven't opened up your motor yet, Maybe you should tell us what you opinion is.....
Rather than trying to debunk our findings.

 

[ottawaair]

I also have real life data, but would have to go out to the shop to take some pics of my broken parts.

 

[GoBigParts]

I also have real life data, but would have to go out to the shop to take some pics of my broken parts.

How many miles before failure? How many miles are on your aftermarket pistons?

 

[mtncat1]

On another note, a member of another forum does a lot of repair work and research on this sled and motor. He has reached some interesting conclusions.
This one, i think could be a problem over time.

Basically, when you are running your sled, and shut it off for 5 to 20 minutes, or so, the engine heat rises to the top of the airbox, warming the air box and surrounding componants. This is why the defrost bag works as it does.

Well, the other thing being heated up is the air temp sensor.
So, when you fire up the sled, you know it already warmed up, so you hammer it.
Meanwhile, the IAT sensor is telling the ECU that it is 100 degrees outside, leaning the motor out until the sensor cools and starts reading the correct air temp.

Just a theory, but seems quite possible to me. Even logical.

Any thoughts. ??

i'm not buying that. the computer is monitoring engine temp ,and engine air temp continually, refreshed several times a second, the air temp in the air box is going to correct it's self very quickly as the engine pulls fresh air into it as soon as the engine starts up. so this lean condition would be corrected by the time you hit the throttle. if you were talking water temp maybe because it changes much slower.