Polaris Engine and surrounding information

[Outlaw]

Fair enough, I will explain.

On the 2006-2014 Polaris 600, 700 and 800.
If you shut your sled off to take a break, Help a buddy or any other reason your engine will heat soak due to the hot coolant in the engine. So you get a heat soak of say 180 degrees sometimes more, Keep in mind that the sled has a 130 degree Thermostat. Due to the heat soak the Thermostat is going to be open. The Pro chassis has a 25 GPM water pump (around 10 at an idle). So. Thermostat is wide open, Engine is heat soaked, Coolant in the tunnel is cooler (depending on how long you have been sitting) 60-80 Degrees. Now pull the rope and start the sled. Due to the open thermostat the coolant from the tunnel runs a direct shot Thru the coolant bottle to the water pump and then hits the cooling ports in a heat soaked motor. This is your Cold Shot.

 

[RKT]

Fair enough, I will explain.

On the 2006-2014 Polaris 600, 700 and 800.
If you shut your sled off to take a break, Help a buddy or any other reason your engine will heat soak due to the hot coolant in the engine. So you get a heat soak of say 180 degrees sometimes more, Keep in mind that the sled has a 130 degree Thermostat. Due to the heat soak the Thermostat is going to be open. The Pro chassis has a 25 GPM water pump (around 10 at an idle). So. Thermostat is wide open, Engine is heat soaked, Coolant in the tunnel is cooler (depending on how long you have been sitting) 60-80 Degrees. Now pull the rope and start the sled. Due to the open thermostat the coolant from the tunnel runs a direct shot Thru the coolant bottle to the water pump and then hits the cooling ports in a heat soaked motor. This is your Cold Shot.

The engine is not heat soaking due to the hot coolant... it is heat soaking due to the ENGINE heat transfer NOT the coolant heat. Remember heat travels from HOT to COLD.. always.. The engine is ALWAYS hotter than the coolant.. ALWAYS..

Take a piece of any metal, and hold it at one end with your fingers... Then put your lighter on the other end (heating it)... You will notice that it takes some time for the heat to reach your fingers... right?

Now, once the heat has reached your fingers and you set down the metal piece.. and remove the lighter (heat source)... Set it on the floor.. Wait 30 seconds and try and pick it up again.. What happens?? It is even hotter than it was before... WHY? Because the heat is still transferring to the colder (where your finger was) area.. If whatyou say was true... the piece would be cooling down not heating up (like it is)... The pieces is trying to obtain temperature equilibrium... Just like your engine... Try it you will see....

Your engine can NOT be cold shocked when running... It simply can not happen... The heat that is being produced by your running engine is FAR more powerful than your coolant that is passing by in the water channels..

This is where the misconception lies... You can not cool the heat SOURCE (engine) you can only cool the components that surround the heat source like the cylinder, head, etc...

Again, this CFI system works NO different than the Cat system.. Flow direction makes no difference.. The difference is thatyou have a temp gauge on your Polaris and you do not on the CAT. If the Cat has a temp gauge, you would see the same thing exactly..

 

[ottawaair]

I will say that i watched a person fill the radiator on a camaro (350 chevy) while the motor was running and overheating.
Started filling the radiator with a garden hose (cold Water), and right there the block split open between cyl 1 & 3
I'd say that was a cold shot.

Now, on the pro motor (or any other, i guess) If the pistons and cylinders are 180 degrees from sitting. The coolant in the coolers is cold, when you fire it up and the cold coolant hits the water jackets, it cools the cyl. and shrinks it. ( already expanded from heat)
You hammer the throttle, and the piston instantly gets extremely hot and expands.
I would say there is going to be a period of time that the piston is expanding, the cyl. is shrinking, and things could get tight.

The theory is similar to a cold seize, but not quite as extreme. As the cylinder isnt starting from a completely cooled state to being started and hammered.

I can really only see the cold shot theory having an effect over a long period of happening over and over.

The occasional start and go shouldn't be a huge issue.

BUT, couple this with my earlier theory of the T-map sensor also being heated from the engine heat in the airbox. Now, the computer is trimming fuel because it thinks it's 100 degrees outside.

Cold shot. ---cyl. shrinks, piston grows, computer cuts fuel. This could be a potential problem ??

 

[ottawaair]

Also, to add to the T-map sensor theory....

The sensor reading has been taken after the engine bay has warmed up.

With the sled idling, it took nearly 3 minutes for the sensor voltage to equal ambient air temp.

Thats 3 minutes of computer having a false reading, and trimming fuel.

 

[RKT]

Also, to add to the T-map sensor theory....

The sensor reading has been taken after the engine bay has warmed up.

With the sled idling, it took nearly 3 minutes for the sensor voltage to equal ambient air temp.

Thats 3 minutes of computer having a false reading, and trimming fuel.

The T Map sensor is not the only sensor determing the fueling from the computer... it does supply an input and its input is used MOST OF THE TIME! There are other inputs in play as well.... The computer places a priority on these inputs and uses algorithims to determine which input carries more "weight" ,, In electronics it is called an interrupt structure.
So, just because the air sensor sees a hot condition... the fuel is not automatically leaned out to try and adjust..

It also looks at rpm, throttle position, water temp, barometric pressure , pipe temp and some others to determine IF fuel needs to be removed..
So, it uses ALL the inputs supplied to make an educated decision on what do to with the fuel delivery.. from our testing, the hot air temp is not causing a lean condition at start-up (after sitting)

 

[ottawaair]

The T Map sensor is not the only sensor determing the fueling from the computer... it does supply an input and its input is used MOST OF THE TIME! There are other inputs in play as well.... The computer places a priority on these inputs and uses algorithims to determine which input carries more "weight" ,, In electronics it is called an interrupt structure.
So, just because the air sensor sees a hot condition... the fuel is not automatically leaned out to try and adjust..

It also looks at rpm, throttle position, water temp, barometric pressure , pipe temp and some others to determine IF fuel needs to be removed..
So, it uses ALL the inputs supplied to make an educated decision on what do to with the fuel delivery.. from our testing, the hot air temp is not causing a lean condition at start-up (after sitting)

That understandable. It's been tested with a resistor inline to fool the computer. It has taken care of some off idle stumbles for others.

To be quite honest, I don't have any issues with my motor.
I was starting to lose some power and compression was a bit low.
Installed kelsey's pistons, and all has been well.

So, i'm just theorizing with you guys.

 

[snoblind04]

I think the engine weight is not the reason behind some of its short-comings (reliability -wise) You can address the reliability concerns and still keep the engine lightweight..

IMO, Polaris just has a few design issues and have opt'd to use some "less expensive" components that attribute to the longevity of the engine..


I don't think casting weight is the issue either. Ski-doo had the lightest 800 engine until they went to the e-tech. It added around 10 or more pounds.

 

[RKT]

OK, here is another "rumor" that is traveling about this engine..

1) There is a new piston for 2014? True or False??

Back on the "cold shot" topic...

Ask yourself this..."When you throw water on a fire.... why does it extinguish it?

Another: "If you set a block of ice on your stove-top on one of the burner grates... does this change the temperature of the burner flame?"

 

[ottawaair]

New piston ??? New part number.... Probably.

water on a fire. Yes it puts the fire out. Is it because of the cooling effect, or creating a lack of oxygen.

Ice on the stove. I'll go try it.

Not sure these have to do with the expansion and contraction of heated and cooled metal objects.

Pour some water in a pot of molten metal.

 

[AKSNOWRIDER]

Interesting theories..but anyone who thinks metal doesn't move under varying temps is nuts..and when applied to a internal combustion engine...really nuts..machined surfaces in motors move as their temps change..it is a basic fact that is indisputable...now how much it moves and in what direction can be controlled (up to a point) but a thin walled cylinder/block/head will contort/flex more then a thick walled piece, again been proven time and time again before any of us were even born.......

 

[snomac]

First of all I'm not an expert here. I have a 2013 Pro and love it. In my group we seem to ride pretty hard, stopping for a minute or two and then continuing on. (don't want to let any powder go to waste right) I put on 1000 miles last year and noticed that consistently when we would stop for a short time, (usually just a couple minutes or so) and then hit it again. The sled at first always seemed weird and not wanting to run for a minute, almost sputtering. I can't help but think that there is something to this cold shot theory. To me cold coolant rushing to a hot motor could cause a bunch of problems for sensors and electrical and not to mention any unwanted strain on an already temperamental motor. I can't help but think that eliminating the cold shot would be a good thing, whether it cures all the problems or not.
This study was done during a 1000 miles between my ears.

 

[RKT]

Interesting theories..but anyone who thinks metal doesn't move under varying temps is nuts..and when applied to a internal combustion engine...really nuts..machined surfaces in motors move as their temps change..it is a basic fact that is indisputable...now how much it moves and in what direction can be controlled (up to a point) but a thin walled cylinder/block/head will contort/flex more then a thick walled piece, again been proven time and time again before any of us were even born.......

aaah.. not seeing where anybody is disputing that temperature effects expansion??

The question here is how "cold" do you really think your engine is after 10 minutes of sitting?? Do we think that it has cooled down to a point like it has set overnight? OR is it still hot and just slightly cooling due to the entire system trying to reach temperature equilibrium?

Again, the Cat runs the exact same cooling type system as does Doo (after we remove the t stat and block the by pass line) and neither suffers nor does the Polaris suffer...

How many have seized their engine after a 10-15 minute "rest" and then a pull up the hill...?? We sit for that and then immediately WOT up a hill for 30sec to 2 minutes.. of course we run forged pistons and we all know that they can not handle this type of condition YET, they do it all season long even in -20 below F...

Point being..this "Cold Shot" phenom is not new,It has always been there.... it has been going on forever.. the difference is that Polaris decided to put a gauge on their dash
Remove the Gauge and the problem disappears. install the gauge on the Cat or DOO and the problem re-appears...

 

[RKT]

First of all I'm not an expert here. I have a 2013 Pro and love it. In my group we seem to ride pretty hard, stopping for a minute or two and then continuing on. (don't want to let any powder go to waste right) I put on 1000 miles last year and noticed that consistently when we would stop for a short time, (usually just a couple minutes or so) and then hit it again. The sled at first always seemed weird and not wanting to run for a minute, almost sputtering. I can't help but think that there is something to this cold shot theory. To me cold coolant rushing to a hot motor could cause a bunch of problems for sensors and electrical and not to mention any unwanted strain on an already temperamental motor. I can't help but think that eliminating the cold shot would be a good thing, whether it cures all the problems or not.
This study was done during a 1000 miles between my ears.

Snomac... Very good point... What you are seeing is directly related to the pipe cooling.. Remember the heat transfers from Hot to Cold.. and guess what is the hottest part of the system?? YUP.. the pipe...

So, when you stop the pipe transfers its heat to the rest of the system.. It cools down!

So, the heart of the two stroke engine is the pipe.. it MUST be at operating temp in order to allow the engine to perform optimumly.. when the pipe is cold, the engine is essentially out of tune.. So, when you start up the cold pipe is not allowing the engine to perform well.. once it heats up.. walla.. performance returns..
This is very common with aftermarket pipes or stock pipes where the heat shield has been removed in favor of ceramic coating,, these pipes will always cool off faster and heat up slower than any insulated pipe... So, if you do not have the heat shiled on or you have a thin walled aftermarket pipe or even an aftermarket can.. expect this situation to be more prevelant at every "rest stop"

Make sense?

 

[ottawaair]

First of all I'm not an expert here. I have a 2013 Pro and love it. In my group we seem to ride pretty hard, stopping for a minute or two and then continuing on. (don't want to let any powder go to waste right) I put on 1000 miles last year and noticed that consistently when we would stop for a short time, (usually just a couple minutes or so) and then hit it again. The sled at first always seemed weird and not wanting to run for a minute, almost sputtering. I can't help but think that there is something to this cold shot theory. To me cold coolant rushing to a hot motor could cause a bunch of problems for sensors and electrical and not to mention any unwanted strain on an already temperamental motor. I can't help but think that eliminating the cold shot would be a good thing, whether it cures all the problems or not.
This study was done during a 1000 miles between my ears.

This goes more with the theory of the map sensor reading hot.
And, i know other sensors are at play here, but maybe the engine is confused.
Hot t-map sensor, hot water temp sensor (according the gauge)
exhaust pipe sensor ?? I would guess that the pipe sensor is reading cooler than a motor thats been running. (flowing exhaust being hotter than heat soak engine compartment)
I know i keep going back to this theory, but i think there may be something to it.
Maybe the computer should have a preset map for 2-3 minutes, then start adjusting according to the sensors. ???
After every shut down and start up, it could run according to a map of cold engine. Add fuel, possibly even limit rpm for the first 3 minutes of running ??

 

[AKSNOWRIDER]

That drastic temp change in the block may not be a issue with other motors(of course they also have more material in them) but yeah shut off a hot pro on the hill, let set 10 minutes and then start and go full throttle every time and you are going to drastically shorten the engines life. maybe a good test would be to take a pro cylinder and document its measurements cold, then place in 180 degree water until stabilized and remove and remeasure..bet it moves more then you think....

 

[RKT]

This goes more with the theory of the map sensor reading hot.
And, i know other sensors are at play here, but maybe the engine is confused.
Hot t-map sensor, hot water temp sensor (according the gauge)
exhaust pipe sensor ?? I would guess that the pipe sensor is reading cooler than a motor thats been running. (flowing exhaust being hotter than heat soak engine compartment)
I know i keep going back to this theory, but i think there may be something to it.
Maybe the computer should have a preset map for 2-3 minutes, then start adjusting according to the sensors. ???
After every shut down and start up, it could run according to a map of cold engine. Add fuel, possibly even limit rpm for the first 3 minutes of running ??

Ya know, I am sure there is something to it..

Keep in mind.. Polaris, cat and Doo ALL run these same type sensors.. they are called thermistors.... All 3 have them and they are all located under the hood in various places (usually the airbox, head and pipe)

Point being.. this is not unique to Polaris.. and the engineers at all 3 know how fast they react and take this in to consideration when doing the ECM programming.. This is why they have more than 1 input variable to the ECM.. so they do not get "confused".

There is no doubt that the underhood heat can heat up a thermistor.. but if it is heating it up on the Polaris, it is heating it up on the Cat and Doo as well.... Ski Doo even adds a 2nd pipe sensor(on the Summit models ONLY) to make sure that it does not get confused.. the MXZ models only have the 1 pipe sensor...

 

[RKT]

That drastic temp change in the block may not be a issue with other motors(of course they also have more material in them) but yeah shut off a hot pro on the hill, let set 10 minutes and then start and go full throttle every time and you are going to drastically shorten the engines life. maybe a good test would be to take a pro cylinder and document its measurements cold, then place in 180 degree water until stabilized and remove and remeasure..bet it moves more then you think....

I am sure that test would be informative..but until somebody actually performs that test it is pointless to speculate on the results.. agreed?? This is what this thread is about.. Speculation vs. hard data.... Hard data is what we need speculation is what people are supplying...

Why 180 degree temp?? Unless you have a 2011 sled, the engine will barely run after 160 water temp.. so if you are seeing 180, then, there is no doubt you have other issues to address.

We see from 118-132 degrees max whenever we ride...180 or even 160 is not an option...

 

[cascadesnowjunky]

I believe ak meens after it heat soaks it will be 180ish

 

[AKSNOWRIDER]

I have seen 160 to 180 many times on first fire up from a 5-15 minute soak on stops...

 

[RKT]

I have seen 160 to 180 many times on first fire up from a 5-15 minute soak on stops...

Well. we never see that high of water temp.. we had a plugged line last season and at 160 the sled would barely run...(on purpose.. by Polaris design) you must have a 2011??

Also, you can be sure that your engine temp is always over 180 degrees.. this coolant temp is no indication of what your engine temp is... this is part of the misconception.....

How to you think your coolant reached 180 with the engine off??

YUP... the engine heated it... You can't heat another object to 180 unless you are AT LEAST 180....so, having 180 degree coolant temp for the short time the sensor reads it after start up, is not going to upset the engine since the heat came from it.. The engine is actually cooling down.. not heating up...

Then once started.. the engine gets hotter and hotter all over again.. No stress on the engine when the coolant temps are hot since it is always hotter and the hot coolant temps only last a VERY short time...