I have reveiwed the parts list for the 800sp cooling system and the 600 rr that was suggested in another post as being a series run cooling system and a better way for the 800 to work the same way. I do not have a 09 rr and these pics are only so so. Here is my take on it. The rr system looks very close to the 800. The only series part of the system is the rear coolers are run as so. The front and tunnel coolers still run in parallel with the only differance is the rr returns coolant from the front cooler to the water pump inlet hose and the 800 returns the front cooler water to the coolant tank. Here are some other diffs, The rr has a large hose front cooler, 800 has much smaller hoses and fittings. The 800 tunnel coolers are much bigger, full length of tunnel and much wider than the rr. No need or room here for a second cooler to run in series. With this said, changing the flow path on these 800 sleds to run in series will likely cause more problems. The front cooler inlet is not big enough for all the coolant to flow properly through if it was run in series with the rear cooler. Also the in series set up would premote huge coolant temp swings due to varing snow conditions. The parallel system can work very well I think, it is designed to use both coolers once the sled gets the t-stat opened. Removing the t-stat will premote coolant only to flow to the tunnel coolers(path of least resistance) and speed the coolant flow rate up, which is no good either. Remember back in the day when your t-stat stuck open you car never warmed up. This is what I will be trying. I have modified a t-stat to be open all the time. With this the designed flow rates will remain and enough back pressure will be there pre t-stat to force flow to the front cooler as well as the rear. This is only a feeler to see what everyone thinks and no way the correct way yet, I will be running a test on this this weekend. Click to view attachment What do you guys think? Stupid simple allways works for me.

After everyone was foaming at the mouth for a cooling system mod to run cooler temps this post has generated zero replies. Does anyone have anything else to add to this or maybe some thing differant? If we work together we can work this out.

I have herd of putting a large washer in the t stat housing. And you keep making the center hole a little bigger to achieve the proper temp you want to run.
Not sure....just heard it a couple times, Never tried it.

Ya Meathead I am all for it man. If you fine something that would be awesome. I simply do not have the time for stuff like this, I work away from home ALOT, but it shouldnt be too difficult. I just made reference to you doing this in my post about what I summed up from DynoTech's testing

Yep, same thing. Just using the t-stat body instead of the washer.

All I'm worried about are those sub zero temps. Will the sled warm up enough?

Meat head you totally lost me, but im reading and trying to comprehend. Keep us updated.

here is something else i have been pondering. the 800 sp uses thermostat
part # 7052433 Thermostat, 120 Degree

the 800 assault uses thermostat part # 7052452 Thermostat

i think the thermostat in the 800 assault has a hole drilled in it which i believe is what meathead is talking about

I cut the t-stat in half and removed the spring and valve seat from the t-stat. Install just the t-stat housing body and seal back in place.

I'm sitting here thinking about this. The front heat exchangers have smaller hoses/ fittings, and if you plumb that in series w/ rear heat exchangers it might reduce velocity. From my reading Kevin Camerons stuff on my own website, we need high velocity coolant to transfer heat quickly from combustion chambers (it's all there for learning). So what if we just remove the thermostat, and let coolant flow at high speed wherever it wants to go? Perhaps we only need maybe a fixed restrictor in the line to the front heat exchanger? Whatever it takes to create the lowest possible average cylinder head coolant temp, as shown on the great digital coolant temp gauge. Operating in snow is the final test for this. He who gets the coolest operating temp gets the lowest deto and the highest HP. Lets see what happens when the snow flies and trails open.

That will be one of my tests this weekend to see if the front cooler still gets good flow without the t-stat. I will have to look that artical up from you site, sounds like good reading...

I'm trying to figure out on snowest what temp the t-stat on the RMK's and Assault opens at. Might be what the short trackers need.

This is the craziest stuff I have ever seen. First, how about trying the sled out as is in the snow.

Hey, let these guys figure it out running the D8 cooler.

They might be onto something.

I guess that is the point! How can you figure it out, if you don't have any snow to ride the sled on in order to evaluate its operating temoerature?

Well if meathead comes out with a coolant fix that produces more hp, and will run good on the snow, let him work his magic.
If it does not work and atleast he tried.
I would like to know if this would work.

I was thinking the same thing. On the Polaris parts web site the 7052433 Tstat says 120, the 7052452 for the Assault and RMK's doesn't give a temp. I'm picking my sled up today I'm going to talk to the service/parts guys and see if they know what temp the 7052452 operates at. Could it be just that simple?

The Assault / RMK 163 thermostat has a bigger hole in the plate because these sleds do not have the front tunnel cooler. The two 800 thermostats open at the same temp...only difference between the two is that bleeder hole in the plate.

I was told by Ron on SnoWest(a very reputable source) that the 800 RMK/Dragon/Assault T-Stat opens at 163 degrees. Part # 7052452 as you said.

He says the #7052433 T-stat opens at 155 degrees, conflicting with Polaris' claim?

Why not get a thermostat that opens at 95 or 100? Would that be the correct fix. How do thermostats work? What triggers the thermostat to open?

I could be wrong on this but, I think that the spring is bi-metal, meaning 2 different types of metal. When the temperature gets hot enough because of different metals reacting to the same temperature the stat opens. Can I get some help on this?

That would work but such a low t-stat temp would be very hard to find, it's worth checking into but not likely to find.

Bummer....Just couldn't be that simple. When I picked my sled up today I asked about the 2 tstats and they didn't have any info on them yet. I was hopeing that the Assault/RMK stats opened at 100.

How do you know that the sled won't run in this range? Meat Head, who is a '07 D7 owner should know all about this.

My 07 dragon allways ran at 120F+, so whats your point?? If it has a 120F t-stat that works correctly then it will run 120F most of the time. It's a no brainer in my book.

Just have a question I have a 07 dragon as you did. why did everyone say it needed to run hotter and not cooler as every other sleds runs better being cooler?

My 07 ran at 104 degrees. My dealer checked the stat and it opened at 120. The problem with my sled was that there was coolant leaking thru the heat exchanger in front of the track between the 2 halves. I fixed that by installing a restrictor in the bypass hose under the stat and viola 126-129 degrees. Then my sled ran a lot better.

There is wax that melts as it gets hotter. More it melts, the more it displaces (ie:gets larger) and when it exerts more pressure than the spring exerts (sp) it opens the t-stats valve. The wax is contained in the part of the t-stat that is installed towards the engine.


I have not seen any stat under 120°F for any application, but that doesn't mean there isn't one. Pretty doubtful though.



The biggest thing with driveability/power in EFI engines in regards to coolant temp is the ECU programming. This is probably why the D7's needed warmer temps. Coolant temp is a large modifier in the ECU's tables.

So that's how they work. Thanks for enlightening me.

The '07 D7 ran the coolant through the tunnel coolant loop when the t-stat was closed, thats why, for most of us, in adequates now conditions, it ran <120-125° depending wich t-stat you have. The coolant couldn't get warm enough to open the t-stat in adequate snow. In '08 they change it so that the tunnel coolant loop flows when the t-stat opens allowing the coolant to rermain more consistant in the 120° temperature range. If they're using the same front cooler that they have been using, and since the cooling capicity of the tunnel is better then '07, then by running the t-stat hose to the lowest fitting on the the front heat exchanger and the head hose to the middle fitting it may give you the lower temps your looking for.

I have no dog in this fight. But have read a few responses. I cannot give data or real world evidence of the 800.

But on our big HP drag race motors. If you pulled the T-stat completly it would run hotter. Some have made reference to a washer etc and they are thinking correctly. What we found by pulling the stat completely and have no restriction is it ran through the radiator too fast and didnt dissapate the heat as you would think.

Many would take the stock t stat housing and just take out the actual thermal part of it and let it flow through. Some places even sell restrictors in varying sizes as obviously as seasons change you may need to change it up a bit.

Just some thought, and it may be completly different on a sled. But just thought I would throw it out there.

Very good point Kevin. I may be wrong on this, but I believe the princple of products like Water Wetter is similar. More surface tension, which promotes more cooling through the walls. Kinda the same as slowing the coolant down with a restictor keeping it in contact longer with that rad.

it could be completely different with snowmobiles though, as they are cooling through the exchanges which would have snow on them - but just a thought if you find it doesnt cool as you should.

Good points kevin, as I had said earlier removing the t-stat would likley speed the coolant up and send all the coolant to the rear heat exchanger. After some time messing around I have found that with the T-stat body only in, both front and rear coolers are heating up at the same pace. Untill snow is on the ground and more testing can happen, this appears to be the way to go todate or untill another idea comes up. To say, I'm pleased with the results so far.

so meathead, what are you doin to slow it down and make er run around 95?

It's not a matter of slowing down, yet. When the t-stat is working the min temp will try to be 120F by running only coolant through the front cooler to keep it at 120F. By gutting the t-stat and installing the t-stat boby the coolant will flow through both coolers all the time at the oem's set speed/flow. This gives you max cooling all the time.

Yeah, testing on the snow is going to be needed. I wonder if drilling a series of bleed holes around a stock themostat would do enough to keep the temps down. It would certainly be more restrictive than the gutted stat.

http://auto.howstuffworks.com/question248.htm

Taking the thermostat out or radically altering the temp when it opens/closes by physically altering the unit , presents alot of issues on TRAIL used FI ecu'd motor..not to say the least of piston washing,(premature wear), condensation ( a milky buildup in crank ),MPG dropping , trouble codes flashing, coolant running thru the sytem too fast(detonation), hot restart issues, Without a reflash, or playing with sensors,an engine computer management system (even in a little 800 cc mill) is designed to work with the engine at ---- degrees. A lower temperature thermostat may keep the engine in open loop not allowing the computer to control the engine.
This may create drivability problems.

Tried messing w/ 2 stroke trail/ / drag Sled.. , by doing all of the above...as long the sled was running 1000 ft. WOT OK.

Almost wiped the rings in one day ,on the trail......so we tried drilling a 1/16steam hole. Experimenting, though,in a controled temp dyno room, w/ a brand new warranty and a new 10 thou. sled..then hit the real world conditions it was meant for..well.. Good luck.

2cents.are deposited.

Very good read and awesome info that is correct .

A sled is a simple open loop system as far I know. To be a true closed loop auto style system generally requires a o2 sensor. Efi cars have been using lower temp t-stats for many years to increase power output and drivability. I been using a 165F instead of a 195F on my gn for years. So you believe that lowering the engine temp by 20F is a big deal? I'm not to sure that concerns me that much. As for flow it's no differant than when the t-stat is fully open.

I just seen your link, and where that style of info was meant for... Auto's and 4 stroke engines. You are now internet smart. This info does not hold much water on a 2 cycle, there are many years of 2 cycle engine use without a t-stat.

I RAN A 160 STAT IN MY 89 PONT. anniv T/A Firebird w/ the Tcharged Buick. Four weeekends, in 1990 w/ 110 fuel and a cool egine;New rings and blow by. Warranty..NOPE> .
After rebuild..Put back a 180 and ran as fast as 11.89 /118mph. on Nitto street radials and a cutout. Used 195 in winter.

IT WAS a link for gen info.Smartass.

2cycles w/ carbs ..yea, Olav.. even would agree. NO problem.

Modern FI 2 strokes. w/ hyper sensitive ECU's. are the issue., Mr. Gates.

lmao for $20 you should have been able to get the info on how they did this !!!!
LMFAO !!!!!!!!!!!!! NO NEED TO REPLY TO MY HONEST POST !

More likely had more to do with the 110 leaded fuel than the t-stat. No problems here with that motor on 93 with 160F stat.

What i think has to be taken into account is what temperature Polaris starts to lean out the mixture to a running mixture and not a fat 'choked' warm up situation. If you use a P.Command to lean it out at 100 degrees and then on a long pull it gets 'up to temp' and leans the map and suddenly your way lean. Is my thinking correct here? There seems to be a temperature which people say they run correct and millage goes way up.

Dave, I think you have the bit about water water backwards.. It actually reduces the surface tension. As for the coolant flow rate, THESE GUYS have said for quite some time that you want a faster turbulent flow for max cooling.

Run it in the real world first and see what we have

It was 100 +UL Sunoco. Actually ran pure stock (cats and 50 mile new, Strret tires)w/ 93 Sunoco ..12.69 @ 109mph. 86-7 GN's were not pleased, at all.

You know what..? ALL the new owners(now, test pilots) of the aformentioned 10+grand sleds SHOULD run w/ no stat or altered cooling systems , to band aid a perceived perf. issue , all winter long, in all conditions .
Ill run @ fact. specs and live w/ my 900 w/ 160+ hp.,111 ftlbs trq.

Please all dont take any of this as advise..Everything I presented was a bunch of BS of course.

Don't be mad. Just tring to see where you were going with your presented info?