Gut the thermostat

whiten · Dec 18, 2014

I know there is a lot of discussion about this in the $28 upgrade thread. However, I haven't read anything about what I am proposing.

Gut the stock thermostat, basically eliminating it from the system.

I know a few that have already done this and swear that it makes a big difference with no negative side effects. Running turbos as well.

Even after pulling the cylinders to inspect the top end, no abnormal wear. Could it be this easy?

Thoughts?

BILTIT · Dec 18, 2014

What do yo think will happen upon startup with no tstat after you are stuck in 3+ ft of snow for 30mins? The engine cyl temp is at say 110, the coolers in the tunnel are at 50 from being packed with snow. You fire the engine and punch it to get out, all that 50 degree coolant is going to go through the engine and drop the cyl temp rapidly (decreasing bore size) all while the piston temp is increasing
(increasing bore size)=cold siezure. This is what the bypass tstat prevents. It also allows quicker warmup and cooler overall running.

You can watch the temps dive after startup with the stock tstat in this situation, the bypass tstat minimizes this fluctuation.

No tstat is on the opposite end of the spectrum, makes the temp drop even worse.

05900 · Dec 18, 2014

So NO it's not that easy.

tuneman · Dec 18, 2014

If aluminum didn't expand so dang much, you'd be onto something. There's a reason Polaris, and all the other manufacturers, choose to put these cheap little thermostats in. They wouldn't be there if they weren't necessary.

Without a thermostat, it would take a lot longer to warm up, you WILL see more wear on the engine and you'll get less power output. Hot engines are more efficient.

The $28 upgrade was done because the existing Poo thermostat creates too much restriction when running the engine hard in deep powder. The lack of cooling will advance the timing and reduce power. It's not to make the engine run cooler going down the trail, although it will a little, but with the consequences I mentioned earlier.

Oregonsledder · Dec 18, 2014

BILTIT said:
What do yo think will happen upon startup with no tstat after you are stuck in 3+ ft of snow for 30mins? The engine cyl temp is at say 110, the coolers in the tunnel are at 50 from being packed with snow. You fire the engine and punch it to get out, all that 50 degree coolant is going to go through the engine and drop the cyl temp rapidly (decreasing bore size) all while the piston temp is increasing
(increasing bore size)=cold siezure. This is what the bypass tstat prevents. It also allows quicker warmup and cooler overall running.

You can watch the temps dive after startup with the stock tstat in this situation, the bypass tstat minimizes this fluctuation.

No tstat is on the opposite end of the spectrum, makes the temp drop even worse.

Good description of what goes on.

BILTIT · Dec 18, 2014

I was so impressed with the bypass tstat performance on my '11 pro that i ordered one for my 04 proxr with carls 910. The 910 is just what you are asking, has no tstat but a restrictor ring. The temps can swing depending on the snow/riding conditions without a tstat. I want a constant cyl temp, makes jetting easier aswell as less worry when riding.

whiten · Dec 18, 2014

I get what your saying... Thanks. However, I would never punch-it after sitting for 30 minutes with any 2 stroke. snow packed or not. Thermostat or not.

Also, I never have an issue on the trails with the scratchers down. The issues show up mostly in set-up snow conditions in the trees when I can't get good track speed. (Washington is like that)

Anyway, I think I'll do the upgrade as it appears to have had dependable/consistent results.

BILTIT · Dec 18, 2014

You would be surprised how many people do punch it, without even thinking.

Even when not punching it it can take sometime for all the coolant to ciculate and stabilize in temp. This is how things were done with old mod motors with no tstats (like my 910). They kept an eye on temps.

The new age of people who have no engine/mechanical knowledge dont understand these things and can cause alot of damage out of negligence.

Reg2view · Dec 18, 2014

FWIW, a related instance for those with front coolers ("standard" RMKs now popular) - the front cooler circuit is actually a full time bypass of the thermostat - it's always active, even if the thermostat is closed. Tunnel coolers act as a secondary system after the t-stat opens on these sleds.

800xtreme · Dec 18, 2014

Mine is removed and many guys around here have done the same. No issues so far or any that i have every heard of. My sled will run at 90 degrees running HARD in deep snow. I hardly ever see temps over 110 degrees. I am no expert by any means but this has been my experience. I certainly let my sled warm up very well and never punch it after sitting.

rmscustom · Dec 18, 2014

BILTIT said:
You would be surprised how many people do punch it, without even thinking.

Even when not punching it it can take sometime for all the coolant to ciculate and stabilize in temp. This is how things were done with old mod motors with no tstats (like my 910). They kept an eye on temps.

The new age of people who have no engine/mechanical knowledge dont understand these things and can cause alot of damage out of negligence.

Or when you've got yourself into a stupid spot and your bud has managed to get himself to you to help out with a ski pull and your like just wait 10 minutes while my temp stabilize because I took my T-stat out. lol

gman086 · Dec 20, 2014

Been covered before: http://www.snowest.com/forum/showthread.php?t=351948

I plan on running without this year as I have also done on ALL of my BRP sleds over the years with MUCH lower temps in marginal Pacific NW conditions. Highly recommended!!!
FWIW Carl's, BJ's, RKTek and many others recommend doing this so for all the naysayers... WHATEVS!!!

Have FUN!

G MAN

Merlin · Dec 20, 2014

whiten said:
I know there is a lot of discussion about this in the $28 upgrade thread. However, I haven't read anything about what I am proposing.

Gut the stock thermostat, basically eliminating it from the system.

I know a few that have already done this and swear that it makes a big difference with no negative side effects. Running turbos as well.

Even after pulling the cylinders to inspect the top end, no abnormal wear. Could it be this easy?

Thoughts?

As others have stated, a good handful of speed shops have been doing this for a while with success.

I prefer TRS's $28 mod or similar bypass system over no thermostat however I think a competent operator can run a machine with a gutted thermostat with no ill effects.

Pay close attention during re-starts throughout the day to prevent cold shocking the engine. It's as simple as letting the engine idle, without revving it at all, until the temps. stabilize & then not taking off until you're close to 100 deg. F.

That said, an impatient rider coupled with an engine that has tighter than desired piston to cylinder wall clearance will quickly discover the downside to gutting their thermostat.

ak · Dec 20, 2014

gman086 said:
Been covered before: http://www.snowest.com/forum/showthread.php?t=351948

I plan on running without this year as I have also done on ALL of my BRP sleds over the years with MUCH lower temps in marginal Pacific NW conditions. Highly recommended!!!
FWIW Carl's, BJ's, RKTek and many others recommend doing this so for all the naysayers... WHATEVS!!!

Have FUN!

G MAN

Carl's runs the stock thermostat but they drill bypass holes in the thermostat. Fyi

gman086 · Dec 20, 2014

ak said:
Carl's runs the stock thermostat but they drill bypass holes in the thermostat. Fyi

That's certainly not what they told me first hand! Maybe something new?

ak · Dec 20, 2014

gman086 said:
That's certainly not what they told me first hand! Maybe something new?

I have there set up sheet for a 660 kit, and there instruction call for drilling two 1/8 holes in the thermostat , I run a 600 but I did drill the two holes in the thermostat and it seems to run cooler.

Maybe the 800/ 900 big bore kit is different.idk

diamonddave · Dec 20, 2014

I have always been a proponent of a t-stat especially in an 07 and later Skidoo. However, I ran no stat last year on a '13 without any issues. I was testing this with a X3 track that likes to heat up on those Freeway Groomed trails in McCall when it's super cold and there's no fresh left off to the sides.

What was a pleasant surprise is the huge high to low temp swings after engine restart were gone.

In the deep snow, temps will drop to about 88'-90'F and if trails have just enough loose snow, temps will be about 110.

Before this, I had always run the extra drilled holes in the T-Stat. This "helps" some with the high to low coolant temps.

I have talked to people that had plug fouling issues but those were on '11-'12's.

tdorval · Dec 20, 2014

Didn't someone say below mid to high 90's caused the ecu to pull timing? Also running an x3 and wondering what the answer is to cooling...

TRS · Dec 21, 2014

tdorval said:
Didn't someone say below mid to high 90's caused the ecu to pull timing? Also running an x3 and wondering what the answer is to cooling...

The ECU and engine like temps north of 98* and south of 127*.

Gut the thermostat

Well-known member

Embrace the BRAAAAAAP!

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Chilly’s Mentor

Well-known member

Life Member

Similar threads