More tunnel cooler talk.

[00Tundra]

True expands a little but no need for an over flow bottle. I just leave about two inches of space at the filler cap. Never have lost any coolant even when at 220 deg.

 

[Dr._Z]

Got to do the no radiator/tunnel cooler maiden voyage today. I'm going to guess it was about 25F out today and I could not get the 08 RMZ450 above 145F unless I was sitting there at idle. I could be full on climb, at idle on a long downhill or on the road in or out and it stayed at 145F no matter what. Totally convinced it's the way to go if you have a dedicated bike. I've got the engine about as covered as possible on all 4 sides. Brian (00Tundra) was able to keep the temps up better with the Selkirk kit on his Yamaha and the exact same cooler setup. I'm thinking I could cut my cooler in half and have the neighbor weld up the end and I'd probably be about where I want to be on temp. I love how consistent it is!

 

[00Tundra]

Mine runs 175-185 very consistently. Love it! Gonna put a barrier between the exchanger and skid to stop it conducting but that should be all it needs I hope.

 

[dooman92]

Dr Z, yeah that's a lot of cooler. Do you know what temp the thermostat is? Should run close to thermostat temp unless still giving up lotsa heat from the exposed areas of the engine.

 

[Dr._Z]

Thermobob web site says it should be a 180F thermostat. I do think it has a bit to do with the exposed areas as Brian's ran warmer with the Selkirk cover. My only issue I need to check is that I see a noticeable coolant flow into the filler neck well below 180F where the thermostat should open.

 

[dooman92]

The thermostat does have a small bled hole, maybe 1/16", that allows some coolant to pass when stat is closed and could cause a bit of movement/turbulence visible if close enough to the cap.
Another thought, if your stat bypass is full flow thru the cooler it will provide a lot of cooling.

 

[CATSLEDMAN1]

dooman 92 is right on, leave the cooler.........size is not the issue, you are loosing heat somewhere, after the years fooling with this issue and to make my bike run at 190 all day/all the time, my 500 ktm engine is covered in a 1/4 inch thick kevlar blanket/pipe covered with he same, couple of slits for spark plug wire, hoses wrapped, hose to heated bars wrapped, no radiators, anything in front of engine TOTALLY sealed, all this covered with plastic to deflect branch's and snow, then it will run 190 like the thermostat says. Bike almost looks embarrassing, but out riding and talking with the other bikers on kinda of enclosed engines somewhat covered radiators with temps all over the place all day and thinking their thermostat is defective, just gotta follow the evidence, you are letting too much heat out and allowing tooooo much snow to touch your motor.

 

[00Tundra]

His bypass is a 3/8" hose would it hurt to block it off? Also at idle it takes a long time for his engine to heat up. (lot longer than mine) I am wondering if his T stat has stuck open. With the engine covering Dr Z is running he did not have issues getting up to temp before we deleted the radiators.

 

[Dr._Z]

Bypass is about 5 or 6 inches straight from the thermobob to the hose entering the pump. I'm actually running more covering over the engine than when I had the rads also. Before the cooler I could sometimes overheat if I left the rad covers on.

 

[dooman92]

If the bypass flow comes off head and back to pump bypassing the coolant hoses and the cooler then losing very little heat, unless, the engine case is cool (exposure/snow dust) and then that cool coolant circulates and keeps temps low. Like catsledman1 says it doesn't take much air or snow dust on that engine. That aluminum engine gives up heat really fast.

 

[CATSLEDMAN1]

this morning my temp gauge showed 38 degrees as we unloaded, started my bike idleing and put on my boots and gear........maybe 7 or 8 minutes. KTM was up to 140 degrees and bars going to be uncomfortably warm, knocked them back to 1/4 open valve. Going up a hard packed road from sleds, and riding some road edge in new snow, it took about 2 miles for my bike to hit 180 or so. Rest of the day it was 190 or a couple of degrees higher. A couple of years ago I was thinking my bike wasn't warming up fast enough, so found some aluminum round stock that was just kind of a tight fit in the bypass hose, I drilled an 1/8' home in a 1/2" of the aluminum round stock , shoved it in the bypass hose, way quicker warm up, more stable temps all around. So yeah, I jetted my bypass hose.

 

[Dr._Z]

Tested the 80C (180F) stat in it and if I look really close, it is starting to crack about 160F. Looks like it might be part of the problem. I don't see how the pinhole bleeder could flow the amount of coolant I was seeing before it even got warm, and that's straight from the head to the stat to the filler neck.
I ordered the 190F stat to try, I'll cover the last small exposed area in front of the head pipe and put a barrier between the cooler and the tunnel and see what happens.

 

[Dr._Z]

this morning my temp gauge showed 38 degrees as we unloaded, started my bike idleing and put on my boots and gear........maybe 7 or 8 minutes. KTM was up to 140 degrees and bars going to be uncomfortably warm, knocked them back to 1/4 open valve. Going up a hard packed road from sleds, and riding some road edge in new snow, it took about 2 miles for my bike to hit 180 or so. Rest of the day it was 190 or a couple of degrees higher. A couple of years ago I was thinking my bike wasn't warming up fast enough, so found some aluminum round stock that was just kind of a tight fit in the bypass hose, I drilled an 1/8' home in a 1/2" of the aluminum round stock , shoved it in the bypass hose, way quicker warm up, more stable temps all around. So yeah, I jetted my bypass hose.

Just saw this after I posted. I was thinking I might need to reduce the bypass also. Thanks for the info!

 

[00Tundra]

Just saw this after I posted. I was thinking I might need to reduce the bypass also. Thanks for the info!

Agreed reduce that bypass

 

[Chadx]

Maybe I'm thinking about this wrong, but... reducing the inside diameter of bypass hose will increase pressure and so reduce flow in the bypass circuit and INCREASE flow through the thermostats bypass hole, which you don't want as that flows through your cooler. You want less pressure and MORE of your thermostat-closed-flow to stay in your bypass circuit, where it stays hot, rather than forcing more through the thermostat bypass hole and through your cooler where it is quickly cooled off. What is the logic in restricting flow in the bypass circuit? I'd think addressing the other areas you mentioned (better blanket coverage, hotter thermostat,, working thermostat, etc) will have a noticable effect. Bypass restriction will not really be noticeable, but based on coolant flow characteristics, restricting your bypass, if your thermostat is also the type with a bypass hole, will actually have the opposite effect because you'll be pushing more coolant through your cooler rather than less.

 

[CATSLEDMAN1]

you might just be over thinking this, on the 3 sno bikes that we put restrictor plugs in the line, way better warm up. I will say, put the restritors in a year before we discovered how far we had to go to make a true 190 all day all the time bike.

 

[dooman92]

Chadx, I had the same analitical tech thoughts when this issue came up few years ago. it didnt seem to make sense. but, i put a restricting valve in my bypass to test and ended up with better warm up and overall temp control. As others on here mentioned in the past, I also had over heat issues with the wide open 3/8" bypass on the thermobob because it flows enough coolant by the temp sensing portion of the stat that it delayed opening of the stat. So, given that that 3/8 line flows alot of coolant, enough to cool a small engine, and that the engine case is very efficient at giving up heat, constantly flowing that much coolant thru the engine allows any little portion of the engine that is cold to extract heat from the coolant and cool the engine. the engine case is a very efficient radiator and the flow is constant. now add a little cold air or snow dust on the engine and there is no need for flow thru the rads as the engine gives up all or more heat than the engine is producing. better engine coverage reduces that radiator effect and helps lots. i agree that the less coolant flowing thru the exchanger/cooler is better as well, that small bled is all that flows on my c3 setup when bars are off and that seems to work. thoughts?

 

[dooman92]

and when I am confused, I just do what catsledman says!

 

[RmK8oo]

Where in the bypass line are you guy’s putting these restrictors (jets)? What size hole do you all suggest I run? I’m running a C3 195 tstat with with the Selkirk kit, so the heat exchanger is plumbed into my bypass circuit. Temps typically stay between 180-200. I’d like to keep the temp a little more consistent at 195. Am I asking too much of the cooling system trying to regulate a steady 195? Bike is a 500 Husky and has always performed well with current setup. Any suggestions would be appreciated!

 

[Dr._Z]

I don't think I'd bother if I were at those temps.
I picked up my friends 90C stat tonight since mine will not arrive til Sat. I should be able to test it tomorrow night.