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Oil cooler control

Oil cooler control

Oil cooler control

I also posted this in the Automotive Engineering Forum ...

I'm trying to come up with a slick (and cheap) way to control oil flow thru/around a cooler on an air-cooled motorcycle.

When the oil temperature reaches, say 190F, I want to gradually switch the flow thru the cooler.

I found a self-contained temperature valve that will close/open with temperature. I could use one in the line from the oil pump to the filter and slowly close it to force oil thru the cooler when it's hot. To keep the cooler out of the loop when cold, I would have to use another (reverse-acting) valve in the cooler line. The problem is that these valves are $132 each. By the time I added the extra plumbing, parts cost would be near $300 ($150 if I used only one valve).

I could also add a temperature switch with a 3-way solenoid valve, but it would not be much cheaper. Besides, I don't like suddenly switching oil flow at 3-8000 RPM.

Does anyone know of a 3-way, self-contained, thermal valve? Know a way to plumb up a carburetor choke control? Anything else that might work?

The oil line is 3/8" (1/4" NPT fittings). Pressure is under 50 PSIG and temperature could reach 250-300F. Heavy vibration and exposed to the elements.

Appreciate any suggestions.

        . . . Steve

RE: Oil cooler control

Bruning, now Parker, has a pressure/temperature thermal valve that I use (TH1000 series is 1 inch size). I think the smallest was 3/4 or 1 inch though. Cheap also.

Some mfrs built these into the inlet of the coolers, but those were much larger industrial coolers.

You want a 3 way device, something that goes through cooler or around it. The  thermal valve is essently a path around the cooler in parallel with the cooler, When incoming oil is cold, the path is open around the cooler. When hot, the path gradually closes down to force oil through the cooler. If over pressure occurs (say a plugged cooler) the valve still lets hot oil aroound the cooler at a certain pressure.

You don't need to block off cooler flow, the path around it is less pressure drop so more of the oil goes that way. BLocking the cooler can be a serious disadvantage: If the oil stays totally stagnant in the cooler, with fan on (or in your case air blowing by), the oil can get so thick that even when the thermal valve closes down, the pressure drop through the cooler is so high that the oil continues to go across the pressure relief feature around the cooler. called 'cold oil slugging' or similar terms.

The cooler is typically at the end of circuit in hydraulic system, going to tank.If you have a single oil pump (not a scavenged sump), you'd need it after the filter but before the engine.

I would look more closely for automative transmission cooler control valves. I can't recall, but when I was looking at coolers for trailer towing, I found a thermal valve for just an application. I think it was higher temp. I would send engine oil through the cooler at 150 or less, not 190. Oil oxidation and breakdown increases rapidaly at hgiher temps. Below 120, there are mositure and acid problems.

How about taking the entire cooler and control valves off a new er mc? lLook around the junkyards or used bike floors until you see one with a cooler circuit. Big heavy air cooled mc rely more on oil cooling. Look at harley aftermarket, or parts for the Honda CBX of Kawaski 6 cylinders of the 70's. Both ran hot and depended on oil cooling.

BW, kcj    (fluid power engineer and mc rider)

RE: Oil cooler control

Thanks for the good info. My applications include a Harley Sportster and a Yamaha V-Star. I figure if I can come up with something reliable and inexpensive, it might help out others. Oil coolers are fairly cheap and available. The thermostatic controls are sometimes more expensive than the cooler.

I may decide to use a 3-way valve (or two 2-ways) and manually switch, but something more passive would be better. The coolers are usually simple loops, with flow up one side and down the other. I do have a concern if both valves are closed (or the line is plugged), but I figure the engine would probably go before the hose bursts. A bypass relief would just add to the cost.

The valve I found comes from Therm-Omega-Tech and is described as a "Heat Actuated Trap" and is typically used for steam jacket heating. Since the application is on a motorcycle (3/8" oil lines), I need something small. This one is 4-1/2" long and about 1" diameter (1/2" connection).

I agree that the cooler should be downstream from the filter, but that would mean an adapter was required (in the case of the Harley), and they run into hundreds of dollars (billet, of course!). The easiest way is to pipe from the discharge of the pump, thru the cooler, then back to the filter.

Do you think I should add a check valve downstream of the cooler(before it rejoins with the direct path)?

I'm not familiar with a transmission cooler valve. The ones I've seen have a constant flow thru the radiator/cooler. Then, I guess I could always flow thru the cooler, no matter the ambient or engine temperatuer. Here in Texas that might be okay, but I don't know about cooler climates.

Thanks again for the ideas.

   . . . Steve

RE: Oil cooler control

Thinking laterally, you could put the cooler in a duct and use a temperature sensor to open a flap that otherwise covers the inlet to the duct.
Obviously you would need to size the cooler for the highest temperature range you need to deal with.
I would have thought a bi-metallic strip would be sufficient to operate the inlet flap. The flap would have to be a butterfly valve or a gate/guillotine valve to avoid it being forced open or closed by air pressure.


RE: Oil cooler control

Page 64 of this catalog shows oil thermostats used by the racing community.  Less than $60 and absolutely bulletproof.  Other suppliers carry them also.  There is a 3/8 NPT version that could be configured with whatever hose ends you wish.


RE: Oil cooler control

P.S. - it works exactly as you wish, as a bypass valve for a cooler until temp rises to 180F at which point the valve directs flow through the cooler.

RE: Oil cooler control

Thanks, funnelguy! This does look just like what I need. I also noticed they recommend the cooler be installed in the tank return (on a dry sump system). That's going to create some plumbing problems, but it's probably a good idea.

Very helpful post!

       . . . Steve

RE: Oil cooler control

those valves are about exactly what I have seen. You should be set. kcj

RE: Oil cooler control

racerpartswholesale, the link from tmoose, has the thermostats even cheaper. Thanks!

I noticed they also have an oil filter sandwich adapter with a built-in thermostat. That would be good for the Harley. It will have to be the remote for the Yamaha, but no problem.

RE: Oil cooler control

This post is for those of you who don't often order racing parts or who have been "bitten" before---I regularly order from both racerpartswholesale and Pegasus Auto Racing.  I can vouch for their speed, knowledge, courtesy and, above all, HONESTY!  Pegasus is now owned by it's original creator --- the service and inventory is even better.  Both these companies serve the racecar owners and fabricators as well as the general public.


PS:  The oil t-stat works well, but I use a "manually restricted" duct to my Mocal 19 row cooler---cheap and efficient.

RE: Oil cooler control

I have worked on cars plumbed both ways.  Pressurized coolers and return line coolers.  I never failed an oil cooler from overpressure, ever.  ( The only coolers I ever scrapped were involved in either a blown motor scenario or impact with relatively immobile objects like tire walls and other cars )If your cooler is currently pressurized, don't sweat it and just add the oilstat and be done with it.  Arguments can be made for both pressurized and non-pressurized.  Purists, please don't flame me but I prefer pressurized coolers to cooling scavenge oil on dry sump set-ups simply because they are more efficient.  Cooling entrained air is a waste of time.

RE: Oil cooler control

The theory I read for having the heat exchanger on the scavenge side is that it allows the oil/air to condense.  I tried it and all I got was overheated oil.  I'm with you funnelguy, I have my cooler on the pressure side just AFTER my filter.  That way when the engine grenades, the cooler doesn't get filled up with crap (not that another hundred bucks would make all that  much difference).


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