Oil Cooler

Claviger said:

...................... I do ride it on the street, it's a street bike first and foremost, so that leans me towards coolant/oil, as you two gentlemen have suggested. Another very real consideration is placement and routing of the coolant hoses if using a coolant/oil cooler, there's no good way that springs to mind to plumb the system.

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Claviger said:

This!! Exactly why I don't have engine bars anymore and plan to put the cooler where it's not adding frontal area.

I've been reading on air/oil vs coolant/oil. I do agree coolant/oil is superior. I may still go that way, finding technical data on this topic isn't the easiest thing, the Google machine generally returns nothing but anecdotal info.

It correlates heavily with PC water cooling, something I know well, but here's what I'm having a bit of a mental fix on.

Water based coolant has much better heat transfer than air over a given structure.
The greater the delta between coolant/air and oil the greater the delta before/after the oil cooler.

The question I'm trying to figure out is; is 100f air more effective a coolant than 180f water?

Secondary consideration is, I do ride it on the street, it's a street bike first and foremost, so that leans me towards coolant/oil, as you two gentlemen have suggested. Another very real consideration is placement and routing of the coolant hoses if using a coolant/oil cooler, there's no good way that springs to mind to plumb the system.

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Speedy said:

Apples and oranges comparison: How much air volume versus how much water volume? Two very different types of systems that can be very different in physical size. The greater the delta the less surface area needed for either type. You can't control the ambient air temperature so you need to size the unit for the smallest delta experienced (highest ambient air temp). Oil outlet temp can be controlled by a thermostat in either system or by cooler size in a glycol/oil cooler where the glycol temp is managed in a very narrow range by the engine thermostat (and the flow rate of the oil is known and fixed by a positive displacement pump and pressure relief valve.) An air to oil cooler will be the larger of the two types for the R3.

If you put an air/oil cooler where there is restricted air flow you move from convective to radiative heat transfer which means that the cooler will need to be way, way larger. Good air flow means you plumb an air duct from an existing high pressure area and to a low one, or you put it out in the breeze. No free lunch to be found here. I will send you some general data off line garnered from GM about glycol and oil heat loads per unit of power. The data can be extrapolated to the R3.

The radiator already cools the oil to a large degree. So going to glycol/oil doesn't add the entire oil cooling heat load to the radiator. You are just increasing the effective heat transfer area above what the block and head (actually the entire oil wetted interior surface area of the motor cooled both by air and glycol) already provide.
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I would look at just below the radiator and above the oil filter. You can tee into both low and high pressure glycol lines to/from the water pump, or plumb in series on the high pressure side, and you are very close to the oil filter adapter. You can look online for marine tube type coolers that are just the ticket. They will be about 2-1/4" to 2-3/4" in outer diameter with glycol flow from end to end. Oil inlet and outlets perpendicular to the long axis. Mota makes very good coolers. There are others too but like intercoolers, watch out for "el cheapo" knock-offs. Most will have 1/2 NPTF oil bosses and 1-1/4" hose nipples. Tranny and engine oil coolers of this type are interchangeable and are sized by length to meet heat load requirements for the application. (My guess would be that a body length of about 7" will have more than enough capacity, but do your homework! The flow rate of the R3 glycol pump is unknown and will need to be tested or estimated closely.) US Plastics and even McMasterCarr market barbed plastic tees that will handle both the heat and pressure of the glycol system. Silicone hose manufacturers make hose in almost any conceivable configuration for adapting sizes and at many angles.

The biggest danger to using an auxiliary oil cooler on the street is over cooling the oil. Modern synthetics oils are happy at 240F as is the engine with oil at that temp for normal use meaning part throttle, stop start, etc. At WOT 220F is close to ideal. If you run under 220F for extended time in daily use, water condensation and the accrued acids that stem from it, are never boiled off. More frequent oil changes are then needed. Bearings also suffer damage at less that 160F under heavy loading no matter the oil viscosity with higher viscosities being the worst.

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