Steve Rance

This oil cooler thread has been very interesting. Many issues with cooling appear to be according to setup and how the aircraft performs in weather temp extremes. Yes I agree that masking over the cooler does work if you have a standard setup but remember that the oil has no choice but to flow through the cooler when fitted with the Jabiru OCA (doughnut). In cold weather the oil flow may be partially restricted due to the viscosity and will struggle to get to the ideal temp range of 85C-95C, If oil pressure is high due to slower flow then it is very possible the relief valve can open dumping oil back to the sump and bypassing the bearings. Oil viscosity is clearly demonstrated in my engine by the dropping oil pressure as it approaches 90C+. Oil pressure is only genereated by the resistance of the oil as it flows to the parts in the engine, bit like putting your thumb over a hose pipe, thumb off = no pressure but full flow, thumb on = high pressure but lower flow, a lot of concern is raised about low pressures but as long as the flow is there then perhaps it is not as bad as thought, the down side with low pressure is it may not flow to the furthest away parts in the engine. With a TOCA fitted the cooler is bypassed until the oil gets to a working temp, this results in a faster warm up time. In cold weather unless the oil reaches at least 85C+ then the TOCA sensor valve will remain closed and no oil will be diverted to the cooler. The actual true oil pressure going to the important parts of the engine can only be measured when the pressure sensor is fitted to the 'gallery port'. With the sensor fitted to the standard port a possible worse case senario is to have a completely blocked cooler circuit (kinked oil hose), a normal pressure reading on the gauge will be seen and no pressure in the 'gallery' leading to dire results. This is why I advise if doing work on the oil system to consider moving the sensor to the gallery or adding a second gauge for comparison. I did this during the testing phase and was surprised at the difference between the two ports, another reason I recommend AN8 hoses. I am having another batch of TOCAs made and should be ready in a few weeks, I plan to be at Sun & Fun in April if all goes well and intend bring a few TOCAs with me just in case anybody going want to see/purchase with price saving. For more info email [email protected] Steve

I was informed resently that my name was mentioned regarding oil temps. Yes I do manufacture the Thermostatic oil control adaptor (TOCA). I suffered the same cold oil problems with my Jabiru during the cold season and removing and replacing the cooler every season was a pain. The problems are compounded if you have a cooler fitted with the original Jabiru doughnut. When the air is cold then blasting colder air over the cooler and sump will chill the oil almost as fast as it heats. The commerially available TOCAs or thermo sandwich plates as they are known work as well but are much bulkier due to being cast and usually come with 1/2" BSP thread. I designed my original one to fit my 2200 cnc machined from solid without the need to use a shorter oil filter, during the development phase it was determined that using AN8 hoses the oil would flow without any persevable pressure loss due to reduced drag, also my TOCA has bigger galleries, when the oil is less than 80C the the cooler is bypassed anyway. It has been proved that on start up on a cold day, when the original Jabiru adaptor that has the brass fittings with 1/8"NPT ports the oil is sluggish to flow through the cooler as it has no choice, there is a significant oil pressure drop that can only be measured if the pressure sender if fitted to the Gallery (lower) port. There is the possibility that with cold oil and restrictions in the cooler circuit the pressure could rise enough to open the bypass valve sending some of the oil directly back to the sump, when my TOCA is fitted this is no longer an issue as the cooler is bypassed until the oil has warmed to 80C+. A significant amount of cooling is done by the sump casting, even with the TOCA fitted in cold weather the oil can still remain cool unless the sump is partrially screened, this will have to be determined by experimantation. I have 2 settings on my sump inlet that I have to adjust according to seasonable OAT. My theory is that you could almost screen of the sump completely and with a large enough oil cooler let the TOCA do all the work. There is more info in the link below or if you need more detail then use my email address http://www.lightaircraftassociation.co.uk/engineering/Standard%20Mods/jabiru_engine.html Steve [email protected]