912ULS High Oil Temperature

Well one thing I have discovered tonight is an exhaust leak - and its blowing back onto the cylinder head. Its funny - because I have pretty sensitive CO detector probes and I have never detected any elevated levels at all. I have a feeling that I may have uncovered at least a contributing element.

Regarding propeller pitch - I have adjusted it at least 3 times. I actually bought the Neuform propeller pitch tool from the factory to set the pitch which makes it slightly easier if at all. Any adjustment of the pitch has made little difference in the numbers. I thought that was the ticket at one point.

Climb rate is around 1000ft/min, just me in the airplane - 5250ish RPM at 70-75kts.. I may do some experiments with that after I resolve this exhaust leak.

“ RPM in a climb is around 5250 - Flat full throttle is 5600-5700 .." strongly suggest the prop pitch is over course, which leads to a labouring engine, higher temperatures and although he doesn't give airspeed and climb rate data, may negatively impact on engine ”

This rpm isn’t over pitched (too corse).

I did a prop study with 14 different props about 8 years ago with four identical Flight Design’s. I had long, short, stiff, flexible, two blade and three blade props. Then I had to weed out as many variables as I could that no one else does. I was the only one setting pitch and we all took off together side by side in pairs. Then we flew side by side within 50’ - 100’ of each other to compare performance and engine stats. This way we had identical planes and one person dictating maneuvers and all flew at the same time of day, same direction, etc… which removed many variables that other Mfg’s have never done. This study did not include in flight adjustable props, only ground adjustable so they could be dialed in. Bottom line was that all these props were fairly equal in performance except the Warp Drive which suffered far more in climb vs the other props. With ground adjustable props rpm and plane design are huge factors.

Now it was also discovered that for a balanced performance the best all around rpm at WOT at your average altitude was 5600 - 5650 rpm.  Prop pitch for each plane and an owners average altitude will change because some owners fly lower and some higher than others. It does no good to set a prop pitch for 2K feet if you always fly at 8K feet. Anything under 5500 WOT was over pitched and caused loss of several things. Remember I said a balanced performance since you can’t adjust it in flight. Now if you had need for a better climb prop then WOT of  5750 - 5800 was good, but it caused other areas to lag behind. This study took me months to do. 
Over the last 20 years I have set hundreds of props on different aircraft and none have had any issues and all had better performance using these things we learned. The areas affected by prop pitch are climb, cruise, fuel economy, engine temps and engine stress.

Roger ,

Jim is concerned about high engine temperatures, in a high ambient temperature environment  - It is in this context that I am suggesting that, in the most demanding phase of flight (take off & climb out) the "load" that the engine is put under, has a significant part to play in heat rise.

The conservative & recommended Rotax method is Static 5200 RPM, not WOT. Static will almost certainly result in the least load on the engine (assuming pilot aircraft management is up to scratch). WOT I have no experience of but would speculate is riskier method of prop "tuning" and much more demanding of pilot technical understanding/inputs than Static.

I am not suggesting WOT can not work for some aircraft/pilots, only that it is a riskier path to go down, probably for little if any gain in efficiency (take off performance, cruise speed, fuel consumption). I believe it has greater potential, if not managed very carefully, to shorter engine service life due to "lugging" and higher engine temperatures.

I don’t think his prop is the cause. I think his real problem is the heat exchanger. They may be okay for cooler climates , but have not had anything good to say about them in hotter climates. The last one I had here we pulled out and went with peerage radiator and cooler. Problem solved.  Living in Arizona in the US where our temps are 105F - 115F during the summer we deal with this all the time and all our aircraft have to deal with it daily. I see tons of owners with what they consider high oil temps. Here seeing 235F - 245F at take off is very normal, but should cool down in level cruise. Even with those high OAT’s in cruise we see 118F - 225F at around 5200 +/- cruise rpm. The factors I see the majority of the time is poor hose setup, poor cowl air flow and poor radiator / cooler direction to the air flow. Plus the way owners take off is a factor too. The prop setup from owners and Mfg’s were problems until we flattened the pitch. Some of these temps are correctable some are just the nature of the beast for that aircraft design.

During my prop research project we found no difference in things like oil temp and the rest after that 5600 - 5650 WOT setup. The extra 150- 200 rpm didn’t change things like, Cht, oil temp, Egt, etc… The only thing we saw from a 5600 - 5650 to 5800 at WOT was better climb, but decreases in cruise speed and fuel economy. I would say generally that a majority in the US cruise around 5000 - 5300 during cruise. Yes some lower and some higher.

Some  aircraft are stuck with different issues over others just due to design.

Roger,

Thank you for weighing in. I converted the airplane to E-LSA from S-LSA because I received absolutely no factory support. A few other owners said they changed the cowling and the problem went away. I'm trying to get the factory to provide me one but don't get your hopes up. I could put some nylon spacers on the bottom cowling (1/2") to open it up a little bit and see what happens.

I've had many discussions with Paul in the U.K (TLAC) and he operates a fleet of C42s in various configurations (A,B,C) and has never, ever seen any run this hot - even in 35C ambient temperatures. Maybe he's pulling my leg but he insists its running hot. They all use the same heat exchanger.

I have attached a thermal image of my coolant radiator after shutdown. I am working on trying to do this during flight possibly if I can think of a way to attach the camera to the cowling. Its a portable USB camera that I would attach to the lower cowl to get a shot of the radiator. 

I may also run a pitot tube to the lower cowling outlets and/or behind the radiator to measure and airspeed at these spots.

I also attached an image of the standoffs on the lower cowling I may try to see if it increases airflow, but I am worried I will introduce some aerodynamic issue. What do you think?

If I added an oil cooler, where would I put it? Behind the coolant radiator?