Comment

Comment by Adel Alyahya on August 4, 2011 at 12:30pm

Thank you for the comments , and would likt to see a lower cowl flap photo to know how it is done , and any tips will be helpfull

Comment by Mike MacLeod on August 3, 2011 at 8:19pm

With my 601XL/Rotax 912S combo I find that engine temps are a real problem.  The issue is the cylinder wall temperature.  The Rotax installation manual (not the operating manual) sets a limit of 375 degrees F.  I installed 2 thermocouples as specified by Rotax on the cylinder walls to measure these temps. They are way HIGH!! easily approaching the limit on climb out on a hot day (and staying there even though the oil and coolant temps are well within the green). I called Rotax to ask about this (and why this is not specified by the operating manual).  I was told that maybe 400 degrees would be safe!!  

I added a lower cowl flap as best I could and that helped some but I am considering cutting holes in the front of the cowl to let more air in.  I also find that increasing speed to > 110 kts helps.  Good luck.

Comment by Bob McDonald on July 31, 2011 at 8:42pm

You might install a lower cowl flap to increase the volume of air exiting the cowl. See pages 5 & 6 of my Can-Zac Spycam photo album to see how cowl flap can be made. My CH750 has no cowl flap, no cooling issues. My CH601HD has an oil cooler located close to the muffler so I built a cowl flap to increase the volume of air exiting the cowls.

Comment by Bill Alexander on July 30, 2011 at 6:31pm

Adel,

Remember that the 912s is cooled by three ways, Water through the heads, an oil cooler, and last, air across the cylinder fins. The cowling you have will work fine as designed. There is a large opening for air to the radiator and oil cooler. the other opening on top of the cowling lets air in across the top  of the engine.I live in SC and right now it is about 102 F every day. No problems with overheating. If anything most 912s have a hard time in a pleasant climate getting up to operating temperature. 

Bill