Jump to content

High OAT's and my engine is too hot on take off


Roger Lee

Recommended Posts

Hi All,

 

I have seen a number of you complain about high oil and or CHT's on take off or in a climb during the high OAT's of the summer months.

I did a little test and now I'm willing to make a comment. I live in Tucson, Az where we can get fairly hot, that said, it has only been in the high 80's and very low 90's for the last several days,. Eat your heart out back east with the high temps and humidity. <_< Ok I just had to say that because everyone thinks we are 150F out here all the time.

 

Now back to our little test. My oil temps and CHT's would climb to 240F or more during certain days and when loaded. So to try a little experiment I moved the clip down on the carb needle which raises the needle itself. This allows a little richer fuel mixture and helps cooling. I wasn't look for a drastric change, but enough to help out a little. Now this will usually really effect the mid range temps and a little higher rpm settings, but not really in play when at WOT because the needle is most of the way out of the main jet by then. Here is the interesting part. All my temps across the board went down. If I fly on a 90F-95F day, which I try really hard not to do, my oil temps now never get over 230F in climb. In cruise at 5100 my oil temps are usually around 205 along with the CHT's. The EGT's are about 60F-80F cooler too. The Rotax 912 can run at the 240F mark all day, but I was trying a little experiment and trying to stress the engine a little less. When it cools down I'll put the clip back up a notch. Oh yes, I use about .2-.3 gph more, not a big deal.

Link to comment
Share on other sites

  • 1 month later...

So you are saying that if climb is at WOT, then your change won't make much difference? My problem is climb at WOT. During cruise the oil temps are fine, and CHT is never an issue. If I use 85 knots for climb and WOT, the oil temps might red line (not for sure since I have not let it go that far), but I have found that WOT and 95 knots keeps the oil down to 240F most of the time (not if its 40C outside like recently). I used to power back and slow down, but I found that keeping WOT and speeding up works as well for the oil temps. WF

Link to comment
Share on other sites

Hi Wayne,

 

Keeping the climb a shallower and the speed up will be cooler. WOT lets more fuel in for cooling and the flatter climb doesn't load the engine/prop as much and more air is forced through the system. 240F is fine and not an over temp for this engine at all and like you said once you level and reduce power it cools some more.

Link to comment
Share on other sites

My 2007 can get pretty hot on climb out of Bisbee as well. I have not tried Roger's trick yet, but am considering it next time I make it up to Ryan. My practice has been to reduce power to 4500rpm and continue with what ever climb I can get at 80-90KIAS until I get up to the cooler altitudes.

Link to comment
Share on other sites

Hmmm, as posted at another thread, I do glider towing from time to time with the CTSW. The glider towing package contains a bigger oil cooler and I dont know, which oil cooler you folks have. If I tow a double seater (1200 lbs) it takes about 10 minutes to lift it up. During this 10 minutes I fly at 60 kt WOT, flaps zero. During this towing, I never saw oil temperatures above 250° F. Not even in summer, when OAT is in the 90ies.

 

I wonder, why you guys have this temperature issue. Maybe the oil cooler of the US model is smaller than mine??

 

Another reason for your problem, could be the use of Evans coolant. As Roger stated on another place, the engine runs a little hotter if you use Evans. I use Glysantine G48 from BASF mixed 50/50 with water.

 

Markus

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...