Redline for 50/50 Dexcool CTSW

[Eddie Cesnalis]

What is the mast CHT when using 50/50 Dexcool?

[Roger Lee]

Rotax SB says 248F. Then engine is okay with 266F, but the coolant will boil at approx. 275F. That's too close so Rotax brought the max 50/50 temp down. Use the oil temp.

[FlyingMonkey]

21 hours ago, Roger Lee said:

Use the oil temp.

Not sure what you mean...are you saying use the same max temp for CHT as for oil, 266°F ?

Follow up question:  What would be a "normal" CHT for say a 75°F day?  I usually see around 205-210°F in cruise at that temp at 2000-3000ft MSL.  That looked a tad hot to me, but maybe it's right in line.  When I start the engine on the ground and let it sit and run for a while (say 15-20min) I can see CHTs up to 230°F or so, that then go slowly back down to the above temps once I'm up and cruising.  CHTs on the ground often exceed oil temps if the airplane sits idling a while.

[Anticept]

If you have the old style cylinder heads, you will read hotter than the new style that goes into the coolant. So that has to be answered first

[Roger Lee]

Your oil temp usually reaches max temp before the CHT. Most of you watch the oil temp more than others readings.

[Eddie Cesnalis]

1 hour ago, Roger Lee said:

Your oil temp usually reaches max temp before the CHT. Most of you watch the oil temp more than others readings.

That's my experience.  I only asked to reset the redline on my dynon.