Cylinder Shock Cooling

[Nev]

Good logic Tim.

[Battson]

My original reason for installing the cowl flaps had as much to do with keeping the engine warm as it did with keeping it cool.

Very relevant comments Tim - thanks for adding that.

I think there's an important point in your post - we can all agree that thermal cycles are hard on engines. They are a proven cause of accelerated wear and tear. To Kestrel's point - the larger the cycle, the greater the risk of accelerated wear. So anything we can do to minimise thermal cycles (number, magnitude, and rate of change) has to be a good thing. Even if nobody cracks a cylinder - I think improved engine management is a worthy pursuit.

[Bcone1381]

we can all agree that thermal cycles are hard on engines...... the larger the cycle, the greater the risk of accelerated wear. So anything we can do to minimise thermal cycles (number, magnitude, and rate of change) has to be a good thing. Even if nobody cracks a cylinder - I think improved engine management is a worthy pursuit.

I flew Continental IO-520's in a C-310R in the 1980's in the upper midwest. (all airports about 1000' msl) With 6 of them flying, we has about 280 individual engine thermal cycles a week on the fleet. To prevent cylinder cracking due to shock cooling we did the following procedure because in order to (academically) flattened the thermal cycle. We had very course poor CHT data with slow moving gauge and nothing ever recorded. Our cockpit data was very poor but we knew.....

-Takeoff using full power mixture rich.
-At first power reduction we left the throttle and mixture full forward and reduced RPM. (to keep mixture richest keeping cylinders coolest)
-At top of climb (6-8000' typically) we reduced to cruise power and leaned the engine (75F rich of peak...Goverment paid for fuel). (so now we had a smaller change in CHT)
-At top of descent we left the mixture alone and reduced power an inch HG/minute. (to flatten the thermal cycle)

The data showed a large decrease in cracked cylinders. Like 75% decrease. Real Data...old data.

[kestrel]

Water cooling would be sooooo nice! Tighter temperature control, no concern about shock cooling, better and safer cabin heat!