Engine Cooling

[Sapphire]

Another feature is that the cyl. head temp guage can show normal temperatures but part of the engine is overheating. The sensor under the spark plug only measures temperature at that one spot. Everytime the engine overheats, a bit of damage is done. If it happens often, then say an 1800 hour engine needs many top end overhauls. I knew a pilot who bought a brand new Jabiru and needed to do te overhaul between 300 and 400 hrs. Now I'll have the Jabiru guys entering the debate as well.

 

 

[boingk]

Very true, Sapphire, but it is still a good indicator of engine stats. This is why many also have an engine oil temp sensor and exhaust gas temperature... in fact I believe these are mandatory for many (non-certified?) engines.

 

The head temp is generally a good indicator of engine temperature as the head is the 'heart' of the engine, if you'll excuse the mixed metaphor. Overheating at the head will most likely also indicate a form of overheating elsewhere (blocked/inefficient cooling duct) or some other sort of problem such as preignition or oil starvation.

 

Cheers - Enoch

 

 

[spacesailor]

The old VW had four cylinders so was cooled from the top, the 1/2 vw has its 2 exhausts at the front with a big fan blowing heeps of cool air at them, other wise I would like to have the

 

inlet at the front with that big fan (prop) charging the inlet, and the exhaust with a "tisy-bitsy-stuby" tuned pipe faceing aft.

 

When I was training the "water-cooled" Rotax plane was flying in 40 degree temps, while the "aircooled"Jabiru's were grounded.

 

Would a 1/2 vw fly in 40 degree day?

 

spacesailor

 

 

[Louis Moore]

Cooling 101:

 

• Aircooling is easy (no plumbing, radiator etc) but inferior. This is due to its generally higher weight (cooling ribs) and lower power (lower tolerances)
   
   
  

I am not sure if the weight figure on air cooled engines is correct. You might be thinking a lot of liquid cooled engines are lighter but this is due to the smaller piston size (or bore size to be correct) and higher revs of the engine, not water cooling (referring to Rotax and auto conversions etc....). As a rule water cooling is far heavier due to the included liquid, plumbing, cooling jacks or sleeves, radiators etc.... Weight is one of the often sighted reason they switched to air cooling for heavier aircraft engines.

 

 

[spacesailor]

Sapphire: with an exhaust temp & head temp gauge, it should be enough, if not, one under each head stud, ie six per head = thirteen temp gauges for the hummelbird (oil temp & 2 exhaust)

 

would be far outside its max takeoff weight, leaving fast taxying only ( better put a couple of temp gauges on the axels to keep an eye on the wheel bearing temp too. LoL Bryan

 

 

[Sapphire]

I thought I should add to this thread before it disappears into the catacombs of the forum vault. Every thread should bring more information on it's subject to light and I think that was achieved. The design of a half vw engine, say in a Hummel Bird, with cyl heads poking out of the cowling provided better than average cooling. Even at idle, the propeller provides unobstructed cooling to the hottest part of the head. Fully enclosed engines have ram air entering then being directed to select parts of the head where the hot expanded air is forced out into a low pressure area. They wont be efficient unless tested and designed on every engine/plane combination. Also, any air cooled system doesnt supply adequate cooling all the time, unless you are winter flying in Alaska where inadequate heating may be more of an issue than inadequate cooling.