Checking temperature

[gainestruk]

Thanks motoman, Well at least I see with your ke thermometer is getting readings close to what my infra red gun is showing :thumbsup:

 

[motoman]

After looking at oil cooler and filter surface temps it looks like the cooler really works . But once the oil dumps into the sump it's like a volcano. When I first looked at the temps it was to see how hot the head gets because of a pushed guide. Since the engineers who really know don't respond here we have to make assumptions ourselves. Mine is that the oil cools the engine , but the head is almost entirely on its own (air) with fan and finning. Some cooling must take place as the "cooler" cylinder (s) and block draw off some head heat to be cooled by the oil. Whadda ya ALL think and know??

I have noticed that once hot (300F) the oil will cool down to 250F in about 5 minutes with the fan on at idle. Then it stays below 280F while mowing for about another 5 minutes , but gradually creeps back up. My fan set- up is not optimal.. It will not keep the temp steady down while mowing in summer , typ 85F, but will control excess heat with 5 minute breaks.

It is not a coincidence that analog oil gauges (sweep pointers) are all calibrated up to 300F. My gauge ends at 320F. (shutting up, for now):laughing:

Edit. If heat is drawn down into cylinders it says blown head gaskets are not good. Reduced contact area and heat flow.

 

[gainestruk]

Ok test #3
Temperature was 82* at start and 86* at finish.
This time oil is Castrol GTX 10w30 regular Dino.

20 min. Oil filter= 147.9*, engine block= 151.1*, drives= 118.4*
40 min = 172.0*, 146.6*, 123.9*
60 min = 165.3*, 141.1*, 123.4*
80 min = 163.0*, 144.6*, 125.7*
90 min = 176.0*, 170.4*, 125.2*

Will drain this oil to use in my pickup.
Next week when I mow it will be Rotella T6 5W40 full synthetic, I'll be running the T6 from now on.
Stay tuned next mow will be 7/23 or 7/27

 

[motoman]

Thanks gaines. On another thread there is a "glowing red" exhaust pipe which Il Eng has said he has seen usually in a darkened area. I requested the head temp while pipe is red.
Incidentally, you mentioned upper limit of AC aircraft head of 500F. I ran accross this before and could not reconcile it with the temp of 390F where aluminum begins to soften. Could the aircraft warning limit be for "immediate" action which makes sense with airflow of ?200mph? accross the hot head which would quickly cool it. On the other hand even the best AC small engine flow is much less (I do not know). I do know that before carbon steel changes state to its hardest it must be held for some time at the high temp for the change to occur (and then be quenched). Perhaps the lawn mower engines once at 390F or even a little below cannot recover quickly (cool) and some soften ??? Or maybe the wrong "mix" in a casting makes it more prone to soften? Also anyone please comment on the upward movement of the valve guide when it moves.... How about this: isn't an overheated head immediately shut down and allowed to slowly cool the same annealing technique used with steel (to soften to machine it)?

I know, I know, few really care. Rave on motoman. :laughing:

PS Earlier I said cyl draws heat from head. It may be wrong and the cooler cylinder heat migrates into the head. Who cares etc

 

[gainestruk]

Heads on aircraft engines are cast iron depending how lean you run engine the head temp will range from 250 to 450+
Once you land you run engine 1000 to 1500 rpm to cool down. You can watch it cool pretty fast, in time you land till shut down is about 15 min and head temp will be 150 to 180.
FYI flying at 75% power which is max contiounious power setting small piston run at 2300 rpm

 

[motoman]

Well the cast iron perhaps explains the 500F limit (instead of ? 375F ? for aluminum). I thought some AC engines had al heads?

Today I looked at oil temp gauges available. Seems like they have improved since I put on the Beedee. I saw some stepper motor sweep style with a linear scale out to 320F (more temp points spaced evenly, easier to read) A couple also had LED readout with the pointers. The mix ranged from China at $25 , through straight led digital read around $90 out to fancy race stepper motor units @$200. IMO the Japan sourced (few) and one lone US unit (really??), plus a Taiwan gauge are the only safe bets for lawn mower application (vibration, heat,accuracy). All use a similar sensor which screws into the pan drain plug (adapter required).

More info than requested, right?

 

[gainestruk]

I rebuilt Lycoming and Contential 4 and 6 cylinder engines for Piper dealer in Norman, Ok from 88 till 90
I just looked it up the Lycoming 0235 engine heads are cast Aluminum alloy,the case halfs (splits down middle with left & right side) Were Aluminum the jugs are Crome Nickel Molybdenum steel (I just looked it up) so I guess my memory wasn't too good about it being cast iron :confused2:
Oil temp ran about 150 to 180, and max head temp of 500*F is right.
For continuous operation manual says keep head temp between 150*F and 400*F, so it must be the alloy they use in casting that lets temp be so high.

This is a great thread for someone wanting to understand the cooling on air cooled engines !

 

[KrashnKraka]

I rebuilt Lycoming and Contential 4 and 6 cylinder engines for Piper dealer in Norman.....
[...]
This is a great thread for someone wanting to understand the cooling on air cooled engines !

Owning a past close relationship with aerotechs I have always held you guys in high regard (respect)
as at anything above maybe 500', below 60Knots, the last thing anyone wants happening is for those
pigeons to die in their cage!
Yes, I am skerred of Al.alloy anything around Air Cooled so much so that such engines in 'stationary'
use I have always idled down when the load comes off, yer just carnt trust the build...IME.

KK

 

[motoman]

Still on aircraft...a while back I did read a lot on the small aircraft sites. One engine design had overheat of the valve gear. Finally, they ran an oil jet across the guide/head and did pull off heat (don't remember but maybe 20+ F). Discussion centered on "morning sickness" which is sputtering and missing at start up . Apparently scares airmen and mechanics and can be sticking valves in guides which can lead to bent pushrods. Anyway my Intek only sees a mist across the guides and cannot be a cooling factor. I even doubt there is much if any oil flow back to the sump with the horizontal cyls and rough , blocked passageways. That brings up the question of why a guide seal?

 

[gainestruk]

I guarentee if an aircraft engine sputtered at start up that plane would stay on ground till I found out what the problem was, aircraft engines use 2 magnetos one running spark plugs on top of cylinder and other mag runs plug on bottom of cylinder and the bottom one tends to get lead deposits.
On your preflight check you run engine up to 1500 rpm and on your ignition switch it has both, left and right setting
You check left then both then right with a max of 50 rpm drop between the two.
I hear about people using LL100 which is low lead 100, but it has a lot more lead than regular gas you put in your car or mower.
I've had to taxi back to parking and take out bottom plugs and clean the lead deposits off before I can fly, I don't know how the high lead fuel would affect newer small engine, I don't think it would be bad for them but might require more spark plug cleaning.

On the valve guide seals I kinda wonder if that might be a way Briggs is using to make sure a little their no oil change engine uses a little oil by not having a seal so you would need to add fresh oil every now and then ?
I haven't looked at service manual to see what they do or do not have.