Can an engine run TOO cold

MyassisDragon

MyassisDragon

Line Up and Wait
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Mr Fred
Dumb question here but after changing my spark plugs from Massives to Fine wires I noticed she can run LOP with less fuel and smoother so now my EGTs are the same (1300-1350F) but my CHTs are 250-260F and dont even show up on the JPI anymore.

This is on a Continental IO-550B with Deshannon baffles and GAMI's

Conditions for flight yesterday:
40F OAT
7000FT ALT
2300-2350 MP
2350-2400 RPM
12.5 GPH
168 TAS (152CAS)

I can also lean further by almost 1GPH but the engine doesn't feel as smooth (still smooth though) and my speed drops a few knots. but the CHTS drop into the low 240F range.
 
sounds like you are running very lean. There is an optimal LOP setting....and beyond that is not an efficient way to burn fuel....and yes, you can be too lean. IIRC 20-30 deg F LOP is the most efficient setting for developing power....and 2500 rpm.
 
Checkout_my_Six said:
sounds like you are running very lean. There is an optimal LOP setting....and beyond that is not an efficient way to burn fuel....and yes, you can be too lean. IIRC 20-30 deg F LOP is the most efficient setting for developing power....and 2500 rpm.
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I hope by "too lean," you mean shutting the engine off. That's about it.
 
Checkout_my_Six said:
sounds like you are running very lean. There is an optimal LOP setting....and beyond that is not an efficient way to burn fuel....and yes, you can be too lean. IIRC 20-30 deg F LOP is the most efficient setting for developing power....and 2500 rpm.
Click to expand...

I use the lean function on the JPI and usually end up with about 30 degF LOP and thats where the engine sounds happiest, but still seems cold.

I was just playing with it to see where the engine sounded rough, and that was the 240 degF, but I dont run there.
 
MyassisDragon said:
Dumb question here but after changing my spark plugs from Massives to Fine wires I noticed she can run LOP with less fuel and smoother so now my EGTs are the same (1300-1350F) but my CHTs are 250-260F and dont even show up on the JPI anymore.

This is on a Continental IO-550B with Deshannon baffles and GAMI's

Conditions for flight yesterday:
40F OAT
7000FT ALT
2300-2350 MP
2350-2400 RPM
12.5 GPH
168 TAS (152CAS)

I can also lean further by almost 1GPH but the engine doesn't feel as smooth (still smooth though) and my speed drops a few knots. but the CHTS drop into the low 240F range.
Click to expand...

You're ok with that, stay above 220° and there's no worries. Besides, the main problem with too cold is the ring seat gets washed out with fuel, but since you are LOP, the fuel condition to cause the problems doesn't exist. The other issue when you start getting below 220° is the head/barrel contraction and you run into potential interference issues, but again, these complications are minimalized due to the LOP aspect of it since it's an all around lack of heat production that is causing the cooling, so the piston cools and contracts as well.

Still the best way I have found to set mixture is by ear. There is a fine line in the mixture as you move it forward from a rough running lean, first the engine starts to smooth out, then there is a transition point where it goes from a 'breathy' sound to a 'throaty' sound picking up resonance. You'll also feel the power surge and see a jump in the airspeed. That's my spot. That's where she's fat dumb and happy to run all day pretty much as fuel efficiently as possible.

If it sounds right, it is right, sound is really the best determinant of what is happening in the combustion chamber unless you have some really sophisticated electronics not on the typical aviation market.
 
Checkout_my_Six said:
sounds like you are running very lean. There is an optimal LOP setting....and beyond that is not an efficient way to burn fuel....and yes, you can be too lean. IIRC 20-30 deg F LOP is the most efficient setting for developing power....and 2500 rpm.
Click to expand...

Yep, too lean and it will not run. :)
 
My engine answered this question with a resounding yes.

It was rusted all to **** inside when torn down for OH. 12 years, 1350 hours, always added camguard, regularly flown, oil changed at 30 to 40 hours (have filter)...

And it looked horrible inside. I struggled wifh keeping temps up, especially oil temps.
 
what aircraft is that 550 in? way to cold .if you have cowl flaps us them 300 dfh is a good place to be .
 
timwinters said:
My engine answered this question with a resounding yes.

It was rusted all to **** inside when torn down for OH. 12 years, 1350 hours, always added camguard, regularly flown, oil changed at 30 to 40 hours (have filter)...

And it looked horrible inside. I struggled wifh keeping temps up, especially oil temps.
Click to expand...

Ouch , What engine?
I started pulling the cap off after flights to let the steam out and decided that a crank case dehumidifier was a good idea, so I am now running one while it sits in the hangar.
 
ok what is the oil temp ? if it is on the cool side as well might want to check vernatherm and seat
 
Oil should run optimally between 180F and 190F. Up to 210-220F I'd not be concerned about (boil out water easier). Below 180F in cruise, I'd get concerned and warm it up. Tim had chronically cold oil, which I suspect caused his engine corrosion.

The CHTs I wouldn't worry about, but it does sound like you're running significantly leaner than you need to. How many degrees LOP are you running?
 
Ted DuPuis said:
Oil should run optimally between 180F and 190F. Up to 210-220F I'd not be concerned about (boil out water easier). Below 180F in cruise, I'd get concerned and warm it up. Tim had chronically cold oil, which I suspect caused his engine corrosion.

The CHTs I wouldn't worry about, but it does sound like you're running significantly leaner than you need to. How many degrees LOP are you running?
Click to expand...
just to be clear.....212C would be way too hot? :yikes::hairraise::yikes:
 
Too lean means; to the point of causing preignition or detonation, which, the damage starts before you feel it or see it. I've seen pictures posted on aircraft maintenance forums where pilots have asked what happened to their engine...
 
GlennAB1 said:
Too lean means; to the point of causing preignition or detonation, which, the damage starts before you feel it or see it. I've seen pictures posted on aircraft maintenance forums where pilots have asked what happened to their engine...
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If you're running LOP, leaner is better. This person wasn't running "too lean" from your definition. You are referring to someone who was operating ROP and leaned out to the range that detonation would occur.
 
Ted DuPuis said:
If you're running LOP, leaner is better. This person wasn't running "too lean" from your definition. You are referring to someone who was operating ROP and leaned out to the range that detonation would occur.
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and that would be "not lean" enough....:yes:
 
Checkout_my_Six said:
and that would be "not lean" enough....:yes:
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It's "too lean" if you're a ROP operator, and "too rich" if you're a LOP operator.

"Wrong" is the best description. :)
 
hotprops said:
ok what is the oil temp ? if it is on the cool side as well might want to check vernatherm and seat
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Not sure, I will have to look next time I fly. I recall the gauge being in the middle of the green arc which puts it between 65-75 C (150-165F??)

May be colder or hotter though I just dont remember.
 
Back to the original question; Can an engine run too cold? Yes, but excessive engine wear, and ultimately, damage, could occur. Engines have operating limitations based on manufacturers research and development. The least amount of frictional wear should take place when the engine is operated in normal temperature range (assuming there are no other problems). That is why it is recommended to idle until reaching operating temps.
 
Ted DuPuis said:
Oil should run optimally between 180F and 190F. Up to 210-220F I'd not be concerned about (boil out water easier). Below 180F in cruise, I'd get concerned and warm it up. Tim had chronically cold oil, which I suspect caused his engine corrosion.

The CHTs I wouldn't worry about, but it does sound like you're running significantly leaner than you need to. How many degrees LOP are you running?
Click to expand...

30 deg LOP using the JPI.

I will have to check oil temp next time I fly. I know its in the middle of the green ARC but cant remember where exactly.
 

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It took me too long to realize my mistake...

I like to cook engines. And oil.
 
timwinters said:
My engine answered this question with a resounding yes.

It was rusted all to **** inside when torn down for OH. 12 years, 1350 hours, always added camguard, regularly flown, oil changed at 30 to 40 hours (have filter)...

And it looked horrible inside. I struggled wifh keeping temps up, especially oil temps.
Click to expand...

What was your oil Temp running at?
 
Ted DuPuis said:
Oil should run optimally between 180F and 190F. Up to 210-220F I'd not be concerned about (boil out water easier). Below 180F in cruise, I'd get concerned and warm it up. Tim had chronically cold oil, which I suspect caused his engine corrosion.

The CHTs I wouldn't worry about, but it does sound like you're running significantly leaner than you need to. How many degrees LOP are you running?
Click to expand...

I found an old panel picture from a trip before I replaced the plugs with fine wires (camera doesnt take good picts of the LED's apparently and CHTS show in the 280f range)

It looks like the oil temp is about 60 C (140F) at 40 deg F OAT running 11.5 GPH LOP. (I was playing with the RPM between 2350 and 2500)

From another post I checked and dont think Continential has a vernatherm valve to rais the oil temp so I will talk to my AP about this.

Any ideas how to warm it up if it needs it?

Although I am a little confused the moisture. Water boils at 212F so even if I boost it up to 170F how would that help with the moisture issue?
 

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I struggled in cool temps to get it up to 180dF. It would run 160 to 170. So, I'd oft, but not always, finish the flight with some slow flight, bringing the temp up to 190dF for at least 10 minutes.

Apparently that wasn't enough. If my new engine runs as cool, I WILL find a plan B of some sort.
 
There's an evaporation rate even if below 212ºF
 
The engine has hot spots. Your 180-190F ideal temp means that the oil will get above 212F in local spots, which will boil the oil out. Also keep in mind that water boils at a lower temp as you go up in altitude. Tim's ending a flight with 10 minutes at 190F I'd say isn't enough, because you need it in cruise to give enough time to boil the water out.

In the end, a lot of it is the poor oils we have for these engines. When was the last time a car engine did this? It's never happened to me, and I've had cars/motorcycles/lawn equipment engines sit for months at a time regularly.
 
Ted DuPuis said:
The engine has hot spots. Your 180-190F ideal temp means that the oil will get above 212F in local spots, which will boil the oil out. Also keep in mind that water boils at a lower temp as you go up in altitude. Tim's ending a flight with 10 minutes at 190F I'd say isn't enough, because you need it in cruise to give enough time to boil the water out.

In the end, a lot of it is the poor oils we have for these engines. When was the last time a car engine did this? It's never happened to me, and I've had cars/motorcycles/lawn equipment engines sit for months at a time regularly.
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Part of the poor oil problems goes back to using 100LL fuel as well. The best automotive oils aren't useful for planes because they aren't made to deal with the formulation of AvGas.

Personally if I am infrequently using an engine I also run some Lucas oil treatment for film qualities. When I asked a noted person about this I was told it's not a bad idea if one doesn't run frequently.
 
Yes, 100LL is part of what hurts us in the oil world as well. Point is, we have bad oils.

I'd be curious what oil Ben runs in his plane as I believe he runs 100LL in it now, or at least a mix...
 
Ted DuPuis said:
The engine has hot spots. Your 180-190F ideal temp means that the oil will get above 212F in local spots, which will boil the oil out. Also keep in mind that water boils at a lower temp as you go up in altitude. Tim's ending a flight with 10 minutes at 190F I'd say isn't enough, because you need it in cruise to give enough time to boil the water out.

In the end, a lot of it is the poor oils we have for these engines. When was the last time a car engine did this? It's never happened to me, and I've had cars/motorcycles/lawn equipment engines sit for months at a time regularly.
Click to expand...


And keep in mind most aviation oil temp senders are placed AFTER the cooler so I doesn't really give true oil temp that is in the motor... My guess is if the gauge reads 190f,, the oil is around 230+ in the motor.. Depending on the efficiency of the cooler itself...:rolleyes:
 
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