Cruise cylinder temps

[rturbett]

Flight to Saratoga NY, I hour at 5500ft, outside air temp low 40's, cowl flaps full closed engine leaned rop, the cylinder temps never warmed up. 

On the flight back, same conditions and settings (alt 4500)  all was normal.

Is the sensor serviceable?

FYI- I really like the yellow mark the previous owner put in place- if I move my head, I can make it perfect every time!

Thanks,

Rob

[PT20J]

59 minutes ago, rturbett said:

Is the sensor serviceable?

Yes. It’s on cylinder 3.

[rturbett]

1 hour ago, PT20J said:

Yes. It’s on cylinder 3.

PT, is it normal to clean and ensure connections, or just plan on replacing?  going in to annual in a few weeks.

Thanks,

Rob

[PT20J]

4 minutes ago, rturbett said:

PT, is it normal to clean and ensure connections, or just plan on replacing?  going in to annual in a few weeks.

Thanks,

Rob

Never hurts to check connections. Always check the simple, inexpensive things first.

[Slick Nick]

I think my sensor has been acting up too lately. Even when I try to get it nice and hot in a climb, the cat never indicates over 200*. That’s with OAT’s in the 0*C—10*C range, but I still think it should get hotter than that. I suspect a connection to the gauge, or the sender itself. My J has the captive type, with the little spring loaded cap that you turn. 90*.

[Shiroyuki]

I have an old EI engine monitor in my plane and I usually see 300-350F on temperature in cruise with cowl flap fully closed. Temperature is around ISA-5 ish. This summer I did see some high temp when it's ISA+15 outside and highest I've got was 390 ish. It is my first year owning a mooney and I'm quite surprised by how cool the cylinders are. However due to the age of the engine monitor I won't put in too much faith in the absolute reading.

My cylinder 4 always reads 50F highers and cylinder 3, and cylinder 1 and 2 are usually somewhere between #3 and #4. Not sure where this differences comes from. 

[Slick Nick]

11 hours ago, Shiroyuki said:

I have an old EI engine monitor in my plane and I usually see 300-350F on temperature in cruise with cowl flap fully closed. Temperature is around ISA-5 ish. This summer I did see some high temp when it's ISA+15 outside and highest I've got was 390 ish. It is my first year owning a mooney and I'm quite surprised by how cool the cylinders are. However due to the age of the engine monitor I won't put in too much faith in the absolute reading.

My cylinder 4 always reads 50F highers and cylinder 3, and cylinder 1 and 2 are usually somewhere between #3 and #4. Not sure where this differences comes from. 

What was your OAT at the time? The other day up at 16,000 it was -30*C and I could barely get the needle to move off the bottom of my factory gauge. Do you still have your factory gauge installed? How does it compare to what’s shown on your engine monitor?

[Shiroyuki]

On 11/18/2024 at 9:35 AM, Slick Nick said:

What was your OAT at the time? The other day up at 16,000 it was -30*C and I could barely get the needle to move off the bottom of my factory gauge. Do you still have your factory gauge installed? How does it compare to what’s shown on your engine monitor?

I dont quite remember the exact temperature, but at ten thousand feet with isa -5 that’s around -5c. ISA +15 would be around 10C.

-30 is freezing at 16k ft. That’s ISA-15.

my factory gauge is on cylinder 3 and i somehow have 2 temp prop on that cylinder. It does agree with my engine monitor though. My factory gauge mostly set pretty low in the green arc.

That’s at 75% power.

I recently had the oil cooler flushed and oil temp prop calibrated which is why there is another red marking to the right of the original red marking. I was getting high oil temp this summer, but now it seems to be pretty cool.

Edited November 22 by Shiroyuki

[A64Pilot]

I too only have the factory instrumentation and in a Fl Winter I have to enrichen a bit to stay in even the bottom of the green in cruise. J model.

I adjust what full close is on the cowl flaps twice a year, the book has an allowance and I can’t pull it from memory but in Winter I’m at the most closed and Summer it’s more open, and as I’m in Florida it’s of course not a real winter so I’d expect in places that get real Winters that you need the cowl flaps full closed, no gap and run ROP just for the heat.

EI Thermistors are normally very accurate and stay that way, in my experience with them they are either accurate or don’t work at all, nothing in between, assuming we are talking a digital EI instrument, before engine start they should display ambient temp pretty accurately. I had an MVP-50P in my Maule and had 14 temp sensors and all would display within 1 deg F on power up if the aircraft had been sitting in the hangar for a few days 

[Will.iam]

8 hours ago, Shiroyuki said:

I dont quite remember the exact temperature, but at ten thousand feet with isa -5 that’s around -5c. ISA +15 would be around 10C.

-30 is freezing at 16k ft. That’s ISA-15.

my factory gauge is on cylinder 3 and i somehow have 2 temp prop on that cylinder. It does agree with my engine monitor though. My factory gauge mostly set pretty low in the green arc.

That’s at 75% power.

I recently had the oil cooler flushed and oil temp prop calibrated which is why there is another red marking to the right of the original red marking. I was getting high oil temp this summer, but now it seems to be pretty cool.

The 2 probes is because your engine monitor is not certified as primary instrument where as your original ships gauge is. So the engine monitor has to use a piggyback sensor. Some are even a ring that fits under the sparkplug. And since the piggyback is not in the same location as the the other 3 it will read higher or lower than the others depending on where the piggyback sits. 

[Shiroyuki]

4 hours ago, Will.iam said:

The 2 probes is because your engine monitor is not certified as primary instrument where as your original ships gauge is. So the engine monitor has to use a piggyback sensor. Some are even a ring that fits under the sparkplug. And since the piggyback is not in the same location as the the other 3 it will read higher or lower than the others depending on where the piggyback sits. 

That would explaining why cylinder 3 reads lower than all other cylinders i suppose

[PT20J]

The hottest part of the cylinder head is usually around the spark plugs, so the spark plug ring probes read higher than the bayonet probe. When I had my EDM 700, I put the ring on cylinder 1 which had a bayonet probe and noted that the ring probe measured 40 deg F higher than the bayonet. Later I installed a 3/8" ring probe on the factory probe on cylinder 3 and it measured about 20 deg F lower than the factory probe which JPI told me was normal since the factory probe is down in a well in the head and the ring is on the surface.

[Slick Nick]

17 hours ago, Shiroyuki said:

I dont quite remember the exact temperature, but at ten thousand feet with isa -5 that’s around -5c. ISA +15 would be around 10C.

-30 is freezing at 16k ft. That’s ISA-15.

my factory gauge is on cylinder 3 and i somehow have 2 temp prop on that cylinder. It does agree with my engine monitor though. My factory gauge mostly set pretty low in the green arc.

That’s at 75% power.

I recently had the oil cooler flushed and oil temp prop calibrated which is why there is another red marking to the right of the original red marking. I was getting high oil temp this summer, but now it seems to be pretty cool.

I didn’t want to clutter up your thread so I started my own, but I’ve determined that my gauge is working fine, it was just reslly, really cold that day! 
 

 

[M20F]

Liquid cooled engines maintain almost an exact temperature to the point most cars don’t even have a temperature gauge anymore.  
 
Air cooled engines are wildly impacted by the temperature and the flow of air.  There is no thermostat to regulate the temperature (vernatherm on oil cooler to some extent).  
 
I love this thread every year because it reminds me winter is here.  Then I wait for its brother and the 5000F CHT while climbing out of Leadville at +25ISA, then I know it is summer.  Got to say spring and fall are pretty boring. 

[geoffb]

Anything that increases the resistance of RTD circuit will tend to increase the temp shown on the gauge.  So, the vast majority of issues with the probe circuit will tend to show a high temp, not low.  Just FYI.