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Low CHT

Nick Sieczkowski

I'm New Here
G'day, this is my first post on VAF as I'm trying to chase some opinions.

I've had my plane for about 18 months (deceased estate and it hadn't flown in 2 years) and had it looked at by a couple of different LAMEs and they haven't seemed to be overly concerned, but I would like to know what other people think. Engine is an O-320D2J.
Main points:
- Low CHT
- Adjusting mixture has slow and small effect on EGT (impossible to determine any discernable peak EGT) and zero effect on RPM
- Carb heat has zero effect on RPM
- Oil temp seems to take a little longer than normal to reach temperature
- Engine runs smooth with about 70 RPM drop on both mags (never looked for an EGT drop)

Wondering if this seems like there is an issue to be concerned about, and if so, is there any other trouble shooting I should be doing?

https://ibb.co/fopJ3y
https://ibb.co/nywb6J

Thanks,
Nick
 
Due to the inactivity, I?d be concerned about the possibility of cam lobe damage from corrosion. You may detect it by comparing valve lifts between cylinders.
 
The 70RPM drop seems high. That in conjunction with no rpm drop when leaning might point to a bad tach. Do you shut down by pulling out the mixture? if so, then the mixture knob is working. I see you have a fuel flow gauge - does that show a drop?

The carb heat might be a very poor design. Many builders do not follow the instructions here and do their own set-up.

Is the temperature probe in the head, or under the spark plug? What cylinder is it on? Do you have a plenum, or baffles? The standard Vans gauges are not very accurate or reliable.

You are going to have to do some digging and exploring on all of these. I would invest in a 4 cylinder engine monitor
 
Assuming:
- Ignition correct
- Valve train correct
- Compression checks correct
The only thing left is fuel. The point that you cannot lean to peak EGT translates to you are alway LOP. The engine is not getting enough fuel to go ROP.

From this go figure out what is wrong:
- Mixture control
- Clogged fuel filter
- Clogged carb jet
- Carb float failed
- etc.

Carl
 
Comments below

G'day, this is my first post on VAF as I'm trying to chase some opinions.

I've had my plane for about 18 months (deceased estate and it hadn't flown in 2 years) and had it looked at by a couple of different LAMEs and they haven't seemed to be overly concerned, but I would like to know what other people think. Engine is an O-320D2J.
Main points:
- Low CHT

Please quantify. How low

- Adjusting mixture has slow and small effect on EGT (impossible to determine any discernable peak EGT) and zero effect on RPM

Need more detailed explanation. What is the effect? They going down, up, up then down, etc.

- Carb heat has zero effect on RPM

This is somewhat common and indicates you need some work to make it effective. Many posts on this issue.

- Oil temp seems to take a little longer than normal to reach temperature

What is the normal reference? This is not a safety issue.

- Engine runs smooth with about 70 RPM drop on both mags (never looked for an EGT drop)

70 RPM doesn't seem out of line. It might be worth checking the timing. Larger drops can be indicative of timing too far advanced.

Wondering if this seems like there is an issue to be concerned about, and if so, is there any other trouble shooting I should be doing?

https://ibb.co/fopJ3y
https://ibb.co/nywb6J

Thanks,
Nick
 
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