High EGT on Cyl 1 and 2, also Oil Temp issue

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StepOnTheBall
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High EGT on Cyl 1 and 2, also Oil Temp issue

Post by StepOnTheBall »

I have an M-7-235-B with an O-540 B4B5. I was flying with an instructor this weekend and he was a little concerned with the higher EGTs on Cyl 1 and 2. It was a cooler day (high 60s), running 22 squared. These cylinders showed 1560s. All CHTs were in the 360 range.

I’ve also noted that when I’m at a higher altitude, it seems I’m not able to lean very much before finding a peak EGT.

Thoughts on this? Pic of JPI attached.

Another issue I have is that my oil temp gauge seems erratic. It will peg to redline but then snap back to the middle of the green. The mechanic thought it may be a loose wire but of course couldn’t replicate it on the ground. My thought is a bad gauge.

Thanks for the help as always. Love this forum.

Brandon
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andy
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Re: High EGT on Cyl 1 and 2, also Oil Temp issue

Post by andy »

If you have an external output connection on your JPI, have you downloaded the history data and analyzed it with JPI's EzTrends app? That would tell you if something has changed. 1560 is somewhat high for EGT on two cylinders and could indicate a valve problem. The JPI calculates peak lean based on the the first cylinder to reach a 15 degree rise in EGT in Rich Of Peak mode. At higher altitudes I often find that less leaning is required to achieve peak lean, which is counter intuitive since air pressure is lower.

I would also suspect a loose or frayed wire connection with an erratic oil temperature gauge. The gauges do go bad sometimes but usually when they are very old. The sensor might be the cause rather than the gauge. I would carefully inspect the wire to the sensor first. You can check the operation of the sensor by removing it and placing it in hot water. There are several threads on the forum such as this one. Try searching on "oil temperature sensor": http://www.maulepilots.org/Hangartalk/v ... ure+sensor
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norcal64d
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Re: High EGT on Cyl 1 and 2, also Oil Temp issue

Post by norcal64d »

My question would be how long as it been running at that temp? I would check the easy things first, JPI should have a procedure in their manual for doing an intake leak check. Basically you compare the EGTs full rich at full throttle and then at like 55% power to see if when you pull the throttle back and increase the pressure differential between the cylinders and ambient pressure, a leak is noticed (a cylinder will run leaner). My understanding of EGTs are that the exact number isn't so important as the trends, but 1500+ seems a bit warm. Another thing I have noticed is the fuel distribution isn't so great with carbureted engines and while my EGTS are more matched at full throttle, as soon as I pull the throttle back they tend to do different things to a degree.

As to the oil temp gauge, just out of curiosity turn your dash light rheostat up and see if it changes the oil temp gauge behavior. I had to clean around the timmerman nuts of the four screws that hold the gauges cluster in to solve my oil temp gauge being affected by the dash lights being on.
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Re: High EGT on Cyl 1 and 2, also Oil Temp issue

Post by VA Maule »

1500 seems a little warmer than aught to be. Swapping probes 1-3 & 2-4 and see if reading follows the probes or stays with the cylinder. Another thing to look at is possibly a bad spark plug in the cylinders of question , as a non firing plug and the other firing normally will present it's self as higher than normal EGT but will NOT be felt as a miss . Next time flying when the EGT's are showing hot try doing a mag check in the air, if it goes to running ruff it' would definitely a lack of spark. 3 things to look further into if the spark has gone AWOL mag. Plug lead. Spark plug any of these could be the possible culprit .
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StepOnTheBall
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Re: High EGT on Cyl 1 and 2, also Oil Temp issue

Post by StepOnTheBall »

Thanks, all for the input. This definitely gives me some direction of where to proceed with this.

I’ll give an update when I figure them out.

Brandon

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Re: High EGT on Cyl 1 and 2, also Oil Temp issue

Post by Millemr »

Did you ever get any resolution to this problem?

I’m having a very similar issue in my M-7-235C as what you’ve described here.

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