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Topic-icon Cool CHTs

  • PETERMUCKLOW
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3 months 1 day ago #1334

I fly a normally-aspirated '77 Lance that has what I consider to be very low CHTs. Normal operation in summer (85F) shows CHTs in the 300F range (280 - 320). In winter, these fall to the low 200's (220-250). I have an Insight GEM-610 6-channel engine monitor, with Insight CHT probes. I run ~50F LOP with GAMIjectors. I am concerned that the CHTs are too cool. Should I be? I get lead deposits in the plugs at those temps, but nothing biannual plug cleaning can't manage.

Last Edit: 2 months 2 weeks ago by PETERMUCKLOW.

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2 months 2 weeks ago #1348

Steve, appreciate your opinions on this if you have the time.

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2 months 1 week ago #1358

Hi Peter;
Sorry for the delay in getting back to you. You're OK with those temps. This debate will go on forever about the "right" temp but Lycoming has published that 150 deg F is the lowest that is OK. So you're fine.
If you're getting lead deposits I suggest that you lean aggressively on the ground. I routinely do my 2000 rpm mag check run ups with the mixture leaned. You'll know when you're too lean because the rpm will fall slowly off when on one mag; just richen it up a little and continue.
There is an additive in avgas that will vaporize the lead so it flows out the exhaust but that additive is only effective at higher internal combustion chamber temperatures; aggressive leaning during taxi and low power ops will reduce the lead build up.
But make sure that you richen the mixture up before take off.

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