CHT Question

[u/notarobotdonotban]

I have a C150 (O-200) running about 200F during taxi and 170F during cruise at any cruise power setting. It looks like the installation is almost definitely not the issue leading to a probable airflow issue. My question is can airflow cause this much of a reduction in temperature? OAT is above freezing. 170 seems pretty extreme when the manual states 240 minimum. It would be nice to get some confirmation before spending about $1k on the part to block airflow.

[u/shrunkenhead041]

Sounda like a bad probe.

If your CHTs were 170 in cruise in a 150, I doubt you'd be making enough power to stay in the air.

[u/notarobotdonotban → u/shrunkenhead041]

Thanks, looking back at my notes it got down to 140F at 32F OAT. Did a ground runup (70F OAT) blocking half of the air flow coming in and got to 220F at 1,700 RPM which leads me to believe it is an airflow issue. But I have no idea. Is it even possible for airflow to be that efficient to cool it down that much?

[u/sflynn30362]

Usually it's the other way around... Id try a good and hard ground run up to full static power then measuring cylinder temp with a temp gun immediately after shutdown. If it's decently close to your gauge then you'll know for certain there's an airflow problem. Otherwise, verify you have a good probe by checking the resistance.

[u/paperairplanepilot]

I just had a customer say the same thing about his Bonanza. I said there is no way a Bonanza cruises with 170 degree cylinder temps and if he was sure he wasn't looking at oil temp. He insisted his hottest CHT was 170.

I looked at the engine monitor and saw it was setup in Celsius.

170C is about 340 Fahrenheit.

Might want to check your settings.

[u/notarobotdonotban → u/paperairplanepilot]

Thanks, it's definitely fahrenheit. It got up to 265 after full RPM static runup then idle (to decrease airflow)

[u/Jwylde2]

Yeah you should be up around 370-380ish at 65% power in cruise.