G1 CHT Operating Range?

[Darrinm67]

I added a digital Cylinder Head Temperature gauge with a sensor that goes under the spark plug. I have been doing some test runs to try and get an idea of operating temperatures for a stock 1981 G1 but they are all over the place 175 - 220. If I run it full throttle on a steep uphill for about a mile it will climb up to 270. Most normal riding around readings are 170-190 range. Anyone have any experience with what’s normal or optimal for this type engine?

[cgtech]

That would be a great question for don plowman (www.plowmanscarts.com), he's a G1 expert.

[mikeasis]

My big bore cart .080 would get about 255 or so cruising the neighborhood I think these temps are normal for a fan cooled engine and that sensor

[slonomo]

Most engines like to run around 190-220 deg F. Look on your car dashboard at the temp gauge, it'll be green around 200. Air cooled engines will naturally be different than liquid cooled. But either way, temps fluctuate based on usage, outside air temps, humidity, and airflow. I studied this back when I was playing with my 6.6 Duramax and Saab 9-3 turbo. Air to air intercoolers work the same way, heat dissipation, heat soak, google that stuff. 300 degrees is HOT for an engine, but not impossible. I'd say keep it under 300 and it will technically be safe. However, excessive heat will cause other issues like detonation/preignition and loss of compression, engine wear, and warping of engine parts.

On the G1, and any air cooled engine, the engine shrouding MUST be used to keep it cool. Also, the cooling fins and flywheel fan MUST be kept clean of debris, grass, mud, etc to allow the air to pull the heat out.

[Dave in VA]

I had a Corvair Corsa back in the day. 164ci, 140hp, 4 carbs. It had a 0-600 CHT gauge in the dash that would normally read upwards of 350. It was a cool car...npi

[slonomo]

Originally Posted by Dave in VA

I had a Corvair Corsa back in the day. 164ci, 140hp, 4 carbs. It had a 0-600 CHT gauge in the dash that would normally read upwards of 350. It was a cool car...npi

My grandpap had 4 of those cars, very cool. All convertibles. The 66 was the coolest. Anyway....

Not surprisingly, the higher the HP, the hotter the engine will run. Some engines were engineered to handle those higher temps, some over 400 degrees F. The Corvair at 140-180hp was much higher than a golf cart engine, so temps would be higher. An airplane engine could have as much as 2000 hp (the big ones).

The danger with temps is that gasoline will ignite at 495 degrees F. So keeping temps below that is a must. It's common practice in racing to let an engine idle for quite a while in order to get CHT down to below 300 degrees before shutting the engine off. This is just to avoid an accidental engine fire should fuel drip into the cylinder while hot. This is one reason why some engines catch fire during an accident when the engine stalls.

Also, if the temps exceed 495 degrees while running you can get "pre-ignition" or "detonation" because the fuel will come into contact with the hot cylinder, causing the gasoline to ignite before the spark plug fires. This can be devastating and can cause engine damage.

So the real answer of correct cylinder head temps? 250-300 degrees F, with brief fluctuations above 350 in high compression engines.

Found this chart about engine/oil temps.

[Dave in VA]

Not to hijack, but...'66 Marina Blue coupe. My dad bought it new, I was 16. We could have driven the car home off the showroom floor that day, with a 4speed. $64 option

"4 speed? That's just another gear to shift". The car was special ordered with a 3speed. Probably the only one...

[Darrinm67]

I was hoping to set a high temperature alarm, in hopes that I would get a warning for an oil injection problem. But with this wide range of temperature values picking a high temp alarm set point is not as straight forward as I thought. I am not sure I have seen the Max normal temperatures yet. Maybe 300 for winter and 350 summer? Or just 350 all the time might work. Any thoughts?

[slonomo]

Originally Posted by Darrinm67

I was hoping to set a high temperature alarm, in hopes that I would get a warning for an oil injection problem. But with this wide range of temperature values picking a high temp alarm set point is not as straight forward as I thought. I am not sure I have seen the Max normal temperatures yet. Maybe 300 for winter and 350 summer? Or just 350 all the time might work. Any thoughts?

Yeah an alarm might not work. If you do some reading on air cooled 2 stroke engines you'll find that some run hotter than others. I'd say just get a baseline off yours during mild temps, then base your range on that. Temps will fluctuate with air temps, humidity, and engine speed, so you won't know the temps of your engine until you monitor it. They're all different. Carb jetting and oil premix level makes a difference on 2 strokes as well.

One other thought. You can get a handheld laser thermometer gun and manually take temps. Obviously you have to stop the cart and lift the hood, but it's instant read. That's what I do with my lawn mower in the summer to make sure I'm not overheating it. On my air cooled 4 stroke mower engine I see temps above 350 degrees at times.

[Darrinm67]

Originally Posted by slonomo

My grandpap had 4 of those cars, very cool. All convertibles. The 66 was the coolest. Anyway....

Not surprisingly, the higher the HP, the hotter the engine will run. Some engines were engineered to handle those higher temps, some over 400 degrees F. The Corvair at 140-180hp was much higher than a golf cart engine, so temps would be higher. An airplane engine could have as much as 2000 hp (the big ones).


So the real answer of correct cylinder head temps? 250-300 degrees F, with brief fluctuations above 350 in high compression engines.

Found this chart about engine/oil temps.

Thanks for the Temp Chart. That is exactly what I needed. I will try the alarm at 330 and adjust to 350 if I get too many nuisance alarms (summer?). Either way it seems like a good idea to back off around 330 and let it cool a bit for best engine life. So having a beep to remind me to drop a few RPMs when I am over doing it, might not be a bad thing.