Good operating temp for or motors.

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nitroheadjones

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I have ran nitro motors for years and most of my nitro motors like to run at about 225 degrees - 250 degrees . But I was wondering what a good operating temp would be for a 2 cycle gas motors. When I finish running mine I can always touch the engine case without burning my hand. I have a heat gun just wanting to check to make sure I am not running to rich or too lean.
 
I have a ESP 30.5cc and same as the other guys you look at the plug and listen to the sound. However, I came from running nitro so I had a temp gun and on a hard long run my motor at the top of the head will hit 200-220 degrees. I always let the motor idle for a few minutes before I shut it down to bring the temp down SLOWLY. Also I run more oil than most people would run. I run 20:1 and that seems to run my motor cooler than running less oil and less chance of wear and tear and over heating. If my motor gets past 220 degrees I will let it idle and cool it down. Check for piles of grass under the motor and inside the cooling fan.

Hills
 
I had just purchased a new motor fully ported from ESP and my last ESP I ran it too hot in deep grass and it got heat soaked and it was never the same compression after that day. Like I said I still had that heat temp gage and that motor I was running at the time 32:1 and it was always around 280 and heat soaked around 300-320 degrees. So I started talking to Doug at ESP and he was saying that the guys who run the boats run as much as 10:1 and it will keep the motor cooler and lubed more. 20:1 is still alot and my temp stays around 200-220. Some say you lose power running that much oil but I cant tell between 32:1 -20:1.
 
I run 25:1 with a 100:1 oil. That is pretty much 20:1 and its true there really is not much a difference between 20-35:1 other then a bit more oil.
The boat guys also say they found the motors to have more power with more oil. Most of the boat motors will never heat like ours because most are not air cooled and are water cooled. It is a great thing you did with keeping tabs on the heat difference between heavy and light oil. Thumbs up!;)
 
Hey thanks. I forgot to mention with my new fully ported ESP 30.5cc and a Dom Pipe with the Walbro 813, I pulled 45 MPH with the radar gun on my FG MT. Thats with changing the gears from 16/48 to 18/46. The 18/46 is such the perfect combo of low end torque and high end gear and at 35 MPH still pulls the front end up. My buddy has a Baja 27.2 Reed and his hits 50 MPH, and off the line it all comes down to who has the best traction. I hope to get a video here soon to post.
 
i have a spektrum DX3S with temp telemetry (so I can spot when I need to clean the grass from the head), and today I found that it'll settle to 50c at idle, but generally runs at 70-80c. max temp today was 96c.

I've only run it once with the telemetry, and need to tune the carb again. When I've figured out what is 'normal' i'll let you know.
 
I tune by sound and plug color, but i spotted a venom temp gauge at the LHS one day for cheap and picked it up. IT has the sensor so exposed that you can get it between the fins and right against the cylinder. I've seen an average of 170 - 225 on a well tuned cy29 with rtr can exhaust. I just got a stock SS pipe on it and when it's dry i'm going to tune it in and then see what the temps turn out to be. but ultimately the tune will be based on plug readings and sound. I only really keep an eye on it because i know they heat soak at over 280* (measured near the exhaust port) and so when i get it tuned how i like it, i use the gauge as a wanring if i'm getting too hot for the engine's good.
 
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Was out running this eve car park basing with slicks on by FG Baja with stock can, was more like drift racing until I got some heat into the tyres.

However.. 2C outside gave a max engine temp of 75C on the telemetry, and about 45C at idle, not that it got much chance to do that with all the wheelspin.
 
Gave it some long runs yesterday, and I was reading 1C outside air temp, about 35c after 3 mins at idle (from cold) and peaked at 100c after 2 mins of almost constant full throttle (I found a good high speed jump spot). it settled to about 70C when driving normaly.

Main thing I have noticed, is that a low idle doesn't give enough cooling air to have any major effect on the temperature. So if you are wooried about engine temp after an extended long hard run, you are best to hold the engine on a fast idle just below the clutch engagement point to get good airflow.


so it looks like the answer is about 70 to 75c when driving 'normaly' but a peak of 100 is pretty normal too.
Idle temp wil take a long time to settle as the fan doesn't do much cooling at low revs.


<edit> Just checked the C to F conversion with Turbos numbers and they agree, which is comforting to know!
 
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