Engine operating temperature and some feedback

[OomD]

Some of you know about my Speedominator project detailed here, here and here.... This thread details some findings with regards to engine temperature.

I have 2 temperature sensors installed, one one each head (sits like a washer between the sparkplug and the head). Normal running temperature on my bike seems to be about 193F (143C). A interesting aspect is that the rear cylinder actually runs coolor than the front cylinder, I expected it to be the other way around.

Ambient temperature around here in South Africa this time of the year is 86F(30C). While idling the temperature goes up to about 347F (175C) and seems to remain at that point. The RPM is then still around 1000.

The engine heats up very very quickly, reaching 210F (99C) by the time I am a mile away from home. During this time the RPM's have been kept at 2000 max. I suppose this is normal for an air cooled engine.

A question I have... On my speedominator I indicate the RPM redline as 3000 until the temp reaches 140F (60C) and then I gradually indicate a higher redline until it maxes out at 5200RPM. At this point the engine temp is 194F (90C). Now, seeing that this temperature is reached so quickly (on the cylinder head), can it be assumed that the oil has warmed up sufficiently too? I don't monitor the oil temp so I don't know what it is at that stage.

It just feels to me that the engine is still a bit cold by the time I indicate a usable redline of 5200, I would prefer moving the lowest temp up to 160F (70C) and the normal one (where 5200RPM redline is reached) at about 210F (99C)... or is that too high?

Sorry for the long(ish) post, but hoping some technically minded folk can give their opinion here.

Cheers!

[mrmetal]

Here is some data that I copied from my thunder max tuning guide.
And they state that the air fuel mixture should reach your target air fuel ratio between 160 and 180 agrees head temperature. Below that temperature air fuel ratio is Richer until the engine warms up to that temperature. And 6200 RPMs is red line limit from the factory on my bike.
If I see my head temperature reached 320° I will pull over and let it cool off if possible.

{THE MOTORCYCLE DOES NOT AUTO-TURN OFF, so do not leave the motorcycle unattended during this operation. DO NOT walk away from the motorcycle while it is running at idle. Serious damage can occur if the head temperature goes beyond 325o F and is allowed to continue upwards without supervision.

Start the engine and allow the head temperature to rise to a normal operating temperature (260-285o F)}

[OomD]

Thanks for the feedback, mrmetal, much appreciated. And you have just given an idea to add to my Speedominator... an overheat indicator. Seeing that the temperatiure itself is not always monitored I'll make the RPM display in red for all the LEDs, not only while you're above the redline. This way an RPM indication of all RED will be a better visual clue as to possible overheating. This can start at about 325F, and if it increases even more (say above 335F) then the LEDs can flash rapidly too.

[SCHMIDTYS]

Injected TC operating temp is 250*, EVO is 284*. These are the optimum temps for diagnostic purposes.

[hdzx]

how fast does the engine warm up? I let mine idle for 15 mins or so when cold before I take off. sometimes 30 mins when I BS with friends at work


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[Dave63]

Originally Posted by hdzx

how fast does the engine warm up? I let mine idle for 15 mins or so when cold before I take off. sometimes 30 mins when I BS with friends at work


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It depends on ambient air, load and AFR. Leaner will get hotter quicker. Generally 3-5 miles.

[OomD]

Originally Posted by hdzx

how fast does the engine warm up? I let mine idle for 15 mins or so when cold before I take off. sometimes 30 mins when I BS with friends at work


Sent from my iPhone using Motorcycle.com Free App

Riding to work, I timed mine this morning. It reached 140F after 2 minutes and 0.5Km (less than 1/2 mile). Further, it reached 240F after 6 minutes and 1.7Km (about a mile). Ambient temp was 73F.

I drive with the RPM's less than 2500 without labouring the engine until its warmed up.