Technical question about engine temperatures

[spencer2004]

Due to the simplistic design of my air cooled engine the cooling performance isn't as good as a liquid cooled engine and there is no way to tell if it is overheating until it catches fire, explodes or seizes up. I was thinking about adding some sort of temperature sensor to my engine so I can keep an eye on the temperature or perhaps add a micro controller to give a visual warning when the temperature is too high or even engage the kill switch when the temperature gets critically high. My question is where would be an easy place to mount a temperature sensor but still get accurate readings and what temperature would be considered dangerous.

[Lao Jia Hou]

Hi Spencer

Getting accurate readings might be difficult, but after-market sensors (easily installed) that give you a general idea of the temperature are available.

I have used the type that looks like a turkey roasting probe, that replaces the oil fill cap on the crankcase - it was not perfectly accurate, but it did give me a general idea of cool, warm, hot, and melt. Because it has the temp gauge on top, it is a very simple install. But you wouldn't be able to wire anything into it (e.g., a kill switch)

There is also one that replaces the oil drain plug, that you would need to wire a gauge to:

http://www.louis.de/index.php?topic=...034662&lang=en

And one that slips under the spark plug, presumably to monitor cylinder head temperature (again, requiring a separate gauge):

http://trailtech.net/temperature_sensors.html

I once saw a guy who had modified his cranckcase and tapped in a sensor for oil temp. Although it looked professional, he confessed it was a constant source of leaks.

Or you could use the farming tractor trick - spit on the engine block ... if spit remains, engine is cold ... if it steams, but doesn't bubble, engine is warm ... if it sizzles off in a few seconds, engine is too warm ... if it vaporizes on contact, shut engine off; lunch time.

[spencer2004]

Thanks for the reply. Measuring the temperature of the oil did cross my mind; I was planning on fitting an oil cooler for the summer so perhaps I could drill a hole in one of the oil passages on the radiator/oil cooler, stick a probe in and seal it up with JB weld. I would imagine that the cylinder head would be the best place to get a reading from however. Do you have any idea what could be considered dangerous temperatures for the oil and the cylinder head area?

[ShuBen]

!!!! Never connect your Kill switch to automatic shut off !!!! Imagine what happens this situation occur in a curve or at a critical take over ....

LJH's idea to use the drain plug and also your idea to get a adaptation in the oil cooler supply line is feasible.
To monitor the oil temperature is enough to make sure your engine doesn't overheat

[Lao Jia Hou]

Do you have any idea what could be considered dangerous temperatures for the oil and the cylinder head area?

I think it depends on the particular bike, particular engine, type of oil and load conditions. I have heard that a general rule-of-thumb for oil temp is >250 degrees F is a danger zone. I think that oil only partially cools an engine.

I have no idea about external cylinder head temp, except that overheated engines can fail for a variety of reasons - overly expanded metal is not healthy, especially if you cycle through a lot of cold/hot, cold/hot runs.

Engine temp is influenced by speed (on an air cooled bike), whether it is a cool or hot day, dry or wet conditions, humidity, and also whether there is dirt & grime covering the engine (which acts like winter clothing).

In my experience, I can feel an overheating engine on my legs, especially at low speeds - it is very noticeable (almost painful).

[spencer2004]

Good point ShuBen I won't have an auto kill switch then.

I think I'll measure the oil temperature with the drain plug thing as that seems to be the easiest solution.

Thanks for the advice guys!

[arancara]

This sounds interesting, where can you source oil coolers and where could you link them up to these engines, surely a pump would also be required?

[Krasi]

Or, if you want to fool a bit with some wiring and electronics, you can use something like this:

http://thesensorconnection.com/cht-s...e-12-and-14-mm

Or just get one "ready to go" from TrailTech :

http://www.trailtech.net/tto-gauges.html

(I would be surprised if there are no Chinese clones of these )

[spencer2004]

Well well well there are 2 ways to add an oil cooler; you can buy a kit or DIY it. You can get a kit from Taobao which includes the radiator, hoses, banjos, and a special adaptor which replaces the oil filter cover, the adaptor comes with a rubber washer that fits behind the oil filter which blocks the oil return passage, the filter cover adaptor has a threaded hole which you can attach a hose to using a banjo bolt, the oil goes through the oil filter and as it cannot go through the oil return passage anymore it is forced through the hole in the oil filter cover, through the hose and in to the radiator, the return line from the radiator goes through another hose and in to a threaded hole in the side of the engine which is used for measuring oil pressure or something.

Here's a good thread on the subject.
http://www.mychinamoto.com/forums/sh...ing-Oil-Cooler

I was going to go the DIY route by drilling and tapping a hole in a spare oil filter cover I have to screw the banjo bolt in to, using braded steel hoses, a cheap oil cooler radiator and banjo fittings from eBay.

A pump wouldn't be required as just about every single engine in the world has an oil pump inside it anyway ;)

This subject is based entirely around the K157FMI engine, it would probably be a bit harder to do this to your engine as you do not have an oil filter.

[arancara]

Hmmm sounds interesting, so your saying the engines (pistons) natural movement will be enough to pulsate the oil?

Regarding my engine, obviously no oil filter, but I've got a strainer, could I not use that as a pick up? Also where could I feed back or does that not matter as I am tempter by a small universal cooler to increase capacity and increase temps, I could always buy a cut off switch to act as a thermostat for the winter. Any idea's appreciated.

I've seen this: http://totalruckus.com/phpBB3/viewto...p?f=34&t=50499

Edit, looking online, some people drill back into sump, others use a universal adapter where the strainer is or the sump is, what would you recommend?

Also I've just seen this: