Technical question about engine temperatures

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.

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.

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?

!!!! 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

Quote:

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Originally Posted by spencer2004

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

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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).

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!

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?

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 :eekers::

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

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

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.

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:

http://www.7victory.com/%5Cupfiles%5...9086%5C895.jpg

I mean that just about every engine has an oil pump inside it, otherwise there would be nothing to create oil pressure to pump the oil around the engine. To fit an oil cooler you need to tap in to a place with high oil pressure and a place with low oil pressure. I don't know much about your engine but assuming that the strainer works in the same way that my engine's filter works you could block off the return hole where the strainer is, get oil from the strainer compartment and return it via the oil filler hole by drilling and tapping holes in the oil filler cap and oil strainer cap and attaching hoses to them. This is just guess work by the way, don't start drilling holes in your engine based on what I just said ;)

Quote:

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Originally Posted by arancara

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

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"Kit" for ur bike looks like this http://item.taobao.com/item.htm?id=4970522844

What you say? Drrrrrrrrrrrrrrrrrr Damn I hit oil :P

Didn't realise a oil pump would exist, just thought the oil just sat in a bowl... Never ever worked with motorcycle engines, only thing I have dealt with is small lawnmower engines and they have been two stroke so this is a new curve for me. I've seen a small rad that I'm tempted by, designed for a 50cc, as its not exactly a powerful bike so I'm guessing it would be sufficient as my aims to lower temps and increase oil capacity, so I imagine it will suffice as I'm having doubts whether this bike really produces 10bhp that is claimed on the tin compared to my yammy. I will try and have a look at my engine to see if there's any feeds too mine, as that is a 156-2a engine in the picture of my other post.

Any other idea's where low pressure could exist, what's the sump like, low or high? Just trying to think of other options before I dive in.

Quote:

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Originally Posted by spencer2004

get oil from the strainer compartment and return it via the oil filler hole by drilling and tapping holes in the oil filler cap and oil strainer cap and attaching hoses to them.

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Usually, on your bike's engine, it looks something like this.

Attachment 11154

Quote:

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Originally Posted by arancara

Didn't realise a oil pump would exist, just thought the oil just sat in a bowl...

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C'mon, small displacement bikes don't carry some old Briggs & Stratton engines. :icon10:

sure they do...
http://t1.gstatic.com/images?q=tbn:A...r1iFRwBs4QS3ig

Briggs & Stratton engines? I don't get the joke :(

On a serious note what places on the engine would be high and low pressure eg sump as I'm tempted by a universal kit for quick delivery. I'm sure I could whip something up to make it fit to different points with banjos.

Quote:

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Originally Posted by arancara

Briggs & Stratton engines? I don't get the joke :(

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Briggs & Stratton engines, as an example of a simple engine that has/had a only splash lubrication.

I wanted to say that small 4T engines on C-motos are not so simple and that they all have a proper pressure-feed lubricating system.

Quote:

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Originally Posted by Zorge

Briggs & Stratton engines, as an example of a simple engine that has/had a only splash lubrication.

I wanted to say that small 4T engines on C-motos are not so simple and that they all have a proper pressure-feed lubricating system.

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So where would you advise me to pick up, I think so far the only high pressure spot people have suggested was off the oil strainer and block the return, anywhere else?

Also what other low pressure area's are on the engine for a return as I've not taken apart my engine?

Did you look the inner side of your bike's head cover?

CG clones have the main oil line that passes through the cylinder, head, and finally enters the cover and distributes on the rockers. I saw on some Ukrainian moto-forum that some guys made ​oil inlets and outlets on this cover and connect oil coolers.

I do not know what it's like on your bike, but a simple modification of cheap cover is not a bad idea. Of course, this is possible if the lubricating of camshaft and rockers is solved in a manner similar to the CG clones. If you do not have photos of the inner side of the cover or can not see it in some manual, the only way is to take off the cover and check it by yourself.

Have you got a link to the Ukrainian forum, it would be intresting to see what he has done.

When I do my next oil change I will have a look around as I completely forgot about lubrication of the overhead cam shafts, may well be a good place for a return if I can see how it gets pumped up into the rocker.

Here's the link - http://moto-rage.com.ua/forum/viewtopic.php?f=9&t=9 , but I repeat - maybe on your engine can not do something similar.

BTW, if you use some online translator, even though forum is Ukrainian, choose translation Russian to English.

Thanks, I dabble in russian so its an easy read. I serviced my bike and the return is back to the sump, you can see it goes where the bolt is, when I shined some light and poked a screwdriver in, so I will block the return off and pick up to the oil filter and return to the sump. Love the help and advice you are giving, think after this it will have to be some more aggressive cams and big bore.