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Where to monitor oil temp from?


Gixxus Christ!
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Ok, so my latest obsession with my Honda cb849 build is oil. Namely cooling it. I went to great lengths to install an oil cooler that works well and doesn't look too shitty. Now I want to monitor the temperature of the oil for a variety of reasons; to make sure it's not getting hot enough to suffer thermal breakdown in traffic or while flogging the dogshit out of it, to collect valuable data for myself and others, and because I must always be doing something with this bike.

 

In stock configuration these bikes did not have oil coolers, the massive heat sink and huge oil galleries in the top end did a great job of keeping it cool. In my penultimate wisdom I have increased the displacement by 113cc, the compression ratio from 9:1 to 10.5:1 and put a high lift, high duration cam in, along with performance exhaust and open velocity stacks because race bike. So it's cooking a bit hotter than stock these days. 

 

So with the setup I have there's a sandwich plate that diverts the oil exiting the dry sump to a cooler, then back down to be filtered and returned to the pan where it is then returned to the oil tank by a scavenging pump. I have the option of monitoring temperature at 4 places: immediately exiting the motor, just before entering the cooler, immediately exiting the cooler and just before going into the filter. 

 

Two of those options are nearly useless as they're only 8" of braided hose away from 2 others, so the choice is really either directly out of the motor or directly out of the cooler. 

 

Out of the motor would give me the hottest oil reading possible, but because the oil exiting the motor has just passed through the head and down the oil drains in the front of the cylinder and exchanged a ton of heat out of those areas, may not be the best reflection of my operational oil temp.

 

Out of the cooler would obviously be the coolest temp reading, but this oil goes on to be returned to the oil tank where it presumably cools further before being drawn into the motor again. 

 

So if you've hung with me this long, congrats. Now let's hear your opinions.

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My Ducati is oil cooled.  They have the temp sensor located in the engine between the oil pump and the filter.  It senses the oil before it gets cooled.  On an oil cooled engine you want to read the max temp the oil gets to so you know how bad your engine is heating/overheating the oil.  Anything above about 300f is cooking it off and really reduces it's life.  If you read after the cooler you won't get a good sense of it's condition.

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20 minutes ago, CrazySkullCrusher said:

Wow, great advice! I never thought of that! :banana::banana:

I have a great plan for you oil breather hose issue too if you want me to pass it along.

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9 hours ago, Tonik said:

I have a great plan for you oil breather hose issue too if you want me to pass it along.

Yeah let's hear it. Still pretty early for your particular brand of old fart snark but I had my Wheaties this morning...

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Most oil temp applications monitor the sump or tank(if dry sump). Oil temp, similar to water temp, flows fast and temps remain consistent throughout, unless revved up or subject to load. Monitoring maximum temp is best done with a temp sensor on the head somewhere. Granted, most motorcycles skip the head temp sensor and go with an oil temp sender. So your choice, return side of cooler for approximate sump temperature, or supply side of cooler for approximate max temperature. edit: or install two senders and gauges... booya!

Edited by ReconRat
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