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Reply to "You already know this, but learn from my mistakes!!!"

@edsnova posted:

Glad you found it Mike and sorry it took so long. Question. You wrote "Dashboard temperature gauge (oil relief) reads steady, but the oil sump sensor reading jumps from 180F to 300F depending on engine speed and temperature."

Why would the dash gauge not give you the correct oil temp reading in this instance?

 

Thanks, Ed. Actually, I think both are "right," but they are two different sensor locations and two different methods of measurement. The dash gauge (914 multi gauge) is just a magnet-wire needle like most of our gauges. I would bet that there's a lot of inertia to the movement and it gives the average reading over a second or so. The oil sump sensor is read by a Speeduino ECU at a fast sample rate (e.g. 180ms between discrete readings). I think the Hoover Mods push a lot of oil into the heads and external cooler circuit. That makes it easy for a hot spash of oil squirting out of the oil returns to raise the sump sensor for a short time.  

That's my theory. I will double check it when I get the deep sump installed and will also try switching around the wires on the sensors. It's always possible that the Speeduino sensor has a wiring flaw that adds the jiggle. Since the dash gauge matches well with my dipstick temperature measurements, and since the Speeduino matches the dipstick when I turn off the engine, I'm pretty sure I'm correct on the oil temp. Figuring out the Speeduino jumpiness will happen, but doesn't worry me a lot. You can actually set the sensitivity of the Speeduino gauges. I'm interested enough to study it a little more before I resort to that.

 

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