The Project Pad

Hey... those of you running standalone EMS on 3Bs or AANs and using the OE coolant temp sensor at the back of the head... what range of temperatures do you typically see on a fully warm engine on a hot day?

Looking in a log I took from the Megasquirt, I went over 215 degrees a number of times today while driving on the highway in 90-degree temperatures. But according to that sensor my engine always runs hot... I looked in a log from last November when it was about 40 degrees out and temps I saw after the engine was fully warmed up ranged from 200 to about 210 degrees.

So I'm kind of wondering how hot is too hot, and/or whether my sensor is miscalibrated (or broken), but would like to know what temperatures others are seeing.

From my 7A and AAN experience you should be pegged on 90˚C.

Make sure your sensor and ECU are calibrated together. Most are accurate to within a few degrees at high temps, but are WAYYYYY off at lower temps. I've noticed this a lot especially with intake temp sensors that generally operate between 0-130F, big discrepencies which are a big deal when you're relying on that for an air density calculation.

That being said, my car usually runs between 92-100C measured at the back of the head depending on outside temp and conditions. The fan usually keeps it from going beyond 100C.

Same here, between 88 and 98 C

Sounds like it's on the way out, you can check sjm's site for a chart, it'll show you ohms vs temps and can guess/calibrate with a ohmmeter while sensor connected. I'm in low 90's on hot days.

Thanks everyone!

I've ordered a new sensor, and think what I'm going to do is check its resistance in ice cubes and boiling water to make sure it measures the way I expect. Then check the Megasquirt with resistors of the same value to see if it reads as expected. Hopefully one of those tests will reveal a problem - otherwise my engine is actually running hot and I'll have to see what's up... other than the temperature.

So now I've got a follow-up question: what thermostat temperature are you folks running?

I'm betting you're all going to say 180F. I just looked back through my records and I'm running a 195F 'stat, so I suspect that's part of the problem.