[chrisbalich]

Originally Posted by al lkosmal

Both sensor locations are a trade off., but the ECUs provide you with the ability to taper off the enrichments, based on the temp from either approach....I remember having this conversation a while back....

Ingo provided this input, which sums it up best.

"In an air-cooled engine the cylinder head temperature (CHT) raises much faster than the temperature of the entire engine block. Megasquirt uses the temperature reading to calculate the enrichment during warm-up. A CHT sensor is not the best solution here to tell what is going on in the engine, especially if you use the washer-style thernocouples at the spark plugs. The 964 and later engines use a sensor mounted into the heads away from the plugs.

In general Megasquirt uses the engine temperature to calculate the warm-up enrichment. You can either use an oil temperature sensor or a cylinder head temperature sensor. In both cases Megasquirt allows you to calibrate the sensor response.

Fact is that the oil temperature goes up rather slow while the cylinder head temperature goes up much quicker during warm-up. Once you decide which way to go take readings of the "cold" engine and the temperature once the engine is all warmed up. Since Megasquirt allows you to modify the calibration curve that translates the temperature into an enrichment factor you can compensate for the sensor characteristics. In other words, if you use the CHT make it richen up the mixture until it is almost at operating temps. If you use the oil temperature, dial back enrichment as soon as you see the oil temperature raise across 140 degrees."

This closely parallels my MS3X experience as well. I've made some adjustments to the warmup curve already. I'll dial in the curve once I get temp readings I'm happy with.

Originally Posted by Mahler9th

For decades performance and racing engine builders I know have used a sensor in the breather cover for engine temp.

Dozens of engines.

My EFI system is a Haltech-- has been since 2001. Engine temp is picked up by an inexpensive GM-style engine temp sensor like this one:

https://www.haltech.com/product/ht-010304-coolant-temp-sensor/

I have a 3.6-based racing engine.

Sounds good to me. This is what I plan to try once I get the breather back off the car and change the Porsche connector for an EV1.

Originally Posted by spuggy

My EFI Ducatis all use an temperature sensor in the rocker cover, rather than a CHT per se. So I believe that's probably an acceptable approach, too. They knock out warmup compensation pretty fast. I think 60C is the magic number almost everyone seems to use. Works for me.

Which jibes pretty well with my experience of driving and riding cars/motorcycles with manual chokes for a few decades; you don't need choke for longer than a minute or 3, as soon as there was heat in the heads/valves - you're good... I would always would knock the choke off when pulling away, and just keep RPMs higher at the next couple of stop lights if necessary.

My $0.2; taking temperature reading from the wrong place gives you, well, inaccurate readings. You don't need the whole block to be completely up to temperature.



IIRC, my chaincase sensor doesn't read 140 - in any temperature scale, Fahrenheit or Celsius - until the oil temp starts to rise off the bottom stop, which is some 10-15 minutes of running with a big FMOC. Perfectly usable as an axis on the boost control table (eg restrict to wastegate spring pressure only until oil is warmed), but didn't provide readings that made any sense for warmup compensation for me.

I mean, heck, I could hear the motor running too rich 4 miles from my house. Because the chaincase sensor wasn't reading over ambient yet. But it didn't need trim at all by then.

Your mileage may vary etc.

Yeah, I don't think I need a full 140*F. I reckon by 100-110*F it'll be plenty warm to run well. (flipping back and forth from F to C is good fun. )

Originally Posted by al lkosmal

Chris,
although the cam chain covers are gasketed, the bolted connections make for a good ground path to the case. Works well.
regards,
al

Good to know.
Thanks, Al!