hardware and megasquirt question

[Tom Notch]

I feel you could have found this quite easily, It took 15 seconds without the search function.

http://www.shoptalkforums.com/viewtopic.php?t=85862

[Sharkey]

Do I need to use a head temp sensor in addition to the tps and wide band o2? The reason I ask is because I visited the ms forum and looked at the sensor diagram which included an air temp and coolant temp sensor. We don't need either of these with an AC vw engine, but I was wondering about the head temp sensor.

Why wouldn't you need an air temperature sensor? Cold air is denser than warm air. Not taking this into account would mean that the engine would run lean when cold and rich when hot.

A head temperature sensor will have to be properly calibrated to work with any aftermarket EFI system -- especially on air-cooled engines where head temperatures fluctuate much more than on water-cooled engines.

Oil temperature sensors are good for providing driver feedback, but aren't very useful to your EFI computer. Oil heats up very slowly compared to the water in a water-cooled engine so any fuel enrichment based off of such data would be far from linear.

[72_bay_simon]

Dont get too hung up on the coolant temp sensor. All it is used for is warm up enrichment. People use oil temp sensors and sensors mounted in the airflow and cht sensors. Either will work, maybe with an oil temp sensor you will need to turn off cold start a little earlier to compensate for the time it takes to warm up.

I use a sensor in the air flow, comparing this with the oil temp gague I have shows them to be fairly close, the air temp seems to lead the oil temp by a few minutes.

The IAT is much more important as this is used in all sorts of calculations. As soon as I get mine sorted I will post up Fuel and ignition maps etc.

[Guest]

i have problems with warming up:
i have a sensor in air flow
when i connect the coolant sensor, the engine rpm increases, and when i pull it out, the idle doesnt change, but runs poorly. this has to be due to warmup enrichments. the warmup enrichment kicks in but i dont want that. how hot do the sensors become and what resistance do they have to have at that temperature? what range of resistance or temperature should i have for a sensor in air flow? i've got a few numbers here:

19.7 °C 1.77Kohms
21.3°C 1.04K
22°C 690ohms
40°C 63

greetz, peter