Seeking input on Coolant sensors for MS with 318i EFI

[richk98]

I'm in the process of acquiring parts for an MSII / 318i EFI install and have read through the many excellent project blogs and the more popular sites (Finkbuilt, Zeebuck, etc) and am still confused about which CLT sensors to use that are compatible with the 318i coolant neck. It seems the Megamanual strongly recommends using GM sensors to measure coolant temp however the sensors don't appear to fit the existing threaded openings in the 318i coolant neck (I'm not surprised) . Does anyone have any practical advice for which sensors to use? Is it cost effective to retro fit the coolant neck to accommodate the GM sensors?

[MAD02]

I bought a 3/8 NPT tap for about $6 and drilled and tapped my 318i waterneck to accomidate the GM coolant sensor. It was fairly easy and straightforward. Now I have the GM sensor on one side and my stock temp sensor on the other. If MS recommends GM sensors then I suggest you use those. Tapping the waterneck is no bid deal, just take your time and do it right. I also had to tap my 318i throttle body for the GM air temp sensor. Hope this helps. Good luck!

David

[Grover]

I used the stock Bosch sensor from the 318 water neck. It is really very easy to calibrate the sensors in megasquirt. I was a little intimidated ahead of time, but once i got down to it, it was really no problem at all. Don't stress.

[JohnC]

I used the stock Bosch sensor from the 318 water neck. It is really very easy to calibrate the sensors in megasquirt. I was a little intimidated ahead of time, but once i got down to it, it was really no problem at all. Don't stress.

I'm with Grover. No big deal. Pretty easy to calibrate the stock sensor.

[richk98]

Thanks for the replies

[H_Krix]

Make sure you know the difference in the sensors!

The big one in the foreground, right side of the pic is a "Temperature Time switch" used to control the additional injector in the intake manifold as a part of warm-up. It will NOT work as a temp sending unit. Ask me how I know...

Foreground, left is the stock '02 sensor. Background middle is a Bosch water temp sensor, part #13621357414.

#6 here:

[richk98]

Thanks Harrison

Do I need to incorporate the temp time switch if I am planning to use the Jeep stepper motor for warm up and not go with an additional injector?

[H_Krix]

no, the time-temp switch is a feature of the L-jet Bosch system on the e30's, you won't have any use for it. Even if you did add a warm-up injector, I don't think MS has any use for a time switch anyways, it would pull all the signal from the coolant sensor.

[richk98]

Thanks, Going the BMW / Bosch route seems best. I have read the blogs regarding calibrating the sensors and realize I need to do that and feed those readings into the MS software. I attempted to take some "room temp" resistance level readings from the used sensors that were in the coolant neck I picked up from the salvage yard (with no luck). Any suggestions or "how to's" regarding how to apply the multimeter probes to the sensors to properly measure their resistance? It could be that the sensors are too old to be useful, but before I abandon them I want to be sure that I am using the proper method.

[JohnC]

Thanks Harrison

Do I need to incorporate the temp time switch if I am planning to use the Jeep stepper motor for warm up and not go with an additional injector?

There's a couple of different issues here. HKrix is correct, there's no need for the temp time switch. The jeep stepper motor is controlled from your coolant temperature sensor's input into the megasquirt box. The box (software) then uses the data from the sensor for several different functions, one of which is to control the stepper motor.

The additional injector is totally unnecessary, and it's unrelated to the stepper motor in any case. I assume that your thinking of "after-start enrichment" and "warm-up enrichment". Your normal injectors will take care of these functions, based on the data from the coolant sensor.

[JohnC]

I attempted to take some "room temp" resistance level readings from the used sensors that were in the coolant neck I picked up from the salvage yard (with no luck). Any suggestions or "how to's" regarding how to apply the multimeter probes to the sensors to properly measure their resistance?

Jonhup's blog describes it pretty well. I don't know what value there is taking room-temp readings. I started with ice-water and slowly heated to boiling.

My biggest problem was setting the bias-resistance value. I set it by trial and error

Here's what I input into my MS using a stock bosch sensor:

Bias resistance: 575

32 deg 1300

120 deg 170

212 deg 30

This may not be totally accurate, but it's all relative. You need the enrichment such that the car start, idles and runs well when cold and such that the enrichment stops it's warm. There's no fixed temperature when these should happen, it's part of the tuning process. Same for the electric fan trigger. I don't really care what the absolute temperature is when my fan is triggered, I just want it to come on before the stock temp needle goes above 3 o'clock.

I know mine is calibrated well at 62 degrees. In the morning, my air intake temp matched my coolant temp at 62 deg. before I started the car. I'm using the GM sensor for my air intake.

[slash02]

I bought a 3/8 NPT tap for about $6 and drilled and tapped my 318i waterneck to accomidate the GM coolant sensor. It was fairly easy and straightforward. Now I have the GM sensor on one side and my stock temp sensor on the other. If MS recommends GM sensors then I suggest you use those. Tapping the waterneck is no bid deal, just take your time and do it right. I also had to tap my 318i throttle body for the GM air temp sensor. Hope this helps. Good luck!

David

Looking back, I'd just go this route. you dont have to piss around with figguring out the resistance vs temp curves of the 318i coolant sensors this way. (I did it wrong, so i'm going ot do MAD02s method soon.)

[richk98]

Where did you (do you) tap the coolant neck? An existing opening or on the side where the appears to be a boss for doing exactly this?

[MAD02]

Where did you (do you) tap the coolant neck? An existing opening or on the side where the appears to be a boss for doing exactly this?

I tapped the hole nearest the head. But my 318i waterneck had only 2 holes. Ive seen some with 3 holes. Tap the largest hole, the one with the thermo switch is the biggest, I think. This is a photo of my engine. You can see the waterneck (sort-of!) Good luck!

David

[richk98]

Thanks, I do have a three- hole coolant neck and will plan to tap the temp time senor's slot as it is the largest.