How can I get digital coolant temp on my 240z?

[Awk34]

I want to get a digital coolant temperature signal to my ECU. Does anyone know of a temperature sensor that would work in the stock 240z sensor location? Apparently it's a M16x1.5 thread, and the only thing I can find to fit there is the original sensor. I haven't found any sort of thread adapters which I think would work there. I'm guessing my best bet is to use the stock single-connection sensor.

 

I have a two-connection GM sensor with 3/8 NPT threads I believe, but I don't think I can get that to work.

[siteunseen]

I'd try and find another upper coolant housing and then figure out what needed to be done to put whatever sensor you need in. 

zcardepot has them for $43.

https://zcardepot.com/products/thermostat-housing-water-outlet-oem-240z?variant=19274718118001&currency=USD&utm_source=google&utm_medium=cpc&utm_campaign=google+shopping&gclid=EAIaIQobChMIsIyr_4aB7wIVgcqGCh17LAGdEAQYAiABEgLX4fD_BwE

[jonbill]

Does your thermostat housing not have a blanked hole next to the standard sensor housing? 

mine does, its a standard size, m12 maybe. 

 

[Awk34]

19 minutes ago, siteunseen said:

I'd try and find another upper coolant housing and then figure out what needed to be done to put whatever sensor you need in. 

zcardepot has them for $43.

https://zcardepot.com/products/thermostat-housing-water-outlet-oem-240z?variant=19274718118001&currency=USD&utm_source=google&utm_medium=cpc&utm_campaign=google+shopping&gclid=EAIaIQobChMIsIyr_4aB7wIVgcqGCh17LAGdEAQYAiABEgLX4fD_BwE

That's what I have

18 minutes ago, jonbill said:

Does your thermostat housing not have a blanked hole next to the standard sensor housing? 

mine does, its a standard size, m12 maybe. 

I bought a new one of these: https://www.thezstore.com/page/TZS/PROD/16-7121

One hole is being used for the coolant through the carburetors. The other is for the stock temperature sender.

[zKars]

This is another route to a solution,

The thermostat housing holes are all BSPT, and that temp sensor hole isn’t a tapered thread. Many have run NPT taps into a spare hole with a little sealant. 

[Racer X]

46 minutes ago, zKars said:

This is another route to a solution,

The thermostat housing holes are all BSPT, and that temp sensor hole isn’t a tapered thread. Many have run NPT taps into a spare hole with a little sealant. 

I was thinking taking an aluminum tee with a pipe thread a diameter that pipe nipple OD is the ID of the radiator hose, cut a nipple in half, dress the ends and stick them in, and bush the side outlet to 3/8" for the sender.

But this is a much more elegant solution, probably cheaper than the bits of pipe, and the only labor is the installation.

Sweet.

 

[Racer X]

2 hours ago, Awk34 said:

I want to get a digital coolant temperature signal to my ECU. Does anyone know of a temperature sensor that would work in the stock 240z sensor location? Apparently it's a M16x1.5 thread, and the only thing I can find to fit there is the original sensor. I haven't found any sort of thread adapters which I think would work there. I'm guessing my best bet is to use the stock single-connection sensor.

 

I have a two-connection GM sensor with 3/8 NPT threads I believe, but I don't think I can get that to work.

The later L series engines had electronic everything, and the thermostat housing has plenty of places to add another sensor, and you can retain the carburetor "cooling" line. 3/8" pipe is 0.675" diameter, and 16mm metric pipe is about 0.629". I was able to run a 3/8" pipe thread tap into the hole in the housing on my race car to allow the mechanical Stewart Warner gage bulb to be used. So you could give that a go. And one of the other holes could be used for a switch for and electric fan.

 

[Zed Head]

2 hours ago, Awk34 said:

I want to get a digital coolant temperature signal to my ECU.

What do you mean by "digital" signal?  You'll need some sort of converter to use a thermistor or thermocouple reading.

That might determine the type of sensor you need which could determine where you put it.

[Captain Obvious]

4 hours ago, Awk34 said:

I want to get a digital coolant temperature signal to my ECU.

I have a two-connection GM sensor with 3/8 NPT threads I believe, but I don't think I can get that to work.

I'm all kinds of confused... Either I don't know what you're looking for, or you don't know what you're looking for. Or maybe both.    

You say you want a digital temp signal to your ECU, but then you say you're running carbs. What is this ECU doing if it's not controlling the engine? Is it some aftermarket ECU who's name we might recognize? Controlling ignition timing only or something?

And I don't think there's any sensor that is going to send a DIGITAL signal to any ECU. I think they're all analog sensors and converted to digital by the ECU. Are they actually using DIGITAL sensors on the new cars?

[SteveJ]

18 minutes ago, Captain Obvious said:

I'm all kinds of confused... Either I don't know what you're looking for, or you don't know what you're looking for. Or maybe both.    

You say you want a digital temp signal to your ECU, but then you say you're running carbs. What is this ECU doing if it's not controlling the engine? Is it some aftermarket ECU who's name we might recognize? Controlling ignition timing only or something?

And I don't think there's any sensor that is going to send a DIGITAL signal to any ECU. I think they're all analog sensors and converted to digital by the ECU. Are they actually using DIGITAL sensors on the new cars?

From previous posts by @Awk34, it does appear as though he is running carburetors. I remember a few years back at a car show, a young man was asking me about what ECU I was running in my car when I was still using SUs. He didn't understand for a while that the car did not need an ECU for fuel or spark.

Perhaps @Awk34 is trying to put a digital gauge in the car to replace the stock water temp gauge. If that's the case, I wonder if he wants to keep the oil pressure gauge.

Remember the old days when most of the signals we used were 4-20mA or 0-10VDC?

[Awk34]

I like the radiator hose adapter option. I think the main downside to that is that it takes the cold temp of the coolant before the thermostat has opened.

It seems like my best option will be to figure out the best way to use the old sensor the get the temp.

I have a custom Speeduino ECU I'm building. I will eventually convert to EFI, but I'm doing everything piece-by-piece.

[AK260]

I’m assuming you are familiar with electronics if you are building a speeduino. I which case if you use an Op-amp in follower mode, you should be able to take a signal from the existing thermostat housing sensor without affecting the impedance / voltage at the sensor.



You can add an offset with something like the circuit below (obviously change resistor values) to get the required 5v input signal to your device if you ADC isn’t capable of taking 12v signals.



Failing that, get the thermostat housing with two holes and either tap the thread or find a sensor with the thread pitch to fit a new / modern sensor. Or do what Jon has done. He too is a Speeduino user / expert.