OT: I'm getting hot warning

[tim eh?]

heh well i had zero options man i would have been skinned alive if i had 'just turned the engine off'. but whatever... the bong works.

[whiskychaser]

heh well i had zero options man i would have been skinned alive if i had 'just turned the engine off'. but whatever... the bong works.

The fact the bong works is good. But its a bit late if you had zero options Would be better if it said ' er.. excuse me.. I'm getting a bit hot.. pull over when you are ready'. I'm after a simple solution that warns we are about to wreck an engine. I guess the question is how hot is too hot?

[tim eh?]

The fact the bong works is good. But its a bit late if you had zero options Would be better if it said ' er.. excuse me.. I'm getting a bit hot.. pull over when you are ready'. I'm after a simple solution that warns we are about to wreck an engine. I guess the question is how hot is too hot?

yes I would have preferred that myself, it wouldn't even need to be so polite .

[DaveVoorhis]

One of these http://www.maplin.co.uk/Module.aspx?ModuleNo=220003 or equivalent, suitable (or modified) for a switch-on temperature up to about 130C, combined with a 12 volt buzzer (I wouldn't trust the bonger -- the speaker in them is prone to failure), would make a good early-warning system.

I'm not sure where to mount the temperature sensor (thermistor), though. It would need to be a location that is suitably reflective of the head's core temperature, that closely tracks any rise in combustion chamber temperature, and is independent of whether there's coolant in the system or not.

Calibration would be straightforward: On a hot day, drive the car hard with the A/C full on and tune the warning to just on the silent side of buzzing. Any rise in temp from that baseline, even slightly, should set it off.

[whiskychaser]

One of these http://www.maplin.co.uk/Module.aspx?ModuleNo=220003 or equivalent, suitable (or modified) for a switch-on temperature up to about 130C, combined with a 12 volt buzzer (I wouldn't trust the bonger -- the speaker in them is prone to failure), would make a good early-warning system.

I'm not sure where to mount the temperature sensor (thermistor), though. It would need to be a location that is suitably reflective of the head's core temperature, that closely tracks any rise in combustion chamber temperature, and is independent of whether there's coolant in the system or not.

Calibration would be straightforward: On a hot day, drive the car hard with the A/C full on and tune the warning to just go off. Any rise in temp from that baseline, even slightly, should set it off.

Thats exactly what-and where from-my colleague recommended. I dont see mounting a board on the side of the engine but you could split it up. Think you have it though-run your motor on a hot day and set the pot to that. Anything above triggers a warning via the 'low coolant' route. Trouble is I think we need to be a bit more precise about what is a hot day But I think we are on to something here. If we can come up with an easy mod that warns of imminent engine destruction its got to be worth a look

[DaveVoorhis]

If I get a chance, I'll pop into Maplin tomorrow and buy the relevant bits, assuming the sensor kit will (or can be modified to) switch on above 120C or so. I think I'll mount the board and buzzer in the interior somewhere -- probably on the removable dash panel above the pedals -- with leads to a thermistor mounted (epoxied, maybe?) on the head. I'll try it on my E30 first, as I don't mind experimenting with it and the temp gauge has a tendency to sneak just above 12 o'clock on hot days.

[whiskychaser]

If I get a chance, I'll pop into Maplin tomorrow and buy the relevant bits, assuming the sensor kit will (or can be modified to) switch on above 120C or so. I think I'll mount the board and buzzer in the interior somewhere -- probably on the removable dash panel above the pedals -- with leads to a thermistor mounted (epoxied, maybe?) on the head. I'll try it on my E30 first, as I don't mind experimenting with it and the temp gauge has a tendency to sneak just above 12 o'clock on hot days.

Hero! If you can sort it and the manufacturers cant its got to be worth a patent.

[genphreak]

Hero! If you can sort it and the manufacturers cant its got to be worth a patent.

Too right. terrific idea this. I've often thought the same thing- what's cool is that it applies to practically all Bimmers.

The thing that wil make (or break) it will be location (and variance). A spare bolt hole on the head would be good, but I expect that even a bolt hole on the head may not provide a consistent, indicative temperature that is reliable enough to trigger above a threshold (without many false positives)

I'd expect that it may need a circuit to smooth the readings so the alert can trigger only based on a set of averages over the shortest period of time that is practical.

For that, a $20 programmable USB board like this would be perfect... www.teensy.com. It'll also do a lot of other things too but this could read the input from the thermistor and allow the levels and times to be easily adjusted programmatically. It can even do the logic to calculate mean, average and be programmed for other scenarios such as certain prolonged (above threshold) readings.

[whiskychaser]

I'm not sure where to mount the temperature sensor (thermistor), though. It would need to be a location that is suitably reflective of the head's core temperature, that closely tracks any rise in combustion chamber temperature, and is independent of whether there's coolant in the system or not.

This is a very good point. If coolant is low you might not get a reading as is the case for the fan switch. This isnt cheap but might be an alternative:
http://tscsensors.com/chtws0722p0kssnchts.html
Apparantly it fits between the spark plug and head so would be easy to install. A feed off that to a Maplin type board and a buzzer could do the trick?

[DaveVoorhis]

This is a very good point. If coolant is low you might not get a reading as is the case for the fan switch. This isnt cheap but might be an alternative:
http://tscsensors.com/chtws0722p0kssnchts.html
Apparantly it fits between the spark plug and head so would be easy to install. A feed off that to a Maplin type board and a buzzer could do the trick?

Unfortunately, that is a thermocouple (voltage-generating temperature sensor) which isn't compatible with the thermistor (varying-resistance temperature sensor) used by the Maplin board, but a circuit to work with it would be relatively trivial. I think I'll start with the Maplin board and try poking the thermistor down a sparkplug well.

I didn't make it to Maplin today. Hopefully I will tomorrow.