temperature to fuel cut off switch

[allblacks]

my mitsubishi diesel has a common problem of over heating, causing the cylinder head to warp, and crack on cooldown. I want to build a temperature sensitive device,which will activate the fuel cut off switch, thus stopping the engine before it overheats. How can I link the temp thermistor to the fuel cut off solenoid, to work at say 95 degrees centigrade? Most boat engines have an alarm buzzer which activates before overheating. how does this work for an NTC thermistor unit?
your help is appreciated.

 

[kenre]

First find the cause of overheating.

A shut off switch like u describe is not a good idea.

What if it shuts off halfway through an intersection, across a railway crossing?

I have seen tractors with shut off switches for loss of oil pressure, but with an override switch for those rare cases where it is not in a paddock and needs to be moved in a hurry.

http://www.retallickeng.com.au

Was told it couldnt be done, so
i went and did it!

 

[Fabrico]

You might look into Murphy products.

http://www.fwmurphy.co.uk/products/temperature/temp_tsb.htm

 

[Fabrico]

There is also their SWITCHGAGE line which has been around for about half a century.

http://www.fwmurphy.co.uk/products/swichgage.htm

 

[Fabrico]

Oops, almost forgot the very popular Kysor engine protection products.

http://www.medallionis.com/products/products.cfm?proID=10056&subnav=commercial&catID=6&type=sensors

 

[allblacks]

Hey thanks guys. I'll get onto it.You may be aware that half of the vehicles being made in europe now are diesel powered. The most annoying and costly to repair fault, which can be avoided is head gasket failure. perhaps I can sell these products to the used diesel vehicle market. We dont have such strict legislation here in New Zealand as you enjoy in the US.But an override system will probably be best to ensure no lawsuits.

 

[patprimmer]

I would NOT hook a temperature cut out to a road going car.

If I had to do something to protect from overheat damage, I would have the sensor trigger a very obvious warning, like big bright flashing warning light on top of the dash in drivers line of normal sight and a loud alarm.

Engines do not suddenly self destruct at a certain temperature, as the temperature rises, there is a range of increasing danger and rate of decay. This allows a short time for corrective action to be taken by the driver, even if it is only lift off to slow down until it can be safely parked.

If drivers deliberately drive a car knowing serious damage might result, then I think they deserve the repair bill. They certainly deserve it a lot more than the following traffic deserves to be confronted by a car that stops suddenly in the middle of a freeway.

Regards

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[WGJ]

Allblacks - some European diesel engines used two temperature sensors. One for traditional coolant temperature and another for cylinder head temperature.

The difference is that the head temp sensor senses metal temperature and not coolant temp. This way the engine control module can make more strategic use of calibrations to try and avoid head casting problems.


Bill

 

[MechanicalChef]

+1 On a warning light or alarm. Murphy's Law.

 

[Fabrico]

The better shut downs do give you a warning first. You should look into them a bit before making hasty judgements. Most truck OEM's now have either a delayed shut down or staged limp home mode. The ECU will protect the engine. Common practice and sense, would have a warning before shut down.

 

[anyoldname]

If your engine is starting to overheat why would you want to turn it off? Its far better to keep it running at a low speed & load (and ideally moving forward to get some air through the radiator) to keep the cooling system running and thus get the temperature at the core of the engine down.

 

[IceStationZebra]

Anyoldname beat me to the punch...if you shut the engine off the coolant flow and fan will stop, which will spike the engine temps higher yet. As others said you are better off fixing the overheating problem. If you still want to add a switch that fine, just make it a warning light so you can decide the appropriate SAFE action to take. ISZ