Have fitted an OBD11 dongle and used it on the weekend on the beach (hot day mid 30's), coolant got to 103C.
Q: what is the max safe temp?

car gauge was half as per "normal"

Cheers in advance

Crap I would hate to know what mine gets to. Ignorance is bliss?

*insert jimny auto debate here.

Boiling is around 120, so I set my warning to 110 and pray!

24 Cummins 1.1 MW 415 alternators and a pair of Cat 1.8 MW 6.6KV alternators

110 is good for the warning light. 110 is high, but not that much of a worry. Things so south pretty fast though.

High exhaust temperatures are a symptom of a lean condition. It has little to do with coolant temperature. Yes, exhaust temperature will show high before oil temp or coolant temp in the event of a lean out, but that's not the same as overheating due to inadequate cooling capacity. There's a relatively wide range of permissible exhaust temperatures and a relatively small range of permissible coolant temps.

If you can get wideband O2 from your OBD2 reader then that is a far better measure of A/F than exhaust temp. Exhaust temp used to be common in petrol cars before the wide availability of wideband O2 sensors.

Most factory computers will do the opposite if they see a fault condition - run the engine rich and retarded to cool it down and prevent damage.

A/F - air/fuel (ratio)

wide band O2 (oxygen) is the sensor your car has in its exhaust that the computer uses to determine the peak efficiency for cruising. At under about 80% throttle the ecu will look at the O2 sensor to check how lean/rich the car is and adjust fuelling to meet a predetermined target.

Normally under full throttle the manufacturer tunes the car fat (rich/cool) in order to protect the motor. This is a set air/fuel map and doesn't reference the sensor.

If the ECU detects a fault, it will retard the timing and run the car rich to prevent damage and put the check engine light on.

Monitoring A/F will allow you to keep an eye on what the computer thinks is appropriate.

However, like any measurement, it's only important if you understand what it means, or care - a good example of which is oil pressure - the most pointless gauge ever for a internally standard motor in a road car - your odometer is about as good a measure of engine wear as an oil pressure gauge, and in a standard motor, exhaust temp or oil pressure are pretty meaningless - the engine is operating within its normal parameters. It will throw a code or get hot on the standard gauge if there is something you need to worry about.

Steve.

Ok thanks guys Makes me wish that car brands would ask the end user (preferably well informed people) what, why and how to improve the next model!

Do you guys think that brands look at forums?

If they asked the wrong people (enthusiast groups on facebook ) and then acted on that input.. then the final models of Sierra would have had a "hectic" g13 turbo with choo choo, SPOA and drop shackles from factory.... oh and no coilys