Exhaust Gas Temperature

[Mr MXT]

Just a quickie - my car has an EGT gauge but it dawned on me yesterday that I don't actually know how high the temperature can get before it gets dangerous.

Anyone have any ideas?

[anonymous-user]

Couple of questions:

1) where is the EGT sensor mounted?
2) what diameter is the EGT sensor?


(measureing true EGT is an absolute 'mare, what you actually measure is the temperature of the thermocouple probe. For example, real exhaust gas temp (as it leaves the cylinder) is fairly constant with rpm (varries massively with AFR and ignition angle) but most EGT sensors read higher at higer rpm. This is because the duty cycle is increasing (less time between firing events for the probe to cool, so the "mean" temp increases.

As ball park figures, anything over 840-860degC in an exhaust port is "warm" as is over 940-970degC in say an exhaust collector (or pre-turbine if turbo'd) (obviously, depending how "exotic" your engine internals are, these values can be exceeded, but for std proddy engines they are a decent starting point

[Mr MXT]

Thanks Max, its turbo'd. I think the sensor is pre-turbo but I'm not sure tbh. I don't see any change with revs, only if I hold it on boost.

[anonymous-user]

It should deffinately increase with revs and boost, but at any rate, assuming you have a std turbo then i'd probably aim for a max pre-turbine egt of 940degC (970 if you wanna push your luck a bit!)

[Mr MXT]

Good stuff. I don't think I've ever seen it higher than 900

[anonymous-user]

The thermal inertia of the system will probably limit the maximum values seen during typical "in-car" short duration full throttle events. It might be worth loading the engine for a bit longer against the brakes (or rolling road etc) and you will probably see the reading creap up a bit. But under 900 is fine, no worries there!

[chuntington101]

can you confirm if the car is a petrol or a deisel? From what i have heard if its a deisel then it needs to be a fair bit lowes or you start to have problems. Thanks chris.

[Mr MXT]

chuntington101 said:

can you confirm if the car is a petrol or a deisel? From what i have heard if its a deisel then it needs to be a fair bit lowes or you start to have problems. Thanks chris.

1.8 turbo'd Mx5

[chuntington101]

Mr MXT said:

chuntington101 said:

can you confirm if the car is a petrol or a deisel? From what i have heard if its a deisel then it needs to be a fair bit lowes or you start to have problems. Thanks chris.

1.8 turbo'd Mx5

OOhhhhh thats fine then. just i heard deisel EGTs should be a fair bit lower than that!