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Discussion Starter #1
Gday Guys,

I realise this is a very general question. Just installed a EGT gauge on my setup. What exhaust gas temperatures are a generally healthy reading for both street driving a racing ? to these also line up with A/F ratios?

My Thermocouple is placed after the turbo. Making aprox 300whp at 20psi.

any advice?

Cheers all
 

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Discussion Starter #4
Back from the dead!

I have a theromocouple in my dump pipe right under my oil pan - Yes i know it probably should be in the exhaust manifold to read more accurately. However more to the point how much difference in temperature would their really be between the exhaust manifold and dump pipe?

Also what would usually be a safe EGT not to go over while under full load. 1000 F ?
 

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it's gonna change quite a bit. your losing a lot of heat by the time it makes it to the sensor. so your getting inaccurate readings. 1800 F would be my personal limit, but with your sensor position who knows...
 

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That was a great read. However at 10.5psi, I most certainly do not make my best power at 12:1 AFR..... Unless my gauge is off..... ?!? Time for a recal.
 

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EGT vs A/F gauges | EGT Tuning | Exhaust Gas Temperature


here ya go feel free to push the lil green + under my avatar
That's a pretty decent article, but it seems to overlook the fact that mixture strength and ignition timing have to be adjusted together. You can adjust timing by itself since mixture strength will stay the same (regardless of what your wideband might say), but changing mixture strength will always change MBT timing to some degree.

I'm glad this article correctly stated that peak EGT occurs around stoich - but that's only true if ignition timing is close to MBT for all data points. If the timing is very off, then a different trend might be observed. Namely, peak EGT will occur at a leaner mixture because ignition timing isn't sufficient for the considerably slower burn rate.

For the purpose of this thread, that article says everything the OP needs to know.

As for an absolute maximum EGT, it depends on where the thermocouple is placed. 1800 degF is reasonable if the thermocouple is placed just after the port. If the thermocouple is placed further downstream, then this maximum temperature has to be lowered. If there is a turbo between the port and the thermocouple (which is likely considering where this thread is), the EGT will drop significantly.

It's also worth mentioning that based on the Ideal Gas Law, EGT will increase with backpressure. All else being equal, more exhaust restriction will raise EGT. There are exceptions though, such as a very efficient exhaust sucking unburned air/fuel through the exhaust valves. In this case, that unburned charge could ignite in the exhaust and considerably raise EGT.
 

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Discussion Starter #9
Well i seem to get around 1000 F at the peak of a full pull - taking the measurement from my dump pipe.

For me EGT's are a way to gauge how low you can go with ignition timing before EGT starts flogging out valve guides and heating up plugs to the point of pre-ignition
 
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