Monitoring turbo temp with EGT?

your intercooler doesn't cool your turbo....

The EGT suggests whether the AFR is relatively rich or lean - has nothing to do with engine temperatures
If you turbo is "overheating", then it has nothing to do with EGT's, and more to do with a clogged turbo oil line, or one of the water lines is clogged.
If one of these lines is clogged, the turbo will die a very fast death.

The way I understood it is that if the fuel pressure is lean the engine will run hot and trigger the EGT.

If the timing is off the combustion can escape into the exhaust and trigger the EGT.

If you don't have a sufficient intercooler the intake temps will go up and the turbo will act as a heat sink and cook.


What I want to know is if I have too much back pressure from restricted exhaust will this heat up the engine and turbo equally in which case having the EGT at the manifold will work to warn me. Or will a plugged exhaust mostly heat up the turbo which could cook while my manifold mounted EGT was telling me everything is OK.

If I were you I'd do more research on these points. You are confusing a few things and I think that is what is leading to your concern.

To answer your question though, having a more restrictive exhaust won't cause your turbo to excessivly overheat. In overly simplified terms if the exhaust isn't as free flowing, then the turbo won't spool as quickly. The higher the RPM's on turbo, the hotter it will get, so if it's not spinning like crazy you won't have the issue of it overheating.

Tenacious-B said:

If I were you I'd do more research on these points. You are confusing a few things and I think that is what is leading to your concern.

To answer your question though, having a more restrictive exhaust won't cause your turbo to excessivly overheat. In overly simplified terms if the exhaust isn't as free flowing, then the turbo won't spool as quickly. The higher the RPM's on turbo, the hotter it will get, so if it's not spinning like crazy you won't have the issue of it overheating.

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So exhaust back pressure does not overheat a turbo, it's only hight boost that heats it up because it will spin faster.

So would it be correct to say that exhaust backpressure could overheat an engine because it would make it work harder but would not directly over heat a turbo because the backpressure makes the turbo spin slower? But back pressure could over heat the turbo indirectly by overheating the engine first? So a free flowing exhaust isn't for the benefit of the turbo but for the benefit of the engine so that it doesn't have to work as hard under high boost.

If I understand it correctly putting the EGT in the exhaust manifold would be the correct spot because the engine would over heat before the turbo.

if your engine is over heating you would notice it on your temp gauge inside of your car... and no restrictive exhaust wont cuz exxesive(sp?) overheating or every stock turbo car would always be over heating

White91GSX said:

if your engine is over heating you would notice it on your temp gauge inside of your car... and no restrictive exhaust wont cuz exxesive(sp?) overheating or every stock turbo car would always be over heating

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I meant a restrictive exhaust with the turbo boosted to 15psi or more.

If all I need to monitor is my factory engine temp gauge then why do so many people install EGT gauges?

The EGT suggests whether the AFR is relatively rich or lean - has nothing to do with engine temperatures.

Huh?
My EGT tells me exactly what the temperature is coming out of the engine via the manifold. When I'm beating the crap out of her (ie. doing a steady 125 mph (on a closed road ) ), she will get up to 1600 degrees
At a steady 65 or so it is no where near that hot. Is the air/fuel different at a different steady speeds, hell, I don't know. All I know is I do not want to go over 1600 degrees and that is what the EGT tells me.

knewblewkorvett said:

Huh?
My EGT tells me exactly what the temperature is coming out of the engine via the manifold. When I'm beating the crap out of her (ie. doing a steady 125 mph (on a closed road ) ), she will get up to 1600 degrees
At a steady 65 or so it is no where near that hot. Is the air/fuel different at a different steady speeds, hell, I don't know. All I know is I do not want to go over 1600 degrees and that is what the EGT tells me.

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When you are pushing the 1600 degree mark what is your stock temperature gauge reading?

about 220-230

the 1600 EGT is just that..the exhaust gas temperature, not the engine temp...thank GOD. I'm sure the 125 mph wind helps the radiator keep the engine cool. In fact, the engine will run hotter in slow traffic than at high speeds

As stated above, and in simplified terms: EGT gauge will tell you if you're reaching the danger zone of melting engine components like pistons. Water Temperature gauge will tell you if your engine is running too hot and in danger of blowing things like head gaskets. Although one is related to the other, they are two different things and therefore it is recommended to monitor both (along with a few other things) if you're running a decent amount of power.

I am not surprised that EGT can be high while engine temp is low. On one freeway cruise I had a glowing exhaust manifold with a very cool engine temp. Since then I adjusted my timing and it seems better but I would like an EGT gauge.

My main concern is that I am planning on running as much power as possible with a bit of an exhaust restriction (ie. the louvered resonator). I can monitor air fuel mixture since I am planning on DSM link but wanted to be able to monitor any problems the restricted exhaust mights cause. This is where I thought the EGT would come in but was confused about whether I should be watching the turbo temps at the O2 housing or the piston temps at the exhaust manifold. Sounds like the exhaust manifold is the best choice and I will just have to let my turbo glow and keep telling myself it is normal.