EGT temperatures

Hi everyone,

I have a modified GQ (turbo + intercooler (up to 20 psi), modified fuel pump, LPG injection, 3' exhaust etc) and am looking at improving the air intake side of the truck (going for larger air filter and 4' snorkel as opposed to the safari snorkel I curently have). As part of the process I'm checking temps etc.

I have an EGT gauge and was told I should never puch teh vehicle when teh EGt is over 650 deg F (343 Cel), but I have also been told it should be fine up to around 750 F (400 Cel) ... or higher. I am finding it difficult to get an answer on this , especially given the setup of the truck. Look forward to your feedback on this. G

I'm no expert at all in this field but I know it depends on where the EGT probe is located in the exhaust, ie pre turbo or post turbo.

Also, I don't think the maximum temp you should run to will change too much on what setup you have, as you are trying to protect the engine and turbo from melting.

My last patrol had a egt pyro post turbo and I ran it a lot higher than 343 deg cel. Don't quote me but I pretty sure it was either 450 or 550 maximum.

Sorry I can't answer exactly but I hope this helps somewhat.

Thanks for that. The probe is located just past the turbo.
Looking at other older threads (took a while to trawl through) some are saying good for up to 550 Deg C .... can that be right? I also noted some of the guys saying that their temps were quite high on normal driving. better keep looking...

Yeah mate your confused on F and C. 550C will be fine post turbo and the odd spike above that will not really hurt you. If you climb above 550 for more than a few seconds you will start doing a little damage.

Making sure that your Pyro is reading Celsius and then never talking in anything else will be a winner mate, same goes for PSI on the boost gauge over BAR??? Why would we confuse ourselves doing that.

PSI for Boost and Post turbo Celsius for EGT.

I'd be sitting on 350C on the HWY at 110kmh lol

Thanks for the feedback. The pyro unfortunately is in F and at this stage I want to spend the $$ on getting it going right/better before I change cosmetics. But I agree that Cel is the better unit of measure here and I agree PSI is better than BAR.

Mate ... 350C at 110 on the HWY. Mine's closer to 240C at that speed unless I'm going up a hill or passing. Must be the warmer conditions over there as oppsoed to here in NZ.

Just had a read fo your post mate & I wouldn't be to worried with your cruise temps as there nice & low at those figures.

The temps you need to concentrate on are your figures with you Rig under load ie: towing up a hill.

These figures you want to keep under 550c as much as possible, 450c to 500c under load is where you should be aiming.

The compressor housing on most turbochargers are cast aluminum which is molten at 660c, that being said its now easier to understand why you don't want to have EGT's above 550/560c max as a safety margin & even then only at 2 or 3 second spikes at most, as beyond this heat transference will begin to occur from the turbine housing into the compressor housing which ultimately spells disaster in the making.

This is only one example on why its necessary to monitor EGT's & there are a few others that come into play as well but I hope this give you some idea of the how & whys.

Thanks for the advice and help. Once my new air intake and manifold is sorted I'll add some pictures. Cheers agin. G

Interesting. My stock 2011 CRD with no mods (only gauges fitted) runs easily 450-500c when cruising at 100km/hr @ 12-14psi boost. Towing and going up hills has seen it spike to over 650c!

The talk around town is that Nissan has 'fixed' the grenading issues in the CRDs but with temperatures like those straight off the factory floor you would have to wonder?

Hi, further to my investigation on this topic, what is the group's concensus on placement of the EGT probe sensor: pre or post turbo?

The logic of pre turbo is that it will record the (dangerously high) temps prior to being 'lost' by the turbo (as turbos will reduce the temperature by a set percentage). Obviously by having the probe before the turbo it could cause an issue it something breaks off....

Post turbo some people are saying the EGT temperatures should be modifed to take into account the temperature drop across the turbo. For example (taken from another vehicle petrol/diesel ??) , a temperature drop across a 65% efficient turbine could show the following: 20psi boost, 20psi backpressure, Pre turbo EGT's of 750 deg C, Calculated post turbo temp is 565 deg C, that's a temp drop of 185 deg C. and ...20psi boost, 40psi backpressure, Preturbo EGT's of 700 deg C, Calculated post turbo EGT's of 411 deg C, that's a temp drop of 289 deg C

But the temperature reading post turbo will be more stable (which could be a good or bad thing).

So what are your thoughts..?
:-)

G