I did a brief test tonight, just let the engine heat up at idle with a probe in the collector and 2 inches behind the v-band clamp on the turbo. Both probes showed the same temp on the gauge and with a thermal gun both were within 10 degrees. Does this somehow get so much different under a load, I hear 300 degrees difference..

 

The exhaust gas expands and looses a whole lot of its heat in the charger's turbine. That's why temperatures post-turbo are lower.

At idle there is no fuel being injected, which means the turbo isn't making any boost since it is far from its efficiency range. You won't see a drop until the turbo does spool up and begins to efficiently convert that exhaust heat to air pressure.

The more efficient the turbo, the more of a drop you're going to see. Somebody with an inefficient (lagging or overspooled) turbo is going to see much less of a temperature drop than a guy running optimally tuned twins.

 

He means post-turbo

It doesn't take nearly as much power to turn the turbo at it's idle speed (I've heard up to 10,000 RPM) as it does at full boost (140,000 RPM). The turbo gets its energy from the hot exhaust gases, so if it isn't using much energy you won't see as much of a drop in exhaust temps. I've heard of pre and post-turbo measurements varying by up to 500*F.

 

That's what I said...

 

So I'll toss another EGT gauge in there and read both while pulling my trailer, cant get more accurate than that.

 

So, the important temp to know would be pre turbo right?

I'm assuming that the super hot exhaust gasses are what would literally melt down the turbine.

Any reason to care about post turbo temp other than that you don't have a pre turbo temp guage?

Whats the max safe operating temp for a CTD? Does it vary for a Ford or Chevy diesel?

Thanks!
Chass
ct

 

Right the important temp is pre-turbo.
It is important cuz the pistons well melt above 1250 deg for an extended period of time.
Some people want a post-turbo gauge because they are worried about the probe breaking off and going into the turbo but that only happens like .000001% of the time or so. (I am Guessing at that number but it is rare).

 

Chass



ct

 

No u want the gauge on all the time because EGT's will go higher going uphill or pulling a load. Air temp, altitude can all affect it and if you are borderline normally it can be easy to go over.

 

I look at things from a different light. If the probe breaks and wrecks the turbo.............upgrade .

 

well then you need new injectors to spool the turbo, head studs, etc......

Down the slippery slope weeeeee!!!!!!

 

I was refering to checking the probe to make sure it was in good shape

Yes I look at my pyro all the time. Its 24 inches from my face!

Chass
ct

 

Ok that makes since too, forgat to read your signature.

 

Yep, the trail is steep and very slippy. My goal is to find out how much a stock A518 will take before it grenades.

 

Pre-turbo temp was 1050 that was mashing on it until 92 mph and I backed off. I was empty and 23 psi boost. I have to do a head gasket so Im gonna port the head and get the pump rebuilt. Funny thing was as I was getting to the onramp I passed a new Cummins and he came running up on my backend, so as I got on the onramp we both hit it. I was surprised to see my tired old truck pulling away at a decent clip.