Is a post turbo ehaust temp gauge ok?

[jfile]

Is a post turbo exhaust temp gauge ok?

[TooMuchMuscle]

That should be fine... but remember that after the turbo the EGT's will be 200 to 300 degrees cooler. There are companies out there that make guages already calibrated with the temperture change. Not really sure which brand.... Good Luck

[pullinpower]

I too would be interested in the company that already does the temp change for ya.

[Dmaxin]

Check out Kennedydiesel.com they have a pre and post turbo gauges.

[Amianthus]

TooMuchMuscle is right. Although, I've seen temperature differances of more than 500 degrees across a turbo. So a good temp limit post-turbo is 900-1000*.
Post turbo is good as an indicator for cooldown to prevent coking of oil by shutting down a hot turbo. Although it sounds like a serious problem, it's really not. You have to shut the thing down at 500 degrees and do it habitually for real problems to start. But why chance it.

[Rebel_Horseman]

Hoot,

Soory for the ignorant question here...the turbos on our trucks (man I like saying "our") are water cooled? What about Ford & Dodge? Are they all water cooled? What's the advantages / disadvantages to pre vs. post turbo installation.

Reb [><]

[Nels]

I experimentally ran a ring eye thermocouple on the exaust side case of my turbo for nearly a year. Normal driving temperatures with that mounting were in the 400 - 425 degree range. I had it up as far as 475 several times when it was working a bit, but I never saw 500 degrees where I had mine mounted. I tried this location because of all the talk about shutting down hot turbos and coking, etc. This is my first diesel, and I wanted some reassurance for safe shutdowns. In my experience with this, I found that a minute or so of idle time will bring the temperature down to under the 400 degree mark in most cases. If towing or working it hard, it may have taken two minutes. I made a point to not shut it down until I saw the needle pass about 375 degrees and falling.

While that position gave me the reassurance I was seeking, it was no fun at all to watch while driving with the s-l-o-w response. Probably not very useful for diagnostics either. I have since installed a probe in the hoot position on the manifold. The gauge is much more interesting and informative to watch now.

[Amianthus]

I have to disagree with you hoot, in that the probe will read exhaust stream temp. If it is running and cooling down, the stream will be picking up waste heat from the exhaust components of the turbo. Not that what you said is wrong. It's very possible to have the housing be 500 and the EGT be 300. But it's not likely. At least that's been my experience.
On the Dodge, the EGT pre-turbo will hit 300* before the post turbo will. How long before? It depends on how hard a run you had and how heat soaked the turbo was.
I don't think the turbo housing is as important to coking as is the turbo shaft. The turbo shaft gets heat from the turbine wheel and that's what causes coking. Yes, the housing plays a part in it, but not as much as the shaft does.
Now, I agree that in the Liquid cooled turbo, this is almost a non-factor. I suppose it could still happen, but I don't see it being very likely.

[hoot]

Amianthus,

I guess I was just thinking out-loud. But remember the exhaust stream is putting a constant flame on the turbo housing but as soon as you drop rpms, the exhaust stream drops temp immediatly. It would be interesting to read the housing temp and the post turbo to see the difference at idle after a hard push. I think you are correct that the housing will continue to induce significant heat into the post stream.

If you hit it real hard that turbo housing gets real hot. I remember taking a Volvo turbo (car) for a test drive at night. We opened the hood after we shut her down and the turbo was red.

Just curoious, do the gas turbos get hotter than diesels Amianthus?

[ 11-22-2002: Message edited by: hoot ]</p>

[mdrag]

hoot,

"Just curoious, do the gas turbos get hotter than diesels Amianthus?"

I'm by no means a turbo expert. The Dmax is my 2nd turbo vehicle, the other being a 1989 Supra Turbo 3.0L inline 6 cyclinder 7M-GTE gasser - which I bought new and is heavily modified. I see 1300* plus to maintain highway speeds with 0 psi positive boost. At +18 psi sustained boost WOT on 92 octane pump unleaded - I'll see 1600 to 1700 on my pre-turbo EGT. I was told that less than 1800* was OK in this application.

I've had the current setup since 1991 and NO turbo problems...but the OEM headgasket didn't last long at these boost levels. BTW, the factory boost level was +7 psi :eek:

[TooMuchMuscle]

"Some guys have gone as far as putting a thermocouple on both sides and installing a simple switch. That way you can watch either side with the same gauge. Gives you an idea of how both banks compare. Could alert you to injector problems too." --Hoot

Instead of having probes on each manifold could you run a probe pre-turbo and a probe post-turbo and have them controlled by a switch? I would think this would tell you what the temp of the turbo is...

[Amianthus]

It's been my limited experience that diesel engines have the potential to run hotter than gassers. I have yet to see a gasser run a 2000F EGT. But know of several diesels that do. Although, like I said, my experience is limited in gasser phenomena. I'm sure a gasser can get there, but just haven't heard of it as much.

[hoot]

TooMuchMuscle,

Yes, but I was referring to measuring EGT's as close as possible to the heat source, that being the cylinders.

You can measure turbo housing temp by putting a thermocouple right on the housing itself. Now if you want to know internal temp at the turbine itself, your idea, with the mid temp between the two would probably give you a close number. I don't think anyone would go that far.

[Kennedy]

One thing to keep in mind back from an earlier post is that the exhaust streams never really join till they hit the turbine wheel. We have a double feed, double scroll turbo. Had they been manifolded together, this would be my choice for probe placement.