Dual EGT gauge

[cranetruck]

I could research this on my own, but since the answers may benefit everybody.....
What can be diagnosed by using a dual pyrometer, one thermocouple in each exhaust manifold section, not possible with a single probe installation?

 

[ken]

On the larger engines we do each cylinder has it's own pryo. So the operator can see if something is going down hill. If a cylinder is running 20deg different than the others you can tell if a injector/rings or valves need attention. Running dual thermos would narrow it down to the front or back 3 on a LD. I use my laser heat gun on the exaust manafolds at each port after running hard to see if a cylinder is getting weak. Being able to do it while running would tell me much more.

 

[cranetruck]

Having two readings would certainly add a lot since there would be a reference comparing one to the other.

 

[Banshee365]

When I drilled and tapped my exhaust manifold I put a port on each half of the divider with the intention of using a dual probe gauge. I definitely think you can benefit from splitting the engine in half because you can diagnose problems easier. Who makes that gauge and what does it and the probes cost?

-Kelly

 

[cranetruck]

Got the image from here:
http://www.ultralightnews.ca/egt/

 

[Polverone]

Would there be a benefit of running one pre turbo and one post turbo?
I think someone did that here. Houdel, was that you?

 

[Jones]

Pre and post turbo would be lost on the likes of me but I do think individual clylinder performance/function might be handy to know.
Worked on the UP 844 steam locomotive and it's set up to sequentially sample each driving axle's bearing temp so I know that pinpointing a problem early on can be invaluable.

 

[Crash_AF]

Westach sells dual pyrometers in addition to other dual (or more) guages in one housing.

WESTACH

Later,
Joe

 

[houdel]

Would there be a benefit of running one pre turbo and one post turbo?
I think someone did that here. Houdel, was that you?

No, not me. I run a single pre turbo pyrometer. I don't see any advantage in running both pre and post turbo pyrometers on a single vehicle. The pre turbo pyro measures the egt of the flow of exhaust gases into the turbine of the turbo, which IMHO is the more important place to measure egt to make sure your turbo doesn't get too hot. I don't see much use for a post turbo pyrometer, as it does not tell you the operating temperatures the turbo is subjected to.

 

[Recovry4x4]

If just a couple of us ran pre and post we could determine an apporximate drop across the turbo. With that info we could guesstimate the pre turbo temps on a post turbo install. Basically one could use that info to do the easier post turbo install.

 

[cranetruck]

You are right Kenny, but the idea is to monitor the two sections of the exhaust manifold for possible fault diagnosis, just knowing the temp at one place is much less informative.

 

[Recovry4x4]

For sure Bjorn. We are reading EGT on half the engine. Should we have a significant injector problem on the other half of the engine, we could have soaring EGTs and potential disaster and know nothing about it until disaster strikes. Wonder if you could run two probes, one gauge and toggle back and forth. Here's one for you Bjorn. Knowing the voltage for specific temperatures, could one rig some type of idiot light that would light at a specific voltage/ temperature?

 

[Jones]

Kenny, a simpler option (if it works) would be a handheld pyrometer. We use them to take pinpoint readings as they have a laser dot that shows where we're sampling. If the cast-iron manifold doesn't transfer heat too uniformly there should be a cold or hot spot at the offending cylinder's exhaust flange. Downside is that you would have to pull over and open the hood.
Reason for my brain-f*rt is that thermocouple leads on all the pyros I've run across are continuous and say NO cutting or shortening 'cause they use the lead's length as part of the known resistance in the thermocouple circuit.

 

[cranetruck]

..... Downside is that you would have to pull over and open the hood....

See, that's just it, it's on the highway when the gauges become critical, sort of like flying.

 

[jimk]

Kenny wrote:
Should we have a significant injector problem on the other half of the engine, we could have soaring EGTs and potential disaster and know nothing about it until disaster strikes.

This was why I installed my probe after.There were other reasons: the probe runs cooler(longer lifespan?) and can't go thru the turbine(OMG), though I feel both are very unlikely. The switching of probes is a good way to save $ and it has been done in racing for decades. The probe works on very low voltage(0-35 millivolts) so good switch may be needed (i.e-gold plated contacts).

The web site below is probably the best, and most experienced, of the turbo kit companies. It is loaded with good info. I couldn't find a coypright mark so here is the part on probe location.

Whether the pyrometer thermocouple is mounted before or after the turbine is usually a matter of finding a suitable mounting location, or of convenience. It should be noted that when the EGT is measured after the turbine, the turbine outlet temperature at full throttle or under a heavy load typically would be 200º to 300º F. lower than the EGT measured in the exhaust manifold. The temperature drop after the turbo indicates the amount of heat energy in the total exhaust gas flow that was used to drive the turbocharger. The temperature drop through the turbine is also related to the total flow and speed of the flow through the turbo. At part throttle, under light load, such as cruise conditions, the turbine outlet EGT may be as much as 500º F. lower than the turbine inlet temperature, but the total exhaust flow is much less than at full throttle. At high turbine speeds (under heavy load) the exhaust gases simply don’t have time to give up as much heat energy as they speed through the turbine. This variance is why installation of the thermocouple in the exhaust manifold is considered more accurate.

http://www.bankspower.com/Tech_whyegt.cfm

I wonder if the last line holds true for the LD/LDT/LDS exhaust manifold.
The 500*F difference across the turbo part, offered the context of, " part throttle, under light load", is also very interesting. I see my EGT fall rapidly under these conditions. I don't think my pre turbo EGT is excessive here, but a second probe would be nice.

I am sure of this. Having a way to monitor EGT is important. A properly designed system may never have a problem but then sometimes settings change. Other times more performance is desired. A pyrometer will let you take more without risk. JimK

 

[jh1990]

why not just use two seperate gauges and two seperate sending units, w/ two seperate probes? and then label the gauges in the dash. Just my 0.02 USD

 

[cranetruck]

why not just use two seperate gauges and two seperate sending units, w/ two seperate probes? and then label the gauges in the dash. Just my 0.02 USD

Simple answer: $