EGT lead length and gauge accuracy???

[Reddog]

Hello to all. Well, what with my problem with idle hands, I decided to add propane injection to Thomas. Easy to do and i really like teh additional power on the hills. In addition to this, I added an EGT. Bought it off of FleaBay with the probe, an Isspro, used. I had to buy 50' of thermocouple wire (or at least that is what I did) to run from teh probe to the gauge, I used 20 ga. Here is where i start to have questions:
  According to my "new" gauge, easily tooling down teh road, I'm running at about 400 degrees F. Have not pulled a hill yet. Temp seems low to me. Does anyone have experience or knowledge aboutt his and can you tell me if I made a mistake choosing 20 ga. wire to make such a long run? Seems like with the low current that this wire handles, 20 ga. should be fine??
  Any and all help is greatly appreciated. Doug@8000'

[Len Silva]

I would talk to Isspro about that.  The current is very low but so is the voltage (millivolts).  I think that thermocouple type gauges are generally calibrated to the wire length.

[luvrbus]

Would help a bunch if you told us what engine you have 400 sounds about right for a 4 stroke under no load

[Reddog]

Sorry, didn't even think of that. Cummins 6CTA 8.3L I6

[luvrbus]

Shoot the probe location with a IR gun and check the gauge you are not far off


good luck

[Reddog]

Thought about that but figured by the time I stop and can only shoot the pipe by the probe, that may not be all that accurate either. I tried to get my wife to stand on the rear bumper and shoot the pipe as I drove down the road but she refused...seems unreasonable to me...

[bobofthenorth]

Let her drive.   

[Bill B /bus]

As far as your bride being unreasonable, I think I understand her position

Anyway your temperature seems about right. Steady cruise at 400F 'ish seems quite likely to be correct.
Remember you are generating a voltage. The current is minimal.

Also your gauge accuracy is somewhat determined by the smallest division measurement. Experience has shown that you can determine less than halfway or more than halfway but nothing more than that. Since your gauge is a 2 1/8" gauge and the smallest division is 100F you can expect accuracy  on the order of 25 to 50F. On a warm day with the engine cold I get an approximation of outside temperature. More than 50F and closer to the 100F mark than the 0F mark.

I have seen thermocouple runs in excess of 1000 feet. Their accuracy before calibration was excellent. We were looking for +/- 50F.

Enjoy your new toy.

Bill

[Reddog]

Thanks for the info and suggestions. I would let her drive, but the whole idea is for ME to get to look at my new gauge.
  I'll do some more driving and get more info compiled. Anybody got an idea where I should be at idle once warmed up? D@*K

[Bill B /bus]

I run about the 300F mark on warmup/build air idle. coasting down a hill without Jake is still about 300F.

Bill

[lostagain]

My EGT gauge on my MC5 with 6V92TA reads about 300 once warmed up no load. Climbing a hill under full load it'll go up to 450 or so. The sender is after the turbo. I should move it just upstream of the turbo where it should be more accurate and meaningfull.

JC

[bobofthenorth]

Pre or post turbo thermocouple used to get thrashed out regularly on the Powersmoke pages.  The choice comes down to one of two compromises:
- pre turbo you get more responsive readings with the risk that if the thermocouple fails it will take the turbo with it.  Not an unheard of event apparently.
- post turbo you get a less responsive system but with no danger of putting the thermocouple through the turbo.

[Reddog]

Post turbo installation, about 6" beyond the turbo. My main concern is high turbo temps while climbing, which is a way of life here. D@8K'

[lostagain]

You shouldn't worry about temps in the less than 500 range.

Compare that to EGTs routinely above 1000 in my Powerstroke Ford pickup pulling a load uphill.

JC

[Reddog]

My only real concern is as you mention, those in the higher ranges, but I'm wondering about the accuracy of my "new" gauge. I'll probably have to pull some grades to see if it seems accurate across a broader range of temps. Thanks for the input, D@8K'