Alternative EGT probe location

[SoCalDMAX]

I have the SPA digital dual gauge with EGT and boost. The EGT uses a K type thermocople and I mounted it on the passenger side exhaust manifold in the same location that many of you have mounted yours.

When the dealer replaced my engine, they acidentally cut my EGT probe wires and I replaced them with the old wires from a previous probe. There must be a compatibility issue, because the gauge is VERY sluggish and reads OK at idle, but won't go very high when driving.

I just got the Edge Attitude and was anxious to install the EGT probe to get some accurate readings. I didn't want to tie the 2 gauges to the same probe, SPA uses ungrounded, Edge uses grounded, and I wasn't sure if the Edge is a K type. I also feel that the reduced circuit resistance of having 2 gauges in parallel (especially since SPA uses an amplifier module to boost the signal) was not going to give accurate readings.

So I climbed under and looked around. I spotted a place on the driver's side manifold that I remember one of our members had a probe installed in. It is on the bottom of the manifold at the rear just before the flange, fwd and above the oil filter.

I drilled a pilot hole, worked up to a larger hole and tapped it all without incident. The beauty of it is that gravity is working for you and all of the chips fall down, away from the hole. So I didn't have to start the truck.

So now I have the SPA gauge in the PS manifold, Edge probe in the DS manifold and I can watch the Edge gauge shoot to 1500* while the SPA gauge lazily meanders towards 450*... LOL! :D Gotta fix the cable.

Heck, it's only 10PM... I'll run out there right now and fix it!

Regards, Steve

[Burner]

Steve,

My thoughts exactly! My only problem is where or how to land the guage other than the "piller" mount. I would really like to see which one reads quicker.


Burner-------> :D

[Murray the Cop]

Anxious to hear the results when you fix the original sensor setup. I have a quad guage and tried to splice both to one sensor. The attitude would give readings using the quad sensor but there was a 150 degree difference(quad higher).I tried the same with the edge sensor and the quad would not work. I also tried each with thier own sensors and still found a considerable difference. Don't think the attitude guage is accurate.The numbers are too low. There is a big difference with the boost numbers also.Edge boost comes from comp. where quad numbers come from vacum. I heard the vacum numbers should be closer to true. Post the difference in the numbers if there are any. I'd be interested to know which guage is telling me the truth.

Anthony

[ 10-26-2003, 10:37 AM: Message edited by: Murray the Cop ]

[OC_DMAX]

I would be interesting to note any EGT differences between the two manifolds when you get you SPA leads fixed.

[letsgo]

To create a thermal couple, join 2 dissimilar metals together and you will have a voltage generated at the junction point, which can either add to or subtract from the circuit voltage.

It is not good practice to make joints in thermal couple wire, the only successful way would be to twist the same color wires together and tape them up (this method would only work for a while) to use stakons, wire connectors or terminal blocks you have introduced a dissimilar metal (big problem), Also something to think about in electronics and electrical the RED is always positive NOT with thermo conductor the red is always put on the negative in that dedicated circuit only, otherwise you will create another thermal couple in your circuit either additive or subtractive.

Hope this helps someone

[SoCalDMAX]

Letsgo, That was really helpful, but brings up a couple of questions.

What is the best way to make the connection to the probe? SPA and Edge used crimp-on lug terminals with a screw and nut, but I can't tell if they are regular lugs or the same material as the wire.

Would it be acceptable to solder the connection, or are you saying twisting the wires together is best?

Thanks, Steve

[maDmax990]

Hi everyone-

I believe Letsgo is right, but I should have access to some info tomorrow that says for sure.

We use a lot of TCs from Omega Engineering (www.omega.com) and we always use K-type extension wire for K-type TCs, and the terminal block connectors they sell are also k-type materials throughout (chromel-alumel) from what I understand.

Obviously at some point in every system, you're going to have a second set of junctions when the TC wires eventually jump to copper somewhere in the guage end. The theory as I've been told is that as long as the terminals at the guage are the same temperature (which can be reasonably expected), the voltages induced there are cancelled and everything is fine.

Where you would be in real trouble is if you put a non-K type material junction somewhere where one connection is a significantly different temp than the other...leading to goofy readings.

Soldering doesn't sound like a great idea IMHO.

Lemme see if I can clarify that tomorrow.

Regards, Mat

[letsgo]

The only points for termination that I have ever made were at the controller and at the sensor, these terminations in the design of the circuit have allowed for the introduction of stray voltages generated at the termination points. I dont think these conductors can be soldered, also the conductor must be placed directly under the screw termination of the controller and sensor, again you cannot introduce another metel in the circuit. I have also accidentally reversed the hookup only to get faulse readings.

good luck

[Longreach]

SoCalDMAX saw your alternate location for EGT probe...can you post a picture. Getting ready to do mine over the weekend and this location sounds like a winner.
Many thanks
Richard

[Burner]

Longreach,


-- I saw that first post......... Welcome to the site!


Burner--------> :D

[sdaver]

yea how bout a picture........less the smoke

[Longreach]

Burner
You're sharp!....thought I'd sneak by unnoticed.
Yep....rookie here as well as with PU truck diesels.
Lots of good info and experience here and I hope to contribute when I can...

Later
Richard