Thermocouple questions

[jc64]

I am finally looking into gauges for the truck. I have found a dual 3" gauge that I like. It's the Westach Model: 3C86T14. It is a 0-30lb boost and 100-1900F EGT gauge all in one.

I have some questions about the type "K" Thermocouple. They talk about the Hot End (probe) and Cold End (wire junction). They say that the temperature on the cold end affects the millivolt output. (Or are they talking about the "J" thermocouple? Or are all thermocouples the same?) They seem to have two calibrations for their thermocouple/gauge setups. One is for warm (70°f) climates and the other is for cold (30°f). I'm at a loss what to get. I live in Mo. and we range from highs in the 100°'s to lows in the -10°'s with in a year. I would say that we have more warm days than cold ones.

So, I should get the warm climate setup, correct? I'll just have to do the math in the winter to get an accurate reading. Which leads me to my next question (I bet Rick knows this one). Say I get the warm setup, and we have a day that is 20°f, what is the temperature in the engine bay, say doing 45mph with a fully warm engine? I know that the bay is 20°f at start up, but what is it when the engine is warm with cold air being forced into it?

OR... is there another "K" type thermocouple that is not so outdoor temperature sensitive? The Westech type K specs are 200°f=2.87mv to 1800°f=39.67mv

Also, I found this statement:
The EGT probe is subject to an extremely violent high temperature / high pressure environment. Over time it could be possible for an EGT probe to degrade and potentially send fragments into the exhaust system and turbo charger. The tip of the EGT probe is designed to slowly burn away and EGT probes normally quit working before degrading to a dangerous point. We have never seen our EGT probe fall apart, never the less we recommend you periodically inspect the EGT probe for signs of damage.

How long does this take. Anyone seen this? (Just wanting to learn.)


Thank Guys,
jc

[blksmok]

I don't know what you plan to do with your truck, but my first question would be, is a 30lb boost gauge enough? I run over 30PSI everytime I get on it...

[Fingers]

30 PSI gauge is not enough.

The Thermocouples work by the varying resistance across the junction between to dissimilar metals in the tip. The wires coming from the thermocouple are made of the same metals. When they hook to the gauge, there will be a junction between these special metals and the copper of the gauge at some point. This will make another dissimilar metal junction. That point will influence the resistance too based on the temperature at that junction.

The best thing to do is to make that connection inside the cab if you can. Figure that way it will at least be some bearable temp like 60*-70*. :)

Even so, the affect is minute when compared to the EGT temps. I wouldn't worry too much.

[James Hess]

what is a thermocouple, what does it look like, and where does it go??????:confuzeld:

[blksmok]

what is a thermocouple, what does it look like, and where does it go??????:confuzeld:

James, we need to get together and do lunch or something. :lol:

The thermocouple they are talking about is the probe that goes into your exhaust manifold for the EGT gauge.




















The lunch comment - I'm just messing with you BTW... It's all good. :thumb:

[jc64]

Well they do make a 40psi gauge with a 200-1400f EGT gauge combo. I would like to have the higher EGT gauge thou (I don't know why). Westech does advertise that they will custom make gauges.

My truck is a daily driver (well... before fuel hit +$4 a gal. and we got the 28mpg beater). IICR, the stock LLY turbo is good for only 30-32psi total? I will be under that, I hope. I'm going for mild power.

Thanks, I was not sure on how much the ambient temp affected the true reading. I was thinking the same on the inside mounting.

jc

[blksmok]

Well, lots of us started out just going for "mild power" ):h At any rate, I don't think that's a good combo either. 1400 EGT isn't high enough IMO.

I would look for a boost gauge to at least go to 35PSI and a EGT gauge to go to 1500 - 1600 degrees.

[Fingers]

I would suggest at least 40 PSI for the Boost and at least 1600 for the EGT. Those are fairly typical ranges to cover. Your next goal is to exceed even those ratings. :D

[blksmok]

That's why I got a 60PSI boost and 2000° EGT... Give me something to shoot for. ):h j/k

[minisub]

Well they do make a 40psi gauge with a 200-1400f EGT gauge combo. I would like to have the higher EGT gauge thou (I don't know why). Westech does advertise that they will custom make gauges.

My truck is a daily driver (well... before fuel hit +$4 a gal. and we got the 28mpg beater). IICR, the stock LLY turbo is good for only 30-32psi total? I will be under that, I hope. I'm going for mild power.

Thanks, I was not sure on how much the ambient temp affected the true reading. I was thinking the same on the inside mounting.

jc

The stock LLY turbo is good until about 32 psi - it will go higher (with bad results) so it would be wise to cover that scenario...

Define "mild power." An Edge on level 4 or 5 can blow through 1400* so fast it's not funny. I've seen a Predator powered truck hit 1850*+ on an on-ramp WOT run....

[James Hess]

James, we need to get together and do lunch or something. :lol:

:thumb:

seriously i am up for that lunch cause i want to know what half the stuff is that yall are talking about.:lol:

[jc64]

The stock LLY turbo is good until about 32 psi - it will go higher (with bad results) so it would be wise to cover that scenario...

Define "mild power." An Edge on level 4 or 5 can blow through 1400* so fast it's not funny. I've seen a Predator powered truck hit 1850*+ on an on-ramp WOT run....Tow tune.
I would like to keep my clutch alive for a while, even thou I doubt that will happen ):h. I'm not ready to replace head studs and such. I'll live my big horsepower threw you guys. I just want a little more gitty-up. I sold my derelict 240Z for $800 to get EFILive. I'll be talking to Nick soon. Just very disappointed with the very slow development of the V2. I do not want to pony-up for a laptop when it comes with the V2. A $750 program turns into a $1000 program real quick.

The 0-40psi/200-1400f gauge is only $122 plus 4 other parts (they list them as part #'s only, trying to figure out what they are), and I haven't read anything bad about Westech yet. I'm going to shoot them an e-mail and see if the can make a 0-40 and 100(or 200)-1900f gauge. $122 isn't a bad price for a dual gauge.

Something that has not been touched on yet is, what is the average life span of the EGT probe itself? I haven't read of one going out yet, but that is just me.

jc

[Fingers]

Shorter the hotter you get and keep it. :D I would expect a full year thou. Mine has been in my truck off and on for about 3 yrs and it is still good FWIW. The probes are a consumable.

[James Hess]

what is the V2? sorry i am asking so many questions i am just very curious is all:lol:

[blksmok]

The V2 they are talking about is the handheld unit of EFILive.

[James Hess]

thats what i figured but i didnt want to make any mistakes

[jc64]

Been shooting e-mails back and forth with Westech. Web sit says one price, they quoted another.
Total setup should be around $200 to $250. Still isn't bad for an all in one setup IMO. It also comes with a warning light for high EGT's.

I thought the probe would last longer than a year.

V2 has been around for about 2(?) years now and still does not do what it was advertised to do. :mad:

jc

[minisub]

...

I thought the probe would last longer than a year.
...
jc

Well, I've had the same one in my Tahoe for going on 9 years....








'course it has never seen the other side of 850* ):h

[minisub]

jc - serious question, where are you going to mount this 3" gauge?

All of the A-pillar, over-mirror and overhead mounts I have seen take 2 1/16" gauges. Are you doing a custom plate in the airbag cubbyhole or something?

[jc64]

I'm going to mount it to the very bottom of the drivers side "A" pillar (on the side so it is tucked down by the dash and corner of windshield) with a gauge mounting cup. I'm going to take the pillar cap off and reinforce it with stock. If it breaks or I "F" it up, should be fairly cheep to replace. I'll get it thou. :thumb:

I'm not a fan of the 1, 2, or 3 gauge pillar mounts. Overhead mounts and airbag cubbyhole are too far away to keep a constant eye on IMO. This way I don't have to take my eye off of the road very much to see the gauge or I can just stare at and still see that MotherF'R pull out in front of me while I'm doing 65mph.

jc

[minisub]

That's the same location I had my attitude monitor, and I really liked it/miss it. I too am not a fan of pillar pods - I have one in the Tahoe and hate making sweeping left-hand turns as it really screws up my visibility.

I have an over-mirror mount ready to go in the Sierra this weekend, hopefully that will be the "sweet-spot" for me.

Post up some pics once your install is done, I would like to see it.

[jc64]

Will do. :thumb:

May be a bit thou. I will be trying to upgrade to LED's for lighting.

jc

[jc64]

Got all my questions answered form Westech. Going to order it Mon.

But... I have one last question for you guys.

What Thermocouple do I want for my BD manifold? A or B?

A) 3/16" OD, 2½" tip, 1/8" npt

B) 1/4" OD, 2½" tip, 1/4" npt


(These two are the only options)

I'm thinking A. Smaller OD. Also, the 2½" tip seems kind of long. With using the 1/4" to 1/8" adapter that came with the manifold, it will back it out of the manifold more. The probe is adjustable, but how much of the probe should be exposed to the gasses? I'm thinking the tip about the center of flow, but with it being 2½" long it will be in the back exhaust port, or half of it on the outside.

I swear, this should be my last question on this. Plus, I am adding content to the new site. :D

jc

[modified]

A thermocouple is two dissimular metals, connected together. The dissimular metals will produce a predictable mV signal at known temperatures.
Thermocouple wire is of the same material as the thermocouple, so if you use TC wire all the way to the pyrometer, (indicator), this will eliminate cold junctions.
Cold junctions are produced when the thermocouple wire is connected to dissimular metals, (such as copper wire), which will induce errors.
Even if thermocouple wire is connected to the indicator, that junction will usually be of different metal, but many indicators will have a built-in reference junction compensation, which will account for this cold junction where the TC wire connects at the indicator.
Below is a link to everything you ever wanted to know about thermocouples. If you click on Technical Links on left, there's more than you may want to read.
http://www.omega.com/thermocouples.html

[minisub]

A thermocouple is two dissimular metals...

Nice to see you here. :hello:

[jc64]

That's the same location I had my attitude monitor, and I really liked it/miss it. I too am not a fan of pillar pods - I have one in the Tahoe and hate making sweeping left-hand turns as it really screws up my visibility.

I have an over-mirror mount ready to go in the Sierra this weekend, hopefully that will be the "sweet-spot" for me.

Post up some pics once your install is done, I would like to see it.
I have pics in my Album. I installed it just after the 4th of July holiday.

The location is good but, the gauge lights are located at the bottom behind the Westach logo and they reflect off the windshield about 3" above the gauge. I'm looking into the visors that are used on the driving lights on Harleys to get rid of the glair. One day I'll remember to stop by the dealer.

jc