What Depth for Pyrometer Thermocouple?

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I have the ISSPRO pyrometer. I know to install it 3/4" of an inch from the back of the flange and to put it in the front or rear exhaust outlet, not in the center.

However how deep should the thermocouple go? It slides up and down in the fitting so I can adjust the depth, but how deep does it go. I can't find any instructions for this.

Thanks,
Bobby


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2000, Driftwood, 2500, automatic, 3. 54, 2WD, LWB, SLT, Quad Cab, most of the options, Grover air horns, tow 5500lb 28'x8' Aerolite TT and two small boys.

 

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You want to know the metal temperature, not the exhaust gas temperature so the tip of the probe should be flush with the inside of the manifold (if pre turbo is where you choose to mount it).

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White 99 3500, QC, 3:55, auto. most options except leather, Line-X bed liner, fiberglass running boards Rancho 9000s, bug shield and window vents, black vented 5th wheel tailgate, 100 gal. aux. fuel tank.

 

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I'm not saying Mr. Smith is wrong but I have my doubts. I for one would like to here from other members on the depth positioning of the thermocouple. I located mine so that about 3/8" of the tip is in the exhaust flow. This is with the ATS manifold and with that manifold the boss where the thermocouple is, is at least 1/2" thick. With my stock manifold I had the thermocouple about 3/4" into the exhaust flow. I feel you need to monitor the the gases, not the temperature of the manifold itself.
Arlan

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98. 5 ISB QC 3500 4X4 3. 54, PowerMax1, DTT TC & VB, TY303 225/70/19. 5's on Rickson Wheels, 275 Injectors, Mag-Hytec Transmission Pan/Differential Cover, 9000 LB Warn Winch, Ultra Board Running Boards, Westach Combo Boost/EGT Transmission Temperature & Fuel Pressure gauges, Pac Brake, 2-lo kit, CB, GPS, Rancho 9000's, ATS exhaust manifold, JRE 4" exhaust with muffler and resonator. Lifetime NRA Member

[This message has been edited by arlan (edited 01-15-2001). ]

 

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I agree with Arlan. I positioned mine to where the tip of the probe is about in the center (roof & floor) of the exhaust manifold.

 

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Hold on there B. G. The probe is not there to register exhaust manifold temperature. The tip of the probe should be positioned in the center of the exhaust gas flow. This will be the hottest area because the exhaust is moving fastest at that point and is also hotter than the manifold temperature. If you are familiar with laminar fluid flow and how it affects heat transfer to the manifold i. e through the fluid boundary layer you would know that if the probe were placed close to the manifold wall the indicated temperature would be lower than actual exhaust temperature. On severely bombed engines this difference in actual and indicated temperature could result in turbine and engine damage.

 

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Can you explain to me why you want to monitor the temperature of the metal and not the gas?

 

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Oops, fingers in gear and brain disengaged. EGT stands for "exhaust gas temperature". I stand corrected. Rob Hanson has a good write up on installing gauges in the Product Review section but he doesn't say how deep to put the thermocouple into the manifold or elbow. Mine is flush with inside of elbow. Reacts slow going up and coming down. I will put it in further and see if it helps. bg

[This message has been edited by B. G. Smith (edited 01-15-2001). ]

 

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I agree with Hemi- with experience in snowmobile applications I would think that the methods would be the same for the Cummins. Put the tip in the center of the flow or ideally 1/4" past the center of flow.
Just my . 02

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Jim Bartsch

97,2500,CC,long box,4x4,5-speed,3. 54,64000 miles,265's,ISSPRO gauges(pyro-boost)pillar mount,15. 3btdc, Lund X-steps coming,tonneau cover coming,cam plate next, where does it end?

Winter fun 99 Polaris 700 RMK heavily modified, Wifes sled 00 Pol 550 Trail
Summer fun 94 ZX-6 Ninja, 93 Suzuki RM 125

 

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The thermocouple should be in the exhaust stream... NO MORE than 1/2 the distance of the runner height (or diameter). After reading up on this for the last several years it seems many have experienced no temperature difference by setting the depth of the thermocouple deeper than 3/8" - 1/2".

SPA states that their 1/8" diameter thermocouple tip should only protrude into the exhaust stream 1/8". SPA states that a 1/8" diameter thermocouple tip is utilized to allow faster more accurate temperature readings.

I believe B. G. Smith was thinking of a Head Temp. sending unit.

[This message has been edited by John (edited 01-16-2001). ]

 

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Originally posted by B. G. Smith:
You want to know the metal temperature, not the exhaust gas temperature so the tip of the probe should be flush with the inside of the manifold (if pre turbo is where you choose to mount it).

????Then why is it called an exhaust "gas" temperature gauge" and not an exhaust "metal" temperature gauge???? When all else fails, read the instructions.

[This message has been edited by arar (edited 01-16-2001). ]

 

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[/b][/QUOTE]
????Then why is it called an exhaust "gas" temperature gauge" and not an exhaust "metal" temperature gauge???? When all else fails, read the instructions.

[This message has been edited by arar (edited 01-16-2001). ][/B][/QUOTE]

Too bad we can't all be smart. bg

 

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Yeah, bg! I didn't care for that post either.
Arlan

 

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Was that true B. G. ? Were you indeed thinking of a Head Temp. sender instead of a pyrometer thermocouple? Easy mistake to make if your mind is on something else.

 

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John, I installed the pyrometer mainly to be able to tell when the turbo charger is cool enough to shut the truck off with out having to worry about the oil cokeing in the turbo bearings. I tow a 12400# trailer a lot in the warmer weather. I think I am more interested in the metal temperature than the exhaust gas temperature although I believe if I were measuring the EGT that the metal temperature would still show above the EGT until the metal come down to the EGT temp. I wasn't thinking of the head temperature. Thanks for the support Arlan, you too John.

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White 99 3500, QC, 3:55, auto. most options except leather, Line-X bed liner, fiberglass running boards Rancho 9000s, bug shield and window vents, black vented 5th wheel tailgate, 100 gal. aux. fuel tank.

 

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Does anyone know how aften do you change the thermocouple. I don't wont it to brake off and go into my turbo.

 

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I decided to look at mine after about 20,000 miles. It looked like new except that is was black. I don't think it's a good idea to be removing them for any reason other than replacement. Mine started acting up shortly after I messed with it, then I had to replace it.
Arlan

 

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I think BG has a good point. If you are using the pyro post turbo for shut down,especially with a auto shutdown addition it makes sense to have the probe tip high up.

When my pryo started reading 100°high I called in for warranty,the fellow asked if I had moved the sensor. He said the thermocouples rarely fail or read wrong unless they are moved,the problem with bad readings is most always with the gauge. So you basically only have one chance to locate the depth of your thermocouple,so take care and don't go moving it around. This is a good reason to remove the turbo for drilling and tapping,you can see how far it's sticking in,1/2-3/8"is good.

[This message has been edited by illflem (edited 01-17-2001). ]

 

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When I install the probe I slide it down till it hits the tip of my little finger resting on the bottom of the exhaust manifold floor. Roughly 3/8 to 1/2" Been doing it this way for twenty odd years and have never had a failure with the probe or the readings. I saw an old pro do this many, many years ago and it just became habit. I have talked to Isspro & Auto Meter about this over the years, and they thought it was just fine that way.

You do NOT want it touching the bottom of the manifold or any other metal. If you did, what would be the reason for going into the inside of the manifold? You could just attach the probe to the outside like some other vendors selling the early cheaper pyro kits. They did not recomend that practice for long!

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Owner: Stabco Repower, The turbo housing guys. '89, CC, SB, 5sp, 3. 54, 16cm2 housing, maxed fuel, KN, Banks exh w/muffler, Horton fan clutch, Autometer liquid filled gauges, Accessory tach option, 100% Dyna-Mat, Borgeson steering shaft, Firestone air bags, Chrysler V-twin air comp, 2. 5" lift, Rancho Shocks, Alcoa LTS wheels, BFG 255/85/R16 MTs (33. 3")

[This message has been edited by Stab (edited 01-17-2001). ]

 

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The metal will vary in temperature due to ambient temperature... . Alaska or Texas? I would guess the Alaskan's "metal" temp would be lower. Where does one find the oil temp. sending unit!


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9535hundred

[This message has been edited by Statland (edited 01-17-2001). ]