Destroying your turbo with EGT probe?!

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A fella at the Cummins distributor was telling me that having my pyro probe preturbo is a bad idea. What is the life of the probe? Should we be changing these every two years or so??
He said on OTR rigs they will switch them to post turbo if they find them preturbo.
Kind of scary thinking about a piece of metal entering the turbo!!:0

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97 Red, slide in camper, Trails West 2 horse slant trailer, K&N air, 255. 85. 16 Big O XT, Banks Stinger Plus(minus exhaust), 4" BD exhaust (minus the muffler), A pillar gauge mounts, after market overload springs

 

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While I would never question the folks at Cummins on a considered opinion, I'm wondering how a probe that is just about the diameter of a 1/4" drill bit would ever break off. I've heard that before. I've also seen posts that claim that Cummins uses pyro probes for their R&D and they are all mounted pre-turbo. Additionally, they also stated that they have never encountered an instance of a probe degenerating to the point that it broke and got sent through the turbo. If you look around this board, and even on the Phord board, you'll probably notice that 9 out of 10 people who install a EGT install it pre-turbo and have not encountered any problems.

John

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1999 Dodge Ram 3500 Quad Cab 5 spd; 4:10 LSD rear; Mag-Hytec diff. cover; Speedliner spray in bed-liner; Amsoil foam air filter; Smittybuilt step rails; Manual transmission filter kit; Geno's EZ Drain oil pan plug; US Gear EGT and Boost gauges on a twin A pillar mount. Towing a 31 ft. NOMAD single slideout TT.
Rammin' and Runnin' the roads


[This message has been edited by John Berger (edited 10-15-1999). ]

 

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Well, if its not pre-turbo and is post-turbo, what if it breaks and goes "valve'ng" around in the intake???? Not that we expect these things to "fall apart". The heat they have to handle in the post install has to be built in to the unit range, soooo.....

If I do go with any guages I'll probably go post to have a better idea whats goin on and how long to idle before shut-down.

\\BF//

[This message has been edited by Ben Stair (edited 10-16-1999). ]

 

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Ben:

If you install a pyro post-turbo it has to be in the exhaust elbow. With the down angle on that thing and the exhaust pressure I don't know how it would be possible for anything to go back up into the turbo and get to the intake side. Could you please explain/clarify that statement. I installed pre-turbo so it doesn't affect me, but I am curious. Thanks #ad


John

 

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If the probe is post-turbo and let's go it's going to go through the cat and the muffler not into the intake. I don't know if it would be able to make the trip all the way out the tail pipe, there may be a restriction in the cat or muffler that won't let it pass. As far as having a better idea of what's going on you're better off being pre-turbo as far as that goes. There is some lag if it's mounted post turbo - you also have to calculate a temperature drop based on the amount of boost. I've heard it's either 100 degrees per inch of boost or 100 degrees per 3 inches of boost - not sure which one is correct. Mines mounted pre-turbo so I don't have to worry about it.

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-Steve St. Laurent
'98 Quad Cab Long Bed (CMNSPWR), 4x4, ISB, 5sp, 4. 10 LSD, Prime-loc remote fuel filter,
boost & pyro gauges, TST Powermax, Permatech spray in liner, Grizzly stainless nerf bars,
BFG 285/75R16 AT KO's
http://my. voyager.net/stevest

 

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Take a look through the CDW archives as I had posed the question about EGT probe position due to erosion. The performance shop here in Calgary also said that the risk of putting the probe pre-turbo (in exh manifold) was too great as the erosion may not happen for a couple of years, but will put small metal particles through the turbine blades #ad
. This could be very costly. Just my $0. 02 On an aside, the pre-turbo probe does not help you when you are cooling the turbo down after a long haul. The exhaust coming out of the turbo on cool down will be higher than the stuff coming out of the engine. This is the reason that all the big truck engines have them down-stream.


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(Lil' Mack)-89 D250 2WD 5Spd 3. 55 Reg Cab. K&N, 3. 5" Exst, E&M Custom seats. Bosch H4 Lites

 

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John, in reply to your ?, I wasn't thinking too clearly when I said "valving". I should have let the brain engage before the fingers. BUT, I'l stick with the post install when I do it, even if I dont calculate the temp EXACTLY after a while you get the "feel" for the shut-down time and I plan to tow later sooo... I'm more worried now about my "lack" of warm-up time in the morn - use the heater and double key it before starting. Idle it out of the park and about the first 1/4 mi, then start the driving. Dont let the rpm get above 1k for about 1/2 mile (temps in the hi 30's lo 40's).

\\BF//

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y2k SLT = Superior; Like Truck! 2500QC/SWB/5sp/3. 54LSD/SLT/Driftwood/Ultimate bed spray/camper @ tow pkgs/fogs(drl's)/truck trunk/AmsOil air/dust guards/flasher hmbl/hr mtr/storage/tinting/CB/fuzzbustr/brake ctrl/etc.

 

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I was in Cummins Southern Plains in OK. City buying some filters and asked the guy about EGT probe. He was adament about putting it behind the turbo. I don't have guages yet but I think I'm gonna put it downstream. It will give you a cooler reading but at least you have an idea of how hard your pushing it. Lou

 

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I was a Cummins engineer for 30 + years, a turbo engineer there for 12 years, and was responsible for setting up and running thousands of tests. We always placed pyro probes before the turbo, nearly always ran the engines at higher power conditions than they were sold to the public and never saw a pyro probe fail and go through the turbo unless something else upstream like a piston or valve failed and hit it on its way to the turbo. Cummins engineering recommended that pyros be installed before the turbo.

Even then most mechanics in the field didn't want to bother with drilling the iron castings, they preferred the clamp on the pipe thermocouples.

The turbo can stand much higher temperatures than the pistons and valves. We checked the turbine inlet temperature to have some idea when the piston was going to give up, not to protect the turbo.

By the way, we also installed probes at each exhaust ports on many of these tests, but the temperature was higher at the turbo inlet than at the port. We figured it was higher because we had the results from three cylinders rather than just one at the port. The probes at each port did lets us know that each injector was performing correctly. If a port was more than 50 F out of line, we'd pull that injector and work on it.