Pyrometer, EGT and Boost Gauge installation

In 1994-1998 Ram Diesel Pickups

Pyrometer Placement


The manifold is the best place for the pyrometer, because it reads actual temperature of the parts that can be damaged.  The elbow will read about 10 degrees cooler per psi of boost, but this is a rule of thumb and temperature spikes in the manifold can be greater than this.  Check the probe tip occasionally to be sure it isn't eroding from the heat.

The two minor advantages to the elbow are:
(a) it will tell you a little more for shutdown because it will tell that the exhaust housing of the turbo is also cool;
(b) the elbow is easy to remove and drill and tap.  If you tap the manifold, either remove the turbo or use a magnet to be sure you remove the chips from the drilling and tapping.


Pyrometer Installation Notes

Subject:     [RAM] pyrometer installation
Date:         Sun, 23 Nov 1997 15:58:50 -0500 (EST)
To:            RTML

To install the exhaust pyrometer in the Cummins exhaust manifold, here are some tips:

Remove the four 15mm nuts and pull the turbo away from the studs, and move aside so its mounting surface rests on the ends of the studs. Be careful not to gouge the surface with the hardened studs. Feeling in the exhaust port of the manifold, you will note there is a center divider, and that the manifold is thick enough to drill and tap about 3/4" away from the turbo mounting surface, and more or less centered in one of the two exit ports. Install the probe so it is not over about 1/2 the way into the port, after tapping the hole deep enough to catch most of the threads on the tip holder, without it extending into the exhaust port itself. With a rag or tape to protect the turbo inlet, drill and tap the manifold, and remove all chips. Using a new mounting gasket, Cummins 3901356 (under $2), replace the turbo with never seize on the studs.

With the 1/4" NPT used by some probes, people get away with removing the chips by a small magnet. There is not enough space usually to get a pencil magnet through the 1/8 NPT hole other probes use. Repeatedly clean out the manifold port until the magnet comes out clean. I prefer to take the time to remove the turbo. There is little clearance between the vanes and the housing inside the turbo, and chips could cause trouble.

The manifold is the most informative place for the probe. It tells you about instantaneous temperature changes and the maximum temperature encountered. If the probe is in the exhaust elbow, or worse yet, downstream in the pipe, you have to infer the actual, maximum temperature by adjusting the reading by 10 degrees times the pounds of boost, as a rule of thumb. 1000 degrees times 20 pounds boost equals 1200 degrees inferred to be in the exhaust manifold, for example.

However, many probes are relatively cheap and do not hold up very well to high temperatures. Over time, they can erode and a part can drop off into the exhaust stream. Not good if it gets to the turbo, so check the probe tip occasionally. Autometer probes are expensive but very durable (all are nominally type K thermocouples). BTW, don't shorten or extend the lead wires as the gauge is calibrated for the resistance of the wire as supplied.

I hope this answers the questions on moving the probe from the elbow to the manifold. I think most of the exhaust brakes also have a cast-in provision for the probe in their elbows, also, if you decide not to reinstall the probe in the manifold.


Subject: gauge installation
Date: Mon, 27 Jan 1997 10:01:11 -0800
From: "William H. Cole" <
To: cummins

I celebrated Superbowl weekend by installing a boost gauge and pyrometer. Who wants to watch others live/play, when you can enjoy the Ram all weekend? I selected Autometer 3.625" gauges, Pro-Comp series pyrometer and Sport-comp boost, because of my good experiences with them in race cars, etc. They do cost more, however, even from Summit Racing in Ohio, which has pretty good prices. At least I can see them even though they are mounted near the floor (kind of like putting your watch on your ankle, but Dodge doesn't leave much space for them anywhere else).

Cummins thoughtfully provides a 1/8" NPT fitting with 7/16" steel hex plug on the side of the intake manifold, facing the Bosch P7100 pump. It is about 5-6" behind the pump's fuel return banjo fitting. A 1/8" NPT street elbow, NPT to tube adapter, and plastic tubing complete the "sender" part. Easy, except for working around the air intake.

I mounted the pyrometer probe in the exhaust manifold, about 1/2" inboard from the 5/8" thick turbo mounting flange part of the manifold. The exhaust manifold does have a center divider, with two oval-shaped ports that match those in the turbo. To clear this divider, I drilled a 21/64" hole about 1.125" forward of the rear turbo-mount stud, which is 2.25" to the rear of the engine from the front turbo-mounting stud. The manifold was plenty thick here--I got about 7-8 threads, or almost all that are available in 1/8 NPT fittings. I cut the threads deep enough so the fitting is almost flush inside, and that left no more than one thread of the fitting showing outside. AFter drilling, I deburred the inside with a small half-round file from the outside of the hole. The chips were not really powder, and there were a few spiral stringers too. I tapped the hole using cutting oil, and got lots of chips in the manifold that way. Drilling and tapping were "easy" using new, good quality drill bit and tap.

Before drilling, I removed the turbo. With the exhaust pipe and oil drain line still attached, there is just enough flex to pull it off the studs and let it rest against the studs with the turbo holes slightly misaligned from their studs. I used rags, but tape would work to protect the turbo inlet. A new turbo mount gasket is only a couple $ from Cummins. I used Never-Seez on the 1/8 NPT threads, turbo studs, and mount surfaces (very thin film here). I tightened the stud nuts in a cross pattern to compress the steel shim gasket uniformly.

Biggest hassle by far was inside the truck. I tapped into the orange 22 gauge wire leading to the radio for dim-able lighting for the gauges. I used the power window hot (tan) lead near the connector behind the knee bolster for a hot lead for the pyrometer. I mounted the gauges in front of, and above, the air bag module by fabricating a bracket that holds the gauge panel and bolts to the base bracket of the air bag module. The four bolts holding the module to the floor have a Loctite type goop on them and they come out with difficulty. I made the bracket to offset the gauges to the left so the 4WD lever and 5-speed shifter would not block them, and to angle them upward to line-of-sight. Now I have to cut a piece of carpet or Naugahyde to cover the module and bracket, so the yuppies won't be grossed out by the sight of functional but un-trendy looking parts inside the truck.

Joe Donnelly

Subject:   Re: [RAM] aftermarket gauges
Date:       Fri, 26 Dec 1997 18:12:35 EST
From:      Drdonnelly <>
To:          RTML

there are two places to mount the pyrometer probe: exhaust manifold, and elbow after the turbo. The former gives the higher readings, and directly tells you if a problem develops. More informative, but if the probe tip breaks off, the turbo may get damaged. I use an Autometer and while expensive, I think it will be much more likely to last. If you go for the elbow, there is no danger to the turbo, but the temp readings have to be extrapolated so you know what the engine, manifold, and turbo were exposed to. The rule of thumb is 10 degrees per psi boost. At 20 lb, 1000 degrees in the elbow is 1200 in the manifold, more or less. If you go for the manifold installation, it is best to take off the turbo so no chips can get into the turbo. There is a divider in the manifold, so the probe must go in front of or behind the center, and about 3/4" from the turbo mounting flange. The manifold is thick enough there. As for restriction, either place seems OK, Be sure to use good stainless steel fittings and anti seeze paste on the threads. The turbo to manifold gasket is only a couple $ from Cummins.

Subject:   Re: [RAM] aftermarket gauges
Date:       Sat, 27 Dec 1997 21:10:02 EST
From:      Drdonnelly <>
To:          RTML

This response regards the installation of a pyrometer onto the Ram Cummins engine. I just drilled and tapped the boss in the elbow after the turbo for 1/8 NPT. No problem. I used Sears yellow drill bits in 3/16 and 5/16, going up in steps so the drilling would be easier. I did not have an R drill (0.339") so I went up to 21/64 and then used a carbide burr to chamfer the inlet a little to help start the tap. It is hard, tough cast iron, but drills and taps smoothly. Of course, you should remove the elbow first so you can get straight onto the boss. When reinstalling it, be careful. You want to align it to the exhaust pipe well so the pipe is straight on it, and the two bolts are cinched down the same number of threads. At the same time, you want it centered onto the turbo outlet. If you don't move it around, the elbow will end up lower than the centerline of the turbo, and there will be a "wall" left for the gases to hit as they exit the turbo. Use anti seize paste on all threads and wear surfaces for best results.


ISB Boost Gauge Plumbing
> I'm looking to putting a two gauge pod in my 99 ISB but can't figure
> out where to plumb the boost pressure from.

Subject:   Re: Boost gauge hookup
Date:       Wed, 24 Mar 1999 21:03:15 -0600
From:      "S. L. Butler" <>
To:          Turbo deisel mailing list

There is no 1/8 plug in the intake in the 24V engine for a boost gauge. There is a 3/4 plug with a 3/8 square indent right behind the fuel filter in the side of the intake manifold.  Take it out, put in a 3/4 by 1/8 reducer and you then have one.  Hard as the dickens to get to unless you remove the fuel filter.

Subject:    Re: Boost gauge hookup
Date:        Wed, 24 Mar 1999 21:41:04 -0700
From:       Larry Olsen <>
To:           turbodiesel
An ISB truck doesn't have a 1/8" plug.  It has a 3/4" pipe plug which is on the left side of the intake manifold, just behind the fuel filter.  Be careful because there are two 3/4" pipe plugs there with the manifold pressure sensor between them.  The plug you want is the one closest to the front.  The rear one is a coolant passage and you will have a mess if you remove it.

Larry Olsen

Subject:  Re: Boost gauge hookup
Date:      Thu, 25 Mar 1999 00:10:16 EST

Best I know there isn't a 1/8" fitting on the 98 ISB, probably same on 99.  I drilled and tapped the intake tube just below the oil dip stick.  Works fine.


Subject:   Re: Boost gauge hookup
Date:       Wed, 24 Mar 1999 22:44:19 -0700
From:      "R. J. Follmer" <>
To:          turbodiesel

Take out the 3/4" plug, driver side, between fuel filter and firewall, put in 3/4" plug tapped for 1/4" pipe, hook up guage.  no fuss, no muss.

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