Cummins 400 pyro and boost gage installation with photos

I installed AutoMeter pyro and boost gages in my M915A1 tractor. AutoMeter because I come from a racing backround and always liked their gages. I mounted the gages on an aluminum block so that I could prewire and plumb the gages out of the truck. I used the existing dash mounting screws to hold the gage block. One problem is that you sit low in race cars, but sit very high in a truck, so there was not enough upward angle on the gages with the stock mounting brackets. I modified these to allow more up angle.

Nice looking setup. Be sure to post a pic or two with them in the truck.

I enlarged the wiring hole for the fan wires in the dash so that I could run the thermocouple wire, the boost tubing, and the electrical wiring down into the dash. It is very tight getting access to the underside of the dash. I had to work thru the glove box and remove the circuit breaker panels to get access. Even then I could barely get the wiring in place. I don't understand how such a big vehicle can have so little room to work. When I drilled the exhaust manifold for the pre turbine pyro, I very carefully measured so that I drilled exactly in the center of the manifold. Didn't realize that Cummins put a divider wall in the middle of the manifold. I guess that was the practice hole. I moved over and redrilled it. I tapped both holes with an 1/8 NPT and plugged the practice hole. The other hole got the fitting that holds the thermocouple. I picked up the boost pressure on the fitting in the aftercooler manifold. This fitting sends pressure to the IP to limit fuel until boost comes up(anti-smoke deal). I replaced the SAE tee with an NPT tee with an SAE fitting for the original boost line and then used the boost gage tubing fitting in the other side of the tee. Feed the boost line and the thermocouple thru the firewall with an existing grommeted hole.

I powered the gages up with a wire to the "on" terminal of the ignition switch. For the gage lights, there are some terminated pigtales for dash gage lighting. I opened up the gage swing down panel and found some of these pigtales and spliced the AutoMeter gage lights into them. It works great-the gages go live when you turn on the ignition and the AutoMeter gage lights go live when you turn on the headlights and dim with the headlight dimmer switch. Makes a really nice installation. Haven't got the truck out with a load yet, but just crusing down the highway at 65 MPH bobtailing runs about 3 PSI boost at 650 degrees F. Idles at about 300 degrees and 0 boost.

Sounds like a done deal. Glad to hear it worked out. From that picture there sure isn't much room to work.

Looks great! Please post numbers when you get a chance to pull a load. I plan to get around to this on mine someday. I bet the boost pressure with a good load will surprise you. Thanks for the great pics also.

Looks like a solid install. I like the spot you chose for the gauges. This is something I would like to do to my M916.

How do you prevent the chips from drilling the hole from ending up inside the turbo? Is that a concern?

Not a concern about the chips. They are, if any, on the hot side and will just blow out. If you really are worried you could drill the hole with the engine running.

Thanks for the compliments. I drilled a little, then blew away the chips, then drilled again,etc. This meant when I broke thru there were very few chips. The chips are so small that I think they just go into the turbo housing and as soon as you start the engine, they get blown out the exhaust. The gage location worked out really well. They are very easy to read. If anyone is interested, I can post a drawing of the gage mounting block.

Is that an X Navy truck?

How did you get 12v to the pyro? I used a voltage reducer when I installed my Autometer pyro in my deuce ( http://www.steelsoldiers.com/deuce/46674-autometer-pyro.html?highlight=pyro ). For the lights I just wired the light for the pyro and boost in series.

In my m818 i used the type of pyro probe that make it own power so the gusge doesn't need any. then i installed a 24v bulb for the light. but i would imagine he got the power from some of the trailer side with the civy 12volt power. but could not have.

great install! good idea.

Autocar said:

Thanks for the compliments. I drilled a little, then blew away the chips, then drilled again,etc. This meant when I broke thru there were very few chips. The chips are so small that I think they just go into the turbo housing and as soon as you start the engine, they get blown out the exhaust. The gage location worked out really well. They are very easy to read. If anyone is interested, I can post a drawing of the gage mounting block.

Click to expand...

When I drilled the exhaust manifold on my deuce for the pyrometer thermocouple, I did it running. The theory is that what few fine chips go into the manifold get blown through the turbo and out the exhaust.

The turbo still works fine three years later. I'd say it worked fine.

The M915A1 uses mostly 12 volts-only uses 24 for starting and military trailers, so it was an easy hook up. If you have a 24 volt system, the best thing to do is to use a voltage converter as mentioned in other threads. You can also make one using a low cost voltage regulator circuit. I could sketch up a circuit if you needed. My trucks and trailer are army out of French Camp GL.