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Have a 1998 Safari Serengeti with a 1997 CAT 3126 rated at 300 hp (22K miles) which apparently is running/performing normally, with the exception of a sooty exhaust pipe and build up on the rear fender. Both the analog boost gauge and the scrolling electronic display are indicating 5 Psi manifold pressure at a 60 mph cruise and no more than 10 psi at full throttle (which I expect is low). What positive manifold pressures do other operators of this drivetrain experience?
v/r,
Taylor Hudson
1998 Safari Serengeti, CAT 3126, Allison 3060
acquired 2018

Hi Taylor,
My best suggestion for finding out the maximum boost pressure YOUR engine should be capable of, is to get your engine serial number, then call the Caterpillar RV Hotline (877-777-3126) and ask what the original test stand maximum boost pressure was for your engine. They should have it recorded, but it will be in inches/mercury. Don't bother asking them to convert that number to PSI, instead go to "www.onlineconversions.com", locate the page for pressures conversions, and convert your inches/mercury number to PSI.
Although such things as atmospheric temperature, pressure, engine rpm, road speed, etc. can all have minor effects on the maximum boost pressure, you engine should be able to produce maximum boost pressure reasonably close to what it originally produced on Caterpillar's test stand. If not, there is a problem.
The maximum boost pressure of 10PSI you mentioned sounds very low. A 300 HP 3126 should typically produce something in the range of 24 to 26 PSI. But again, its best to find out what your specific engine produced on its original test stand run and go from there.

Glenn Barney
1997 Safari Continental/CAT 3126

Glenn wrote: ↑Sun May 10, 2020 10:03 pm Hi Taylor,
My best suggestion for finding out the maximum boost pressure YOUR engine should be capable of, is to get your engine serial number, then call the Caterpillar RV Hotline (877-777-3126) and ask what the original test stand maximum boost pressure was for your engine. They should have it recorded, but it will be in inches/mercury. Don't bother asking them to convert that number to PSI, instead go to "www.onlineconversions.com", locate the page for pressures conversions, and convert your inches/mercury number to PSI.
Although such things as atmospheric temperature, pressure, engine rpm, road speed, etc. can all have minor effects on the maximum boost pressure, you engine should be able to produce maximum boost pressure reasonably close to what it originally produced on Caterpillar's test stand. If not, there is a problem.
The maximum boost pressure of 10PSI you mentioned sounds very low. A 300 HP 3126 should typically produce something in the range of 24 to 26 PSI. But again, its best to find out what your specific engine produced on its original test stand run and go from there.
Glenn Barney
1997 Safari Continental/CAT 3126

Glenn
Excellent advice

Just off of the top of my head, my '98 Serengeti with a 3126 - boost maxes out somewhere around 25lbs.

fpengr@gmail.com wrote: ↑Sun May 10, 2020 5:26 pm Have a 1998 Safari Serengeti with a 1997 CAT 3126 rated at 300 hp (22K miles) which apparently is running/performing normally, with the exception of a sooty exhaust pipe and build up on the rear fender. Both the analog boost gauge and the scrolling electronic display are indicating 5 Psi manifold pressure at a 60 mph cruise and no more than 10 psi at full throttle (which I expect is low). What positive manifold pressures do other operators of this drivetrain experience?
v/r,
Taylor Hudson
1998 Safari Serengeti, CAT 3126, Allison 3060
acquired 2018

There are many things that can cause low boost and smoke. Some of the causes can be, clogged are intake and/or air filter (many safaris have the air intake box under the engine, which allows debris like a plastic back to get sucked in), exhaust manifold leaks (you will see a lot of soot in the leakage area), charge air cooler and/or the compressed side of the intake air leaking, turbo waste gate stuck partially open. Some of these can be easily checked by a visual inspection. I surprised that the engine smokes, as the electronics in the CAT engines are supposed to match the fuel output to the boost.

I would strongly suggest calling Dave Atherton, [ 605-997-0720 ]. He is a retired CAT master troubleshooter who really knows his stuff, and is always willing to help.

Agree, Dave is #1 when it comes to diagnosing diesel engine issues.

And, you can tell him I SAID SO.

Brett