RPM's - Diesel Forum

kfjensen · 04-30-2006, 02:53 AM

Hey guys,

Was hauling some horses earlier and was thinking about what the tyical RPM range to run at when pulling a grade. I have this 94, 4:10's, around 10k i was pulling, 7% grade, I was at about 2500rpm or so, maybe a little higher doing 55+, that about right, or is that turning the motor to fast? I know fuel consumption sucks at that but I was pulling against an 04 cummins of my buddies and wanted to see how it did.

Believer45 · 04-30-2006, 07:40 AM

The biggest consideration is if you are lugging the engine. Good test is if you can accelerate (not a fast increase in power but the ability to increase your speed at all) in the gear you are in. If not you probably need to drop a gear.

Another good telltale is exhaust temperature if you have the gauge. If the temperature is rising it would probably be a benefit to downshift one gear as well. With the modifications you have listed it would bed a good idea to keep track of exhaust temps to keep from overheating things if you pull on a regular basis.

Dave / Believer45

kfjensen · 04-30-2006, 01:16 PM

[ QUOTE ]
The biggest consideration is if you are lugging the engine. Good test is if you can accelerate (not a fast increase in power but the ability to increase your speed at all) in the gear you are in. If not you probably need to drop a gear.

Another good telltale is exhaust temperature if you have the gauge. If the temperature is rising it would probably be a benefit to downshift one gear as well. With the modifications you have listed it would bed a good idea to keep track of exhaust temps to keep from overheating things if you pull on a regular basis.

Dave / Believer45

[/ QUOTE ]

Thanks Believer, yeah I was able to increase in speed if I wanted to, but I didnt want to burn THAT much fuel, as for the guages I am going to order pyro/boost/water temp in about a week or so, thanks.

CascarFan · 05-01-2006, 12:29 AM

When pulling hard, I don't let mine drop below 1900 and when I downshift it'll bring her back up around 22-2300 or so.

I notice your tranny & gears are the same as mine, not sure about tire size, I have 215/85R16's. At 22-2300 in 5th, I think I'm around 60 mph. About 2700 gets me up around 75, that's about as high as I take it. I really don't like running it that high, I try to keep it down below 2400, but on the long runs I usually end up in the 2700 rpm range.

I'm getting about 8.5 mpg with a GCW of probably around 20-22,000

SmokeyWren · 05-01-2006, 08:46 AM

[ QUOTE ]
... around 10k i was pulling, 7% grade, I was at about 2500rpm or so, maybe a little higher doing 55+, that about right, or is that turning the motor to fast?

[/ QUOTE ]

That's about right.

Diesel engines are designed to run right up against the red line all day long. Of course, they will gulp down the fuel when they run wide open, so I like to back off a few hundred RPM. Usually when mountain climbing, I put it in direct drive and cruise at about 2,400 to 2,500 RPM to the top of the pass.

But yeah, you need a pyrometer to be sure you aren't working the engine too hard. On mine, I usually climb mountains at 1,100º to 1,200º exhaust gas temp (EGT), which usually works out to about 55 to 60 MPH on 7 percent grades when grossing 17,500 pounds, or a bit less EGT when grossing 16,000 pounds.

Allister73 · 05-02-2006, 10:47 PM

Fellas, after reading this thread, I called Dale at Tymar, and his thought were so. He said that the Marine Strokers are designed to run at 2655 all the time, so that in his opinion was the max that they should be run all day long. Running higher than that for short periods should be fine, but that diesels are not designed to be high rpm engines. Just thought I would share Dales advice on this thread. Do not know if that helps or not, just what he said and probobly what I will follow for my personnel towing limits.

kfjensen · 05-04-2006, 10:18 PM

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Do not know if that helps or not

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Yeah it does, thank you.

Coolinthem · 05-07-2006, 11:40 PM

Pulling heavy, 23500 in the mountains I will go into the hills at 2800 rpms or so and down shift around 2200 to keep the torque and horepower higher. Works good for me. 130000 miles and still on the original stock trans and engine uses no oil between changes.