draft cross

Hey, I am a new owner of an 03, 3500 dually with a cummins. My buddy said I was lugging it unless I keep it over 2200 rpm. It has a 6 sp. What are the facts about the engines power band. This is my first diesel and I will never own anything but a cummins. Also what rpms are the most efficient for fuel milage. Thank David

wannadiesel

You are lugging it if the engine cannot accelerate easily. Lugging is load dependent. If you are in 5th going up a hill at 35 mph empty, you are not lugging. Doing the same thing with a 10,000 pound trailer behind the truck is lugging.

ramdez

Makes sense cuz my auto tranny is crusing unloaded at about 1800-1900rpms (60mph) roughly. HeH i have little choice, try telling that one to the trooper. "I was going 80 because I didn't want to lug my motor...honestly ossifer.

TexasCTD

If im not pulling a load, mine will shift into 4th about 50 to 55 mph at like 1500 rpms. Doesn't feel or sound like it is hurting anything.

danram11

Does you're buddy have any experince with diesels?

Jeff in TD

When I got mine, I e-mailed Cummins with a question about proper RPM operating range. I got a pre-canned, but very nice reply which I'll just paste in....

In summary, they do not recommend running the engine with load below 1600 rpm, or up a hill in a gear so high that the rig won't accelerate when floored...

Anyhow, here is what Cummins Powermaster had to say:


In the Dodge application, the rpm of the advertised or maximum rated power of the engine is 2500 rpm (prior to 1996 models), 2600 for 1996 and newer models with 12-valve manual transmission and 2700 rpm for 24-valve. Peak torque is reached at 1600 rpm on all models. The Maximum Full-Load Governed Speed is 2800 rpm for 12 valve and 3200 for the 24-valve. The Maximum No-Load Governed Speed is 2950-to-3300 rpm (3500 for 24-valve).

Therefore, your normal operating range for the engine is between 1600 (peak torque) and rated rpm (2500-to-2700, depending on your model). These engines should not exceed 2800 or 3200 rpm downhill (depending on model year), under load, since that is the governed speed of the engine. At no load (i.e., if you were to push the accelerator to the floor and hold it, sitting still in neutral), the no-load governed rpm is about 10 percent over the full-load governed rpm.

The engine is designed for maximum torque or twisting power at lower RPM (1600 rpm), for hard pulls on long grades. The torque curve of the engine is nearly flat from peak torque (1600 rpm) to rated power (2500-to-2700 rpm), however, torque does drop off slightly near the rated power rpm. Typically, the 'sweet spot' rpm for cruising would be about midway between peak torque and rated engine rpm, however, any rpm between peak torque (1600 rpm) and rated speed is fine and will not harm the engine. Overspeeding above rated speed and lugging the engine under load below peak torque is not recommended.

Also we mention that on downhill operation, the weight of the truck and any load you have on it, or towing, will cause the rpm to exceed governed rpm. Even though the engine is governed while under power, the load can push the engine beyond its rated speed. We would not recommend going too much over the no-load governed rpm or you could cause valve/piston contact, which can cause major engine damage.

Any rpm between peak torque (1600) and full-load governed rpm is acceptable and will not harm the engine. However, if you are concerned about fuel mileage and long engine life, then the lower rpm is recommended. At higher rpm's, the engine uses more fuel and all internal components turn faster and wear out quicker, which will shorten the life of your engine. There is less horsepower and torque at maximum rpm and the only reason to run the engine at maximum rpm would be for higher road speeds.

For the best fuel mileage, Cummins engines should be operated between peak torque and rated speed. Do not lug the engine when running in this RPM range. What is "lugging"? Lugging the engine is when, at cruising speed, the engine is accelerated and it will not increase the vehicle speed. Also, lugging is operating the engine, under full load, below peak torque rpm.

We do not have information about shifting into or out of overdrive in the Dodge application, since Dodge designs and supplies the transmissions for their products.

If your engine is still within the Dodge warranty period or you need information about the Dodge Ram truck, please feel free to use the Dodge dealer locator or contact Dodge: (http://www.4adodge.com/frameset_main.html?dealers/index) on the Dodge website (http://www.4adodge.com/).

We thank you for your interest in Cummins products. Please let us know if you need assistance in locating the nearest Cummins-authorized Dealer or Distributor Service Provider. For assistance in locating a Service Provider, feel free to use Cummins North America Dealer Locator, which can be found on Cummins website:
http://www.cummins.com/service_locator/index.cfm

Please let us know if you have other questions and if away from your computer or have a time-critical request that needs more urgent attention, feel free to call us toll-free (from North America) at 1-800-DIESELS (343-7357). Customers may also call Cummins switchboard 1-812-377-5000 (worldwide toll call) and ask for the "800-DIESELS Call Center" for assistance.

Email direct: powermaster@cummins.com

siotwo

Nice reply, and good information for us newb's

Texcowboy9

When driving in the city, I keep my Tow/Haul on if I am going 45 mph or under, mostly to save the transmission from shifting so much, plus that keeps it between the 1600 and 1900 rpm.

nickleinonen

i'll run in 3 & 4 from about 1000rpm and up, 5th i won't usually go below 1200rpm, 6th i don't like going below 1500rpm... i've seen about 3800rpm downshifting though...