Engine/Transmission (1998.5 - 2002) what's better for the motor? Hi RPM/Low temp vs Low RPM/higher temp

[PCarbonaro]

Guys, this has annoyed me for some time. At about 50 mph, I'm probably at 2000 rpm (I'm doing this from memory, so these numbers may be a little off), and engine temps on flat ground/no towing can run 600 degrees (again, just estimating numbers from memory).



The engine is not screaming a 2000 rpm, but shifting into 6th gear gives me maybe 1300 rpm, and the engine seems happier (at least to my ear). However, engine temp reads maybe 900.



So, is 2000 rpms and 600 degrees better for engine life, or 1300 rpms and 900 degrees? In racing, the saying is that rpm kills motors. I realize that 1300 vs 2000 isn't much, but I just want to shift into 6th when I see the engine at 2000 (mind you, I often shift at 2300 or more when going through the gears from a stop).

 

[Mad Bomber]

The power band is between 1800 and 2300 run it the all the time. 1300 is lugginmg the moter

 

[PCarbonaro]

By the feel of my pants, I know that 1000 rpm or less is definitely lugging, it just seems that maintaining 2000 rpm for extended periods (like driving for an hour for example) is making the engine scream a little. But you say this is fine? I believe you, it's just that my ears tell me, "downshift!"

 

[RustyJC]

With 4. 10 gearing, 70 MPH in 6th = 2350 RPM. I've run there (and higher) towing a 5th wheel for days on end. No problems at all - no oil consumption, etc.



Rusty

 

[FDNYMOPARGUY]

I have the same set up as you, but with a transmission temp guage. When towing in 6th the transmission temp rises up to 30 degrees more than in fifth. So more than just the engine is affected by low rpm cruising. Remember, this engine will operate just fine for extended periods up to its peak hp rpm of 2700.

 

[RJPotts]

When I'm in 5th at 50mph I'm turning around 2100-2200 rpm and I will usually keep it in 5th up to around 55 mph or 2500 rpm, It is my understanding that if you're cruising along not accelerating and unloaded if you are around 1500-1800 you're not "lugging" it until you try to accelerate hard then you feel it lugging (lots of vibration and great exhaust noises). I will typically shift to 5th around 35 mph if I'm cruising along and that leaves me at around 1500 rpm and everything feels fine and the gauges all ready in the green.

All in all though, I'd say keep it around 2000-2200 cruising unless you're on the highway.

-R. J.

 

[Donn]

Guys, this has annoyed me for some time. At about 50 mph, I'm probably at 2000 rpm (I'm doing this from memory, so these numbers may be a little off), and engine temps on flat ground/no towing can run 600 degrees (again, just estimating numbers from memory).



The engine is not screaming a 2000 rpm, but shifting into 6th gear gives me maybe 1300 rpm, and the engine seems happier (at least to my ear). However, engine temp reads maybe 900.



So, is 2000 rpms and 600 degrees better for engine life, or 1300 rpms and 900 degrees? In racing, the saying is that rpm kills motors. I realize that 1300 vs 2000 isn't much, but I just want to shift into 6th when I see the engine at 2000 (mind you, I often shift at 2300 or more when going through the gears from a stop).

I hope the engine temp your are talking about it the egt not the engine, My engine temp never gets over 208* F

 

[Hohn]

"Lugging" is entirely dependent upon engine load. Heck, you can pull 3rd from 1K rpm empty in most cases.



I'd keep RPM over 1500 for a steady cruise in any of the upper gears. Towing, you want it even higher-- probably 1800rpm minimum.



You are more likely to hurt these engines from too low an rpm than from too HIGH an rpm.



JLH

 

[DHayden]

What Hohn said. I try to keep it above 1500rpm, sometimes I will fall down to 1100 or 1200 if I'm putting around the city and not accelerating fast. I run at 2000 to 2200 on the highway and I usually shift around the 2k rpm mark, 2200rpm if I'm towing.



Don't know how long you've driven diesels but I had the same ear you do when I got my Cummins. It sounded like it was winding out to much, 1600-1700 sounded like the happy spot to my ear, I got used to it though.

 

[PCarbonaro]

Ok All, thanks for the wisdom. I feel much better about keeping the rpms up, and keeping EGTs (didn't mean to say engine temp) low. I do have a transmission temp gauge, so I'll see if that stays lower while towing now. Once again, I have underestimated the mighty Cummins.

 

[Rdunkin]

If you look at the VP44 torque sheets you will see the ECM makes it, make almost Max. torque from Approx. 1400 rpm. to govener cut out. The "sweet" spot is going to be 1900-2100 rpm for Max. efficiency and cooler EGT. I had a hard time adjusting to 2000rpm while driving in 5th. on county roads to the hiway. It has given me better milage doing so than lugging [1200-1400] in 6th.

Richard

 

[PCarbonaro]

If you look at the VP44 torque sheets you will see the ECM makes it, make almost Max. torque from Approx. 1400 rpm. to govener cut out. The "sweet" spot is going to be 1900-2100 rpm for Max. efficiency and cooler EGT. I had a hard time adjusting to 2000rpm while driving in 5th. on county roads to the hiway. It has given me better milage doing so than lugging [1200-1400] in 6th.

Richard

I think my 4" exhaust doesn't help me adjust to 2000 rpm. Just seems to loud, but I'll be thinking of that improved fuel efficiency, and I'll just turn up the tunes.

 

[OTRPU]

You can believe it or not, I didn't until I ran the loads and logged the miles, I get better mileage loaded running in 3rd @ 2,400 revs than I did running 4th @ 1,700 revs. But then I'm happy enough doin 60 while loaded. . . nobody else is.



Cheers,

Steve J

 

[MRose]

I spin my 12v engines at work @ 2500 and 3000rpm all day long, just where case/cummins designed them to be, all day long. Difference is in the pickup you hear just the motor. In my Case SPX3185 I hear the hydralics, not the motor, and that motor stays pegged at 3 grand 12hrs at a time, except when I refill. Have over 3400hrs on the engine with no oil consumption, I just remember that when I think I'm buzzing my pickup's engine at 2000rpm!