Freeway RPM's

[jlord]

I have my first CTD in the driveway tonight, details in signature. During my drive home from the dealer (120 miles away) I was wondering about the RPM's at highway speeds. At around 72 mph, I was at 2,000 rpm's, with 3K being redline. How much faster could I go for long periods of time without harming the engine? (3. 73 rear with stock tires)



By the way, I can't believe how powerful the HO CTD is!! Even in 6th gear, it was pulling the largest hills on the Mountain Parkway in Eastern KY like they weren't even there. According to the overhead console, I got 20. 9 mpg during the trip as well. I'll figure my next tank manually.

 

[MMeier]

It appears 3150 is all I can shake out of my truck which equates to 108 MPH , be making a run up north Friday and see if anything changed in the last 2500 miles And that is at 8400 lbs with no trailer. (mobile detail shop in back of truck)!!!

 

[EnLjones]

Enjoy your CTD! You have selected one of the best powerplants ever produced for use in a street vehicle. The way I understand it you can run this thing allllllllllll day long at any speed you desire as long as you are below the "Red line". Even that is pretty forgiving with the accidental straying into that zone. Your mileage probably isn't as good as what your computer has indicated... these things seem to run as much as 2-3 miles over actual mileage. Figure is be hand to be sure, but still concidering we are running approximately #7000 lbs of steel down the road at better than 70 miles an hour I guess 18 mpg isn't bad either!!

 

[Bill Stockard]

Diesel engines are designed to run at full load at governed speed for days, weeks, months or even years at a time. Unlike a gasoline engines, diesels can run at max load and "against the governor" for hours and hours.



The Cummins B series engine is used in many applications around the world where they run at governed speed and a constant load for weeks, months, and years at a time... one of the most versatile, durable diesel engines ever built.



About the only way you can "over-speed" a Cummins B engine is to shift down to a lower gear while traveling too fast.



Bill

 

[jlord]

So, now in my second day of ownership, I am wondering about shifting range for RPM's. The HO has a very different feel than my 318 manual did (obviously), and I'm not sure about the gears yet.



My inclination is to shift around 2000 rpm's, but since redline is 3,500, and everyone is telling me to wind it up, should I be shifting at higher RPM's? The way I'm shifting now, I'm going through all 6 gears in a matter of seconds. I'm usually going into 6th around 50mph.



Any of you guys with the 6 speed have a different feel?

 

[Prairie Dog]

jlord, You aint see nothin yet! Wait till you've got a couple K on her and she gets all loosened up. The throttle response will get dramatically better and you'll need even less throttle to climb those mountains. It actually gets more quiet too.

As far as RPM's, 2000 feels about rite to me too but these things are bullet proof. Don't be afraid to work it once it's a little broken in.



Scotty

 

[Ladders]

Just for reference,

when driving the HO 48RE yesterday, the 70mph rpm was 2k w/3. 73 rear. This was on a 4x4 LB which shouldnt make any difference. Did like the "tightness" of that auto, tho... .....





Da Diesel-less SOTSU!!

\\BF//

 

[Swayse]

Confused

I've got 3. 73 gears in my 5 speed SO, and if I put the truck where the speedo shows 70 it turns 2150 rpms. Is the OD gear different on the 5 speed than the 6 speed?

 

[Snow man]

jlord,shifting at 2000 is fine for babying around and trying to get good mileage. If you are towing heavy i would wind it up tighter on the upshifts,especially on hills,you dont want to lug or labor the engine below 1600 or so with a heavy load. Light loading is fine. I wouldnt worry about hurting the Cummins by overrevving it,its not going to happen,just let her warm up berfore you put a good sized load on her,and keep the oil/and all filters changed regularly,and run that truck. Ive found the trucks that get broken in the hardest seem to last the longest,and have the most power. Dont be afraid to run that truck when its new,just get her up to temp first and stretch its legs .

 

[Parshal]

I shift just before 2000 rpm until the temp gauge starts to move in my SO 5-speed. Once the needle move to about 145 - 150 I shift around 2500. I'll even run it in 4th at 2300 - 2400 to get the engine warm since my trip to work is less than 9 miles. On the interstate I run around 75 - 80 for 5 - 6 hours at a time which is around 2300 rpm. When towing, I run it up to redline and the truck doesn't lose a beat. I've run it up to 3400 a few times by accident and didn't notice anything adverse.



I discovered recently, as someone pointed out here, that shifting below 2000 all the time doesn't really affect my mileage. I ran it hard for one tank and it got one of the better tanks.



This is my first diesel (truck, that is) and it's really nice. Pulls hills in 5th gear like they're not there and wind is not a factor. I was following a guy back from a hunting trip a few weeks ago and his F-150 gasser was having trouble with a headwind. I didn't even know it was there until he said it and I still never felt it.

 

[jlord]

You're right, the rpms are closer to 2150 at 70mph. I'm still get used to this monster, can't seem to get rid of this permanent grin on my face.

 

[Fred Swanson]

jlord, if you think it's great now, wait till the bug bites, for more power. This motor is awesome.

Unloaded, there isn't any reason to rev past 2100 RPM. Unless you're in a hurry.

Loaded down, keep the RPM's up above 1600 or so. Not 5K, not 10K, stick 15K behind it, and watch it work. No gas truck is going to match it.

 

[jimnance]

Originally posted by Bill Stockard

Diesel engines are designed to run at full load at governed speed for days, weeks, months or even years at a time. Unlike a gasoline engines, diesels can run at max load and "against the governor" for hours and hours.



The Cummins B series engine is used in many applications around the world where they run at governed speed and a constant load for weeks, months, and years at a time... one of the most versatile, durable diesel engines ever built.



About the only way you can "over-speed" a Cummins B engine is to shift down to a lower gear while traveling too fast.



Bill

Most applications which require constant RPM are generally governed at an RPM somewhere between best torque and best HP. While the 5. 9 is a great engine, running it at 3200 RPM all day long is not good for the long term life of the engine. Also, economy and performance suffer since you are way beyond optimum RPM range (1700-2600 RPM).



I know several boat operators with the B engines. They never run them against the governor (2500 RPM). Mostly, they like to run them around 1900 RPM which, you guessed it, is near peak torque.



This engine is NOT designed to run at 3200 RPM's all day.

:-{}

 

[Greg Boardman-RIP]

Originally posted by Snow man

jlord,shifting at 2000 is fine for babying around and trying to get good mileage. If you are towing heavy i would wind it up tighter on the upshifts,especially on hills,you dont want to lug or labor the engine below 1600 or so with a heavy load. Light loading is fine. .

The new powerplant makes the most torque at 1400 rpm's. If you shift at 2200 you will drop into the best of the torque band and be fine. Pulling a hill I rev to 2500-3400 rpm's with no problems at all. But keep in mind it drives the same at 1400 rpm's.

 

[pstillo]

I got my 97 2500 CTD one week before Daytona bike week. I loaded one bike in the bed 4 bikes in a enclosed dual axle trailer. I ran red line 1400 miles just stopping for gas. I had call the CTD tech line they said break it in hard don't baby it. The truck had about 50 mile on it when i left. I never had a problem with the truck.

 

[Casey Balvert]

Originally posted by jlord

You're right, the rpms are closer to 2150 at 70mph. I'm still get used to this monster, can't seem to get rid of this permanent grin on my face.

After having owned this truck for five months now I am REALLY happy with it. My wife thinks it's her.



Casey

 

[jimnance]

Originally posted by Greg Boardman

The new powerplant makes the most torque at 1400 rpm's. If you shift at 2200 you will drop into the best of the torque band and be fine. Pulling a hill I rev to 2500-3400 rpm's with no problems at all. But keep in mind it drives the same at 1400 rpm's.

Greg, you have the Ege EZ which brings peak torque in a little sooner than stock. Looking at the Dyno results for the '01 H. O from the Edge site (I ASSUME the numbers for the '03 are similar) your truck will peak around 1600 RPM and stock will be about 1900 RPM.



http://www.edgeproductsinc.com/ez-eth-chart.html



I find that my stock '03 with a big load likes to pull the hills between 2,000 and 2,500 RPM. Below 2,000 it loses power quickly.

 

[Greg Boardman-RIP]

Jim,

You are right. I just checked and stock it pulls from a little higher in the R's. If you get the EZ you wont have the problem of loss of power under 2000 rpm's.

 

[Rosco]

My HO/48RE with 3. 73 gears is at 72 MPH at 2,000 RPM.



I also am impressed with how hard it pulls while cruising down the highway. I thought my SO/47RE was awesome when compared to my 5. 9 Magnum but the HO takes the cake. I can be going 70MPH and if I want to pass a car it's just a matter of changing lanes and that cars history. MY 5. 9 gasser used to dog until the pedal was near the floor then it would drop out of OD wind the RPM's up and even then it could barely drag it's sorry butt down the road. That pig even had 4. 10 gears.

 

[Fred Swanson]

jimnance, stock with a big load(14K) and hit a grade and it will load it down, and occasionally you might have to downshift into 5th. On flat roads, I can pull from 1500 to 2000 RPM from 2nd to 6th, and it doesn't even feel like the truck is working that hard.



Now with just the EZ, it pulls harder, and still feels effortless, and if I hit a grade, it holds 6th longer before needing to downshift. Again, this is only on a big grade.



Same thing with the EZ off and the DD2's, power is smooth and pulls very strong no matter what.



Haven't ru nboth while towing, I feel it would be too much for the turbo and EGT's. But I will be testing the combo out.