Rpm

[Frenchman]

Can some one explain the to me why my engine is turning 1250RPM @ 55MPH.

At 70MPH its Turning 1650RPM? Is that lugging the engine?

I have 2450 miles on it.

 

[odinjunior]

Can some one explain the to me why my engine is turning 1250RPM @ 55MPH.

At 70MPH its Turning 1650RPM? Is that lugging the engine?

I have 2450 miles on it.

Are you talking about the truck in your Sig?

 

[JKeith]

If you want too tow at 55mph with those tall rear gears, push the button and lock out overdrive.

 

[04blackcherry]

Speed versus RPM calculator
Try this. It will verify what you're seeing. You will need to know a couple things about your gearing and rolling diameter of the tires. It is accurate. I used it to get a good reading on the change in speed when I went to 35's. The speedo on my wife's GPS confirmed my calculations.

 

[Frenchman]

No, I have 2009 QC Long bed.



I Have been real busy these past few weeks and didn't have the time to check the replys. I did not put enough info into the post.

I have 342 diff and 17/65 tires. I really need to know the torque @ RPM as well as CPL location. If I can find the CPL number then I can look it up. As well as the sweet spot for fuel economy.

Just where can one go for that type of info??



Frenchman

 

[HBarlow]

Your truck is geared wrong for any possible application other than cruising unloaded at 80 mph. Someone ordered it with 3. 42 gearing. A very bad choice.

Your engine is producing peak torque at 1500 rpm so no, that's not lugging if you run it at 1500 rpm or higher.

Peak efficiency occurs at around 2150 rpm according to Cummins charts and articles I have read in TDR magazine.

You'll have to downshift with the toggle and run in lower gears to tow.

I don't know why Dodge offers those trucks with 3. 42 gears.

 

[FDrake]

3. 42 gears!! Wow, that means it is made to cruise. But for towing you'll need to run in a lower gear. At 65MPH my truck is at about 1950RPM. Anywhere around 2000RPM is where you want to be for the best all around towing/driving mileage and power. I'd change out the gears if it were me. My 1997 had 3. 54 gearing and that was too tall to tow effectively. It was great on the highway running empty though.
Frank

 

[Frenchman]

Yea I know that the 342's is a bummer. I was tired when I bought the truck and just figured it had 373's. I may ask the dealer if he could fix that problem under warranty!



As of today (24 Apr 09) the mileage is 3260. Boy I sure need to get busy on that, maybe in may I can get off to GA, then Fla and back in two weeks.



Frenchman