Extended RPM's

[Silver91Hatch]

Well after seeing the lugging RPM thread I am wondering what you guys recommend for extended rpms? My truck has 4.10's and a T-19 so it turns a good bit going down the highway. Is 2500 rpm to high for hours on hours of driving? If not what is, higher or lower??

 

[argve]

I have always flown by the rule of you can run them against the gov all day long as the gov should keep it from over reving...

In fact on the Cummins website in one of their memo's posted about their engines (which should really hold true to any engine) that lugging is considered abuse but running all day long against the gov is not.

 

[david85]

2500 is no problem at all. Great for hills and towing.

It will hurt your fuel bill though.

 

[Silver91Hatch]

I love the sound of a gasser turned up tight, but for some reason 2500 sounds like its going to fly apart in this truck. What is the govoner set at on these trucks, 3300??

2500 is great for pulling hills, but I am still not keeping up with traffic. I think I will keep upping the rev's until I feel safe.

 

[icanfixall]

A new test motor on the dyno can stay at red line almost forever. Thats how international tested these motors in this manner. Some run them on this site against the govener all day long going cross country.... I personally can't do that to my motor. Others are more trusting than me.

 

[Black dawg]

icanfixall, you would be really hauling the mail with your gearvendor on top of the e4od with the motor on the gov.If my math is correct youd be doing 158 mph

 

[icanfixall]

BlackDawg.... At 85mph I'm turning 1800 rpm.... I wonder at what speed the brick would take flight. It gets really quite at 85 to 90 mph... Only the wind noise is what I hear. Get it on a shaved freeway and its smooth as glass going down the road. My final drive ratio in double overdrive is 1.97.... Kinda tall but the motor pulls it easily..... Gotta get the rig on a dyno soon... Keep forgetting to do that.

 

[NapaBavarian]

My duallie did fine cruising on the governer at 88 miles an hour

 

[towcat]

BlackDawg.... At 85mph I'm turning 1800 rpm.... I wonder at what speed the brick would take flight. It gets really quite at 85 to 90 mph... Only the wind noise is what I hear. Get it on a shaved freeway and its smooth as glass going down the road. My final drive ratio in double overdrive is 1.97.... Kinda tall but the motor pulls it easily..... Gotta get the rig on a dyno soon... Keep forgetting to do that.

I run off the governor in top gear
as long as you throw a load on, it's good to go
It does get a little noisy from the wind noise above the century mark.

 

[david85]

Well I guess I should formally concede defeat to icanfixall. I suspected he had taller gearing but now this confirms it. Think my final drive works out to 2.18:1 so I am out.
For me, 1800 is still on the speedometer.
Empty, the truck holds steady on a 5% hill @ 60MPH which is the comfortable limit. Any lower and I need to downshift.
And yeah wind noise pretty much drowns everything else out, but the truck tracks surprisingly good after running off the speedometer.

 

[Diesel JD]

Pek torque is 1400-2200 and peak HP is rated at 3300. People here have roven burying these things against the governor won't kill them. The best fuel economy is in that 1400-2200 band, and probably anything below 1400 is lugging under certain conditions. To the OP I think you will need a turbo to really be able to keep up with traffic easily, can't be positive though. That's what it took or me, even at that, I rather drive a little slower and get better economy.

 

[1320Cummins]

We run my buddies 72 passenger 7.3 IDI bus @ 3200 all the time. Makes for about 6 MPG.
Exhaust valve in my s-1600 came apart doing that same thing.
IDIs in the U-Haul 26ft trucks are lucky to make it to 100,000 before failure. I am sure people just let them sit on their 2800 limiter for hours at a time.

 

[david85]

I certainly wouldn't want to pull too much below 1400 even if the engine could do it. Oil pressure isn't as good at those RPMs and the bearings could be put at risk. Lugging AND smoke rolling will wash down the rings and contaminate the oil like a crappy old carby gasser thats running too rich.

On rare occasions I did idle it along close to 1000 RPM on flat ground completely empty. Load is very light that way but still I wonder what my oil pressure would have shown for those few clicks that I rolled along like that.