Turning up power. Pros and cons

You obviously don't have a clue about mechanics if you think horsepower effects what speed you will be traveling at a set rpm.

 

My thinking is I'd be able to cruise at a higher speed with lower rpm considering id be using less power to accomplish it if I turn it up.



If that's your thinking, you'll be very disappointed. Unless you're doing a gear change, your rpms will stay the same. The only thing that will change is you'll have more power. But if the gearing is wrong for the application, you're wasting your money. I pull tankers. The last truck I drove had a 550 Cat, 13 speed and 3.36 rears. Pulled like a mule, but wouldn't pass a fuel pump. My current truck is a 475 Cat, 10 speed and 3.70 rears. It pulls the hills just as well as my old one, and I'm getting nearly 1 mpg better in fuel economy.

As far as e the longevity, turning the HP up shouldn't affect it, as long as it's driven properly. But the chances are, you're already using every ounce of power you have. Add more power, and you're going to be using all of that up, too. Unless you're incredibly disciplined.

 

3.36 rears? Man that truck was built to fly. On 11r24s you were probably doing 70 at idle.

 

It is on 11r22.5 rubber. At 70 mph I was at 1400 rpm. The truck was not governed, and I know it would go at least 95 mph. Beyond that, I wasn't about to find out

 

The biggest issue was the fuel mileage. Pulling tankers in the hills of central and eastren PA, you were always in the throttle. And the rears made it really miserable at times. But put it on I-68 in Maryland, and it did ok.

 

Thinking of having the ECM remapped and putting a different tune on the computer? If that's all you're planning to do, you'd better get a digital pyrometer so that you can keep an eye on the engine EGTs (exhaust gas temps) when you're on a long uphill pull.

There are ways to keep the EGTs down...bigger turbo, free flowing ceramic coated exhaust manifold and a aftermarket muffler. And after that, if she cant keep her cool, you will have to upgrade the factory radiator to a bigger unit.

And they're right about your cruising rpm. If you want a lower rpm, go with a taller tire or change the rear end gear ratios, or put an auxillary box on the back of your transmission (that costs around $10k)

 

68 is full of hills I used to run liquid wax from Jersey to Flinstone MD... 68 is no better the 322 422 220 80 even 78 got some hills... come on 68 is just as bad

 

68 does indeed have more, and bigger hills.

The difference is you can actually get a running start for the hills on 68. And you don't have the clowns on 78 running 50 mph to hold traffic up.

 

If you take it to Cummins, they will more than likely do their due diligence and run the engine s/n to see if it came with all the right goodies to handle 50-150 extra ponies from their program (especially if there is still a warranty of some sort on the engine). May need to check that your clutch, transmission, driveline and axles are rated to handle it too. It would suck to twist a driveline off or shatter gears/shaft/housing of the transmission because its too light.