Fuel

High levels of humidity displace oxygen in the air and *reduce* the themodynamic potential of the air.
Of the total air pressure, any humidity will consume a certain vapor pressure, reducing what is left for the partial pressure of oxygen.

Cool, dry, and low altitude are your three best friends for making power.

If you feel a difference at higher altitudes, your motor may be running too lean. Was 2011 at DPF year? I can't imagine 425 hp would not be enough unless you're towing a Hummer.

I would have a truck service center re-program that computer. 425 is enough HP. we run a 350 ISC at 400 on a Banks intake and exhaust kit with a programmer, and it will do any grade with no problems.

If you are in the Seattle, make an appointment at Motor Trucks in Everett and have it inspected and set up properly. They made a huge difference with ours

What was all that hype about mixing water vapor with the fuel mixture to improve performance, was that just gas engines?

I agree that the altitude makes a difference. Cool, dry air helps.
Some locations in the West sell lower octane fuel because it still functions well in fuel injected engines at higher elevations.

farmingdad wrote:
My 425 Cummins seems like it’s got 50 more Hp out West , we are out here on vacation I guess no humidity. Back in ky seems like it’s runn in a strain all the time. Gets about 6 mpg. It’s in a 2011 Newmar m h must not be enough hp

If you're talking 6 mpg overall for everything and over a period of years, then you're well inline with reality. I depend on the ECM and a digital readout for mine, which is a 6.2 average for 11yrs.
As for any difference in power, I'm not complaining with what I've been experiencing here in the east and in fact, am impressed with the way it climbs in the Appalachian range. Haven't had this one over the Rockies as yet, but would sure like to.
10HP per foot is what many use as a gauge, if that's of any help and usually equates to a torque to weight ration as well, for a production line coach. Top end and Converted buses, are something else and are powered accordingly.

Mile High wrote:
What was all that hype about mixing water vapor with the fuel mixture to improve performance, was that just gas engines?

You are talking about water injection. Well known, and, yes, it works on gas engines, until junk science, marketing, and advertising hype gets a hold of it. It doesn't improve performance. It restores performance that would be lost to preignition/detonation in engines that have too much compression or turbocharged engines that run excessive boost with insufficient octane fuel.

The down sides are too many to list, that's why water injection is "on the shelf" in all but the most critical applications. IMO, everyday driving isn't one of them.

Chum lee

Chum lee wrote:

Mile High wrote:
What was all that hype about mixing water vapor with the fuel mixture to improve performance, was that just gas engines?

You are talking about water injection. Well known, and, yes, it works on gas engines, until junk science, marketing, and advertising hype gets a hold of it. It doesn't improve performance. It restores performance that would be lost to preignition/detonation in engines that have too much compression or turbocharged engines that run excessive boost with insufficient octane fuel.

The down sides are too many to list, that's why water injection is "on the shelf" in all but the most critical applications. IMO, everyday driving isn't one of them.

Chum lee

Ah, thanks for the explanation. I just remember it at all the car shows.

There are variations in fuel from State to State.. I will see if I can find the article or web site that explains it.
State Fuels

this is the start to the path of knowledge on this subject. NOTE I am not an expert on the issue. Just good at Google.