It seems that since you know so much about snowmobiles that maybe you can help me with a tow vehicle. Why are the Turbo Diesels so powerful in the mountains pulling trailers? I’m considering buying a Ford Super Duty truck, do you know anything about the “High Altitude Principal Use” option (option code 428) offered on the gas engine? My local Ford dealer isn’t much help (no surprise there). Or, am I better off with a 7.3 Power Stroke diesel?
Just like the engine in your snowmobile, normally aspirited gas engines in tow vehicles loose between 3 & 4 percent of their horsepower for every 1000 feet above sea level. This means that at 7000 feet, the gas engines have lost over 20 percent of their rated horsepower and torque. In contrast, trucks with turbo diesels (like the Ford Super Duty F-350 7.3L Power Stroke) maintain full horsepower and torque up to about 10,000 feet. The turbocharger maintains a full fuel/air charge to all cylinders, maintaining full horsepower and torque. Above 10,000 feet, even the turbo can’t keep up with the thinning of the air.
The High Altitude Principal Use option 428 is a no-charge option for Super Duty F-Series trucks with gas engines and consists of some revisions to the EEC-V calibrations and often a change in the rear axle ration to provide greater towing capacity with the reduced horsepower that will be produced at higher elevations. This option is recomended for trucks that will be operated primarily at elevations above 4000 feet.
This is also the main attraction of turbos for use in snowmobiles. The power robbing nature of high altitude isn’t as apparent, and sleds with turbos running at altitude make almost as much power at 8000 feet as they do back East. The issues of reliability and stresses on the drivetrain are something to consider, but the attraction of making an actual 150+ HP at 8000 feet is tempting, very tempting.