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Old 02-15-2020, 05:14 PM   #1
BAPotter
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Tow Guides

Interesting note in March 2020 "Trailer Life, page 9. Owner of a 2019 Ford F-150 5.0L states that his owners manual list tow capacity of 7,000 lbs, but must reduce that tow capacity by 2 percent for each 1000 altitude. (10,000' is down to 5,600 lbs). I know 3% applies to normally aspirated generators, but didn't know it was in the truck manuals.
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Old 02-17-2020, 09:22 AM   #2
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I was thinking that increases in elevation and corresponding reductions in air density do have a direct effect on horsepower because of reduced torque. I didn’t know that it had an effect on towing capacity. I mean, if the available torque is reduced, you compensate by slowing down. Power = torque x rotational speed x a constant. One other thing to keep in mind is that in less dense air densities, heat transfer is reduced...
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Old 02-17-2020, 09:33 AM   #3
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In any normally aspirated internal combustion engine altitude will affect output power. If you have a gasoline engine running let's say a 14:1 ratio of air to fuel then the less air means less fuel which equals less power.

A supercharged or turbo charged engine will have the advantage of keeping boost up to the limit of the blower/wastegate capacity.
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Old 02-17-2020, 02:43 PM   #4
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Quote:
Originally Posted by flybouy View Post
In any normally aspirated internal combustion engine altitude will affect output power. If you have a gasoline engine running let's say a 14:1 ratio of air to fuel then the less air means less fuel which equals less power.

A supercharged or turbo charged engine will have the advantage of keeping boost up to the limit of the blower/wastegate capacity.
I am a little confused by the term "towing capacity" when in comes to elevation. If the engine is turbo charged, it is more like running at lower elevations. If a tow vehicle must slow when pulling a load at "altitude" because available Hp is less, does it mean that towing capacity is decreased?
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Old 02-18-2020, 06:17 AM   #5
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I am a little confused by the term "towing capacity" when in comes to elevation. If the engine is turbo charged, it is more like running at lower elevations. If a tow vehicle must slow when pulling a load at "altitude" because available Hp is less, does it mean that towing capacity is decreased?
What it means that you are towing 7,000 at the bottom of the hill and every 1,000 Ft increase the truck will lose power. The trailer will still weigh the same but the truck will work harder to pull the trailer. A naturally aspirated truck can only suck in so much air. The higher you go the less air there is. With a boosted truck the turbo or supercharger will make up for the less air by increasing the airflow into the motor. Now unlike the old carburetor days the computer adds or takes fuel out of the engine but it can only do so much. Carburetors only did so much and there was no way to adjust air flow like today's trucks.
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