Gas Combustion Engines At Elevation

October 24, 2018

Small CFM gas driven air compressors won’t perform as well at 5,000 feet of elevation as they do at sea level. They may fail, bog down, or supply less air power. But why is this?
It all comes down to the physics of gas combustion engines.

Oxygen, Fuel & Spark

Combustion engines work by combining three critical elements: oxygen, fuel, and a spark. Engines need the right amount of each of these elements, at the right time, for optimal performance.
But a change in elevation changes the available oxygen. As elevation increases, air density decreases, which also decreases the amount of oxygen in the air. This decrease in oxygen makes it harder for combustion engines to do their job. The engines will try to compensate with more fuel, but this compromise won’t always be enough.

As the amount of available oxygen decreases, there is also proportional decrease in horsepower, and the engine must work harder to meet demand. Therefore, combustion engines start to bog down, stall, or fail to start when the elevation gets too high.

Why Engine Size Matters

Not all engines experience issues with elevation. Larger engines can typically handle the decrease in oxygen because there is more available horsepower for auxiliary equipment. Even at higher elevations, large engines usually have enough power to meet those needs.

However, smaller engines don’t tend to have horsepower to spare. Small combustion engines, like those found in standalone gas driven air compressors, generators, and pumps, are susceptible to performance issues at elevation.

VMAC G30 at High Elevations

In terms of VMAC air compressors, extraordinarily high elevations can impact the G30 gas drive rotary screw air compressor, which uses a Honda combustion engine.

Our field testing shows that the G30 will provide full air output at over 5,000 feet of elevation, as with any gas engine this is dependent on ambient temperature and humidity. These types of elevations are typically only found in larger mountain ranges.

Operators running the G30 in areas of frequent high temperature and humidity may experience performance issues above 3,500 feet of elevation.

How to Solve High Elevation Issues

Now that we’ve identified the problem, let’s talk about two solutions that may work for gas combustion engines:

  1. Carb Rejetting – Using the G30 as an example, Honda offers parts for carb rejetting that enable the G30 engine to run at elevations up to or above 10,000 feet. Carb rejetting changes the air-fuel mixture so that it’s closer to the air and fuel levels at lower elevations, which helps the engine perform better at those higher elevations. Operators who want to rejet their engine can purchase the parts and perform the modification, or work with an authorized Honda equipment dealer.
  2. Air Receiver Tank – Alternatively, an air receiver tank can be used to build up a storage of compressed air. This stored air can often provide enough compressed air to complete intermittent tasks in small bursts.

Of course, if the elevations are too high and the air compressor is failing (or won’t function at all), you may need to use a different air compressor system. VMAC products designed for work at high elevations include: