Emissions Testing Results: Hydraulic Hybrid Delivers Major Emissions Reductions

Home>Emissions Testing Results: Hydraulic Hybrid Delivers Major Emissions Reductions


Over the past several years, Lightning Hybrids has worked with SGS Environmental Testing Corporation, with their testing center in Aurora, Colorado, for regularized, independent emissions testing of vehicles equipped with our hydraulic hybrid drive systems.

We did this to get certified results to quantify the emissions reductions that our hybrid solution delivers to truck and bus fleets, proving a key value of the system, along with fuel and brake savings. (You can read the full report here.)

By design, many hybrid drive systems provide benefits during a vehicle’s braking and subsequent acceleration phases, so not all drive  cycles will take equal advantage of the system. For example, an urban delivery truck which stops many times per mile will benefit strongly, whereas a truck that spends most of its time on the highway would not be a good candidate for regenerative braking hybridization.

With this in mind, SGS tested the LH systems according to documented standard drive cycles which are accepted for regulatory certification and which are representative of city drive cycles:

Both drive cycles were based on city bus routes, and define the speeds and times, including idling, that are reproduced during testing on the dynamometer at SGS.


GM Mule Gen 4.2SGS Dec2014_smallThe vehicle, a 2010 GMC 3500/4500 Savana Cutaway with a GM 6.0 liter gasoline V8 engine, was placed on SGS’s dynamometer and driven on the Orange County and Braunschweig drive cycles. The vehicle was loaded with a concrete dummy load to bring the weight up to 10,800 lbs. Exhaust gases were captured in order to measure the vehicle’s emission of carbon dioxide (CO2) and nitrous oxides (NOX), both of which are criteria pollutants which are written into United States EPA regulations on air quality, and into equivalent European Union legislation.

Baseline comparisons

You may remember that our previous testing at SGS provided two sets of baseline results which we use for comparison to allow the improvements provided by the hybrid system to be quantified. These sets of results are:

  • The same GMC Savana with the hybrid system removed (gasoline baseline results)
  • A GM 4500 chassis with GM Duramax 6.6 liter diesel engine, hybrid system disabled (diesel baseline results)


On both drive cycles, the hydraulic hybrid’s most dramatic improvement is the reduction of nitrogen oxides, or NOX, emissions. Results for the gasoline vehicle show a 50% (or slightly greater) reduction in NOX with the hybrid system on. A key contributor to air pollution and smog, NOX reduction is significant for cities, states and nations that are working to meet air quality targets.

The results become even more dramatic when comparing these gasoline results against the equivalent diesel vehicle. Take a look at this chart:nox_diesel_US

The gasoline-powered truck with the Lightning Hybrids hydraulic system emitted just 5% of the NOX emitted by the conventional diesel vehicle. This is especially interesting to European fleets, who are concerned that new emissions regulations will make diesel vehicles difficult to justify.

In many cases, diesel trucks are chosen over gasoline for their greater low-end torque. However, the Lightning Hybrids hydraulic system delivers additional power during acceleration from a stand-still, which means that a hybridized gasoline-powered vehicle has advantages of both very low NOX emissions and great power for acceleration.

The benefits of the hydraulic hybrid system extend to fuel savings and corresponding reductions in carbon dioxide, or CO2, emissions with results that show 14-15% reduction in CO2 emissions for both cycles, and a corresponding fuel economy improvement of about 18%.

Fuel use and CO2 emissions are closely correlated, so an improvement in fuel economy will show an similar reduction in CO2 emissions. As noted above, these tests are preformed in a laboratory. Therefore while they are appropriate for testing, we have found that the do not correlate precisely with our customers’ real-world drive cycles. Our customers in urban delivery and bus routes report over 30% fuel savings (so we can assume the parallel 30% CO2 savings as well).

Not every hybrid technology is capable of these levels of emissions savings, especially in urban delivery and transit bus drive cycles. Lightning Hybrids’ hydraulic drive system provides intense torque (up to 850 ft-lb) for acceleration, a time when emissions are generally at a peak. This allows us to achieve higher reductions in criteria pollutants than battery or ultra-capacitor based hybrid designs.

At the first hybrid technology developer to focus primarily on emissions for medium- and heavy-duty vehicles, these results prove Lightning Hybrids hydraulic drive system is a clear winner.

Read the full Report