In the U.S. propane is a staple on many farms, fueling home and shop heat as well as vital grain drying energy.

At one time, however, the-clean-burning liquified petroleum gas was a go-to for farm tractors before the widespread adoption of diesel engine technology eclipsed it as a motor fuel. 

The times could be changing, however, with the rush to meet lower carbon emissions.

Innovations which allow the direct injection of propane directly into the combustion chamber of internal combustion engines (ICE) is showing promise to expand opportunities for the now-renewable and once-popular farm fuel as OEMs seek low-carbon solutions to their engine portfolios.

Today, roughly 75% of all vehicle and off-road engines use high-pressure direct injection, which enables lower emissions and higher engine efficiency via higher compression ratios and forced-air induction. Until now, no engine technology existed to use propane in such systems.

In a recent Engine Technology Forum webinar representatives from the propane industry and two internal combustion engine technology companies introduced research outlining propane’s potential to produce power and torque on par with gasoline-fueled power plants —  without complex emission systems.

Katech Engineering and Stanadyne, supported by the Propane Education and Research Council (PERC) have successfully demonstrated a 250-hour durability test on a 6.6L GM L8T (direct injection V-8 gasoline bench engine) using propane through their new combined-technology fuel delivery system. 

Until recently nearly all ICE applications of propane fuel relied on traditional port injection – whereby gaseous propane was introduced just ahead of the intake valve — a system now made obsolete in automotive and over-the road gasoline-fueled engines. 

In addition, Stanadyne has overcome propane’s historic propensity for vapor-lock problems stemming from it’s low-temperature boiling point. 

The company offers a newly-designed fuel pump and fuel injector improvements to keep propane pressurized (and liquid) from fuel tank to the time it enters the combustion chamber. 

Industry First Technology

The technology is the industry’s first medium-duty engine capable of delivering propane at a constant 350-bar (5,000+ psi) directly to the engine. Unused fuel at the fuel injector is returned (as a pressurized fuel) to the fuel tank.

Stanadyne engineers also tweaked the test engine’s fuel injectors to create an optimal spray pattern that addresses the unique properties of liquid propane under high pressure.

Unique spray hole characteristics and a targeted fuel stream ensures optimal air-fuel mixing for efficient combustion. 

Direct injection avoids the 20% power reduction associated with traditional LPG port fuel injection due to gaseous propane replacing air volume in the intake stream.

Stanadyne President David Zimmerman says ICE engines are the workhorse the nation’s society and notes the recent tests shows good potential for LPG fuel in many applications.

“The opportunity to partner with Katech and PERC on this initiative aligns with our commitment to developing solutions bridging the significant adoption gap between traditional fossil-fueled propulsion of low-carbon and zero-carbon vehicles,” he says.

Propane’s Benefits

Propane as a motor fuel emits roughly 20% fewer carbon emissions compared with diesel fuel when total lifecycle figures for both fuels are compared.

While no one expects propane to fully supplant diesel fuel as energy for ag and off-road engines, the potential of Katech’s and Stanadyne’s innovations exists to maintain existing ICE technology in a world transitioning to fuel cell and hybrid battery-electric vehicles. 

An engine capable of matching horsepower and torque curves of gasoline-fueled off-road designs with only a simple catalytic converter to please far-away desk-bound decision makers has to stir some interest in OEMS. 

Just think: No DEF, no DPF, no down-time regenerating the emission system, no need for a “limp mode” and overall reduced design complexity.

Propane, traditionally a byproduct of petroleum refining of liquid motor fuels, is also now a potential drop-in “renewable fuel,” with recent development of its production from camelina seeds and other vegetable oils. 

And, don’t forget, there’s also an established distribution system for propane through more than 3,500 dealers across the nation.