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Re-engineering Internal Combustion Engine Could Deliver Big MPG Boost at Lower Cost with Fewer Emissions

Internal Combustion Redesign

For all the advances with hybrid and pure electric vehicles and the attention they are grabbing, personal, commercial and government vehicles around the world will be using enormous volumes of gasoline and diesel fuel for decades to come. Investors and innovators know there is a lot of money to be made improving the efficiency of internal combustion engines. If that can be accomplished at a lower cost and with fewer emissions, all the better.

Well that day of reckoning  may not be far off.

One of the handful of companies trying to re-engineer the internal combustion engine  – San Diego-based Achates Power – has been sharply focused on new engine architectures since 2004.  Its “opposed piston, two-stroke” design initially for government and commercial vehicles is drawing significant interest from investors. And it’s now working with a customer it’s permitted to identify:  the U.S. Army’s Tank Automotive Research, Development and Engineering Center. (The center’s web site was unavailable at this writing due to the federal government shutdown).

internal combustion improvements

One view of the Achates Power A48 internal combustion engine

Now I’m no auto geek. My two family cars have logged more than a combined 400,000 miles.  My wife and I are waiting as long as we can to make one of our next purchases the most efficient internal combustion sedan on the market. So I’m tracking the auto industry’s progress (or lack thereof) in achieving the fleet-average miles-per-gallon requirements set by California and the U.S. government. I’ve got high (and perhaps unrealistic) hopes that emissions from any improved design will be less, power won’t be sacrificed, the price tag will be affordable and they’ll be quiet-enough to drive.

At least three other U.S. companies are in hot pursuit of such a game-changing engine design:  Pinnacle Engines in San Carlos, CA; EcoMotors in Detroit; and Transonic Combustion in Transonic Combustion in Camarillo, California. Toyota and General Motors have been tinkering with “homogeneous charge compress ignition” (HCCI) technology with no public results I could find. Here is why Achates Power caught my eye.

Today (Wednesday) Securing America’s Future Energy shined a spotlight on Achates Power as a finalist for its Emerging Innovation Award created to showcase technologies that are “driving fundamental improvements in energy security, and that have the potential to reach the market within the next five years.”

This award comes when a lot of people interested in more secure energy sources are taking stock of what’s been achieved since the Arab Oil Embargo 40 years ago this week. Earlier this year, the research firm Frost & Sullivan selected Achates Power for its New Product Innovation Award for North American Medium and Heavy-duty Commercial Vehicle Engines.

Just last week, Achates Power secured a Series C round of funds from its venture capital partners led by Sequoia Capital Partners and RockPort Capital Partners. To date, according to CEO David Johnson, Achates Power has raised $90 million and secured 21 U.S. patents and 11 foreign patents relevant to its engine design.

Heavy and medium-duty trucks are understandably the initial target markets for Achates Power. But Johnson is quick to point out that their design can work just as well in passenger vehicles. In addition, the engine can be configured to use unleaded gasoline, natural gas and certain biofuels. He said more than 4,500 hours of rigorous laboratory tests are showing diesel fuel savings of at least 20 percent and gasoline savings exceeding 50 percent.  With those efficiencies, passenger vehicles with Achates-designed engines, in time, could approach a fleet average of 100 miles per gallon.

global engine markets

This table illustrates the multi-billion dollar market for re-designed internal combustion engines. Sources: IHS Automotive, CleanTech Group, Achates Power

Frost & Sullivan researchers weighed a typical heavy-duty truck scenario where a convention diesel-engine powered travels an average 120,000 miles a year at an average fuel efficiency of 6.5 miles per gallon. That comes to about 18,460 gallons. With the fuel efficiency benefit of Achates’ engines advances in the lab that translate to 3,690 gallons of fuel saved, or about $14,000 savings in fuel costs annually.

What makes such a huge advance in an engine design that has served as a basis for internal combustion engines since the 1930s and currently powers small marine motors and even some household outdoor appliances like weed whackers?  Johnson said the company’s 50 engineers and scientists have assembled the necessary computer technology to work with high pressure fuel injectors and far more advanced turbochargers. It is far easier, he said, to determine what engine parts are needed and which ones aren’t.

The Achates Power design eliminates two of the traditional four engine strokes – intake, compression, power and exhaust – into just the intake and exhaust strokes.   There are just three cylinders, versus four or more cylinders in virtually all vehicles today. There is a piston at both ends of each cylinder.

In a conventional engine, a piston moves inside each cylinder, compressing fuel and air against a cylinder head. A significant amount of energy in the fuel is ‘used’ to heat the cylinder head rather than drive a piston thereby hindering efficiency. There are no cylinder heads in the Achates Power design. This design also negates the need for a valve train, camshafts, pushrods, rocker arms, valves and valve springs. Their absence lowers friction, reduces engine size and weight and minimizes cost.

Opposed-piston, two-stroke engines fire in every cylinder during every engine revolution. This, combined with having two pistons per cylinder, leads to a larger cylinder volume per fuel injected. The resulting air-fuel mixture is leaner, making the combustion more efficient and reducing emissions. With higher thermal efficiency, more energy from the fuel is transformed into mechanical power rather than lost as heat.

The opposed-piston engine architecture has enjoyed only marginal market potential until now due largely to the entrenched position of conventional, four-stroke internal combustion engines. That has been the only engine technology available in the industry from small cars to large trucks. Reliability, durability on long-haul, on-highway usage and unproven emission compliance are additional hurdles that must be overcome.

The invention of the opposed-piston engine is credited to German engineer Hugo Junkers as the 1800’s drew to a close. While variations of the subsequent “Junkers Jumo” design have improved power density and fuel efficiency, the “basic design contains a number of deficiencies,” according patent applications by Achates Power’s chief scientist, James Lemke, who founded the company with an investment from John Walton, son of Wal Mart founder Sam Walton.

James Lemke photo

Achates Power Founder and Chief Scientist James Lemke

For history buffs, Wikipedia outlines how Junkers was forced to work with engineers designing German’s Fokker combat aircraft leading up to World War I. In that war’s aftermath, Junkers butted heads with the Third Reich.  Nazi authorities responded by securing ownership of his patents and the majority of shares of his remaining companies.

Emission and fuel efficiency regulations in North America are the most stringent in the world. They’re about to get even tougher with regulations on greenhouse gases phasing in starting in model year 2014, expanding in scope through model year 2018. With medium and heavy-duty trucks accounting for about 22 percent of all transportation-related greenhouse gas emissions, major truck and engine equipment manufacturers, as well as, truck owners invariably are looking for cleaner and leaner diesel engines that deliver the lowest upfront cost and reduced lifecycle costs.  With progressively higher adoption, passenger cars and light-duty trucks might not be far behind.

Which commercial truck manufacturer will be the first to commit to adopt the Achates Power design? Or might a company such as Cummins Engine be the first? Johnson says non-disclosure agreements prohibit the company from identifying prospective customers. Neither GM, Ford, BMW North America nor Cummins responded to emails and/or phone inquiries.

Jim Motavalli, a prominent auto writer and clean energy advocate whose work is often carried online by The New York Times and the Mother Nature Network, withheld judgment about Achates Power for an assessment about a year ago.

In September of 2012, Motavalli wrote:  “Before I proclaim this engine the greatest thing since sliced bread, I’d like to see it much further down the road. I’d want to see independent fuel economy and emissions validation. I’d want to see noise, vibration and harshness studies . . . Frankly, I’ve had other meetings with ‘breakthrough’ engine companies whose tech never amounted to anything.”

The next few years will tell if Achates’ new design is the real deal.

Jim Pierobon's picture

Thank Jim for the Post!

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John Miller's picture
John Miller on October 17, 2013

Jim, very interesting Post.  The Achates Power 2-stroke engine design appears to be very innovative and potentially a huge improvement over conventional 4-stroke engines.   Two-stroke engines have historically been lighter and fairly efficient compared to alternative ICE designs (gasoline or diesel), but are challenged to develop higher, low speed torque and minimize exhaust emissions.  The Achates Power 2-stroke design has apparently addressed these engine power performance issues by effectively adding superchargers (a second air compressor piston-cylinder) to increase compression ratios, which increases horsepower-torque.  This being the case, a more reasonable comparison to 4-stroke engines of similar displacement should be based on turbocharged (or supercharged) designs vs. the apparent Achates Power 2-stroke engine comparison to conventional 4-stroke engines without combustion air compression.

Historically 2-stroke engines have been challenged to meet increasingly strict tailpipe emissions due to the lubricating oil consumed (required to provide adequate cylinder/crankshaft/bearing lubrication) and resultant CO/VOC/PM emissions.  The Achates Power experts have performed detailed testing of oil consumption that apparently indicates their new design consumes very small amounts of the required lubricant and the resultant impact on tailpipe emissions should be relatively small.  One detail that I noted in reviewing their laboratory procedure used to measure oil consumption is that it might have a significant procedural flaw; ozone oxidation to remove nitrous oxide could also convert sulfur dioxide to sulfur trioxide.  I know this is a lot of technical detail, but one that could cause them to under-measure actual oil consumption.  However, as you state:  “The next few years will tell the real deal”.

Thomas Garven's picture
Thomas Garven on October 31, 2013

I know we are not voting but my vote goes to Eco Motors, LOL Their design seems to be less resource intensive since only one crankshaft is used. Crankshafts are heavy and expensive to manufacture as are the additional connecting rods. Other than that they seem to be pretty much the same. I might also mention that OPEC is currently, in partnership with a Chinese company, building a factory for the production of the OPEC engine.

The one distinguishing feature I find interesting about the OPEC is its ability to add or subtract active power modules as power needs change. Why is this important you might ask. Take for example my Dodge Ram 1 ton pickup truck which sits idle in the driveway about 10 months of the year except for some limited local trips. When it is used for around town or for a short trip it is of course running empty on all 6 cylinders since it is a 6 cylinder engine. Most ½ and ¾ ton trucks purchased today are used this way. People love their trucks but we waste huge amounts of fuel driving them empty back and forth to the grocery store, LOL.

Using an OPEC engine with modules that can be switched off and on would allow people to drive around town on say 2 cylinders instead of 6 or 8 cylinders which could result in significant fuel savings. But when I connect my truck to my 5th wheel trailer or someone wants to haul a ½ ton of decorative rocks home, then the other OPEC module[s] could be brought on line. HUGE savings in fuel for what appears to be the most popular vehicles in America which are small trucks.

About the same can be said for the OPEC in automotive use. The power needed to move a Chevy Malibu sized vehicle down the highway at say 70 MPH is about 27.87 HP yet we build automobiles in this size category with 300 HP engines. Why not a 4 cylinder OPEC with 2 power modules. One module for around town and one module for highway driving. That should put a dent in oil imports.

Link to HP ref.

So based on my tiny bit of knowledge, I vote for the OPEC. Combined with things like hybrid technology, carbon fiber weight reduction, downsizing of vehicles or vehicles designed for around town service, I see no reason why we couldn’t achieve an automotive fleet average of 100 MPG. But at the age of 73 I will certainly never see this day arrive. There are too many lobbyist dedicated to the continued consumption of oil for as long as possible.  

Jim Pierobon's picture
Jim Pierobon on October 31, 2013


Many thanks for the comment. If the creation of sulfur trioxide out of sulfur dioxide proves to be problematic, do you think that’s a show-stopper? Where has this been a challenge with other engine upgrades?


John Miller's picture
John Miller on November 1, 2013

Jim, accurately measuring the lubricating oil consumption is basically a technical detail in designing and testing the new motors.  The ultimate test will be if the new 2-stroke engine’s actual tailpipe emissions can reliably meet U.S. EPA or similar EU environmental standards, and the fuel efficiency complies with CAFE standard, while meeting customers’ horsepower/torque performance expectations.

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