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FEV Developing Efficient Two-Stroke Diesel Engine

FEV Engine Technology is working on a new, two-stroke, light-weight, high-efficiency diesel concept engine that also promises to address the emissions issues associated with two-stroke designs. The approach could support a family of engines applied either as standalone engines in vehicles, as power sources for APUs, or as powerful and efficient engines in a hybrid configuration.

The OPOC (opposed-piston, opposed-cylinder) engine combines two engine designs pre-dating World War II: an opposed-piston, two-crankshaft diesel aircraft engine developed by Hugo Junkers and the opposed-cylinder boxer engine developed by Ferdinand Porsche. (Diagrams below left. The diagram below right depicts the design of an OPOC module. Click to enlarge.)

Opoc1 Opoc2_2

A two-stroke cycle engine differs from the more common four-stroke cycle by having only two linear movements of the piston instead of four, although the same four elements of the cycle (intake, compression, power, exhaust) still occur.

The new engine thus generates one power stroke per each crank revolution per cylinder. The OPOC configuration consists of two cylinders per module. Each cylinder has two pistons moving in opposite directions, and the crankshaft is placed between the two cylinders.  (See diagram above, right.)

There are no valves or camshafts in this design; intake and exhaust ports are at opposite ends of the cylinder. The crankshaft controls the position of the pistons in such as way as to open the exhaust ports before the intake ports and then close the exhaust ports before the intake ports. This asymmetric timing is a must and provides for proper exhaust-blow-down and enables intake supercharging.

The combined intake and exhaust process in a two-stroke engine that clears the cylinder of exhaust gases and fills it with a fresh mixture of air and fuel is called scavenging. Managing combustion control and cylinder scavenging have proven problematic in the past, and have led to one of the major problems with two-stroke design: emissions control.

The OPOC engine optimizes its scavenging over the entire engine range through the use of uniflow scavenging controlled boost pressure, pulse turbocharging and the asymmetric intake and exhaust timing noted above.

An electrically-assisted turbocharger (both exhaust gas driven and electrically driven) allows the boost pressure to  be independent of the engine operation. Thus, high pressure boost is available for acceleration at low engine loads and low rpm without any associated mechanical drag.

Without the turbocharger, according to the designers, the reduction of emissions along with other engine benefits are unachievable.

[Turbocharging] also helps to reduce the NOx emissions by enabling higher than normal EGR rates and enables monitoring and maintaining a constant fuel to air ratio. The electrically-assisted turbocharger can rapidly compress and recycle air in order to heat to 100ºC in less than one second to ensure easy start in cold weather without needing glow plugs, which are costly and add complexity. Compression ratios in the range of 15-16 could be achieved resulting in lower fuel consumption and reduced NOx emissions.

With this optimized scavenging process, the OPOC engine offers:

...a significant step towards the theoretical potential of the two-stroke engine having double the power density of a four-stroke engine. An estimated 90% scavenging efficiency has been achieved with unique gas exchange characteristics of the opoc engine and the use of APT’s electric assisted turbocharger.

— Peter Hofbauer, FEV Engine Technology

The engine offers a number of advantages:

  • High power-to-weight ratio

  • High power-to-volume ration

  • Use of a variety of fuels including gasoline, diesel, natural gas, JP8 and hydrogen

  • Assisted HCCI combustion using proprietary diesel fuel system

  • Conventional parts, materials and maintenance

The original OPOC concept was invented by Prof. Peter Hofbauer, prior to his joining FEV as executive vice president for Research and Development. The intellectual property and trademarks relating to the original OPOC design have since been acquired by Advanced Propulsion Technologies (APT). FEV is working under contract to APT, DARPA and other interested parties to design and develop for-production variants of the basic OPOC concept. FEV has been selected by APT as their exclusive development partner for the OPOC engine.

It would be very interesting to see how this might work in an aggressive hybrid or plug-in hybrid application, as well as to get initial fuel efficiency and emissions data.



Britt Borden

Here is a good link to a basic description of how a diesel two stroke works:
Britt Borden


HELLO EVERYBODY! I must say , the OPOC engine is for the future! even if it burns diesel or Hydrogen, it's the next big thing :-) , BUT I have received an answer from Tyler Garrard(the site), that these engines, the OPOC's , are going to be first FOR THE MILITARY USE, and then for the rest of the world... this is like the CASE OF THE KAWASAKI DIESEL KLR-650 ENGINE... THE SAME THING... I AM BEGINING TO THINK THAT THEY DON'T WHANT THESE ENGINES TO BE USED BY THE ONES THAT ARE INTERESTED .... OR MAYBE IT'S TOO GOD TO BE RELEASE TO THE PUBLIC... FEAR THAT EVERYBODY WILL ABANDONE THE PETROL CARS... AND THAT WOULDN'T BE GOOD FOR SOME PETROL SUPPLIERS, and car manufacturers...

DOES SOMEBODY KNOWS WHEN will be this type of engine available? the OPOC one!
I am asking HERE because I would love one on my MOTORCYCLE and maybe a 500cc aprilia maxi-scooter CVT transmission!


I just finish a program on diesel engine. I developed much interest in the diesel engine generator, can anybody assist me in knowing how to syncronise two or more generator. Thanks,

Fernán A. Febres

German engineers D/E JunKers Jumo 205 engines during 2 WW and modified it along FEV Peter Hofbauer's RD&E. Did
Mr. Hofbauer or FEV knew about this situation ? Regards
Fernán A, Febres, Ordnance Engineer/Germany specialized

Fernán A. Febres

Currently D&E 2 proven vehicles for new US-version mkt.
1) "Kondor" automatic trail-bike made Spain 1975-1980 with "Sachs" 1 cyl 360cc 36HP. New US-version trail & street legal w/diesel engine and similar automatic-dr. expecting @ 145mpg range.
2) "3-R" 4 pax.microcitycar L3000mm xW1498mm XH1300mm, latinam. made 1990-1993 w/Renault R5 1108cc gasoline-engine-trans. New US-version with new diesel engine expecting average street-highway-street @ 113mpg range.
3) offered exclusive east-coast slack-time assy.lines for 1) 15.000 sq/ft; #2) 15.000 sq/ft+ starting 2008.
4) #1) us-version prototype tests & eval. 1st half 2008
production 50 units "Kondor" us-version 2nd half 2008.
production 150 to 250 each us-version during year 2009.
#2) us-version prototype tests & eval. 2nd half 2008-to-mid-2009. Initial 25 us-version "3-R"2nd half 2009.
5) If green car congress forum private or corporate participants be interested share us-version costs and expenses for us-version prototype preparation, tests & evaluations, could discuss proportional sharing excl. us-version assy.license or royalty fees. Best regards, Fernán A. Febres

David Williams

I've just stumbled across this site, so this might be somewhat late, but it's aimed at Peter Hughes who posted a note on March 14th. 2007.

I have a Detroit 12V-71TT two-stroke diesel and I can say the design is nothing like that of the truly dreadful petrol two-strokes found in scooters, lawn mowers, jet-skis, out-boards etc.
Detroit V-71s have 4 valves per cylinder, but these are exhaust only, as the air intake is via ports in the cylinder wall.

Fuel system:

There are no high-pressure pipes as fuel is brought via a lift pump at low pressure to the injectors. These are actually pump-injectors, one for each cylinder being situated in the heads in the centre of the four valves.

You really need to get hold of an engine manual for your series of engine (-53, -71, -92 -110, -149 etc.), (which can be found via the internet or "e-bay"), then all will be clear. Should you need a new one I think M.T.U. now have the manufacturing licence for Detroit Diesels, so should have manuals, as there are millions of these engines in service all over the world. The only difference if it is a marine installation is that the engine will have raw water cooling where the engine coolant is pumped into the tubes of a heat exchanger which are surrounded by sea or river water.

I hope some of that might be useful!



David Williams

Kenneth Rickman (June 2005) is either mistaken or has mis-printed his e-mail in the rush to write about the world's most perfect diesel engine, the Napier "Deltic" opposed-piston two-stroke. This was designed using technology bought from Hugo Junkers in the 1930s, and was three banks of JuMo 205s but with three of the crankshafts thrown away, so it has a triangular form, albeit inverted, hence the name Deltic.
His description applies to a Tilling-Stevens TS3 engine.

John Sutherland

Sir Harry Recardo worked on high speed 2-cycle diesel single sleeve valve engines from the late twenties until the early forties, ultimately resolving the various engineering problems he ran into. This engine layout accomplishes the same end of optimized scavenging suggested above with a far lighter, more compact and less expensive mechanical solution that does not require opposed pistons. It is unfortunate that in spite of the engineering being basically done, nobody has taken the concept and run with it. You can find more information on this and other promising single sleeve valve engines in his classic book: The High-Speed Internal-Combustion Engine. I believe he dropped the information on sleeve valve engines after the fifth edition; I have the forth edition which provides fascinating reading with an in depth history of the development of single sleeve valve engines along with excellent info on engines in general.

Anybody seriously interested in developing the engine concept mentioned above would be doing themselves a favor to obtain a copy of Ricardo's book and familiarize themselves with the various merits of the single sleeve valves as used in 2 and 4 cycle engines of both Otto and Diesel design. Most people either don't know or have long since forgotten that single sleeve valve engines were perfected by the British before and during WWII and where used in most of the British fighters and many of their bombers during the war.

John Aherne

JS: certainly the Bristol Centaurus and Napier Sabre engines were sleeve valve, but the RR Merlin and derivatives were poppet valve engines. Were not the RR Merlin engines the main engine of the fighter and bomber fleets? And in many US aircraft like the Mustang?

hans vanzonneveld

Has anyone taken a look at the Zoche radial 2 stroke aircraft diesel. It has a lot going for it when used in aircraft. For some reason it just isn't making it to market.

Alexander Hallam

Having " Been there, Done that" regarding the main engines used in WW 2 aircraft, I was weaned on the RR Merlin and RR Griffon V12's and the Bristol Centuarus 18 cyl radial fitted to the Sea Fury. Without a doubt, most aircraft engines in WW2 were Poppet valve, the Spitfire, Hurricane were the mainstays, the Fury didn't come into its own until the war ended. British aircraft like Lancasters, Mosquito, Fairie Battle and the like were in-lines, and the Swordfish torpedo bomber, Hercules bomber, to mention some, were radials. Most American large aircraft had radials, ie. B17's. Heavy fighters and fighter/bombers had radials, but the swifter lighter fighters were inlines, ie. Mustang, Tomahawk, Kittyhawk. etc..

Henry Gibson

The dual free opposed piston Pescara engines that had no crank but used a Turbine output should be mentioned here.

The INNAS NOAX engine could also be interesting to some readers.

The TS3 and TS4 engines seem to have a great deal of merit.

The Fairbanks-Morse dual shaft opposed piston engines seem to have been forgotten here, but they were widely used in diesel submarines because they could be fit into the hull with ease and dismantelled and removed piece by piece through the standard openings. They were later used in locomotives with little success.

The DELTIC engines were first fitted to naval craft and then had a brief use in diesel electric locomotives. World wide standardisation on American locomotive builders stopped their use as did electrification.

When turbines become more efficient, the piston engine can become obsolete as it is in combined cycle power plants, but in small sizes, there is no more convenient way to get high compression and high power and high efficiency in a small space.

Because of their high efficiency, the large piston engines have replaced steam turbines in large ships in recent years. When used in the Still cycle, an original combined cycle, these engines may again exceed the efficiency of the gas-turbine combined cycle whilst burning heavy oil.

A modern version of the Kitson-Still locomotive should yet be built and run instead of diesel electrics for much cheaper cost and higher efficiency.

Southern-Pacific-Railroad burned oil in most of its locomotives and should have brought the Kitson-Still locomotive to its tracks and run it for sixty years as a local shunter.

Many great ideas were lost in the 1930s as a result of US economy mismanagement by allowing rampant speculation in its stock market. This spread to the whole world. The example of the DOT.COM burst did not prevent the US from allowing rampant speculation in stocks and comodities in the past year.

Microsoft was and remains the best example of speculative pricing of stocks rather than price according to company production and net income. The stock's continued over pricing has fueled the desire of other people to get rich by speculation instead of investing in useful productive companies. This has concentrated wealth in the hands of the wealthy by taking money from the hands of small investors who have neither the time or the money or the connections to play the speculation game.

Who knows how many great ideas have been lost or died stillborn because of the high energy prices or died years ago in the dot-com collapse.

Not one OPOC engine has been sold to the public since this announcement. Design, manufacturing and production should have been moved to China years ago. There is not as much opportunity to make money in China by speculation so they produce and sell stuff.

Scuderi, APT, INNAS, Firefly et cetera do not want to sell product; they want people to buy intelectual property. They have mostly wasted their money which could have been wasted or improved easier by knowing when to invest in Microsoft. Or how to set up a dot-com company that doubles it share price in a day.

Time-Warner did not know that a proven track record in producing profits was detrimental to massive increases in stock prices, so it allowed itself to be bought by AOL that never had made a profit in hopes that the public would forget that TIME-WARNER was a real productive company and bid up its stock prices.

IBM and ATT sold off their companies piecemeal without achieving any great wealth for their stock holders. Neither the general public, IBM or ATT were helped by the opposite actions of the US government in regards to them in 1984. Research done by ATT that produced the solar cell and transistor and many other things has stopped. And cell phone service is very expensive. Text messages that cost a thousandth of a cent or less to deliver are charged at 20 cents. In some poverty areas of the world text messages are free. Text meassges should be free in the US; public air is used to send them. ..HG..

Julian Phillips

The concept of the Rootes TS3 2-stroke diesel engine offers many benefits, one I favour is minimal piston side thrust due to the low rod angularity.
I suggest the fitting of a variable compression means by which the CR may be adjusted during running or when the engine is stopped. At its simplest a long rocker fulcrum shaft with eccentrics on one bank of rockers suffices, turning it a whisker to alter the tdc position for 3 of the 6 pistons. Option to adjust all six pistons at more cost and complexity.
Imagine if Subaru WRX adopted such a multi-fuel diesel concept!

Brian Rands

I am undertaking a research paper on the Bourke engine, my Grandfather helped to machine some of the parts to the Bourke 400 and was well aquinted with the man Bourke. From the personal accounts of my Father, Uncle and Cousin, this engine did run, extreamly fast, loud, and effieciently. The application for electrical power generation for hybrid cars and trucks seem to be a good fit for a small scale version. The patents have expired and the information is public domain, why has this technology remained undeveloped?


A response to the comments about electric alternatives: great concept, numerous hurdles for efficiency. As far as I have researched, electrical generation on the vehicle is the most efficient possibility. Also, battery technology today is still not feasible for global scale. Lithium Ion is not a "green" or renewable or sustainable solution. Current methods of Lithium extraction are either too inefficient (sea water extraction) or too limited in quantity to scale up for global mass adoption (mining). In addition, there's no real recycle process in place for used Li batteries. Hydrogen fuel cell still holds the most promise of being the ideal strategic electric solution. Lots of hurdles still to overcome including distribution. Until those hurdles are overcome, Diesel is the most practical interim solution having a higher energy content than gasoline (better fundamental efficiency) and being capable of being obtained from multiple sources; in fact, Diesel was originally a NON-PETROLEUM based fuel, and it took time for the Petrol industry to figure out how to produce it from crude oil refining processes. Petrol Diesel has had a high sulfur content making it smelly. In 2006, the US mandated a lower sulfur content for Diesel fuel. Bet you didn't notice that driving behind trucks doesn't smell as bad. Conventional Diesel technology engines are improving efficiency further, and this OPOC design holds additional promise.


I am excited by the progress being made on alternative vehicles. I am a big believer in 2 stroke biodiesel electric vehicles. I agree with the in hub electric motor design. I believe computer controls can deliver the correct torque to assist cornering and handling. I think that aluminum as a material is under used. An electric car with an aluminum body will provide years of motoring with lower long run cost.
The main problem with cars is their fashion status. If people learn to accept eco cars as a statement, i.e. anybody else who drives a non eco car is an uneducated selfish redneck, then we can change consumer habits.

I think the wastefulness of today’s Car Industry, turning out model after model, and crushing perfectly good cars is a disgrace. And soon as consumers learn that driving a car that is initially more expensive but cheaper in the long run, the quicker we'll see these cars on the road.

I am a CPA and can travel worldwide providing assistance to Automotive finance departments. I am sure if the people on this forum got together, created a new company, raised the capital, we could create a new force in motoring. By cutting waste we could attract the world best engineers. Locate in China or Vietnam or perhaps Africa. If interested please contact me birojek at hotmail dot com

Ricardo Perez

On my opinion this invention is a great good compressor but not as motor. Sorry for the engineer. Pls see my invention of diesel motor 2 strokes by valves only, save the 30% of fuel. rgds.

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