ExxonMobil, UW-Madison partner on biomass-to-transportation fuel research
DOE to issue $56M funding opportunity for vehicle technologies in January

EPS advancing diesel engine for general aviation applications; 30-50% lower fuel consumption than gasoline

Engineered Propulsion Systems (EPS) has developed and is advancing a 4.3-liter, 8-cylinder diesel engine for general aviation (GA) applications. Based on a CGI (compacted graphite iron) cylinder block, the Graflight V-8 (formerly called the Vision 350, earlier post) will enable 30-50% lower fuel consumption and emissions compared to conventional aero engines, according to the company.

As an example, EPS suggests that a Cirrus SR22 (a single-engine four- or five-seat composite aircraft) fitted with the Graflight V-8 could carry the equivalent of two additional passengers flying the same distance as with a Continental gasoline 315 horsepower engine while still realizing a 40% reduction in fuel cost. Engine and flight tests are currently underway and EPS expects Federal Aviation Authority approvals during 2017.

Initial testing of the pre-production engine has demonstrated specific power of 105 horsepower per liter (77 kW/l), resulting in an output of 450 horsepower (332 kW). The installed wet weight of the 450 hp diesel engine package is within 45 pounds (20 kg) of alternative 350 horsepower (257 kW) air-cooled turbocharged engines currently used in aero applications.

The diesel combustion process, together with the design freedom provided by high strength CGI coupled with steel pistons, enable the lowered fuel consumption and emissions. Flying range and payload are also increased.

CO2 emissions for ten different GA engines. Avgas engines (solid and dashed black curves) require the abrupt fuel consumption increase at 262.5 hp to prevent destructive detonation and pre-ignition; turboprop engines, (single dotted black curve); and diesel engines (colored curves).

At optimal cruising speed, the Graflight V-8’s output of CO2 is 30% less than comparable Avgas engines and 17% less than comparable diesel engines, using conversion values provided by the US Energy Information Administration to convert fuel use into CO2 output at the rate of 18.3 pounds per gallon of Avgas burned and 21.1 pounds per gallon of Jet-A fuel burned.

Source: EPS. Click to enlarge.

The Graflight V-8 engine employs an electronic control system designed and manufactured by Bosch General Aviation Technology; the system reduces to dramatically reduce pilot workload and ensure efficiency and ease of operation. The engine is controlled with a single power lever, leaving traditional pilot chores such as propeller pitch, fuel mixture and controlling engine temperature to the computer, reducing the risk of pilot error.

The use of extremely rugged technologies such as the steel pistons and CGI iron crankcases result in a targeted Time Between Overhauls (TBO) of 3,000 hours—a 50 to 100 percent increase over the industry’s current values of 1,500 to 2,000 hours.

CGI offers approximately double the fatigue limit of conventional grey iron and aluminium alloys, thereby achieving bottom-end durability requirements without increasing the size or weight of the main bearing region. The strength and stiffness of CGI also improve the dimensional stability of the cylinder bore to reduce piston slap, bore wear, oil consumption and blow-by, notes EPA partner Sintercast.

With the prospect that avgas (leaded aviation gasoline) will be prohibited, the ability of the EPS engine to use widely available and low cost jet and diesel fuels provides a significant global growth opportunity, the company suggests. The Graflight V-8 can run on a variety of heavy fuels, including Jet A, JP-8 or straight diesel.

With series production awarded to the Grainger & Worrall foundry in the UK, using the SinterCast process control technology, the engine is intended for use in single and twin engined aircraft, small helicopters, unmanned military aircraft, and potentially marine applications.

Building on our design experience with automotive diesel engines, we knew that Compacted Graphite Iron was the optimal material for the crankcase of our Graflight V8. The aero-engine industry has been relying on outdated engine technology and fuels for more than 20 years. Our use of modern technologies such as CGI, steel pistons, common rail fuel injection and electronic engine control form the basis of our competitive advantage, our contribution to the aviation industry, and our market opportunity. Our partnerships for the supply of critical components and technologies, with proven world class suppliers like Grainger & Worrall and SinterCast, are a key element of our ability to meet the necessarily stringent requirements set by the aviation authorities.

—Michael Fuchs, President of EPS

SinterCast is a leading supplier of process control technology for the reliable high volume production of Compacted Graphite Iron (CGI). SinterCast technology, with 44 installations in 13 countries, is primarily used for the production of gasoline and diesel engine cylinder blocks and exhaust components for passenger vehicles, medium-duty and heavy-duty cylinder blocks and heads for commercial vehicles, and industrial power engine components for marine, rail, off-road and stationary engine applications.


Bob Niland

«…and emissions compared to conventional aero engines…»

An unfortunate moment in history to be making emissions claims about new diesel engines (speaking as an owner of a pre-Tier2 TDI, by the way).

«…single power lever, leaving traditional pilot chores such as propeller pitch, fuel mixture and controlling engine temperature…»

A dual-lane FADEC (EECS), in case anyone is wondering.

This apparently is not the first piston aero engine with a FADEC. General aviation has historically been deeply suspicious of anything more advanced than dual magnetos, but jet engines have been on FADECs for decades.

The EPS site is silent on the specific pump, except to say that it's a Bosch. I trust it's not a CP 4.1 (google HPFP TDI for why).

«…run on a variety of heavy fuels, including Jet A, JP-8 or straight diesel.»

The EPS site is silent on whether this engine can run biofuels. Perhaps they are waiting for one to be widely certified for aero use.


The good part is dropping the leaded gasoline; the bad part is it's still a fossil fuel burner/polluter ICE.
I would like to see the money spent on developing a fuel cell airplane that produces electricity to run electric motor ducted fans and produces no emissions.



I agree. I would like to see an electric plane with reformer on board turning jet fuel into hydrogen. That design could also be used for airline APUs.


I'm pretty well known on this site as a supporter of fuel cell vehicles, which I think provide interesting options.

However the story of why diesel instead of fuel cells in aircraft can be read from the energy density characteristics -77 kw/Litre, many times that of fuel cells, which run at around 2.5 kw/Litre:


Of course, a fuel cell is not the engine, but that just makes things worse, as the engine comes in on top of that.

So diesel, perhaps with some fuel cell or battery assistance for take off, in a hybrid at best, or simply fuel cells for APU use seems the practical way forward for most aircraft, although the HY4 may prove me wrong:

No reason an on board reformer should not use diesel, and for taxiing etc would greatly reduce emissions.


You would use jet fuel because that is what the airliners use. The problem with Delta Hawk or other diesel plane engines is fuel. Airports carry aviation gasoline and jet fuel. If the diesel people want to use jet fuel in their engines, they have to sign a waver.


I like hydrogen reformed on the ground and delivered as a fuel for the FC. The design should also include a buffer battery for safety. The FCA (Fuel Cell Airplane) is surely a future product right now; but, it may become reality when people realize how polluting jets and ICEs are at altitude, especially in GHG.



Installing diesel pumps at airports does not sound impossible onerous, although for the jets APU's might use jet fuel in the reformer.


As more diesel engines are used in private planes we could see diesel pumps at the fueling ramps. It is a restriction however, the airport you are flying to has to have one, if they don't you can't go there.



Check out my link on the HY4.

Batteries are needed anyway for take off power.

The reliability of fuel cells is now excellent, as was shown by their performance as the most reliable back up in Hurricane Sandy, where they beat all comers.

Their inherently modular nature means that designing in fail safe supplies should be (relatively) easy.

But the link also shows the limitations of pure fuel cell aircraft at present.

Here is more on the HY4:

I don't have info on how much reformers weigh at present, but the aim is to avoid the very large weight penalty of carbon fibre tanks to contain hydrogen.

That penalty is manageable for cars, but a lot harder for aircraft.


@SJC - Changing fuels in an aircraft requires an STC (Supplemental Type Certificate) not a "waver".

As Davemart correctly points out, the power to weight ratio is the driving requirement here. It will probably be a very long time before hydrocarbon based FC systems are used in General Aviation applications, if ever.

Battery electrics become viable at 400Wh/kg. Three small trainers are already in development.

Hybrid powerplants are under development, but there's very little opportunity for efficiency gains in a vehicle that spends almost all of its time at 75% of max power.


Hybrids are useful for take off, and might greatly reduce pollution.

Fuel cells may work for very light aircraft within the forseeable future, and for APU's, but aren't on the horizon for anything much bigger.

Ships and cars are a different and much more hopeful ballgame.



The article I read called it a waver of responsibility for the oil company, if Chevron was providing the fuel at that airport you would sign it there.


A supplemental type certificate (STC) is a national aviation authority-approved major modification or repair to an existing type certified aircraft, engine or propeller.


"There's a waiver they can sign indemnifying ExxonMobil from liability if something goes wrong. "We're recommending [diesel aircraft owners] sign the waiver and continue using jet fuel," Diamond's Maurer said."
I misspelled "waiver", but my statement IS accurate.


Two observations:

  1. The aerodiesels are DEFINITELY coming.  One of the outfits I've been watching since the 90's just announced a major investment and production of certified engines.
  2. These guys show better BSFC than DeltaHawk.  I wonder what they're doing, and how their iron construction affects cost and mission weight comparatively?


This is quite a breakthrough (well evolutionary step). It will add 30-50% range to light planes, which I am sure they would like.
The emissions brohaha won't apply as you fly planes around cities, rather than through them.
You just can't beat the energy density of liquid hydrocarbons for aerospace applications, especially at the lower end where you don't have that much space (or money) for hybridisation.
Expect to see this coming to drones asap.
It can't be that difficult to provide diesel at aerodromes - it is not a volatile fuel.

I think we may see hybrid aircraft in 10-20 years, I do not see battery powered aircraft in anything but very limited use (short flights, replaceable batteries), and solar powered aircraft are a stunt rather than a realistic transport approach (You might see solar surveillance drones, however).

Henry Gibson

This company is well aware of the existing diesel aircraft engines that have many diesel/jet-A planes flying already. Jet fuel is the appropriate universal fuel for cheaper more efficient flying. Since the weight of the fuel rather than the volume is some what more important; eventually, liquid methane can supply at least as much as 90 percent of the energy required for flight with an additional tank for it and slight modifications of controller programming and fuel injection. Such systems have long been available for diesel emergency generators.

Many of the Zeppelins used diesel fuel but some used a manufactured gas with the same density as air stored in fabric compartments to keep proper flotation. Water was sometimes condensed and collected out of the exhaust of the diesels for the same reason.

Hybrid engine powered vehicles have been around for a very long time; and diesel electric locomotives are an old example; but in the case of aircraft it is now possible to look at small lightweight hydraulic systems; perhaps an Artemis digital hydraulic powered propeller combined with multiple INNAS NOAX free piston diesel powered pumps for more reliability and life.

The Artemis digital displacement system can eliminate for automobiles half the fuel use for the same travel and should be required for all automobiles. INNAS NOAX can get good efficiency with their hydraulic devices. Neither requires heavy electric batteries.

Diesel piston engines have efficiencies that are equal to many fuel-cell systems with less weight and much less cost.

The large Mars rover is powered with a very safe material, and a plane that could fly without landing for twenty years or more for refueling could also be built with such or similar materials at great cost.



A waiver of liability to a fuel supplier (how convenient!) would have zero effect on any pilot or aircraft owners ability to legally use a fuel other than the specific fuel authorized by the manufacturer when the aircraft was originally granted its airworthiness certificate.

It is simply irrelevant to to topic.


DM> Hybrids are useful for take off, and might greatly reduce pollution.

I encourage research in this area, but consider that the supplimentary power plant would only be used for take-off, which is just a few minutes, but would be dead weight the rest of the flight, which would typically be a few hours. Really hard to make that math work.


As usual you babble non sense pretending you know something.


Except ECI is right.


Gee, SJC, I hope you feel better now that you got that off your chest. What are your qualifications to weigh in on this subject, other than looking up STC in wikipedia?

I own a Diamond Aircraft (not one of the diesels in question) and follow the company's products very closely, including Airworthiness Directives and Advisory Circulars for more than just my model.

I'm not sure if you just didn't read the AV article carefully, or just don't understand the issues but this line from the article is helpful:

"Maurer noted that the Thielert engines in his company's aircraft are specifically certified to use jet fuel only"

The comments to this entry are closed.