Ruston Marine and Industrial Engines

Ruston was a Lincoln engine builder whose lineage runs from agricultural steam plant in the 1840s to medium-speed diesels still in naval and rail service in 2026. The name most engineers know today, Ruston & Hornsby, was formed in 1918 by merging Ruston, Proctor & Co. of Lincoln with Richard Hornsby & Sons of Grantham. That merger joined two distinct competences: Ruston’s heavy fabrication and steam-engine volume, and Hornsby’s oil-engine patents, the most consequential of which was the Hornsby-Akroyd hot-bulb engine of Herbert Akroyd Stuart. Across the twentieth century the firm built diesels for ship propulsion, generator sets, rail traction, and stationary power, then passed through English Electric, GEC, and Alstom before its diesel business reached MAN and its gas-turbine business reached Siemens. The RK engine family is the part of that history most often found at sea, in gensets aboard Royal Navy and Royal Fleet Auxiliary vessels.

This article covers the corporate history, the engine families, and Ruston’s place in marine and naval power. It does not assign power, fuel, or efficiency figures to specific engine types unless those values come from a cited source, because the surviving published record for individual Ruston ratings is uneven. Where a general engine metric is discussed, the relevant calculator is linked so a reader can run the number for a known input. For the wider taxonomy of British and European builders, see marine engine makers.

The two firms before the merger

Ruston, Proctor & Co. traced to a Lincoln engineering partnership of the 1840s and grew into one of Britain’s larger makers of portable and traction steam engines, threshing machinery, and later excavators. The works sat by the River Witham in Lincoln, and the firm built an export trade across Russia, Eastern Europe, India, and South America. Ruston’s strength was volume manufacture of heavy iron and steel plant, plus a sales reach that few provincial English makers matched.

Richard Hornsby & Sons of Grantham, in the same county, was the more important firm for engine history. Hornsby was an agricultural-machinery maker that took up internal-combustion work in the late nineteenth century, and it held the rights to the work of Herbert Akroyd Stuart. That single decision put Grantham at the center of the early oil engine, a position that mattered far more than the firm’s size at the time suggested.

The First World War reshaped both companies. Ruston, Proctor built aircraft and aero-engines under contract during the war, which expanded its plant and workforce. By 1918 the two Lincolnshire firms had complementary rather than competing lines, and they combined to form Ruston & Hornsby Ltd, registered in 1918. The Lincoln site became the heavy-engineering and oil-engine center; Grantham work was reorganized into the combined business.

The merger logic was straightforward. Ruston had the larger works, the heavier plant, and the export sales force, but its engine knowledge was rooted in steam. Hornsby had the oil-engine patents and the field experience of building and selling internal-combustion machines, but it was the smaller firm with less manufacturing capacity. Joining the two put Hornsby’s oil-engine design under Ruston’s production scale, which is the pattern that let the combined firm move into volume diesel work in the following two decades. The choice to keep heavy engineering at Lincoln, rather than splitting design from manufacture across two towns, set the geography that lasted until the consolidations of the 1960s.

It is worth being precise about the founder name often attached to the firm. Joseph Ruston ran the Lincoln business through its growth in the nineteenth century, and the Ruston name carried into the merged company and every successor brand after it. By the 1918 merger Ruston was already a substantial Lincoln employer, and the addition of Hornsby’s Grantham engine work broadened the combined firm rather than rescuing it.

The Hornsby-Akroyd hot-bulb engine

Herbert Akroyd Stuart patented his oil engine in 1890, and Richard Hornsby & Sons built it as the Hornsby-Akroyd engine. That date matters. Akroyd Stuart’s patent predates the engine patent of Rudolf Diesel, and the two machines work on different principles, which is why the Hornsby-Akroyd is not a diesel even though it burns the same class of fuel.

The hot-bulb engine carries a separate combustion chamber, the bulb or vaporizer, cast into the cylinder head. The bulb is heated by an external lamp to start, then held hot by combustion once running. Fuel sprays into the hot bulb, vaporizes, and ignites from the heat of the bulb wall rather than from the heat of compressed air. Compression ratios are low compared to a diesel, so cylinder pressures and the structural demands on the engine are lower. The trade is efficiency and the awkward starting routine: the operator preheats the bulb with a blowlamp for several minutes before the first stroke.

That distinction sets the Hornsby-Akroyd apart from Diesel’s compression-ignition cycle, where air alone is compressed hard enough to raise its temperature above the fuel’s ignition point, and fuel is injected at the end of compression with no separate heated chamber. Diesel’s engine is more efficient and more demanding to build. The hot-bulb engine is simpler, more tolerant of crude fuel, and cheaper, which is why hot-bulb designs stayed in production for stationary, agricultural, and small-marine use long after the diesel arrived. The same logic kept Scandinavian builders such as Bolinder selling hot-bulb marine engines for fishing craft and coasters well into the twentieth century.

The starting routine is the feature that fixes the type in any engineer’s memory. The operator lights a paraffin blowlamp under the bulb and waits, often several minutes, until the bulb glows hot enough to vaporize the first charge of fuel. Only then can the engine be barred over and fired. On a fishing boat in cold weather that wait was a real operational cost, and it is one reason the diesel displaced the hot-bulb once electric and compressed-air starting made cold cranking of a high-compression engine practical. The hot-bulb’s tolerance of cheap, heavy, dirty fuel kept it alive where fuel quality and cost mattered more than starting convenience.

The hot-bulb also runs at low speed and large displacement for its output, which suits a directly coupled propeller shaft on a small vessel but makes the engine heavy for its power. A diesel of the same output is lighter and runs faster, so the diesel won every application where weight or power density mattered. The two cycles divided the market along those lines for decades: hot-bulb for the cheapest, simplest, lowest-duty installations, diesel for everything that needed efficiency or compactness. Ruston & Hornsby built across that divide in its early years, then followed the market toward the diesel as the firm’s main line.

The engineering vocabulary of the hot-bulb fed into the diesel work that followed. Fuel injection, combustion-chamber shaping, and the handling of heavy fuel were problems the Grantham engineers had already met on the Hornsby-Akroyd, and that experience carried into the firm’s compression-ignition designs. The continuity is part of why the merged company moved into diesel production with a credible product rather than starting from nothing.

The Hornsby-Akroyd’s place in oil-engine history is secure for two reasons. It was an early, commercially built compression-assisted oil engine that reached real customers in numbers, and it gave the merged Ruston & Hornsby firm a head start in oil-engine knowledge that carried into its later diesel work. The relationship between Akroyd Stuart’s work and Diesel’s is still debated by historians, and this article does not resolve priority claims. What is documented is the 1890 patent date and the production of Hornsby-Akroyd engines by the Grantham firm before the merger.

From oil engine to diesel

Through the inter-war years Ruston & Hornsby moved its engine line toward true compression-ignition diesels for industrial, marine, and power-generation duty. The firm built single-cylinder and multi-cylinder horizontal and vertical engines for pumping, electricity generation, and small marine propulsion, alongside its continuing trade in agricultural and excavating machinery. The Lincoln works also kept a large stationary-engine business serving water boards, mines, and overseas utilities that needed prime power away from any grid.

A diesel’s output for a given size is governed by how hard each working stroke pushes on the piston, averaged over the cycle. That single number, brake mean effective pressure, is the cleanest way to compare engines of different bore and stroke, and it is the figure that rose across successive Ruston designs as turbocharging and better materials arrived.

The inter-war stationary business is easy to overlook but it set the firm’s engineering habits. An engine sold to a remote water board, mine, or overseas utility had to start reliably, run for long hours, and be serviceable by local staff with limited support from Lincoln. Those requirements pushed Ruston toward simple, durable designs with long overhaul lives, and that bias carried straight into the firm’s marine and naval work, where the same demands apply at sea. The stationary trade also gave Ruston a worldwide service footprint that later helped sell engines into Commonwealth navies and merchant operators.

By the Second World War Ruston engines were in wide service. The firm again took on war production, and its diesels powered generating sets, pumps, and auxiliary plant for military use. The post-war period is where Ruston’s marine and naval engine work took its mature shape, organized around a small number of engine families rather than a long catalog of one-off designs. Concentrating on a few families, each built in several cylinder counts, let the firm hold down the cost of design, tooling, and spares while still covering a wide power band, and it is the structure that made long product lives like the RK’s possible.

The engine families

Ruston’s twentieth-century engine line is usually grouped by family rather than by individual model, because each family spanned several cylinder counts and a long production run. The naming is not always consistent in surviving literature, so the descriptions below stay to what the type designations denote rather than assigning ratings.

The vertical engine ranges carried letter codes such as VG and VR for the earlier medium and smaller vertical diesels, offered in several cylinder counts for stationary and marine genset duty. These were the workhorses of the firm’s general-purpose diesel business, the engines that went into pumping stations, standby plant, and small ship installations through the middle of the century.

The multi-cylinder ranges were built in 6, 8, 9, and 12-cylinder forms across different families, giving customers a span of outputs from one basic design. A buyer specifying a generator set could take the cylinder count that matched the load rather than commission a bespoke engine, which is the same modular logic that medium-speed builders use today. For the engineering context of that engine class, see medium-speed four-stroke marine engines and the underlying four-stroke marine diesel engine fundamentals.

The RK family is the design most associated with Ruston in both rail and marine service. It was a medium-speed engine built in V configurations, and it became the firm’s principal product across the 1960s, 1970s, and 1980s. The RK appeared in three main roles. It was the prime mover for diesel-electric locomotives, most famously the British Rail Class 37, where the 12-cylinder RK drove a generator feeding traction motors; many Class 37 locomotives remained in service in 2026 after multiple heavy overhauls. It was a marine and naval genset engine, fitted aboard Royal Navy ships and Royal Fleet Auxiliary vessels. And it served as a stationary prime-power and standby engine across British and Commonwealth sites.

The RK’s value to Ruston was that one engine family served all three markets with the same parts, the same overhaul procedures, and the same trained fitters. A rail depot, a dockyard, and a power station could draw on a shared spares pool and a shared body of maintenance knowledge. That commonality is why the design earned long production and long service: every operator who ran one had a reason to keep running it, and the installed base supported the spares and service business that justified continued support after new build slowed.

The diesel-electric arrangement on the Class 37 is the same arrangement Ruston used in many marine gensets, which is part of why the rail and marine sides reinforced each other. The engine turns a generator, the generator feeds either traction motors on a locomotive or the ship’s electrical board on a vessel, and the engine itself never drives a mechanical output shaft directly. That decoupling lets the engine run at its best speed regardless of the load’s speed, and it is the reason a medium-speed four-stroke suits both jobs. The arrangement is covered in the general engineering articles linked above.

Building one family in several cylinder counts also let Ruston quote a power range without redesigning the engine. A customer who needed more output took more cylinders of the same bore and stroke, which kept piston, liner, valve, and injector parts common across the range. That modularity is standard practice among medium-speed builders now, and it was already Ruston’s practice on the RK and on the earlier vertical ranges.

The AP designation belongs to the part of Ruston’s later history that ran with Paxman. Ruston’s diesel business and the Colchester firm Paxman were both pulled into the same corporate group, and the combined operation traded for a period as Ruston Paxman. Paxman’s high-speed engines, including the Valenta and later the VP185, sat alongside Ruston’s medium-speed RK rather than competing directly, because the two covered different speed and power bands. For that side of the story see Paxman marine engines.

Putting Ruston and Paxman in one operation made commercial sense once both were inside the same parent. A high-speed engine and a medium-speed engine answer different duties: the high-speed Paxman suits a fast naval craft or a compact installation where weight rules, the medium-speed Ruston suits a genset or a small-vessel propulsion job where overhaul life rules. Selling both from one sales and service organization let the combined firm quote across a wider band of naval and industrial requirements than either could alone. The two engine ranges kept their own designations and their own factories, but the customer faced a single supplier.

How the medium-speed class shaped the engines

Ruston’s marine and rail engines belong to the medium-speed four-stroke class, and the choices that define that class explain the engines’ shape and service pattern. A medium-speed engine runs faster than a deep-sea two-stroke and slower than a high-speed engine, which lets it use trunk pistons rather than the crosshead arrangement of a large slow-speed engine. That makes it lighter and shorter for its power, at the cost of higher specific fuel consumption than the largest slow-speed units. For a genset or a small vessel, the compactness wins; for deep-sea propulsion, the fuel economy of the slow-speed engine wins, which is the divide that kept Ruston on the auxiliary and small-craft side of the marine market.

The four-stroke cycle gives the engine a separate exhaust and intake stroke, which simplifies the gas exchange and suits turbocharging. Across the RK’s production life turbocharging and charge-air cooling raised the output available from a given engine size, the same trend that lifted brake mean effective pressure across the wider medium-speed industry. The general engineering of this class, including the gas-exchange and turbocharging detail, is set out in the linked fundamentals articles rather than repeated here.

Overhaul life is the metric that medium-speed marine and rail operators watch most closely, because it sets the interval between major maintenance and so the running cost over an engine’s life. Ruston designed for long intervals, which is consistent with its naval, rail, and overseas-stationary customer base, all of whom run engines hard for years between heavy overhauls. The Class 37 service record is the clearest public evidence of that design choice.

Ruston in marine and naval power

Ruston’s marine presence was concentrated in generation rather than main propulsion. The RK and the earlier vertical ranges were a natural fit for ships’ service-generator sets, where a medium-speed four-stroke driving an alternator gives a compact, maintainable source of electrical power. The arrangement and redundancy logic for that kind of installation is set out in marine auxiliary engines and generators.

The Royal Navy and the Royal Fleet Auxiliary were steady customers. Ruston engines were specified as generator prime movers and, in some classes, as propulsion engines for smaller naval craft such as minesweepers, survey vessels, and patrol boats through the 1960s to the 1980s. The pairing of a British engine builder with British naval procurement gave Ruston a protected base of orders that outlasted much of the merchant market it once shared with other domestic makers. For the general engineering background of the propulsion engines themselves, see marine diesel engine.

The fuel behavior of these engines follows the same physics as any other medium-speed diesel. Brake thermal efficiency is the share of the fuel’s heating value that becomes useful shaft work, and it is read off the specific fuel consumption once the fuel’s net calorific value is known.

Charge-air temperature changes that consumption. A warmer intake lowers the air density reaching the cylinder, which moves the specific fuel consumption by a small amount per degree, and on a ship with a tropical engine room that drift is large enough to matter over a long voyage.

Naval and auxiliary work suited Ruston’s strengths. The engines were built for long overhaul lives and for service in places far from the factory, which is the same requirement the firm’s overseas stationary-power customers had imposed for decades. That bias toward durability over peak output is part of why Class 37 locomotives, sharing the RK heritage, were still running so long after build.

Why generation, not main propulsion

Ruston’s marine business sat on the auxiliary side for a reason that is structural rather than accidental. Main propulsion on a large merchant ship rewards the lowest specific fuel consumption, and from the mid-twentieth century that pushed deep-sea propulsion toward large slow-speed two-stroke crosshead engines that medium-speed builders like Ruston did not make. Generator sets, by contrast, reward compactness, fast response to load change, and the ability to run several units in parallel for redundancy, all of which suit a medium-speed four-stroke. Ruston’s engine class fit the genset job and did not fit the deep-sea propulsion job, so the firm concentrated where its product was competitive.

The naval case is different again. Warships and naval auxiliaries value power density, redundancy, and the ability to keep running with battle damage more than they value the last percent of fuel economy. Multiple medium-speed gensets feeding an electrical distribution board give a warship survivable, reconfigurable power, and that is the role Ruston engines filled across several decades of Royal Navy and Royal Fleet Auxiliary service. The same engineering that made the RK a good rail and standby engine made it a sound naval auxiliary.

Smaller naval craft were the exception where Ruston engines did drive propellers. Minesweepers, survey vessels, and patrol boats are small enough that a medium-speed diesel can serve as the main engine, and on those classes Ruston supplied propulsion rather than only generation. Mine countermeasures vessels in particular favored engines and mountings chosen for low magnetic and acoustic signature, a specialist requirement that British naval builders met with domestic engines through the period.

National procurement and the British engine base

The Royal Navy’s preference for British-built propulsion and generating plant gave Ruston a base of orders that did not depend on the open merchant market. That base mattered as the merchant diesel market consolidated around a small number of large licensors and as British merchant shipbuilding contracted. A naval order book is smaller than a merchant one but more stable, and it carries a long support tail because warships serve for decades and are refitted rather than scrapped early. Ruston’s naval and rail work together gave the firm a domestic customer base that outlasted the merchant trade it once shared with other British makers.

The corporate path: English Electric, GEC, Alstom, MAN, Siemens

Ruston & Hornsby’s independent life ended in the consolidation of British heavy engineering. In 1966 the diesel-engine business was acquired by English Electric, which already held a large diesel and traction interest; the combined operation traded under English Electric Diesels. The history of that parent’s own engine work is covered in English Electric marine engines.

In 1968 English Electric was absorbed into the General Electric Company, GEC, in one of the largest reorganizations of British industry of the period. Ruston’s diesel and gas-turbine activities passed under GEC ownership, which set the stage for the later split between the two product types.

The split is the part most often confused, so it is worth stating plainly. Ruston by this point ran two distinct engine businesses: medium-speed and high-speed diesels, and industrial gas turbines. These had different customers and different technology, and they went to different owners. The diesel-engine lineage, carrying the Ruston and Paxman names, moved through the GEC and Alstom corporate chain and reached MAN, where it is supported within MAN Energy Solutions as legacy product. The industrial gas-turbine business, which had grown into a major line built around the Ruston-named units, passed through GEC and Alstom and then to Siemens, where it sits within the industrial gas-turbine portfolio.

GEC formed a power-systems joint venture with the French firm Alstom in 1989, creating GEC Alsthom, which later became Alstom. Ruston’s businesses moved into that structure. The diesel-engine operations were sold on from Alstom around 2000, and that sale is the point at which the Ruston and Mirrlees Blackstone diesel lineages came under MAN. The related Stockport firm’s history is covered in Mirrlees Blackstone marine engines.

The gas-turbine line followed a different exit. Siemens acquired the industrial gas-turbine business that carried the Ruston-named units, and the Ruston gas-turbine designations continued under Siemens ownership for the installed base and for new industrial and offshore power orders. The same family of small and medium industrial turbines that began at Lincoln became part of a much larger turbine portfolio.

The reason the two halves of Ruston went to different owners is worth holding onto, because the brand name attaches to both and that causes confusion. A diesel engine and an industrial gas turbine are different machines built by different engineering disciplines for overlapping but distinct markets. When a conglomerate breaks up its power businesses, it sorts the assets by technology and by which buyer can run them best, not by the legacy brand printed on them. So the Ruston diesels went where the diesel expertise and the rail and marine support network were, and the Ruston turbines went where the turbine portfolio and the oil-and-gas customers were. One historical firm, two technologies, two buyers.

This split also explains why a search for the Ruston name today returns two unrelated current product lines. On the diesel side, the RK heritage sits inside MAN Energy Solutions as supported legacy product. On the turbine side, the Ruston-named industrial units sit inside the Siemens industrial gas-turbine range. A reader who finds a Ruston gas turbine in service and a Ruston diesel in service is looking at the two descendants of the same Lincoln firm, now owned by different companies.

The Lincoln site and the closure of independent engine building

The original Lincoln works, long known by its iron-works name, was the heart of Ruston engine building. Through the consolidations it kept engineering and manufacturing activity, but the era of an independent Lincoln engine maker setting its own product strategy ended once the firm was inside English Electric and then GEC. Decisions about which engine families to keep, and which to drop where they overlapped a parent’s own range, were made above the Lincoln level.

Diesel-engine manufacture in the Ruston designation wound down as the installed base aged and as new orders went to the parent companies’ own current engine brands. By 2026 the Ruston name on the diesel side functions as a legacy-support brand within MAN Energy Solutions rather than a line of new engines, while on the turbine side the Ruston-named units continued as a documented product family under Siemens. The Lincoln industrial site retained engineering and service work under successor ownership.

The closure of independent Lincoln engine building is part of the wider contraction of British marine and industrial diesel manufacture in the second half of the twentieth century, the same contraction that ended independent production at Stockport, Manchester, and Colchester. Ruston outlasted many of its domestic peers because of its naval and rail base and because both its diesel and turbine lines found homes inside larger groups that had reasons to keep them.

The pattern of that contraction is consistent across the British industry. A provincial engine maker with a strong domestic order book gets absorbed into a national conglomerate during a wave of consolidation, its product range is rationalized against the parent’s own lines, new-build volume drops as orders move to the parent’s current brands, and the original works settles into service and support work for the installed base. Ruston, Mirrlees Blackstone at Stockport, Crossley at Manchester, and Paxman at Colchester all followed some version of that path. What distinguished Ruston was that both halves of its business, diesel and turbine, were valuable enough to keep, so neither was simply closed.

The installed base is the reason the support work persists. A medium-speed diesel or an industrial gas turbine runs for decades, and the operator needs spares, overhaul parts, and engineering support for the whole of that life. A locomotive fleet still in traffic, a warship still in commission, and a power plant still on load each generate support demand long after the last new engine ships. That demand is what keeps the Ruston name on current parts lists at MAN and the Ruston turbine designations current at Siemens, even with new build in the original designations ended.

Legacy

Ruston’s legacy rests on three documented things rather than on any single record-setting engine. The first is the Hornsby-Akroyd hot-bulb engine and its 1890 patent, which places the Grantham firm in the early history of the oil engine before the diesel reached production. The second is the RK family’s service life, shown most plainly by Class 37 locomotives that were still working in 2026 after decades of overhauls, a durability record that carried into the marine gensets sharing the design. The third is the survival of both the diesel and the gas-turbine lineages inside MAN and Siemens, which keeps the engineering alive even though independent Lincoln production has ended.

For the consumption arithmetic that owners of any surviving medium-speed installation still run, the cube-law relationship between speed and fuel demand is the most useful single tool, because it converts a small speed change into the fuel saving or penalty that follows.

Surviving Ruston and Hornsby engines are held and run by preservation bodies, and the firm’s records are split between public archives and successor-company holdings. The Anson Engine Museum at Poynton runs Ruston and other historic engines, the Science Museum Group holds Ruston and Hornsby material in its collection, and Lincolnshire Archives holds business records of the Lincoln firm. These are the sources a researcher should reach for rather than the secondary engine sites, because the type histories in the secondary literature are inconsistent on ratings and dates.

The preserved Class 37 fleet is the most accessible living example of the RK family’s marine and rail heritage, because a locomotive in heritage traffic can be seen and heard running on a public railway. The engine in those locomotives shares its design lineage with the gensets that went to sea, so a visitor to a preserved Class 37 is close to the marine product even though the vessel installations are far harder to reach. Naval and auxiliary engines are mostly inaccessible once a ship is decommissioned, which is why the museum-held examples and the rail fleet carry most of the public memory of Ruston engine building.

For the company history itself, the archive holdings matter more than the engines. Business records, drawings, and order books at Lincolnshire Archives and The National Archives carry the firm’s corporate story with dates and identifiers that the secondary literature often gets wrong. A researcher building a reliable type history or corporate chronology should work from those holdings and from the successor companies’ own documentation, and treat the popular engine sites only as a finding aid, not a source. The same caution applies to ratings: where this article declines to state a power or consumption figure, it is because the public record does not support a single trustworthy value, and the safer route is to compute the number from a sourced input using the linked calculators.

Limitations

This article gives no power, torque, fuel-consumption, or efficiency figures for specific Ruston engine types, because the surviving published record for individual ratings is uneven and much of it appears in secondary sources that this site does not treat as authoritative. Where a number would be expected, the relevant calculator is linked so a reader can compute it from a sourced input.

The engine-family descriptions stay to what the type designations denote rather than mapping every variant. Ruston’s naming across its long history is not consistent in surviving literature, and cylinder-count and configuration details for sub-variants should be checked against the builder’s own records or museum holdings before use in any technical decision.

The priority dispute between Herbert Akroyd Stuart’s 1890 patent and Rudolf Diesel’s engine is a live question among historians, and this article does not settle it. The documented facts stated here are the 1890 patent date and the production of Hornsby-Akroyd engines by Richard Hornsby & Sons before the 1918 merger.

The corporate chronology is stated at the level the public record supports: the 1918 merger, the 1966 English Electric acquisition, the 1968 GEC absorption, the 1989 GEC Alstom formation, the diesel-business sale around 2000 that reached MAN, and the turbine-business move to Siemens. Exact transaction structures and dates for individual asset transfers should be confirmed against company filings at The National Archives or the relevant company registry before being relied on.

See also

• Paxman marine engines
• English Electric marine engines
• Mirrlees Blackstone marine engines
• Bolinder hot-bulb marine engines
• MAN Energy Solutions corporate history
• Crossley Brothers marine engines
• Marine diesel engine
• Medium-speed four-stroke marine engines
• Four-stroke marine diesel engine fundamentals
• Marine auxiliary engines and generators
• Marine engine makers
• Auxiliary engines N-1 redundancy check
• IACS UR M66 type testing of diesel engines