Although RET usually looks at engines competing at the top levels of motorsport in one way or another, the one discussed here perhaps has no natural home and is certainly not one of them. Its roots are in a historic engine, and the four-cylinder unit it is based on the Austin A-series engine as used in the original Mini, an engine that has manufactured in the millions.
It is the first piston engine produced by a long-established business, which has taken a refreshing and open-minded approach to manufacture, throwing itself in at the deep end. Ascaso Engineering is an offshoot of A&M EDM, a manufacturing company in England. A&M EDM has a far wider range of manufacturing techniques in-house than its company name suggests.
As a manufacturing company, A&M has an extensive conventional modern machining capability, along with EDM (electro-discharge machining) and laser welding. Its customers include aerospace companies, Formula One teams and motorsport engine manufacturers, and it has its own products, including Wankel rotary engines.
The Ascaso A+5 with its crankshaft removed. The double-studded centre main bearings are clearly visible (Images courtesy of Ascaso/A&M EDM)
For its first piston engine, the Ascaso A+5, it has exploited its familiarity with a wide range of manufacturing techniques. EDM for example is used on cylinder blocks, con rods, some types of cylinder head, crankshaft, head gasket and timing pulleys.
Ascaso is a separate entity under the A&M umbrella, and was set up to produce its own products and to be a viable business. However, what it is producing is also an impressive showcase of what it and A&M can do. Many of the components are over-engineered for a relatively modest Mini engine with its roots firmly in the middle of the 20th century.
New engine, historic roots
The Ascaso A+5 is based on the Austin A-series unit, originally launched in 1951 and continued until 2000; its design began during 1944. In terms of its basic design it was typical of many engines of the time, having four cylinders and three main bearings.
Ascaso’s co-owner Gary Surman quickly realised the limitations of the three-bearing crankshaft for a race engine and set about designing and remanufacturing a modern A-series with a five-bearing crankshaft and a two-valves-per-cylinder OHV (pushrod) cylinder head.
Some might say Ascaso is 60 years late to the party. Nissan had a licence for the A-series and designed its own engine based on it (the Nissan E) in the late 1950s, which incorporated a five-bearing crankshaft among other improvements. Austin itself introduced a substantially improved A-series, called the A+, in 998 and 1275 cc versions from 1980 onwards, but these continued to use the three-bearing block and crankshaft.
The Ascaso A+5 is compatible with the original A-series and fits in an original Mini. It is strongly inspired by that engine, but is made using modern techniques and materials. It offers the owner of a racing Mini the chance to fit a more modern engine but one that is fully compatible with the original car, transmission, cylinder head and so on. For many, it is going to be a more appetising prospect than fitting a completely different engine.
Heads and valvetrains
An A+5 engine uses a range of available cylinder heads, and there are three basic options here – a head based on the original A-series engine (the 12G490 head), a much more modern four-valves-per-cylinder option from a BMW motorcycle with double overhead camshafts, and a bespoke racing head produced by Ascaso’s engine build and test partner Kent Auto Developments, which is also has four valves per cylinder.
The A+5 is unusual because it is designed from the outset to take both OHC and OHV heads, allowing customers the choice of remaining true to the pushrod two-valves-per-cylinder design philosophy of the original engine, or to choose something more modern with much greater performance potential.
The BMW head requires some very minor modification before fitting. It is not from the latest four-cylinder engine in the BMW S1000, but an older one with horizontal cylinders. The draining of oil from the head is thus very different in an engine with vertical cylinders, and the modification to the head ensures that oil can drain freely back to the bottom end rather than accumulating in the head.
The top end of the engine has many possibilities, depending on customer preference, and the aim is for the customer to specify inlet system, cylinder head and exhaust.
The serrated con rod face joint is actually tapered, preventing movement without using dowels
There are a range of capacities, ranging from 1.0 litre to just less than 1.3 litres; there are also naturally aspirated and turbo variants. Besides the BMW and Mini cylinder heads, there are plans to fit other heads, including the Yamaha R1. There are options to fit the original underslung transmission as per the standard, front-wheel-drive, transverse Mini engine installation, or to have the engine configured for a longitudinal installation.
Bottom end
Mechanically, the engine has several features of interest, starting with the cylinder block assembly. The block itself if machined from solid, which takes around 100 hours of manufacturing time. In recent years, machining from solid has become more common, but there are crucial differences to the usual billet blocks. The block material is 6082-T6 aluminium, which in the UK is really the workhorse of medium-to-high strength alloys. It is notable for its excellent weldability.
The A+5 block is machined with 2 mm of stock left on and then vacuum stress-relieved. It is then machined to leave a recess in the top surface. A deck plate is fitted, laser-welded in place and the top surface is then ground.
There are several unusual operations in this sequence. Access for cutting tools is improved by having a plate that is fitted later and welded in place. Laser welding is a very controllable process that can produce deeply penetrating welds but with highly-localised heating.
The process is often used for repair work and fitting inserts into existing finish-machined parts. The low heat energy input results in very little distortion compared to other welding processes.
The resulting geometry after welding has the advantages of the strength and accuracy of using a machined wrought alloy but the detailed internal geometry more normally associated with casting. Grinding aluminium is also relatively unusual, fly-cutting or face milling being more usual processes.
As per conventional engine practice, the cylinder block uses main bearing caps, made from steel. Each of the central three caps is secured by two large fasteners of equal size, with those at the ends secured by two large and two small bolts each. Surman says there are plans to design and manufacture a ‘ladder frame’, which incorporates all five main caps into a single, stiffer component, as is common practice in many modern race engines.
The cylinder liners are finned and made from steel, with a chromium nitride coating on the outside to prevent corrosion and a conventional Nikasil-type bore coating. The liners are individual, providing improved cooling by allowing water all around the circumference; it represents an important difference from the original engine, which had cast-in cylinders with no gap between them.
The joint between head and block is achieved using a copper gasket and wire rings.
The con rods are an unusual design, which Surman calls “hixbeam”. They incorporate aspects of traditional H- and I-beam sections but with an additional stiffening rib on the centreline of the rod. It still remains usual for a racing con rod to have an interfered copper alloy bush in the small end, in which the piston pin runs. The Ascaso rod has a plain-bored small end so that the DLC-coated piston pin runs directly in the rod.
The con rod joint has a unique design. On each side of the main bearing are two tapers produced on the joint faces in opposing directions, preventing the rod and cap moving independently in any direction. The caps are secured by a pair of race-spec bolts designed for a Honda Civic.
Cylinder blocks proudly displayed by Gary Surman (left) and Mark Wingfield (right), co-owners of Ascaso. The blocks are machined from solid 6082-T6 aluminium
Surman has worked with experts from a specialist steel manufacturer with links to Formula One engine suppliers to arrive at a material specification for his rods. Ascaso uses W360, a 0.5% carbon chromium-molybdenum-vanadium hot work tool steel that is more usually specified for forging tools, and is heat-treated to a final hardness of 52-54 HRc, which equates to a tensile strength of about 1800-1915 MPa (186-278 ksi).
Surman says the Ascaso rods are nitrided and superfinished. It is clear that, in the case of a Mini engine, this is probably a case of significant over-engineering. However, what is does show is that Ascaso can produce a working con rod to a specification more suited to significantly higher duty.
The pistons are three-ring aluminium alloy and are of conventional design.
The crankshaft is machined from an existing component and is used with racing bearings for a Suzuki Hayabusa engine. The Suzuki is a very powerful engine, even in production motorcycle guise, and has spawned a wide range of successful racing variants and is widely used to power cars in many types of racing with demanding duty cycles. The bottom end is known to be very strong, and using these bearings is a sensible choice.
The output features an Ascaso-produced tapered spline joint, which has also generated additional work in reclaiming cranks that were previously considered unsalvageable after suffering spline wear.
The oil system has been redesigned in order to promote engine durability, with the oil now being filtered before being fed into the pump and the main bearings.
As with the development plans for fitting stiffer bottom-end components and providing the ability to fit other cylinder heads, Ascaso has foreseen the development potential for the engine and that, sooner or later, someone will want to turbocharge it. As it happens, one of the first engines installed in a car was a turbo version, so there are water and oil take-offs in place for turbos requiring a specific feed of these. There are also piston squirt jets to cool the undersides of the pistons.
Ascaso uses EDM widely in the production of its components. This photo shows its wire-EDM and die-sinking machinery
The result of using aluminium for the cylinder block rather than the original cast iron is that, for the A+5 the whole ‘short engine’ – that is, up to the top face of the block, as built – is lighter than the original, bare Austin cylinder block.
Testing, racing and breaking records
At present, the engine has been run on the dyno to 9250 rpm, which equates to a mean piston speed in excess of 23 m/s. That is no mean feat, and some customers aim to run the engine to 10,000 rpm and beyond, for which dyno testing is yet to take place.
A Mini fitted with a turbocharged Ascaso A+5 has already lapped the Brands Hatch track in England in 52 seconds, and one customer aims to produce a turbocharged version of the engine with around 350 bhp to set a record as the world’s fastest Mini. Some people have of course have skilfully shoe-horned large-capacity V8s into modified Mini shells for many types of speed competition, but competition between Mini owners running four-cylinder engines respecting the A-series design is strong.
Summary
The original Mini was a very popular car, with more than 5 million sold and with production lasting for over 40 years. Although the A-series in any of its many guises and capacities – from 803 cc naturally aspirated to 1275 cc turbocharged – were fitted to a wide range of cars, it is only really the Mini that is still being raced in any numbers.
Some companies specialise in producing highly tuned competition versions of the A-series for historic racing, where the engines have to use original components such as three-bearing crankshafts and systems such as points ignition and SU carburettors, but there are many classes where highly modified and tuned Minis compete, and those who compete in these classes are naturally customers for Ascaso’s engine.
The Ascaso A+5 removes the mechanical limitations of the three-bearing crankshaft and gives a range of possibilities for competitors to have much higher performance without ruining the car’s handling and originality by fitting a physically larger engine.
It offers a great deal of development scope for customers to race with an engine compatible with the original A-series. With a range of modern cylinder heads compatible with the Ascaso A+5, and the five-bearing crankshaft being better suited to high speed, there is the opportunity to reach a higher power output.
The engine shows what is possible when considering a mixture of production methods, even within the relatively cost-constrained arena of Mini racing. Surman did the design work on the engine himself, so he has naturally conceived components that have been designed for cost-effective manufacture. He knows which cutting tools work well and has designed around these, rather than just modelling something that then requires a large collection of bespoke tools to be bought in.
After planning only a small number of the engine, Ascaso has had many more orders than anticipated.
Acknowledgement
The author would like to thank Gary Surman of Ascaso Engineering for his input into the article.
ANATOMY
The Ascaso A+5 is in inline four-cylinder gasoline engine, based on the Austin A-series engine. It features a machined-from-solid aluminium block produced from 6082-T6.
The block has options for cast iron or steel liners, but high-power variants use a steel liner with Nikasil plating internally and chromium nitride externally. The water circuit in the block now cools the whole circumference of each liner.
The pistons are conventional aluminium alloy three-ring types. A steel DLC-coated piston pin runs directly in a non-bushed bore in a very strong steel con rod made from W360 tool steel. The rod features a double-taper design on the joint face that eliminates the need for dowels. Compression ratio varies widely depending on application, with naturally aspirated and turbo versions of the engine being produced.
Early versions of the crankshaft were produced by extensively reworking existing race components, but a new design based on a forging is planned.
The big-end and main bearings are Suzuki Hayabusa race shells, and the main bearing caps are machined from a tool steel more commonly used to produce mould tools for plastic components.
Oil system changes have improved filtration.
The engine is compatible with Mini transmissions or, in longitudinal installations, a racing transmission providing rear-wheel drive.
Cylinder head options include original five-port Austin OHV heads, BMW K-series OHC motorcycle heads, and a racing head developed by Kent Auto Developments. For OHC heads, cam drive is via toothed belt.
Customers specify the head, inlet and exhaust systems based on their particular application.
SPECIFICATIONS
ASCASO A+5
Race series: various
Inline 4
Bore and stroke: various
Naturally aspirated or turbocharged
Gasoline
Aluminium block and crankcase
Steel liners
Aluminium pistons, three rings
Five plain main bearings
Steel crankshaft, four pins
Steel con rods
DOHC or OHV, depending on head, belt-driven camshaft
Two or four valves/cylinder, depending on head, one plug
Valve angles vary, depending on head
Valve sizes vary, depending on head
Butterfly/barrel/slide/other throttle, depending on inlet system
Compression ratio varies according to application
Maximum rpm varies according to application
SOME KEY SUPPLIERS
Block castings: Billet Ascaso
Head casting: Kent Auto Developments
Block and head machining: in-house
Liners: Ascaso
Liner coating: Poeton
Crankshaft: undisclosed
Con rods: in-house
Rod bolts: ARP
Pistons (for turbo version): Omega
Pistons (for naturally aspirated version): Kent Auto Developments/Jenvey
Piston rings: Omega
Piston pins: Omega
Main bearings: ACL
Big-end bearings: ACL
Thrust bearings: BMW
Circlips: Omega
Valves: Kent Auto Developments
Valve seats: Kent Auto Developments
Valve guides: Kent Auto Developments
Valve springs: Kent Auto Developments
Spring retainers: Kent Auto Developments
Cam drive components: in-house
Cam drive components: Kent Auto Developments
Cam drive components: Honda
Camshafts: Kent Auto Developments
Cam followers: Kent Auto Developments
Cylinder head seal (or gasket): in-house
Fuel injectors/carburettors: Pico
Ignition and engine management: ECU Master
Data acquisition: Kent Auto Developments
Sensors: Kent Auto Developments
Throttle bodies: Kent Auto Developments
Oil pumps: standard A-series, modified in-house
Oil filters: standard A-series
Exhaust: Kent Auto Developments
Fluid lines and adapters: Kent Auto Developments
Wiring loom: Sileck/Jim Speed Racing
Fuel: 99 RON
Oil: Millers
Dyno testing: Kent Auto Developments