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EVERY DETAIL COUNTSMAKING THE CASE THAT IT’S POSSIBLE TO BUILD A KIT CAR PERFECTLY

WHAT TO DO IN 2017WHERE TO GO, WHAT TO DO31 GREAT EVENTS LISTEDCOMPLETE YOUR BUILDUPGRADES

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ROTARY EVOLUTION

31 GREAT EVENTS LISTED31 GREAT EVENTS LISTEDCOMPLETE YOUR BUILDCOMPLETE YOUR BUILDUPGRADES

Ecoboost turbo poweredracer for the road

Classic looks,BMW Z3 platform

The most refinedkit car ever?

001 Cover.indd 1 25/11/2016 11:15 am

FUTURE POWER

66 January 2017 www.completekitcar.co.uk

THE ROTARY CLUBBritish engine manufa turer d an ed nno ati e ngineering has teamed up with estfield to reate a

sports ar with a uni ue powerplant. ill you e using it any time soon

Words: Chris Pickering Pictures: AIE and Cenex LCV

066 Rotary engine.indd 66 23/11/2016 3:16 pm

AIE 650S ROTARY ENGINE

January 2017 67www.completekitcar.co.uk

he rotary engine is still in the phase, with produ tion ost and emissions ontrol still to e addressed, ut neither is insurmounta le.

The kit car scene is a never-ending source of inventiveness and diversity. But it’s not often you come across a completely new engine design. Lurking under the bonnet

of this West� eld, however, there’s a totally bespoke 650cc Wankel rotary engine developed by Lich� eld-based Advanced Innovative Engineering (AIE).

� e company can trace its roots back to Norton Motorcycles. Managing director Nathan Bailey and several of the senior engineers formerly worked at UAV Engines, which was one of the companies formed from remnants of Norton Avback in the early ’90s.

� e motorcycle � rm used rotary engines for over a decade, picking up an outright win at the Isle of Man TT and several British Superbike Championships along the way. Meanwhile, on four wheels NSU and later Mazda experimented with similar concepts to varying degrees of success – the latter famously winning the Le Mans 24 Hours with the shrieking 787B Group C car.

Over the years various people have put rotary engines into kit cars. � e very � rst Sylva Striker used a Mazda rotary engine, built for company founder Jeremy Phillips’ brother and raced extensively. Other intrepid builders have followed suit, usually in Seven-type cars, where the engine’s low weight and compact stature can be exploited to the full.

Rotaries are hard to beat when it comes to power-to-weight ratio, but they have traditionally su� ered from a number of drawbacks. � ey can be extremely thirsty, often quite loud and they have a reputation for poor reliability and high emissions. AIE, however, uses a pioneering new design which it says could be used to address these issues.

“� e UK is something of a centre for niche vehicle production, but these independent car makers are struggling to � nd engines,” comments Nathan. “� ere’s a desire to � nd a homegrown engine and the rotary has always had a bit of a mystique about it. It’s very di� erent to most of the engines out there. From our perspective, we’re very keen to establish ourselves as a niche engine supplier within that specialist car industry.”

� at may sound like a rather lofty ambition, but although AIE is a relatively new company it’s backed up by decades of experience. � e new engine, known as the 650S, is handbuilt, so while AIE will sell you one they are by Nathan’s own admission “not cheap”. Ultimately, though, the aim is to develop the engine to the point where it will be available o� the shelf, a bit like a 21st century counterpart to the Coventry Climax units that powered numerous British sports and racing cars in the 1950s.

he rotary engine is still in the phase, with produ tion ost and emissions ontrol still to e addressed, ut neither is insurmounta le.

have a reputation for poor reliability and

It’s not often you come across a completely new engine design

066 Rotary engine.indd 67 23/11/2016 3:16 pm

FUTURE POWER

68 January 2017 www.completekitcar.co.uk

DIFFERENT STROKESTo appreciate what makes the AIE powerplant stand out from the others, it’s worth recapping on the inner workings of a rotary engine. �ey rely on the same four-stroke cycle as most piston engines, but the way they achieve it could hardly be more di�erent.

�e rotor, which is roughly triangular in shape, rotates about a central driveshaft. Rather than spinning on a simple bearing, however, there’s an eccentric mechanism comprised of a pair of synchronising gears, which changes its centre of rotation as it goes round. �e upshot of that is that the three cavities created by the gaps between the rotor and its housing grow and shrink as they move around.

Inside each cavity (or chamber) this has much the same e�ect as moving the piston up and down in a reciprocating engine: the volume of each chamber increases as it passes the intake port, sucking in the air; it then shrinks as it moves round towards the spark plug, compressing the charge; the chamber starts to grow again on the power stroke, as the expanding gasses push the rotor round; then �nally the volume shrinks once more as it approaches the exhaust port.

�at means one chamber will �re for each complete shaft rotation, unlike a four-stroke piston engine where any given cylinder takes two crankshaft rotations to complete its cycle. �e upshot of this is generally a much higher speci�c output if you assume the cubic capacity of both engines to be comparable. �e 650S AIE engine, for instance, is rated at 120bhp, giving it an impressive 185bhp per litre straight out the box.

One of the things that di�erentiate the main rotary engine concepts is their approach to

cooling and lubricating the rotor (or rotors). �e Mazda engines accomplish this by injecting oil into the rotor housing and passing oil through the centre of the rotor. (Incidentally, the resulting oil consumption is very much intentional to lubricate the sealing surfaces.)

In contrast, the initial Norton method, pioneered by German �rm Fichtel & Sachs, was to use charge cooling. Here, the air-fuel mixture is �owed axially through the centre of the rotor to cool it before it reaches the combustion area to burn. �is is neat and simple, but it reduces the thermal e�ciency of the engine because it raises the charge temperature. It also has similar drawbacks to a two-stroke in that it brings the fuel mixture past the lubricated surfaces, which requires quite a lot of oil to maintain lubrication.

Norton later addressed this issue by using a peripheral port to supply the intake charge directly, while blowing fresh air through the centre of the engine for rotor cooling. Somewhat confusingly, this is known as an air-cooled rotary, despite the fact it is sometimes combined with water cooling for the block itself. �e downside to this approach is that the cooling air picks up oil as it travels through the engine.

AIE uses a patented concept developed by former Norton chief engineer David Garside known as the Self-Pressurising-Air Rotor Cooling System (SPARCS). �is uses the blow-by gasses for cooling, resulting in a lighter engine that’s said to reduce oil consumption and emissions.

“David was looking for a system that would combine the simplicity and lightweight of an air-cooled system with the bene�ts of an oil cooled system,” comments Nathan. “His response was to seal the engine, so the pressure would build up from blow-by gases past the rotor seals. In a piston engine this would have the detrimental e�ect of pressing against the underside of the piston, but in a rotary engine it pressurises equally on all sides of the rotor.

“�is pressurised gas can then be used as a cooling medium. Even though it’s quite hot to begin with, the pressurised environment and increased density allows it to absorb additional heat. It’s passed through the rotor, out to an external heat exchanger and then back into the rotor in a closed loop system.”

Of the traditional rotary designs, it’s closest in concept to the air cooled Norton engines. �e peripheral port layout is virtually the same, leading to very similar power densities. However, due to the improved cooling from the SPARCS system, AIE says it’s able to sustain higher power levels for longer (or run in a higher state of tune).

In theory, the SPARCS motor should also be more e�cient than the Mazda-style engines because it uses a simpler seal arrangement that incurs less friction.

“We’ve worked with a lot of rotary engines and the �rst time we ran the SPARCS engine we were amazed,” comments Bailey. “It works phenomenally well. It’s very progressive and very eager – it just keeps pulling.”

’s 6 engine loo s tiny mounted to a azda - gear ox. he pa aging ad antages are o ious.omponent ma hining handled in-house at .

�e aim is to develop the engine to the point where it’s available o� the shelf... like a 21st century Coventry Climax, which powered numerous ’50s sports and racing cars

066 Rotary engine.indd 68 23/11/2016 3:16 pm

AIE 650S ROTARY ENGINE

January 2017 69www.completekitcar.co.uk

APPLICATIONS�e current test car is very much an R&D project and it’s been led by AIE, with the support of West�eld and the Niche Vehicle Network. For the time being, it’s purely a testbed, but the ultimate goal is to o�er it in a production model.

One of the key bene�ts of a rotary – particularly the AIE unit with its single rotor design – is its minimal size and weight. �e Ford Duratec that was used as a benchmark for the West�eld project weighs around 110kg fully dressed, while the AIE rotary tips the scales at well under half that with all its ancillaries – the core engine weighs a scarcely believable 28kg!

“It’s a huge weight reduction in the nose of the vehicle and it’s also physically much smaller,” says Nathan. “We mated the 650S to the Mazda MX-5 gearbox and it looks tiny in the West�eld’s engine bay. When we displayed it at Autosport International last year people mistook it for some sort of advanced gearbox because the combined powertrain is so small.”

In particular, the axial length of the engine is just 383mm nose-to-tip. �at means it can be packaged right up against the gearbox, shifting the weight towards the centre of the car. �is is something of a Holy Grail for sports car builders, particularly those working on lightweight Seven-type cars, which can be extremely sensitive to weight distribution. In the West�eld, we’re told, this shifts the balance from approximately 60:40 (unladen with the Duratec) to almost 50:50.

Nathan reckons that 140bhp would be easily achievable from a naturally aspirated version with a little more development. At this relatively modest power output you’d need a very light car to tip the power-to-weight ratio in favour of the 650S compared to, say, a 200 bhp Duratec. You could also argue that four-cylinder bike engines – which start at around 60kg – tick most of the same boxes.

Ultimately, though, the rotary is di�erent in character to either, with a distinctive noise and power delivery. �ere’s also a lot of potential for future development, with AIE now looking at the possibility of forced induction. Plus, as Nathan points out, it’s a bespoke engine that can be tailored to the demands of specialist car manufacturers.

“�e 650S is so small and light that you can almost forget the packaging of the engine, plus we can adapt it to the form of the vehicle,” he comments.

�ere are still challenges to overcome in terms of manufacturing costs and emissions control, but Nathan believes these are both eminently doable. �e goal is to release a variant of the 650S as a Euro VI compliant engine, which means it should be more than up to the job of the IVA emissions test. It remains to be seen whether or not that will be enough to tempt kit car builders en masse, but it’s certainly good to see something that opens up another option for those who like to stand out from the crowd. n

may e a relati ely new name, ut the team

ehind the ompany come with decades of experien e.

n show at enex , the e ent for low ar on ehi les. otary engine is set to omply with uro emissions regulations, whi h would ma e omplian e easy.

ngine sits well a in the estfield hassis.

Advanced Innovative Engineering T: 01543 420700

: www.aieu . om

CONTACT

066 Rotary engine.indd 69 23/11/2016 3:16 pm