Stroke of Fortune

Another future postponed. Today we look at an engine technology from the early 1990’s which, for a short time at least, looked like a certainty.

Where do ideas go to die? Are blueprints simply rolled up and secreted away, to be dusted off by historians in decades hence or are there engineers in a quiet workshop somewhere in Australia (or Toyota City) still burning with religious fervour for what now appears to have been something of a lost cause?

Founded by engineer, Ralph Sarich, the Orbital Engine Corporation was based in Perth and during the early 1990’s attracted the interest of a number of big name manufacturers for a clever reworking of the time-honoured but somewhat flawed two-stroke engine design. For a short period of time, it sounded tantalisingly like the future, but seemed to have quietly died without eulogy, leaving many wondering exactly why.

There were a number of inherent problems with traditional two-stroke engines as fitted to the likes of early Saabs, DKWs, Trabants and Wartburgs. Amongst them were issues surrounding symmetrical port timing, which allowed unburnt air / fuel to escape through the exhaust port, contaminated unpurged gases affecting clean combustion and the crankshaft lubricating oil (which needed to be added to the petrol) being drawn through the transfer port to be burnt along with the fuel.

The combined effects added up to a power unit with admirable advantages in compactness, lightness, simplicity and cheapness in manufacture, but with potentially malign traits of noxious emissions, power losses and poor running characteristics. Many of these issues were addressed, if not entirely dismissed by the (predominantly Japanese) motor cycle manufacturers, but given the lack of interest in two-strokes within the mainstream motorcar industry, these developments had not been incorporated into a suitable two-stroke car engine design.

The Orbital two-stroke was different in that direct air-assisted low pressure sequential fuel injection ensured that a strictly monitored amount of fuel was injected only after all ports were closed by the action of the piston, eliminating the scourge of incomplete combustion. The plume of injected droplets was said to provide a natural charge stratification (where the ratio of fuel to air within the combustion chamber is optimised), giving a claimed immunity to detonation (knock) and giving rise to fewer oxides of nitrogen (NOx) being produced, especially at light-load conditions. Also key to this was the use of electronic engine management and a catalytic converter.

Built in two forms; the lower powered versions which employed traditional internal scavenging through the crankcase, (the underside of the piston acting as a pump), using a highly developed lubricating oil which was injected into the crankcase through reed valves on induction. Any oil mist burnt during combustion was oxidised by the catalyst, obviating the once familiar plumes of blue smoke. More powerful versions would employ an external scavenger – in the form of an engine-driven supercharger.

Claims by Orbital were ambitious: fuel savings of 15% compared with contemporary four-stroke rivals and exhaust emissions in advance of those then required for the ultra low emissions vehicles being considered by the US state of California at the time. NOx emissions were claimed to be far less than that of a conventional, non-catalysed engine, while in hydrocarbon terms, exhaust gases were claimed to be cleaner than the air being drawn into the intake in many cities.

Couple this to an engine configuration which was, like-for-like, 40% lighter, 50% more compact and around 17% cheaper to make and the argument in favour of Orbital appeared highly convincing. Having successfully demonstrated the promising characteristics of the power unit to the World’s motor industry, licencing arrangements were promptly made with Ford, GM and Fiat, amongst others. Ford at one stage had around 25 test vehicles running Orbital-based two-strokes, mostly Fiestas and Australian market Festivas. Chrysler were also believed to be working on a two-stroke at the time, but to their own design.

In 1993, Pininfarina showed two Orbital concepts (Ethos 1 and 2), to demonstrate how the two-stroke could be packaged in a compact and lightweight mid-engined 2-seater. Arguably the last truly intelligent and attractive concept from Cambiano, the delightful little Ethos twins charmed the World’s press and lent the Orbital engine a degree of sex appeal it hitherto lacked.

But the real business of work was taking place in Australia, in the US and in Europe where fleets of Orbital powered family hatchbacks were evaluated. Part of this regime involved the UK’s Surrey police force taking delivery of an Orbital-equipped Fiesta for 15 months and 30,000 miles, where it acquitted itself rather well.

The primary power plant (as fitted to Fiestas) was a 1.2 litre three cylinder developing 80 bhp at 5000 rpm and 90 lbs/ft of torque at 4000 rpm. A 800cc twin and a supercharged 2.0 litre in-line six were also developed, as indeed was a 330 bhp 3.2 litre V6, believed to have been taken up with some seriousness by Jaguar.

In 1994, the eminent LJK Setright penned a laudatory piece on both the Orbital two-stroke and concurrent developments from Toyota (and Ricardo) which combined camshaft driven poppet valves for both inlet and exhaust porting with an externally scavenged two-stroke cycle. The results, especially from the Anglo-Japanese design appeared to set the industry upon an innovative and potentially exciting course in engine design. Ford talked of Orbital production by 1995. Then it all went silent.

While it appears Orbital’s claims for the power unit were entirely credible, it’s believed that Ford engineers found it incredibly difficult to successfully marry them all in practice. So while an Orbital could be made to run incredibly smoothly, economically, or cleanly, it’s been suggested it was nigh-impossible to make it do all three simultaneously.

Furthermore, the likely level of investment required for two-stroke was probably deemed prohibitive by cost-obsessed carmakers. Another nail in Orbital’s coffin (in Europe at least) was the rise of the high speed diesel, in particular Volkswagen’s turbocharged 1.9 litre ‘Umwelt’ unit. And with EU politicians pushing for lower CO2 emissions, a grubby deal appears likely to have been done which diverted resources towards diesel engine development.

Another way of looking at it perhaps is this. The four-stroke Otto cycle engine has been the predominant configuration, perhaps because it’s repeatedly proven itself as the least flawed compromise. Add to this a risk-averse industry who are in the business of, if not always making money, at least not losing vast quantities of it. The two-stroke, be it Orbital, Chrysler or Toyota’s seemingly revolutionary concept, may have held promise, but against the zeitgeist, probably hadn’t a chance.

But if Toyota’s recent projections are correct, the internal combustion engine has a good three decades of development left in it, which leaves a lot of scope for clever solutions. So who knows, with petrol fuelled engines having to get smaller and ever more efficient, perhaps the Japanese car giant still has something up its sleeve. Could we yet see the two-stroke’s rise?