Aussie two-stroke engine breakthrough

Aussie two-stroke engine breakthrough
Aussie two-stroke engine breakthrough

By John Oxley

A former South African engineer and top-level racing driver, now living in Australia, has come up with a remarkable invention that could revolutionise plug-in hybrids, motor-cycles, and outboard motors, as well as stationary engines and generators.

What’s more, the CITS (Crankcase Independent Two-Stroke) engine, as it’s called, heralds a return to smooth and cheap two-stroke engines – but without their associated high exhaust emissions, noise, and haze of blue smoke.

The engine is the latest in a series of inventions from Basil van Rooyen, who raced Formula 1 cars, among many others, and results in a two-stroke engine which has more power for its weight than current four-stroke engines, while costing only half as much to make.

Basil (78) was a stalwart of motor racing in South Africa, starting on bikes in the ‘50s and then moving onto cars right through to  the early ‘80s, and apart from F1 drives in Cooper and McLaren, is notable for his development of the Chev Can-Am which raced successfully in both saloon racing and rallying in that country. On the way he won three championships, and raced in six countries and three continents, one of which included sharing a Holden Torana with British driver Gerry Marshall at Bathurst.

He moved to Australia in 1987 to run a plastics manufacturing business, retiring in 2004, and since then has occupied his time with a number of inventions, some of which have proven quite lucrative.

“Firstly there are two possibilities for the CITS technology to revolutionise several markets – in particular the outboard motor, the Plug-in Hybrid Vehicle (PHEV), and industrial power market for large hospital or small home back-up generators, and portable water pumps,” he told me.

“Basically V-twins from 25 to 125kW, up to say, a V12 with over 1,000kW. Certainly they will be important for the transition period to electricity from non-fossil fuels, until batteries have a lower carbon footprint from  mine to showroom,  and at a cost affordable to the mass-market – including the present massive 10-year or so replacement cost in dollars and in waste”.

The CITS engine differs from a normal two-stroke.

  • In comparison with a typical four-stroke engine, the normal two-stroke engine is famous for:
  • More than 80% fewer parts and far lower production costs.
  • Far superior power-to-weight ratio, and reduced maintenance.
  • Superior fuel-economy with direct fuel injection (DFI).

Basil says the problems with a normal two stroke engine vs the four-stroke, are that it:

  • Mixes oil-in-petrol in a ratio of about 1:50, needing costly roller bearings, and which results in:
  • High HC (unburnt fuel/oil) emissions that cannot meet strict regulations such as EU5.
  • Has an 85 percent weaker de-compression ratio, which reduces efficiency, and to address that
  • Requires an early exhaust port opening, causing a noisier exhaust, and incomplete combustion.

The patented CITS engine technology resolves these problems by:

  • Eliminating total-loss-lubrication and the complex fitment of costly roller bearings.
  • Having better than 95 percent less oil consumption with significant reductions in HC emissions and
  • A three-times higher de-compression ratio, which results in
  • An even more economical and more powerful two-stroke engine and a quieter exhaust.

Also inherent in the V-twin CITS is a common crankcase, allowing closely aligned connecting rods resulting in smooth running, by having more than 60 percent reduced imbalance forces than twin-cylinders before CITS, and an output of up to the typical 100kW in today's four cylinder cars, from just two cylinders.

At the same time the V-format is easily scaled-up in pairs to even a V12 from 25kW to 1,000kW, yet it’s less than half the size, cost and weight of a typical equivalent four-stroke engine per kW.

The unique geometry of the CITS V-format allows a perfect placement and alignment of the patented pivoting inlet valve which is self-driven by the alternating pressures under the opposing pistons, and eliminates the tension flow-restriction of reed valves used by most normal two-stroke engines.

This patented pivot valve’s integral by-pass valve eliminates the throttle, (as does a diesel) which progressively de-activates the cylinders equally as required, with optimal fuel-economy, thus reducing CO2 emissions commensurately at all power conditions for the first time.

Says Basil: “CITS is the ideal light, powerful, economical, low-pollution engine, at a lower cost per kW from industrial engines to auto applications, and everything in between. This will help reach the mass-markets of the world, and reduce the growing smog issues in many cities.

“These CITS attributes are beyond proof-of-concept stage, with major predictions confirmed in our prototype V-twin. Now what’s needed to interest the engine industry and for commercialisation, is final scientific quantification, with the essential DFI, fitted and optimised by a specialised industry-respected facility, which is beyond our resources, and for which a manufacturing partner is sought, or funding via a formal capital-raising document and share-offer by the company owning the international patents, as detailed in the CITS website.

“In the growing field of Plug-in Hybrid Electric Vehicle (PHEV) technology of today and tomorrow, the CITS engine can run at its sweet spot rpm, super-efficiently tuned and emissions-controlled, and take advantage of its ultra-low friction and inertia. This feature also applies to the huge market for portable industrial power units, such as generators and water pumps.”

The prototype CITS engine was built on an 800cc V-twin Suzuki Boulevard crankcase, to which were adapted Rotax 800 Etec parallel twin cylinder-jackets and heads, cut into two to make this adaption possible and to fast-forward the proof-of-concept stage, confirming five major predictions and to secure patents.

These are:

  • The engine runs under load without thermal or lubrication issues on clean petrol;
  • The novel pivoting inlet valve can pivot at 7,000rpm.
  • The by-pass valve replaces the need for a throttle, and the pumping losses throttling causes.
  • The engine runs smoothly, with 70 percent less vibration compared to the Rotax engine..
  • The three-times-higher primary compression ratio becomes a three-times-more-powerful de-compression ratio on induction.

Basil has already received much acclaim for the engine, including an SAE nomination for “Excellence in automotive engineering”.

Check out the CITS website for more details, and to see a video of the prototype engine running.




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