Aussie two-stroke engine invention

2 stroke CITS engine

A Sydney engineering company has developed a new two-stroke engine that they believe could be used in motorcycles.

It’s called Crankcase Independent Two-Stroke (CITS) and was invented by former South African motorsport engineer Basil van Rooyen, Director of CITS Engineering, St Ives.

He says advantages over four-stroke are that the CITS engine is more powerful, lighter, smaller, cheaper, more economical and with lower emissions.

Two-stroke motorcycles have been phased out in recent years by tough pollution laws and fuel economy targets.

However, KTM has released a raft of new direct-injection two-strokers and Honda recently registered patents for direct-injection two-stroke engines, so they look like making a comeback.

Basil’s CITS also uses direct injection, but has a by-pass valve that replaces the throttle and provides progressive cylinder deactivation ensuring minimised pumping losses.

It also uses a typical four-stroke’s oil sump and does not mix the oil with the fuel in the combustion chamber like normal two-stroke engines. CITS therefore eliminates total-loss lubrication of a typical two-stroke.

“CITS technology is applicable to any engine application from V-twins of 25 to 125kW up to V12s of over 1000kW for hospital generators etc,” he says.

The prototype 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 secure patents.2 stroke CITS engine

They are:

  • It runs under load without thermal or lubrication issues on clean petrol;
  • the novel pivoting inlet valve can pivot at 7000rpm;
  • the by-pass valve replaces the need for a throttle, and the pumping losses throttling causes;
  • the engine runs smoothly; and
  • that the three-times-higher primary compression ratio becomes a three-times-more-powerful de-compression ratio on induction.

Basil hopes to sell the royalties to his invention to engine manufacturers, rather than making any engines himself.

He is currently seeking an investor or a motor manufacturer as a partner for the final stage to commercialisation. He can be contacted via Linked In or email.

Basil says the cost and weight per kilowatt with CITS engine technology can be less than half that of popular three- and four-cylinder four-stroke engines.

The prototype Rotax 800cc Etec two-stroke produces 148hp (110kW) compared with the Suzuki Boulevard 800 which makes 66hp (50kW).

The Rotax with CITS has three times higher decompression, runs on pure fuel and has 70% reduced vibrations.

Basil says he envisages a lower rpm version with about 90hp (67kW) at 5500rpm would be suitable for most applications.

The CITS concept needs no changes in today’s production methods, but grasping the fluid dynamic advantages is complicated and mechanics and engineers are advised to check out the CITS Engineering website for further details.

It also shows this video of the unique self-driven inlet valve and the by-pass calve in action.

5 Comments

  1. It seems to be trying to ‘fix’ a non problem of two strokes, their pumping losses, two strokes dont have significant pumping losses. This motor will need extensive 3D CFD optimisation to improve its total air pumping and efficiency to compete with all the others, even the Bill Gates funded EcoMotors 2 stroke after $150 million invested failed due to their being no buyers. They had a well optimised design after many iterations and changes, highly optimised by the best engineers and it failed. So I don’t think sticking some hacked head on a 4-stroke bottom end is going to cut it in the world stage somehow.

  2. Basil hopes to sell the royalties to his invention to engine manufacturers, rather than making any engines himself.
    There is something really wrong with that sentence.
    The correct version would be; sell the rights to
    or license his invention.
    That said there is really nothing new about this idea look up two stroke diesels and you will find numerous examples that were in use upto the early eighties before emissions legislation killed them off. Many had crankcases that were not part of the induction system and they had intake vales but the exhaust was a port in the cylinder wall, most required a blower to run.

    With direct injection and no lubricant in the fuel a two stroke could be made to run as clean as a modern four stroke. The only issue will be nox emissions but water injection should take care of that. I really hope the don’t go for EGR as it is the stupidest way to reduce emissions.

  3. Innovative intake or exhaust valve systems always end up taking 100x the effort and understanding the actual dynamic pressure wave action they​ operate with, sealing along all the peripheral axis in all conditions, effects of all the forces and moments, inertial, heat, acoustic, pressure waves, sealing force requirements. It always requires extensive experimental sensor measurements combined with computer modelling and simulation to meet emmisions regulations in all operating conditions. I.e. Big $$$ and highly skilled Engineering talent normally only found in F1 and MotoGP engine manufacturers

    This work is how F1 teams fund themselves.

  4. Emmisions, fuel efficiency and cooling requirements will really define it’s​ chance of success. With 4 stroke engines now achieving 47% thermodynamic efficiency in F1 + 3% from hybrid using Australian innovation of Jet ignition and 2 stroke engines languishing in the 20-25 from memory even when Jet ignition used they barely reach 30%. Maybe this engines features will improve those peak numbers. The compromises in the 2 stroke design to be cleverly efficient in producing power pulses eliminates the opportunity to do the things to improve thermodynamic efficiency as effectively

  5. Interesting.
    Lots of people may have ideas to improve engine design but very few ever turn those ideas into metal.

    I suppose if a few parts were beefed up it could be a direct- or indirect-injected diesel as well.
    I don’t recall seeing the compression ratio of the combustion section mentioned. The CR will have implications for NOx emissions and consequent exhaust gas recirculation needs.

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