Orbital's Direct Assualt

Orbital has sure come a long way since Ralph Sarich invented the Orbital rotary engine 30-odd years ago. As of July 2000 OEC was valued at $A671.6m, with its 50% share in the Siemens/Synerject EFI-component venture worth $A130.5m.

Since 1973 Orbital has concentrated on developing fuel-injection and combustion technology, and in the early '80s it recognised that its technology could be applied to two-stroke engines to overcome traditional deficiencies.

This led to a decision in 1983 to focus on two-stroke automotive applications as an innovative, lower-cost engine. But with tough new emission laws on the horizon, OEC also set about developing a system for marine engines and apparently in 1985 the Orbital Combustion Process (OCP) system almost ended up in OMC's then newly-released V-six loopers. However Brunswick Corporation (Mercury's parent company) saw the real potential of the OCP system and quickly became a licensee, leaving OMC to look for other low-emission technology.

OMC still holds a licensing arrangement and rumour has it that there's an OCP-equipped V-six stored in OMC's US R&D headquarters!

Over the past decade Orbital has broadened its focus and developed applications in four market segments - four-stroke automotive and two-stroke automotive, motorcycles and marine. All products utilise variations on the OCP system.

For each cylinder there are two injectors. One injects air into the fuel rail at 90psi, which is then mixed with the fuel pressurised to 70psi and directed to the combustion chamber/second injector. The fuel/oil ratio differs from each licensee or engine manufacturer and with Mercury and its Optimax system varies from 44:1 at Wide Open Throttle (WOT) down to 400:1 at Dead Slow Troll (DST) - currently these ratios are a little richer - while Tohatsu's Low Pressure Direct Injection (TLDI) system varies from 50:1 to 450:1.

Attending Orbital's Sydney Product Demonstration day on November 2, I had the opportunity to meet with OEC executives and discuss at length the corporation's future. And what a future it has!

Provided for evaluation were the Tohatsu TLDI 50 outboard, which was reviewed in Trailer Boat (October 2000 issue); twin Optimax 135 outboards on a 6.8m Seafarer Voyager; the Sea.Doo RX DFI PWC and Aprilia's Orbital SR 50 DITECH Scooter.

Trailer Boat readers may ask what's so important about a scooter engine in marine applications?

NO SMALL MATTER
In fact there are several reasons. The DITECH 50 is the smallest engine ever to be fitted with Direct Fuel Injection and proves that a DFI system could be fitted to an outboard as little as 2hp!

Controlled testing by Aprilia has shown that fuel economy is 40% better than the standard carburettored model. Even a 50cc four-stroke engine provided only 30% better economy than the standard two-stroke 50cc powerhead, but performance was considerably lower. According to Aprilia, oil consumption is reduced on average by 50% and pollutant emissions are reduced by 80% over the traditional 50cc two-stroke powerhead.

But there's a lot more, as I found out on the test day. The engine is no bulkier than a comparable SOHC four-stroke, starts instantly hot or cold, and has a surprisingly smooth idle for a two-stroke single.

And when I placed my nose close to the exhaust outlet there was absolutely no oil smell and never any oil smoke, even when the automatic scooter was accelerated rapidly from a standing start. The fuel/oil ratios vary about the same amount as the TLDI 50.

There was also no hesitation in acceleration, as occurs on transition from the idle to main jets in carburettored engines, and the DITECH engine felt much more throttle-responsive than other scooter engines of this displacement I've tested.

Perhaps the most interesting aspect of the DITECH engine is that by attaching a 'Gameboy' device through an interface developed by OEC the engine's performance characteristics can be completely altered. For example, to comply with Italian Government road safety regulations scooters of this size are limited to a certain speed. But by going through a series of prompts on the Gameboy display (which, of course, will void the manufacturer's warranty) and then hitting the 'okay' button the SR50 can be made to achieve 137kmh!

DEBUNKING THE MYTH
Tohatsu's TLDI 50 also has this facility, which will open up a range of possibilities for owners interested in racing. And talking about the Tohatsu TLDI 50, there's a misconception in the marine industry (and one reported incorrectly in a well-known boating magazine recently) that Mercury supplied Tohatsu with the TLDI 50 technology.

According to Kim Schlunke, Chief Executive Officer of OEC, Tohatsu developed its own system independently of Mercury using an ECU (Electronic Control Unit) developed by Mitsubishi Electric Company (MELCO), not Motorola. The TLDI 50 also doesn't need a laptop computer to diagnose faults in the ECU and, in my opinion, has a more compactly-engineered air compressor assembly.

Sea.Doo's RX DFI provides mind-blowing performance and under the right sea surface conditions will achieve 100kmh. But cleverly, Sea.Doo and Orbital have achieved this by using a relatively simple twin-cylinder, 951cc engine that still develops 130hp!

By fitting massive exhaust expansion chambers, the absence of pulse tuning (as used with other manufacturer's three-cylinder engines in this horsepower range) has been overcome. Two-cylinder engines also eliminate the possibility of excessively lean air/fuel ratios in the middle cylinder that affect some of the competition's three-cylinder motors and cause seizing and/or premature engine wear.

Judging from the performance on the test day the acceleration out of the hole was brilliant with none of the lag that afflicts carburettored PWCs. Yet because Sea.Doo has used an underwater exhaust the RX DFI was surprisingly quiet and would offend few waterside residents!

Another clever feature was the 'Learning Key' function, which limits top speed to 48kmh for inexperienced riders.

The RX DFI's engine also forms the basis of the twin-cylinder engine installed in a people mover built by Indonesian industrial company Texmaco, which employs about 30,000 people. According to Orbital, this vehicle has been operated successfully over an 18-month period in the harsh Indonesian environment.

Based on the 1197cc Suzuki DT85 engine but fitted with a one-piece crankshaft and Mercury-designed capped connecting rods, a three-cylinder OCP engine has been used in the Genesis project, where this engine replaced the standard 1.3lt, four-stroke unit in 100 Ford Festiva cars. Over a five-year period some of these vehicles clocked up more than 160,000 with apparently no operating problems encountered.

One feature that I really liked about the Optimax 135s on the Seafarer Voyager was their ability to hold revs within a plus or minus 100-rev range when the throttles were left untouched, a feature developed by OEC. And although 2900 revs were needed to plane a four-adult load, adding another two adults required only an additional 100 revs to get us out of the hole, such was the mid-range torque of these engines. Interestingly, when manoeuvring there was a slight oil smell which did not occur with the TLDI 50, DITECH engine or the Sea.Doos.

With companies such as Honda concentrating on four-strokes, I asked Kim Schlunke how the aspect of oil pollution with two-strokes would be overcome. According to Schlunke, zinc is added to four-stroke oils to lubricate the camshaft/rocker faces and this will not break down, apparently forming a worse pollution hazard than a two-stroke oil, two-thirds of which burns completely in an OCP engine.

And unlike a few four-stroke outboards I've tested which don't have pinned cylinder rings to prevent some oil passing them on cold start-up, OCP engines never emit oil smoke and subsequently concentrated pollution. So although a DFI two-stroke will always use more oil than a watercooled four-stroke, the pollution created by oil burnt in the latter may be higher than that from a two-stroke!

But primarily for the European and US markets, Orbital has developed an OCP system for four-stroke automotive engines, which Schlunke says will eventually filter down into the marine market.

Orbital replaces the standard cylinder head with its own design and controlled testing in a Ford Mondeo showed a 13% fuel economy improvement over an identical vehicle fitted with the standard two-litre engine having multipoint injection fuel. The tough Euro 4 exhaust emission requirements (expected to come into force in 2005) for a two-litre engine are no more than 1.0g of carbon monoxide per kilometre, 0.08g of NOx (Oxides of Nitrogen) and 0.10g of hydrocarbons. Yet the test Mondeo achieved 0.229, 0.035 and 0.069g respectively.

Imagine what such low levels of pollution could do for the marine environment!

'BRIGHT SPARKS'
But the development doesn't stop there and Orbital and Delphi Automotive systems are jointly working on a combined spark plug and fuel injector, which will require only one entry point to the combustion chamber for both air/fuel and spark. This will enable the OCP system to be fitted in much smaller four-strokes.

And in the not too distant future...

Apart from more Sea.Doo PWCs being fitted with OCP engines, Mercury Marine plans to replace four-strokes such as the F75/F90 with Optimax engines and eventually filter its Optimax DFI technology down to the smaller models.

Trailer Boat readers already know about Tohatsu Corporation's plans to implement TLDI technology from 40-140hp by 2003. And having tested the Aprilia DITECH engine, I can see few reasons why Mercury and Tohatsu would persist with four-strokes at all down the track...