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Ricardo's engine, called 2/4SIGHT, uses valves like a four-stroke engine, but in two-stroke mode, the engine keeps both the intake and exhaust valves open at the same time so that the fuel and air in the cylinder are replenished each cycle, rather than every other cycle.
There has been a lot of interest in developing a low-emission two-stroke engine. But it's a difficult configuration to perfect because there is little time to get the fuel-air mix in and the exhaust out, says Larmi. "The danger here is that the fresh air intake can go directly out through the exhaust outlet," he says.
Ricardo is using a couple of tricks to get around this problem. First, the design of Ricardo's piston head uses reverse tumbling, a process in which the air intake is directed away from the exhaust valve, to reduce the chances of it flowing straight out of the cylinder. Ricardo has also swapped the cam-controlled valves for electro-hydraulic valves, which, along with the fuel injector, can be controlled by software.
Car manufacturers have showed an interest in building this sort of hybrid engine in the past, says Kee. "But there are a lot of challenges," he says. Indeed, both Toyota and Ricardo looked at this issue in the late 1980s and early '90s.
But in the past, the technology simply wasn't there. According to Ricardo, the only reason the company is able to make a viable system now is because of the software that controls the gas exchange and engine modes. "The engine's control system monitors driver demand," says Jackson. When more torque is required than would be possible in four-stroke mode, it switches, he says. However, the company will not reveal details about when, in the engine cycle, the mode is switched.
Ricardo's prototype, an adapted 2.1-liter V6 engine, has been tested by researchers at the University of Brighton and has been found to be able to produce the kind of performance one would normally expect from a three-to-four-liter engine. Based on the New European Driving Cycle, which is a standard performance test designed to gauge engine efficiency and emissions under typical car usage, the prototype has demonstrated fuel savings of 27 percent, and it reduces emissions by a similar amount. The next phase is to try to incorporate a prototype engine into a working vehicle, says Jackson.
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This is not a "Hybrid" system. It is not two systems, it is just one engine designed to run two ways.
If an engine kicks off two cylinders when they are not needed is it a hybrid?
If an engine can burn gas and 85%ethanol, is it a hybrid?
No. Hybrid means you have two sources of propulsion that directly couple to the output.
Even the Volt is not a hybrid. It is an electric car with a power resupply system.
It seems everything is a hybrid today.
As for the technology itself, too complicated, too expensive, and raises emissions. I am sure the government will not give it a pass.
For all the trouble, a small turbo would give the engine good power under load, and not have the complexity and emissions problems.
It is a hybrid in the sense that it is both 2 stroke and 4 stroke. Although you raise a good point, debating semantics is hardly a constructive activity.
If they add compressed air regen braking, it could be more of a hybrid, and it shouldn't cost much more (compared to, say, a prius battery pack and electric motor) while still having significant efficiency gains, especially in urban areas (lots of starts/stops).
I wonder how the 2 stroke / 4 stroke concept compares to combining regular ICE with diesel (compression engine) design.
Johnson and Evenrude, now owned by the Bombardier family, has been building an advanced two stroke engine for over 5 years. It uses skip charging to operate as a "multi stroke" engine in some operating ranges. Direct injection avoids fuel lost due to scavenging. All Recardo did was add the complexity of added intake and exhaust valves.
Orbital Engine of Australia was working on a similar concept 20 years ago.
Nothing new here!
4cyl to 2cyl - fuel modification
I was wondering if it's possible to shift from 4 cylinder to 2 cylinder and use Ethanol based fuel that is doped with "2 stroke" oil to increase the mileage. All my lawn tools run on a simple 50:1 blend, and have a good amount of horsepower for their size. Is this transferrable to larger engine sizes too?
Can anyone see a drawback - benefit?
Re: 4cyl to 2cyl - fuel modification
Emissions control is a huge challenge with 2 stroke engines. With today's emissions regulations, something as seemingly trivial as the shape of the crevice created by the crush of the cylinder head gasket has a serious impact on HC emissions because of the hydrocarbon molecules it may trap. Even a tiny amount of oil mixed with the fuel is problematic. Oldsmobile experimented with a 2 stroke 455ci(7.5L)V8 in the early 70's. It had the strangest exhaust, sounding like a herd of snowmobiles! General Motors actually made a very substantial investment in development of 2 stroke technology decades ago. They showed break through engines in terms of power density, both space and mass. Unfortunately, fundamental problems with emission control doomed the program. As emissions regulations tightened,in fact, Japanese motorcycle makers who had been exclusively 2 stroke: Suzuki, Yamaha, & Kawasaki, were compelled to convert their entire line ups to 4 stroke engines. It was a heart breaker to those of us who love high specific output engines!
Re: 4cyl to 2cyl - fuel modification
2 strokes as you describe are antiques.
Modern 2 strokes have a wet sump like 4 strokes & used forced induction (superchargers &/or turbochargers) rather than crankcase scavenging. Meaning lubricants arn't dirting the emissions. also modern 2 strokes have direct injection mean no unburnt fuel out the exhaust, just a wee bit of air. How do you think 2 stroke deisels work?
It's obvious to anyone with commonsense & a lack of ignorance in this field that any multimode 2-stroke/4 stroke would have forced induction via an ext. compressor not crankcase scavenging, together with a sump. Plus of course electronic engine management, poppet valves or rotary valves (no piston activated barrel porting) VVT with the cam lobes having 2 profiles each, & electronic direct injection.
Now if you check out Orbital patent direct injection supercharged 2 stroke outboards with a wet sump (or a ext 'dry sump') you'll find these have emissions compatible with fuel injected 4 stroke cars built arround the same year.
Judging 2 strokes by old lawn mower engines is missing the whole point.
Why go to complications such as switching from Four Stroke to Two Stroke etc, when low rpm torque can be easily improved with some grinding of the cylinder head to improve compressin ratio and cutting grooves on the cylider head, which will also reduce fuel consumption by 20 plus percent. The engine oil also will last longer. Hundreds of cars in India, USA and elsewhere have been modified successfully.
For details and additional information please see web site www.somender-singh.com.
I want to create a hybrid engine which is capable of using less fuel and generate suffiecient power with emmissions standards i want sum support nybody interested in my project pls contact me www.sagarbaishya@gmail.com
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152 Comments
Regen braking
They may still want to add a small pressure vessel (compressed air) to store some of the energy normally wasted as heat when braking.
Adding a small thermal storage system (couple of pounds of steel or something), using waste heat from the engine, could improve thermodynamic efficiency of the compressed air regen system, as the air can be expanded into the cylinders further by heating it through the thermal resevoir.
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