Automotive

Toyota's astonishing new Atkinson Cycle engine delivers 78 mpg

Toyota's astonishing new Atkin...
In order to achieve significant improvements in thermal efficiency, the Atkinson Cycle engines have been lavished with numerous innovations including a reshaped intake port, increased compression ratio, idling-stop, Variable Valve Timing intelligent Electric (VVT-iE) and a cooled Exhaust Gas Recirculation system (highlighted in image)
In order to achieve significant improvements in thermal efficiency, the Atkinson Cycle engines have been lavished with numerous innovations including a reshaped intake port, increased compression ratio, idling-stop, Variable Valve Timing intelligent Electric (VVT-iE) and a cooled Exhaust Gas Recirculation system (highlighted in image)
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In order to achieve significant improvements in thermal efficiency, the Atkinson Cycle engines have been lavished with numerous innovations including a reshaped intake port, increased compression ratio, idling-stop, Variable Valve Timing intelligent Electric (VVT-iE) and a cooled Exhaust Gas Recirculation system (highlighted in image)
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In order to achieve significant improvements in thermal efficiency, the Atkinson Cycle engines have been lavished with numerous innovations including a reshaped intake port, increased compression ratio, idling-stop, Variable Valve Timing intelligent Electric (VVT-iE) and a cooled Exhaust Gas Recirculation system (highlighted in image)
The Japanese manufacturer plans to introduce 14 variations of the 1.0-liter three-cylinder (pictured) and its 1.3-liter four-cylinder bigger brother by 2015
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The Japanese manufacturer plans to introduce 14 variations of the 1.0-liter three-cylinder (pictured) and its 1.3-liter four-cylinder bigger brother by 2015
Toyota's new just-announced Aygo delivers 60 mpg (US) - when the new Atkinson cycle engine, it will achieve 78 mpg (US)
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Toyota's new just-announced Aygo delivers 60 mpg (US) - when the new Atkinson cycle engine, it will achieve 78 mpg (US)
The Japanese manufacturer plans to introduce 14 variations of the 1.0-liter three-cylinder and its 1.3-liter four-cylinder bigger brother (pictured) by 2015
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The Japanese manufacturer plans to introduce 14 variations of the 1.0-liter three-cylinder and its 1.3-liter four-cylinder bigger brother (pictured) by 2015
Diagram showing the reshaped intake port designed to generate a strong tumble flow of the air-fuel mixture in the combustion chamber
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Diagram showing the reshaped intake port designed to generate a strong tumble flow of the air-fuel mixture in the combustion chamber
Toyota's new just-announced Aygo delivers 60 mpg (US) - when the new Atkinson cycle engine, it will achieve 78 mpg (US)
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Toyota's new just-announced Aygo delivers 60 mpg (US) - when the new Atkinson cycle engine, it will achieve 78 mpg (US)
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Toyota has announced the development of two hyper-fuel-efficient small-displacement petrol Atkinson cycle engines: a three-cylinder 1.0-liter and four-cylinder 1.3-liter which will be introduced across the range from next year in 14 different variations. The smaller engine will deliver 78 mpg (US) in the Toyota Aygo, an improvement of 30 percent.

The fuel-efficiency of the one-liter engine in particular is remarkable. The engine it will replace won the One liter category of the International Engine of the Year awards four years in a row from 2007-2010.

At this year's Geneva Motor Show just a month ago, a revised version of the award-winning three-cylinder 1.0-liter engine was announced as the powerplant for the new Aygo.

Toyota's new just-announced Aygo delivers 60 mpg (US) - when the new Atkinson cycle engine, it will achieve 78 mpg (US)
Toyota's new just-announced Aygo delivers 60 mpg (US) - when the new Atkinson cycle engine, it will achieve 78 mpg (US)

Numerous tweaks were used on the reengineered engine such as a higher 11.5:1 compression ratio, an improved combustion chamber design, reduced frictional losses and a weight reduction courtesy of a cylinder head with a built-in exhaust manifold.

With all these changes, the unit's fuel economy had been reduced to 3.9 l/100 km (60 mpg US) at the same time as more power (68bhp – 51kW @ 6,000rpm) and more torque (95Nm @ 4,300rpm).

Now the new improved unit will be replaced again with an Atkinson Cycle engine of the same three-cylinder, 1.0-liter layout, which it has jointly developed with Daihatsu.

Though Toyota has previously used Atkinson cycle engines in its hybrids, it's the first time that the Atkinson design will be used as a stand-alone unit, and Atkinson Cycle engines aren't known for their low- and mid-range torque, but Toyota claims it has addressed this issue with a number of innovations.

Diagram showing the reshaped intake port designed to generate a strong tumble flow of the air-fuel mixture in the combustion chamber
Diagram showing the reshaped intake port designed to generate a strong tumble flow of the air-fuel mixture in the combustion chamber

These innovations include a reshaped intake port designed to generate a strong tumble flow (whereby the air-fuel mixture flows in a vertical swirl) inside the cylinder, and a cooled Exhaust Gas Recirculation (EGR) system, Toyota's Variable Valve Timing intelligent Electric (VVT-iE) technology, an idling-stop function, high compression ratio and various unnamed fuel consumption reduction technologies.

The end result is a maximum thermal efficiency of 37 percent and a fuel efficiency improvement of "approximately 30 percent over current vehicles" – that's the difference between 60 mpg (US) and 78 mpg (US) and it's an astonishing improvement.

The Japanese manufacturer plans to introduce 14 variations of the 1.0-liter three-cylinder (pictured) and its 1.3-liter four-cylinder bigger brother by 2015
The Japanese manufacturer plans to introduce 14 variations of the 1.0-liter three-cylinder (pictured) and its 1.3-liter four-cylinder bigger brother by 2015

Toyota Aygo owners prize the car for its performance at the petrol pump, not the traffic light Grand Prix, and the Aygo is largely purchased for use in tight, congested, urban roads. The appeal of the Aygo and the other compact Toyota vehicles which will use the unit will be greatly increased.

The Japanese manufacturer plans to introduce 14 variations of the 1.0-liter three-cylinder and its 1.3-liter four-cylinder bigger brother by 2015.

The Japanese manufacturer plans to introduce 14 variations of the 1.0-liter three-cylinder and its 1.3-liter four-cylinder bigger brother (pictured) by 2015
The Japanese manufacturer plans to introduce 14 variations of the 1.0-liter three-cylinder and its 1.3-liter four-cylinder bigger brother (pictured) by 2015

The larger 1.3-liter Atkinson cycle engine uses a high compression ratio (13.5) and all the same engine innovations to achieve thermal efficiency of 38 percent. The efficiency results in the 1.3-liter engine aren't quite as spectacular as the one-liter engine but fuel efficiency gains of approximately 15 percent have been realized by comparison with current vehicles.

40 comments
Tom Swift
stick the 1.0L engine in the Prius.
Rusty Harris
LOL, you'll need a BIGGER torque engine, or with 2-3 people in the vehicle, you'll never be able to climb a slight incline on an interstate highway without getting out to push.
Daishi
@Rusty Harris laughing at small Japanese engine design is part of what was responsible for the downfall of Detroit. Have you seen Detroit lately? It's not that they aren't able to make more power with a 1000cc engine, its that they aren't able to do it as efficiently. 1000cc motorcycles make close to 200hp now but they aren't designed for fuel efficiency. My first car was a manual 1989 Ford Escort that only made 90 HP and it still had more oomph than was legal to use on public roads. I think it only takes 10 to 20 HP to maintain highway speed so even then there is enough power left for a slight incline or 2. You rarely actually use the full power of most engines and even when you do its only for a few seconds at a time. For the rare cases you do need the extra kick it's been proven more fuel efficiency to use a hybrid electric design than to throw a large displacement engine at the problem that serves as overkill 99% of the time.
VoiceofReason
VW has sold the Polo for years with a clean diesel that gets in the 70's range of mpg. They won't sell it in the US.
Erik Unger
It would have been interesting to learn what the Atkinson Cycle is, instead of quoting press release data.
Synchro
30% is a big improvement, and 68bhp is tons for a small car. @Rusty - I've suffered the indignity of a car not having enough go to get up a hill, but that was a 3.5litre V6 Mustang coming out of Yosemite... Heap of junk that was!
Mel Tisdale
To be pedantic, the engine does not have an extremely high compression ratio because the inlet valve stays open at the start of the compression stroke and only closes when a significant portion of the fuel charge has been pumped back into the inlet manifold. This reduces the final compressed pressure below that which would cause pre-ignition or detonation. The compression ratio is what is left of the compression stroke in relation to the cylinder-head volume. The expansion stroke is not affected and can thus legitimately be described as 'extremely high' when the cylinder-head volume is compared to the expanded volume measured from t.d.c. to b.d.c. This expansion ratio, when placed in the 'r' term in the formula for thermal efficiency instead of that for the compression ratio leads to the improved fuel economy figures. I imagine they need a fly-by-wire throttle to manage the ram effects around the point of valve closure. I personally know of a certain British motor manufacturer that could have had this in development as long ago as the mid-eighties, but it relied on having a management that was worthy of the term. It is a matter of conjecture as to whether the size of these engines should be that of the b.d.c. to t.d.c. value, as at present, or should be that of the actual compressed volume that remains after closure of the inlet valve, which will surely be important when taxation, insurance and such like are taken into consideration. That assumes, of course, that one can fix an actual value for a variable valve timing system.
notarichman
nothing is mentioned about it's exhaust...will it be approved for california for example? also nothing is mentioned about repairs, i.e. easy to repair?, how long does the engine last?, expensive parts? Is it louder or quieter than the usual engine? a 1000cc engine seems to be the standard now days for a UTV...will it withstand shocks?, cold weather, cold water splashing on it when it is hot? Can it be modified for small airplane use? How about use in boats? Motorcycles? Speaking of which...my sister had a smaller Harley back in the days of AMC and the plastic parts of the carb broke due to vibration. you couldn't buy the parts, you had to buy the whole carb. so my bro-in-law bought a standard carb from NAPA and fitted it on. It got 78 mpg and had more power! Who would have thought a carb could make so much difference?
VirtualGathis
@Diachi - Quote: "You rarely actually use the full power of most engines and even when you do its only for a few seconds at a time." This is why a properly designed hybrid gets stupid good milage. The ICE engine is sized for average load not peak load. The battery or hydraulic acumulator makes up for the peaks and charges during braking and between peaks. This is also why most hybrids foisted on the public by traditional mindsets like Rusty's get only marginally more power. They are thinking of the battery only as a recovery tool, not as a reservior. The first time I saw a hybrid car it was an excersize in cross disapline research by a school. They had the hydraulics engineers build a car for mileage. The students put a 10HP engine in the back running at 3/4 open all the time and a hydraulic accumulator with a reversable pump/motor as the prime mover. It had regenerative braking and got 80mpg while pulling 0-60 in 5.5s. Unfortunately the traditional companies looked at it and claimed it was impossible, despite the working prototype, and missed the concept. This is why vehicles like the volt will never get great milage and cost far more than needed. When you buy a Volt you are buying two cars not one. You are buying an electric vehicle with a range of 20-30 miles and an ICE vehicle that only gets 30mpg. If they had rigged it the same way the students did they could have used a battery half the size and a 25hp diesel engine while selling for a 10% markup and giving a much better ROI.
LowFlyerXX
It makes me mad, all these "attempts" (and as off lately Governmental push) to lower gas consumption - as VoiceOfReason said - Europe (not only VW) has had cars that get well over 70 MPG!! Althouhg, gas is more expensive - about a third more than ave US. And unfortunately, back in late 50's Ford did well over 100 MPG with experimental carb from Rochester fitted on a Flathead motor - I have this from a trusted source... Makes me wonder if it is all another form of political "muscle flex", every gallon sold = taxes to the state and federal!! OUT of our pockets. HHHMMMMM... But if I choose to ride a big comfortable and powerful SUV - do I suffer the extra added cost for fueling it? I have a choice, or do I?? Open for debate...