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Larger displacement Atkinson cycle engines may be in the future for Toyota

A number of automotive manufacturers have begun to move away from larger displacement naturally aspirated engines to smaller displacement turbocharged engines. The general idea was that smaller and lighter engines would use less fuel while offering the same sort of performance thanks to the addition of a turbocharger. However, in the real world many drivers have discovered that turbocharged small displacement engines are often unable to deliver on their fuel efficiency claims.

Toyota is considering bucking the industry trend and rather than going with smaller turbocharged engines, is considering larger naturally aspirated engines to improve fuel efficiency. Senior managing officer in charge of drivetrain R&D for Toyota Koei Saga recently said that Toyota believes gasoline engines could benefit more from upsizing capacity in conjunction with Atkinson combustion cycles than going smaller with turbochargers.
 
Atkinson engines today are typically only used in hybrid vehicles like the Prius, Ford Fusion Hybrid, Hyundai Sonata Hybrid, and Honda Accord Hybrid.


Toyota Camry
 
Increasing the displacement of an engine using the Atkinson cycle would deliver a specific output less than that of similarly sized conventional combustion cycle engines, but fuel economy would be better. Toyota believes that fuel economy would be better than the smaller engines they replace.
 
Toyota has offered no timeframe for bringing larger displacement Atkinson cycle engines to market and hasn't hinted at which models might get the Atkinson cycle engines.
 
Mazda experimented with similar “delayed valve” Miller Cycle technology over a decade ago in the Millenia midsize sedan. But instead of using electric motors to make up for the reduced power density like today’s Atkinson-engine hybrid vehicles, the Millenia used a supercharger.
 
Saga also talked a bit about the next generation Toyota Prius saying that the vehicle will use a mixture of battery technology including lithium-ion and nickel batteries. The reason for mixing battery types is that lithium-ion batteries are better for performance, but the durability and lifespan is better for nickel batteries. 

Source: Green Car Reports



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RE: According to whom?
By Mint on 10/16/2013 4:20:00 PM , Rating: 2
Slow acceleration doesn't help efficiency much.

If you ever look at an engine's BSFC chart, they're most efficient at ~80% throttle (low RPM, of course). Even for small engines, there's enough power there to avoid "merging onto a highway doing 35-40".

The biggest style factors on efficiency is speed (due to air resistance) and number of acceleration-deceleration cycles (especially with non-hybrids). The latter usually goes up with lead-foots, tailgaters, and pathological lane-changers even when they obey speed limits.

The other factor, of course, is your route. Lots of stop signs make your fuel efficiency tank. The EPA city test is representative for a lot of people, but not everyone. I only average 10-15 mph when off the highway due to traffic, stop signs, and lights.


RE: According to whom?
By Reclaimer77 on 10/17/2013 4:19:07 PM , Rating: 2
One thing I hate about new drive-by-wire throttle systems is that it's almost impossible to gauge your throttle position, due to electronic trickery. You might only be using 30% of the pedal, but the engine is electronically advanced to 60%. Think you're only using 50% throttle under acceleration? Wrong, you're using like 80%!

I get why they do it, it makes the car feel faster and quicker at all times, because it's always using more throttle than your foot is applying.


RE: According to whom?
By superstition on 10/19/2013 12:51:44 AM , Rating: 2
Is this true for current diesel cars? My Passat TDI 6 speed "automated manual" (in automated mode) seems to get much better mileage (according to the computer) when I accelerate leisurely.


"So if you want to save the planet, feel free to drive your Hummer. Just avoid the drive thru line at McDonalds." -- Michael Asher














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