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Print 65 comment(s) - last by superstition.. on Oct 19 at 12:54 AM

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 Spuke on 10/16/2013 12:18:35 PM , Rating: 2
I'm driving a 2007 Pontiac Solstice GXP with a 2.0L turbo DI engine. 19/28 are the EPA figures and I get 28 mpg (last few weeks getting 29). Too much boost will lower your fuel economy. If I keep my boost at 5 psi or lower I get 33 mpg but that's no fun. I fully believe it's driving style killing mileage not car capability.


RE: According to whom?
By dgingerich on 10/16/2013 12:40:04 PM , Rating: 3
You're right about driving style killing mileage, but also the driving styles of the testers are inflating the numbers. I'd bet the numbers some of these car companies are putting out are done with a driving style that would have people merging onto a highway doing 35-40.


RE: According to whom?
By fic2 on 10/16/2013 1:04:28 PM , Rating: 2
You mean like people around here normally do? Freaking kills me that most people don't know to accelerate on that long strip of asphalt before they hit traffic.


RE: According to whom?
By dgingerich on 10/16/2013 2:04:02 PM , Rating: 2
Yeah, I've lived in 4 different major metro areas, and I've seen that in every one, but a little more pronounced in certain areas of Chicago. (NW suburbs of Chicago are DANGEROUS. you have a mix of super aggressive, from downtown, and super passive people, from the local area. Getting caught between them is a really bad idea.) Stupid is everywhere.

I recently saw an old woman in the Denver Tech area in the evening rush hour merge onto I-25 doing about 40, and move over two lanes at once. It caused a 7 car accident across those two lanes from the people who had to slam on their brakes to avoid her, and she didn't even seem to notice the chaos and damage she unleashed. Luckily, I was in the third lane over and missed it all, and managed to pass her. She didn't even signal in any of her lane changes and moved all the way over to the left lane, doing 55 in a 65 zone, causing all sorts of traffic problems behind her, all in the less than 3 miles I watched her until I got off the highway.

A lot of the people I talk to who drive that way think it's safer, clueless of what they unleash on other people. I've tried explaining it, and they just come back with "those other people shouldn't be going that fast anyway." It's the Dunning-Kruger effect in its full glory.


RE: According to whom?
By Philippine Mango on 10/17/2013 6:40:51 PM , Rating: 2
Your story about the old woman driving reminded me of this video:http://www.youtube.com/watch?v=QKcSZfY1sf4


RE: According to whom?
By Jeffk464 on 10/16/2013 5:18:20 PM , Rating: 2
No you accelerate faster when you need to like getting on the freeway and mellow out when its not necessary. Watch most people on the freeway, when a car moves out of the lane in front of them they gun it immediately to fill in the gap.


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.


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