Toyota Not Ready to Jump on Small Displacement, Turbo Engine Bandwagon
October 16, 2013 9:26 AM
comment(s) - last by
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
Honda Accord Hybrid
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.
Green Car Reports
This article is over a month old, voting and posting comments is disabled
RE: Low-power operation
10/16/2013 7:34:05 PM
I believe that most of the benefit of the Atkinson cycle engine is an improvement in the thermal efficiency of the engine. The Otto cycle engine sucks a volume of air into the cylinder compresses it and heats it by burning fuel in it to increase the pressure in the cylinder (heat plus combustion products) it then expands the gasses to the same volume as prior to compression before exhausting the gasses. This means that the still heated gasses are going to be exhausted while considerable pressure energy remains meaning that pressure energy is no longer able to do useful work in the engine. That remaining energy is effectively dumped via the exhaust system. A true Atkinson cycle engine has a shorter compression stroke than power stroke and so extracts more of the pressure energy available before exhausting the gasses. This would improve the thermal efficiency of the engine (more of the heat from burning of fuel is converted to work) while at the same time reducing its power density.
While the engine would probably spend more time with its throttle further open due to its reduced power density if the engine was built with a larger displacement to compensate, that would have the effect of normalizing the throttle position and pumping losses would be greater due to induction air passing into and out of the cylinder on the intake side. Pumping air into the cylinder past the intake valve and then pushing some of it back out again past the intake valve. This would be an extra double pass of the intake valve for gasses that are back flowed out of the cylinder on the intake side with a small pressure drop or energy loss for each pass. A larger displacement could allow larger intake and exhaust valves for an easier breathing engine. It would also mean bigger pistons and heavier crankshaft and consequently bearing surfaces with a larger area and increase sliding velocities for greater frictional losses. Also the increased engine weight would negatively affect the vehicles overall efficiency.
RE: Low-power operation
10/17/2013 6:58:57 AM
A shorter compression stroke does the exact same thing as putting less air-fuel mixture into the cylinder. You get the same number of molecules of air/fuel in there compressed to the same volume and expanded to the same volume after ignition.
The big difference is that Atkinson does that more efficiently. Air doing double passes though open valves isn't nearly as bad as air going across a throttle that is more closed. The pressure drop is clearly far less with the former than the latter.
You're right that there are negatives with a larger engine, but it's a matter of magnitudes to see whether they are worth it.
"Well, we didn't have anyone in line that got shot waiting for our system." -- Nintendo of America Vice President Perrin Kaplan
2014 Honda Accord Hybrid to Start at $29,155, Rival Prius in Fuel Economy
September 24, 2013, 10:01 AM
Toyota to Release 15 New Hybrids by 2015, Reveals Specs for Next-Gen Prius
August 29, 2013, 12:18 PM
Consumer Reports: Small Turbo Engines Don't Meet Efficiency Claims
February 5, 2013, 9:29 AM
2013 Ford Fusion Hybrid EPA Certified at 47 MPG (City/Highway)
September 18, 2012, 8:10 AM
37 MPG 2011 Hyundai Sonata Hybrid Priced from $26,545
December 16, 2010, 11:19 PM
BMW Testing Tech to Allow Users to Auto-Park, Summon Cars Via Smartwatch
December 16, 2014, 9:30 AM
Lamborghini Offers Up $6,000 Leather-Bound Android Smartphone
December 12, 2014, 3:12 PM
Quick Note: GM Teases Next Generation Chevrolet Volt
November 20, 2014, 3:26 PM
Audi is Latest to Step Into the Hydrogen Game, Delivers A7 Sportback h-tron quattro
November 19, 2014, 1:41 PM
Toyota’s Mirai Hydrogen Fuel Cell Vehicle Priced from $57,500 in the U.S.
November 18, 2014, 10:23 AM
Honda Still Pushing Hydrogen, Introduces FCV Fuel Cell Concept
November 17, 2014, 8:27 AM
Most Popular Articles
Android-Powered BLU Studio 7.0 Claims to be the "World's Largest Smartphone"
December 19, 2014, 2:40 PM
Paramount Bans Team America Screenings, Cowers Submissively to North Korea
December 18, 2014, 10:26 PM
Miyamoto: Nintendo is Prepping Successor to Troubled Wii U
December 22, 2014, 6:28 PM
Amazon's Kindle Fire HDX 8.9 Drops to $299 (30 Percent Off) for a Day
December 22, 2014, 10:57 AM
News Corp's Fox is Terrified of North Korea, Kills Upcoming Steve Carell Film
December 18, 2014, 4:09 PM
Latest Blog Posts
Sceptre Airs 27", 120 Hz. 1080p Monitor/HDTV w/ 5 ms Response Time for $220
Dec 3, 2014, 10:32 PM
Costco Gives Employees Thanksgiving Off; Wal-Mart Leads "Black Thursday" Charge
Oct 29, 2014, 9:57 PM
"Bear Selfies" Fad Could Turn Deadly, Warn Nevada Wildlife Officials
Oct 28, 2014, 12:00 PM
The Surface Mini That Was Never Released Gets "Hands On" Treatment
Sep 26, 2014, 8:22 AM
ISIS Imposes Ban on Teaching Evolution in Iraq
Sep 17, 2014, 5:22 PM
More Blog Posts
Copyright 2014 DailyTech LLC. -
Terms, Conditions & Privacy Information