JSAE Exposition 2015: Toyota and Honda showcase direct-injection turbo engines
New engines feature improved thermal and fuel efficiency along with usable torque
|The Lexus RX200t fitted with a 2.0-liter direct-injection turbo engine that was unveiled at the Auto Shanghai 2015 in April and is slated for market launch in Japan after the fall of 2015 (photo courtesy on Toyota).|
This report focuses on three gasoline engines newly developed by Toyota and a new engine developed by Honda that were exhibited at the JSAE Exposition 2015.
Toyota exhibited 1.2-liter and 2.0-liter direct-injection turbo engines and a 1.5-liter naturally-aspirated engine. In April 2014, Toyota announced that it would introduce 14 engines of high thermal and fuel efficiencies by the end of 2015. Toyota launched nine of them, including the three mentioned above, by the end of May 2015.
Honda has developed three direct-injection turbo engines consisting of 2.0-, 1.5- and 1.0-liter models. The 1.5-liter engine was fitted in the all-new Step WGN in April 2015 and was exhibited at the JSAE 2015. It achieves high fuel efficiency and high torque in a practical range that are almost equivalent to those of 2.4-liter engines.
Toyota and Honda adopted several advanced technologies including the dual VVT and strong tumble flow generation to develop engines of high fuel efficiency and performances.
<JSAE Exposition 2015 reports (Jun. 2015)>
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Toyota: 14 fuel-efficient engines in two years from 2014 to 2015
In April 2014, Toyota announced that it would develop a total of 14 highly fuel-efficient engines by the end of 2015 and launch them in sequence. So far, Toyota has launched 9 engines including three that were exhibited at the JSAE 2015.
Toyota will leverage combustion improvement and loss reduction technologies that it has acquired in the course of developing hybrid engines, and develop a group of highly fuel-efficient engines that will achieve one of the highest thermal efficiencies in the world. Toyota intends to achieve at least 10% improvement (in JC08 test method) in fuel efficiency over the current engines.
According to Toyota, rapid combustion and a high compression ratio are the keys to improved combustion. Toyota achieved rapid combustion by adopting a high tumble flow (vertical swirl) and a high compression ratio by using a 4-2-1 collector exhaust pipe system that increases scavenging efficiency. The company also corrected knocking by using a water jacket spacer to control the cylinder bore's wall temperature.
An Atkinson cycle engine is used in the turbo engine series. The turbo engine is paired with Variable Valve Timing-intelligent Wide (VVT-iW) systems to achieve optimum control over the engine. The naturally aspirated engines are fitted with a large-volume cooled EGR system.
|Rapid combustion resulting from a high tumble flow (photo by Toyota)||Knocking due to a high compression ratio prevented by increased scavenging efficiency (photo by Toyota)|
Toyota: Key technologies in the new engine series addressing combustion improvement and loss reduction
|Past efforts||⇒||New engines|
|HV technologies||Conventional technologies||Natural aspiration engines||Turbo engines|
|Combustion improvement||Rapid combustion||●||●||●|
|High compression ratio||●||●||●||●|
|Loss reduction||Pumping-loss reduction||Atkinson cycle||●||●||●|
|Large-volume cooled EGR||●||●|
A new engine lineup (Global rollout started from 2014)
|Natural aspiration engines||Turbo engines|
|Displacement||1.0 liter||1.3 liter||1.5 liter||2.0 liter||2.0 & 2.7 liter||1.2 liter||2.0 liter|
|Models||Passo||Vitz||Corolla||Camry for overseas||Hiace||Auris||Lexus NX|
|(Notes) 1.||Three new engines exhibited at the JSAE 2015 are identified by bold letters.|
|2.||The all-new Hilux fitted with the 1GD diesel engine (2755cc) was launched in Thailand on May 21, 2015, increasing the number of engines in the new engine lineup to nine.|
Toyota: 1.2-liter inline 4-cylinder direct-injection gasoline turbo engine (8NR-FTS)
|Toyota's 1.2-liter direct-injection turbo engine 8NR-FTS|
This is a downsized turbo engine that competes with the TSI engine developed by Volkswagen (TSI is a trademark of VW's engines sold since 2006 under the "direct injection, turbocharged and small displacement" slogan). The 8NR-FTS engine was originally developed for European markets. In addition to the eco-friendly hybrid engines, however, Toyota decided to introduce the new engine in Japan as well because of its high fuel efficiency and acceleration feel that adds to the fun of driving. It was made available on the partially remodeled Auris in April 2015.
The exhaust manifold is integrated with the cylinder head and is mated with a single-scroll turbocharger to achieve outstanding turbocharging efficiency. The turbocharger was reduced in size to minimize turbine inertia and increase the turbine's effect in the low rev range.
The engine is fitted with an intercooler to cool the intake air and also fitted with a VVT-iW (on the intake side) that increases the variable angle. These have enabled the use of the Atkinson cycle system.
The Auris fitted with a standard start-stop system and the CVT has fuel efficiency of 19.4km/liter (in JC08 test method). By improving combustion efficiency and reducing loss, the engine has achieved maximum thermal efficiency of 36%, one of the highest among turbocharged production engines in the world. According to Toyota, the 8NR-FTS engine delivers dynamic performance of a 1.8-liter engine with a fuel efficiency of a 1.5-liter class naturally aspirated engine.
1.2-liter inline 4-cylinder direct-injection gasoline turbo engine (8NR-FTS)
|(Notes) 1.||An Atkinson cycle is a highly fuel-efficient combustion cycle and improves thermal efficiency by increasing the expansion ratio over the compression ratio. The valve timing is varied as needed to deliver a high power output.|
|2.||VVT-iW (Variable Valve Timing-intelligent Wide) is a type of VVT system that has a expanded variable intake valve angle.|
|3.||The intercooler is a cooling device for intake air that gets hot when compressed by turbocharger.|
Toyota: 2.0-liter inline 4-cylinder direct-injection gasoline turbo engine (8AR-FTS)
|Toyota's 2.0-liter direct-injection turbo engine 8AR-FTS|
The exhaust manifold is a 4-2 collector system that is integrated with the cylinder head. It is mated with a twin-scroll turbocharger to reduce the interference (pulsing) of the exhaust gas and maximize the turbo efficiency.
The VVT-iW has a larger variable intake valve angle needed for optimal control of valve timing. The engine also features the Direct-injection 4-stroke gasoline engine Superior version with Turbo (D-4ST) that has two injectors for direct injection and intake port injection. According to Toyota, this generates strong torque in low revs that contributes to delivering smooth and nimble acceleration feel.
The Lexus NX, the first Lexus fitted with the 8AR-FTS engine, is mated with the 6-speed automatic transmission that was newly developed for the turbo engine. It has JC08 fuel efficiency of 12.8km/liter and delivers maximum torque of 350N-m in a broad rev range from 1,650 rpm to 4,000 rpm.
After the Lexus NX, Toyota unveiled the Lexus RX200t, powered by the same 2.0-liter direct-injection turbo engine, at the Auto Shanghai 2015 in April. The RX200t is slated for launch in Japan after the fall of 2015.
2.0-liter inline 4-cylinder direct-injection gasoline turbo engine (8AR-FTS)
|(Notes) 1.||D-4ST stands for Direct-injection 4 stroke gasoline engine Super version with Turbo. It has two injectors for direct injection and port injection that are used selectively as well as simultaneously to improve the efficiency of combustion.|
|2.||The twin-scroll turbocharger has two separate passages from the exhaust manifold to the turbine housing. This ensures necessary response at low revs and power output at high revs.|
|3.||The engine features a 4-2 exhaust manifold integrated into the cylinder head in which cylinders 1 and 4 are joined up and cylinders 2 and 3 joined up. This collector piping system reduces the exhaust gas interference. It is mated with the twin-scroll turbocharger to maximize the turbo efficiency.|
Toyota: 1.5-liter inline 4-cylinder naturally aspirated gasoline engine (2NR-FKE)
The 2NR-FKE is the naturally-aspirated engine that is fitted in the Corolla Axio and Corolla Fielder that were partially remodeled in March 2015. It features an Atkinson cycle system with a high compression ratio of 13.5, a large-volume cooled EGR and an electric VVT (VVT-iE) on the intake side (an ordinary hydraulic VVT on the exhaust side). The 2NR-FKE achieves one of the highest fuel efficiencies and dynamic performance in class.
Toyota drew visitors' attention to the display panel showing the effect of cylinder bore's wall temperature control by using a water jacket spacer with formed rubber. Normally, the temperature gets high at the cylinder top near the combustion chamber and it gets overcooled at the bottom. The spacer is used to lower the temperature at the top to correct knocking and increase the temperature at the bottom to minimize the temperature difference in the cylinder and reduce frictions.
The 2NR-FKE engine is an engine for vehicles powered by an internal combustion system but delivers a thermal efficiency of 38% which is normally expected from hybrid engines. It achieves high fuel efficiency (in JC08 test method) of 23.4km/liter on the Corolla Axio (2WD and CVT model with a start-stop system) and 23.0km/liter on the Corolla Fiedler.
|Toyota's 1.5-liter 4-cylinder naturally-aspirated engine 2NR-FKE||Water jacket spacer is used to control the cylinder wall temperature and prevent knocking.|
1.5-liter inline 4-cylinder gasoline engine (2NR-FKE)
|(Notes) 1.||VVT-iE (Variable Valve Timing-intelligent by Electric motor) is an electric VVT used in the intake side (a hydraulic VVT is used on the exhaust side). The VVT-iE costs more but has a larger variable angle that offers several advantages such as quicker operations while the engine is cold and faster operating speed than the hydraulic VVT.|
|2-1.||Water jacket spacer is a resin-made spacer about half the height of the water jacket and inserted in the water jacket. It reduces the amount of cooling water at the cylinder bottom to increase the cylinder wall temperature and increases the amount at the top near the combustion chamber. This minimizes the temperature difference between the top and the bottom. The 3GR-FSE launched by Toyota in 2003 is the world's first engine equipped with such a spacer.|
|2-2.||The water jacket spacer with formed rubber and fitted in the 2NR-FKE engine is a stainless steel sheet on which Expad, a thermal expansion sheet, is attached. The thermal expansion sheet quadruples in thickness as the cooling water temperature rises after engine starts. It is used to fill gaps in the water jacket.|
|3.||The 4-2-1 exhaust manifold is a collector piping system in which four exhaust manifold are first joined up into two, and finally into one. This reduces the interference of exhaust gas and increases the scavenging efficiency.|
|4.||The cooled EGR (Exhaust Gas Recirculation) system has a cooler that cools the exhaust gas being recirculated. It enables recirculation of a large amount of exhaust gas which reduces the NOx emissions and contributes to the reduction of pumping loss and knocking problem.|
Honda: 1.5-liter direct-injection VTEC TURBO engine fitted in all-new Step WGN
|Honda's 1.5-liter direct-injection VTEC TURBO engine|
Honda has developed 2.0-, 1.5- and 1.0-liter direct-injection VTEC TURBO gasoline turbo engines under the "Earth Dreams Technology" approach. Among the three types, the 1.5-liter engine was fitted in the all-new STEP WGN that was launched in Japan in April 2015 and exhibited at the JSAE 2015.
The 1.5-liter engine features a direct-injection turbo system and an intake and exhaust dual VTC (a Honda terminology, an equivalent of VVT) to maximize advantages of turbo engines that generate ample torques from low rev ranges. They also help maintain combustion of high efficiency which leads to a class-top fuel efficiency of 17.0km/liter on the Step WGN (in JC8 test method). The car ensures stress-free, powerful driving even with multiple passengers.
The turbocharger has a small-diameter turbine that spins even at low revs with low exhaust gas flow. This means turbocharging is available in low revs. The turbocharger also features an electronically-controlled wastegate to freely set the turbocharging pressure. This contributes to low fuel consumption by reducing the exhaust loss in the turbocharging range.
The direct-injection system injects fuel into the cylinder where it is gasified. This lowers the temperature inside the combustion chamber and prevents knocking to stabilize combustion. This, in turn, increases the freedom of valve overlap control by the dual VTC (the duration in which both intake and exhaust valves are open). This contributes to optimum valve control according to the driving condition.
Optimum valve overlap is controlled based on driving conditions as described below; at engine start and idling, overlap is minimized to stabilize the engine revolution. In the largest practical rev range, overlap is controlled in such a way that fuel efficiency and emissions are optimized. When accelerating from low revs, overlap is maximized for smoother scavenging and response and to reduce pumping loss. In high rev range, overlap is reduced to deliver higher power output.
Honda: Newly-developed 1.5-liter VTEC TURBO engine
Main technologies and performances
●Direct-injection system * Cylinders cooled by direct fuel injection into cylinders * Specifications for rapid combustion - High-tumble port - High-tumble sustaining piston - Small-diameter bore and long stroke
●Intake and exhaust dual VTC for valve overlap control * Improved fuel efficiency: Effect of increased internal EGR which occurs when the residual combustion gas remaining in the cylinder at the end of the exhaust stroke is mixed with the incoming charge using valve overlap. Internal EGR reduces pumping loss) * Improved turbocharging efficiency: Effect of increased overlap on scavenging (when accelerating in low revs, etc.) * Improved power output: Effect of smaller overlap on reducing residual gas (in high revs)
●Turbocharger with an electronic wastegate * Small-diameter turbocharger of high responsiveness * An electric wastegate reduces exhaust gas loss in turbocharging range and contributes to increasing fuel efficiency
|Engine type||In-line four-cylinder|
|Injection system||Direct injection|
|Maximum power||110kW (150PS)/5500rpm|
|Maximum torque||203Nm (20.7kgf･m)/1600-5000rpm|
|JC08-mode fuel economy||17.0km/L (New Step WGN)|
Honda: 2.0-liter turbo engine fitted in the Civic TYPE-R
(Not exhibited at the JSAE 2015) Honda exhibited, at the Geneva Motor Show in March 2015, the Civic TYPE-R fitted with a 2.0-liter turbo engine. The vehicle is already being produced at Honda's UK plant for market launch in Europe in the summer of 2015. It delivers the highest performance among the TYPE-R models in the past with maximum output of 310PS and maximum torque of 400N-m. The engine is mated with a 6-speed manual transmission to achieve driving performances that includes 0-100km/h acceleration time of 5.7 seconds and top speed of 270km/h.
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