Daihatsu Move Teardown (Part 2): High fuel economy and improved performance

Turbo engine and CVT with 3-shaft gear train has lightweight and compact design

2015/03/02

Summary

Daihatsu Move Teardown

 The Daihatsu Move teardown was held on January 21 through 27, 2015, by the Hiroshima Industrial Promotion Organization. The Part 1 of the teardown report (No. 1378 posted on February 19, 2015) focused on equipment and components comparable to those in B-segment cars. Part 2 focuses on the engine and transmission fitted in the fifth-generation 2014 Daihatsu Move X-turbo VS model (see Note).

 The turbo engine of the fifth-generation Daihatsu Move is based on a long-stroke engine and fitted with one of the smallest turbochargers in the world (supplied by IHI). The engine provides good responsiveness, powerful torques in low- to mid-ranges, and high fuel economy. The aluminum engine block features a carefully design rib reinforcement for extra rigidity to reduce noise and vibrations while achieving substantial weight reduction. This block, plastic intake manifold, throttle body and other components were developed to make the Daihatsu Move the lightest car in class. Nearly a decade has passed since its debut in 2006 and the Move is still leading the highly competitive mini vehicle market.

 The Move is fitted with Daihatsu's proprietary CVT as detailed later in this report. A planetary reduction gear with forward and reverse switching mechanism is located on upper-stream of the belt and pulley transmission unit. This design has made it possible to reduce the number of gear shafts from four as in the conventional CVT to only three. This leads to reducing the unit in weight and size. In addition, the speed reduction function of the planetary gear reduces the rotation speed of the CVT belt and pulleys. This helps reduce friction loss, which, in turn, improves fuel economy.This report focuses on the turbocharged engine and the CVT unit used in the Move.

 (Note):The fully-redesigned Move (sixth-generation Move) was launched in December 2014.


Previous teardown reports:

Daihatsu Move (Feb. 2015)
  (Part 1): Equipment comparable to B-segment cars

VW Polo (Dec. 2014)
  (Part 1):Engine compartment and driver's seat area
  (Part 2):1.2-liter TDI diesel engine and suspensions

Nissan Note (Sep. 2014)
  (Part 1):Major safety technology and advanced driver
               assistance systems

  (Part 2):Drive unit and supercharger

Honda Accord Hybrid teardown (Feb. 2014)
  (Part 1): PCU and vehicle chassis components
  (Part 2):Battery components and brake system
  (Part 3):Sport Hybrid i-MMD drive unit

Honda Fit Hybrid teardown (Dec. 2013)
  (Part 1) Battery components and brake system
  (Part 2) Engine and transmission

Toyota Aqua (Nov. 2012)
  (Part 1) Part suppliers and battery components
  (Part 2) Hybrid systems behind the 35.4km/liter car

Nissan Leaf
  (Part 1) Benchmarking systems and components (Mar. 2012)
  (Part 2) Main components disassembled (Sep. 2012)
  (Part 3) Nissan Leaf body cutaway (Nov. 2012)

Specifications of the 2014 Daihatsu Move

Daihatsu Move Daihatsu Move
Vehicle specifications Model name/Grade Daihatsu Move X-turbocharged VS grade,
special version with Smart Selection SA (Smart Assist)
Price JPY 1.33 million plus JPY 60,000 for optional Smart Assist
Dimensions Length: 3,395mm, Width: 1,475mm, Height: 1,620mm
Curb weight 820kg
Seating capacity 4
Engine KF-type water-cooled inline 3-cylinder intercooled turbocharger
Transmission CVT with a torque converter and lockup mechanism
Fuel efficiency (JC08 mode) 25.20km/liter


Three-cylinder DOHC 12-valve turbocharged engine with intercooler

KF-DET engine KF-DET engine

 The KF-DET engine is a 660cc three-cylinder DOHC 12-valve gasoline engine fitted with an intercooled turbocharger. It provides 47KW(64PS)/6400rpm of power and 92Nm(9.4kgm)/4200rep of torque. It is a very high-performance engine with 71.2KW(97PS) of power per liter. It is a long-stroke engine intended for torque over power with 63mm x 70.4mm bore and stroke and a bore/stroke ratio of 1.12.

 The exhaust system is located in front of the transverse-mounted engine toward the front of the vehicle. The turbocharger is located directly behind the exhaust manifold. The air supercharged by the turbocharger is cooled by the air-cooled intercooler located above the engine before it reaches the intake system (throttle body, intake manifold) in back of the vehicle.

 

Air-cooled intercooler

 The air-cooled intercooler (supplied by T.RAD) is located over the engine. It takes air from the air inlet located under the hood to cool the intake air that is heated by the turbocharger. The intercooler is located over the engine rather than behind the front grille for a specific reason. This layout was chosen to reduce the length of the intake path so as to improve the intake response. If the intercooler is located behind the front grille, more cooling air will be drawn in to reduce the temperature of intake air more efficiently which, in turn, will produce more power and torque. But the Daihatsu Move is designed to ensure better response.

air-cooled intercooler Air-cooled intercooler
Location of the air-cooled intercooler Air-cooled intercooler (by T.RAD)

 Located at the top of the engine head cover to cool the intake air by using cooled air from the fresh air duct located under the hood.

 

Turbocharger

 The Daihatsu Move is equipped with the RHF25 turbocharger supplied by IHI. Developed in 2008 by IHI for Daihatsu, it is one of the world's smallest turbochargers reputed for lightweight and compact design along with outstanding performance. The exhaust turbine has an outside diameter of approximately 70mm, and the compressor has the outside diameter of approximately 80mm. The inner turbine blade with a small diameter helps increase the response of supercharging performance in low speeds. As a tradeoff for high power output, the rotational speed has been increased by 20% from 250,000rpm to 310,000rpm to ensure sufficient supercharging capacity. The bearing has been redesigned and the reliability of the turbine and the compressor improved to withstand high speeds.

RHF25 turbocharger Exhaust turbine Compressor
RHF25 turbocharger (by IHI) Exhaust turbine outside diameter approx. 70mm Compressor outside diameter approx. 80mm

 

Intake/exhaust valve train

 The intake and exhaust valve train consists of 12 DOHC valves, four valves per cylinder. The Dynamic Variable Valve Timing mechanism (DVVT) is used on the Daihatsu Copen that was fully redesigned in 2014, and also on the sixth-generation Move. However, the DVVT is not used on the turbocharged version of the fifth-generation Move which was torn down this time. It was available for the naturally aspirated engine version of the fifth generation, and to allow parts sharing with other models, the space for fitting the DVVT is kept and a dummy weight is fitted at the front edge of the camshaft.

 Shim-less valve lifters are used to eliminate the need for valve clearance adjustment with shims after the engine is assembled. This helps reduce work load and costs. Twenty-five different kinds of valve lifters that are finished to precise dimensions are prepared and those of specified sizes are selected and built into the valve train without the need for shim adjustment.

Exhaust and intake camshafts Shim-less valve lifters and valve springs
Exhaust and intake camshafts Shim-less valve lifters and valve springs

 

Intake manifold and throttle body

 The intake manifold is made of plastic and an electric throttle body is built into it. The long intake port is connected to the cylinder head forming a 3/4 arc from the throttle body. This design helps increase the flow speed in the intake port at low speeds. This, in turn, helps improve fuel economy while increasing torque in low- to mid-ranges.

Plastic intake manifold Plastic intake manifold
Plastic intake manifold: A long intake port is tightly built into the manifold for higher torques in low- to mid-ranges

 

Engine block

 The aluminum engine block is light and compact in design. The block has a long skirt and is connected to the CVT unit via rib reinforcements and oil pan. Every detail is designed most carefully to ensure high rigidity to reduce vibrations and noise.

Aluminum engine block Aluminum engine block
Aluminum engine block: Carefully designed rib reinforcement is used to ensure high rigidity and weight reduction

 A plastic water jacket spacer is used to surround the cylinders in the engine block. It covers the lining and the coolant is heated faster so as the warm-up period is reduced after cold starting.

long skirt design Plastic water jacket spacer
The engine block has a long skirt design and is covered with an oil pan. This design enables the engine block to enfold a crankshaft and hold it tight against vibrations. Plastic water jacket spacer

 

Cylinder head and pistons

 The engine has a compression ratio of 9.0, standard for a turbocharged engine. A pentroof type combustion chamber is formed in the cylinder head with concave spaces in the piston side.

Pentroof type combustion chamber in the cylinder head Pistons designed in consideration of an ideal air swirl in the cylinder
Pentroof type combustion chamber in the cylinder head Pistons designed in consideration of an ideal air swirl in the cylinder

 

Three-way catalytic converter

 The three-way catalytic converter is located directly behind the turbocharger and is contained in the engine assembly. Palladium in the converter is self-regenerative to last over an extended period. The three-way catalytic converter and the exhaust muffler assembly are supplied by Futaba Industrial.

Three-way catalytic converter Three-way catalytic converter
Three-way catalytic converter (by Futaba Industrial)

 

Engine electric parts

 Engine electric parts are shown below in photos.

Ignition coil Alternator
Ignition coil (by Diamond Electric Mfg.) Alternator (by Denso) It regenerates energy during decelerations.
Camshaft rotation sensor Knocking sensor
Camshaft rotation sensor (by Denso) Knocking sensor (by Denso)
Engine ECU Engine ECU
Engine ECU (by Denso)

 

 



Unique CVT with torque converter and lockup mechanism

Transmission specification Type CVT with a torque converter and lockup mechanism
Gear ratio Forward 3.327-0.628
Final reduction ratio 4.8

 The CVT developed for Daihatsu's mini vehicles is characterized by the forward and reverse switching and reduction functions that are placed in front of the belt and pulley transmission. This design has made it possible to reduce the number of gear shafts from four in the conventional CVT to only three as illustrated below.

External view of the CVT unit Three-shaft design
External view of the CVT unit Three-shaft design

 

Basic structure of the CVT

 The input power from the engine is transmitted via the drive plate and the torque converter to other drivetrain components as shown below. (1) Torque converter (2) Input shaft (3) Planetary gear (4) Primary pulley (5) Metallic belt (6) Secondary gear (7) Differential drive pinion (8) Differential ring gear (9) Differential gear (10) Driveshaft Basic structure of the CVT
Source: Daihatsu

 

Three-shaft gear train for lighter and more compact CVT

 On a front-wheel drive car driven by a front transversely mounted engine and traveling forward, the direction of the engine rotation is the same as that of the wheels. Therefore, the direction of rotation of the engine’s output shaft reaching the transmission is also the same as that of the wheels. Likewise, the direction of rotation of the output shaft of the transmission and differential gear unit is also the same as that of the wheels since it is directly coupled with the driveshaft that drives the wheels. In other words, the input shaft and the output shaft of the transmission and differential gear unit must rotate in the same direction.   A conventional CVT has four shafts as shown to the left in the graph below. A CVT changes the vehicle’s speed by driving the belt-driven pulleys. This means the primary and secondary pulleys rotate in the same direction. Therefore, a fourth shaft, a reversing gear, must be added so that the final gear, the differential gear, will rotate in the same direction.

 The CVT developed by Daihatsu has a unique way of reversing the direction of rotation. When the vehicle's forward rotation is transmitted to the sun gear in the planetary gear from the torque converter, the carrier locks so that the direction of rotation is reversed by the ring gear. Since reversing takes place on the same shaft, a reversing gear is no longer necessary in the new three-shaft CVT layout.

CVT
Source: Daihatsu

 

Less friction loss and higher transmission efficiency

 The belt and pulley structure of the CVT is prone to an increase in friction loss as the pulley speed increases. This leads to lower efficiency of transmission. As written above, the CVT uses a planetary gear to reduce the speed of rotation before it is transmitted to the primary pulley. To prevent the friction loss and increase the efficiency of transmission, the gear ratio is carefully chosen so that the speed is reduced and the direction reversed at the same time. CVT pulley and belt
CVT pulley and belt CVT pulley and belt
CVT pulley and belt (built into the housing) CVT pulley and belt (separated)
Reduction gear Reduction gear
Planetary gear (reduction gear) reduces the input speed of rotation from the torque converter and reverses the rotation before transmitting it to the primary pulley.
CVT unit housing Differential gear
CVT unit housing (Differential gear mounting seat to the lower left) Differential gear
Housing Housing
Housing (input from the torque converter to the left) Housing (CVT belt and pulley assembling side)
Housing Housing
                                        CVT housing The planetary gear (reduction gear) mounting seat is to the right. The differential gear mounting seat is to the left. CVT lower housing Valve body assembling side and oil pan opening
The differential gear and the reduction gear The case
The differential gear and the planetary gear assembled in the housing. The case on which the housing (shown to the left) is mounted.
Valve body Valve body
Valve body

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