More Details on the Lexus CT 200h Hybrid Powertrain; 42 mpg US Combined
13 September 2010
|2011 Lexus CT 200h. Click to enlarge.|
Toyota has released more detail on the powertrain of the new Lexus CT 200h premium compact dedicated hybrid (earlier post); Toyota plans to introduce it to the US market in early 2011.
Lexus engineers have focused on enhancing both the environmental and driving performance of the full hybrid series/parallel system, as well as its low NVH levels. With a total system output of 134 hp (100 kW), the CT 200h will accelerate from 0-60 mph in 9.8 seconds; its EPA estimated fuel economy rating is 42 mpg US (5.6 L/100km). The new Lexus full hybrid targets class-leading emissions and also generates significantly less NOx and particulate emissions than an equivalent diesel engine vehicle, Toyota points out.
The new CT 200h utilizes a full series/parallel powertrain architecture. The CT 200h’s hybrid system features a 1.8-liter, 98 hp (73 kW) VVT-i gas engine, a 60 kW (80 hp) electric motor, a generator, a high performance NiMH battery, a power control unit, and a power split device which employs a planetary gear set to combine and re-allocate power from the engine, electric motor and generator according to operational requirements.
The electric motor, generator and power split device are all housed in one lightweight, highly compact transmission casing directly comparable in size to that of a conventional gearbox. Drive to the front wheels is provided by the full hybrid system’s shift-by-wire, Electronically Controlled continuously Variable Transmission (ECVT).
During deceleration and under braking, the electric motor acts as high-output generator to effect regenerative braking, optimizing energy management in the Lexus Hybrid Drive system by recovering kinetic energy (normally wasted as heat under braking and deceleration) as electrical energy for storage in the high performance battery.
In a switchable EV mode, the new Lexus full hybrid can drive for up to one mile (1.6 km) at speeds of up to 28 mph (45 km/h).
1.8-liter Atkinson Cycle Engine. The lightweight, highly compact, four-cylinder, 16-valve, DOHC, 1798 cc Atkinson Cycle gas engine generates 98 hp (73 kW) at 5,200 rpm.
Combined with a cooled Exhaust Gas Recirculation (EGR) system, the adoption of the Atkinson Cycle offers significant gains in fuel efficiency and the reduction of emissions.
In conventional four-cycle gas engines, fuel enrichment is sometimes necessary to cool the exhaust gases, preventing degradation or destruction of the catalytic converters. In an Atkinson Cycle engine, compression and expansion are not symmetrical, and the valves close late, delaying compression. This creates a high expansion ratio for less compression, reducing intake and exhaust energy losses and converting combustion energy to engine power more effectively. As a result, the exhaust temperature is lower than that of conventional engines.
Via a stainless steel exhaust manifold, EGR reintroduces precisely metered exhaust gas—cooled from 1,292 °F (700 °C) to 266 °F (130 °C) into the intake system, further reducing engine operating temperatures, while also reducing engine pumping losses through a reduction in intake vacuum pressure.
Together, these technologies minimize situations when fuel enrichment is necessary to protect the catalytic converter from overheating damage, thereby improving fuel economy and lowering emissions.
To improve cold weather fuel economy and cabin comfort, the engine heat management system combines a heat recovery system with an electric water pump. To reduce mechanical losses, an electric system replaces the water pump drive belt. The adoption of an electric water pump not only controls the coolant flow rate with greater precision, but also allows for the use of both air-conditioning and heating without the engine running, all of which contributes to greater fuel efficiency.
In addition, via a valve built into the exhaust assembly, a smaller, lighter, more efficient, exhaust heat recovery system redirects exhaust gases to heat up the engine coolant at start up. As well as allowing for a more rapid delivery of effective cabin heating, this system improves hybrid system efficiency and fuel economy by significantly reducing engine warm up times, allowing it to be shut off earlier for longer electric motor-only operation, particularly in cold weather.
The 1.8-liter engine features numerous further enhancements to both improve performance and minimize fuel consumption and emissions. Variable Valve Timing with intelligence (VVT-i) helps boost response levels across the entire rev range by varying the air-fuel intake and exhaust valve timing to suit the conditions at any given time. As well as improving torque at low and medium engine speeds, the system also reduces emissions and enhances fuel efficiency.
The engine also features roller rocker arm valve-train control, a resin intake manifold with an optimized port configuration, a highly efficient, taper squish combustion chamber design and 12-hole, atomizing, long nozzle injectors. Thin, long reach spark plugs contribute to enhanced anti-knocking performance, and lower tension piston rings, reduced piston friction. A standing oil jet for piston cooling and a stainless steel pipe exhaust manifold further enhance engine efficiency. In combination, these advanced technologies further contribute to improved power output with reductions in both fuel consumption and emissions.
Engine NVH. Ultra-low Noise, Vibration and Harshness (NVH) characteristics are one of the key attributes of Lexus Hybrid Drive, and particular attention has been paid to minimizing engine noise and vibration. The rigidity of engine parts including the cylinder block and crank case has been optimized through in-depth Computer Aided Engineering (CAE) analysis. A highly rigid, ribbed aluminum cylinder head cover combines light weight with reduced noise and vibration.
The engine itself is mounted on a four-point suspension system with mounting rubber characteristics optimized for the suppression of noise and vibration. And a two-step, dynamic damper is integrated within the engine mount to further minimize noise and vibration generated, as well as reducing engine start/stop shock.
Hybrid Transaxle. Housing the electric motor, the electric generator, the power split device and the motor speed reduction device in one lightweight, highly compact transmission casing directly comparable in size to that of a conventional gearbox, the transaxle lies at the heart of the Lexus Hybrid Drive system.
The full hybrid drive system’s seamless Electronically-Controlled Continuously Variable Transmission (ECVT) is controlled by Shift-by-Wire technology, using an electronic shift lever system. The shift lever itself is designed to always return to its ‘home’ position when released, and the shift position can be checked on the shift position indicator integrated within the driver’s instrument panel.
Adjacent to the shift lever, a parking switch with integral indicator light is used to engage or release a parking lock mechanism within the transmission gearing. The parking lock is automatically deactivated when driving off, and automatically re-engages when the car is switched off.
Numerous measures have been adopted to reduce component noise and energy losses, further lowering hybrid system fuel consumption. A highly-advanced, internal gear machining process offers enhanced planetary ring gear precision, minimizing transmission noise. The lubrication system has been designed to reduce oil agitation losses and transaxle component friction has been significantly reduced through the adoption of tapered bearings instead of ball bearings.
60 kW Electric Motor. The high performance, permanent magnet, synchronous 60 kW (80 hp)electric motor works in tandem with the gas engine to boost acceleration and power the driven wheels alone when the CT 200h is operating in EV mode. During regenerative braking, the motor also acts as a high-output generator, recovering kinetic energy as electrical energy to charge the system battery.
Air cooled, the motor generates a maximum 152 lb-ft (206 N·m) of torque from zero rpm, available torque being boosted through a reduction gear device in the transaxle. Maximum drive voltage amplification is 650V DC. However, under ordinary driving conditions, unless maximum output is required, the motor is driven at an unamplified voltage whenever possible to enhance fuel efficiency.
Generator. As with the electric motor, the generator is also of the AC synchronous type. The generator performs numerous functions within the Lexus Hybrid Drive system.
Because the system has no starter motor, the generator is used to start the gasoline engine. Under normal driving conditions, engine output is divided according to system requirements to both drive the wheels and power the generator which, via the Power Control Unit (PCU), drives the electric motors and simultaneously charges the high-voltage battery. Moreover, in order to optimize engine speed control for maximum full hybrid system fuel efficiency, engine speed is also controlled by the generator.
When its operation is not required by the hybrid drive system, the generator stops the engine. However, if the CT 200h runs under electric motor power alone for sufficient distance to necessitate battery charging, the generator will start the engine, which itself provides the power for the generator to charge the battery.
High Output Battery. The Lexus Hybrid Drive system’s 202V NIMH battery allows the new CT 200h to operate in EV mode, driving under electric motor power alone. Located beneath the rear loadspace floor, the fan-cooled battery pack size has been minimized to reduced impact on cabin accommodation.
Power Control Unit. Similar in size to a 12 V battery, the Lexus Hybrid Drive system’s Power Control Unit (PCU) consists of:
- A voltage boost converter, which boosts electric motor, generator and battery voltage to increase hybrid system power output;
- a highly compact inverter for the motor/generator, which converts the DC power from the battery into 650V AC power for driving the electric motor and, occasionally, the generator; and
- a DC/DC converter, which reduces the high voltage of the 202V system battery pack to 14V, supplying power to the accessory systems and charging the auxiliary battery.
Lexus Hybrid Drive in Operation. Over the course of any journey, the Lexus Hybrid Drive system operates in several different modes to maximize the CT 200h’s overall efficiency: At rest, the engine stops automatically to conserve fuel. Under operating conditions of low engine efficiency such as start up and low to mid-range speeds, the vehicle runs on the electric motor alone, thus eradicating NOx and particulate emissions.
Under normal driving conditions, power allocation is constantly adjusted between engine and electric motor to combine optimum performance with maximum fuel efficiency. Via an Electronically Controlled Braking-Regeneration (ECB-R) system, the electric motor acts as high-output generator during deceleration and under braking to effect regenerative braking, optimizing energy management in the Lexus Hybrid Drive system by recovering kinetic energy (normally wasted as heat under braking and deceleration) as electrical energy for storage in the high performance battery.
At all speeds, the Lexus Hybrid Drive system monitors itself for optimum performance and fuel efficiency with minimum emissions, either running the electric motors in isolation, the engine in isolation, or a combination of both. Furthermore, battery power level is constantly managed via the engine driven generator to obviate any requirement to recharge the system from an external source.
Three ‘on-demand’ drive modes supplement the Normal drive mode (earlier post), increasing the capabilities of the CT 200h’s full hybrid powertrain. An EV mode allows for ultra-quiet running on electric motor power alone, resulting in zero fuel consumption and emissions; an ECO mode maximizes hybrid system efficiency and fuel economy; and a SPORT mode boosts system performance.
Air Conditioning Performance. Allowing for independent control of left and right hand sides of the cabin, the new CT 200h is equipped with a compact, lightweight air conditioning unit incorporating an electric, variable capacity compressor. The use of a hybrid battery-powered electric compressor reduces the load on the engine, improving fuel economy, whilst the surplus power of the unit allows it run below full capacity, with greater efficiency and with less noise.
The integrated-inverter electric compressor contains a centrifugal oil separator that removes oil from the refrigerant, reducing the amount of oil escaping from the compressor. This allows for a more efficient refrigerant cycle, optimizing the air conditioning’s cooling performance.
The use of a lightweight, MF (Multi Flow)-IV sub cool condenser reduces refrigerant volume to further improve system efficiency. And the characteristics of the brushless blower motor have been refined to suppress noise while delivering a large volume of cool air.
Exhaust Heat Recirculation System. Because of the need to heat the cabin and de-fog the windscreen, hybrid vehicles can suffer a drop in fuel economy during winter months. To counter this, Lexus engineers have incorporated a third-generation exhaust heat recirculation system.
The exhaust heat recirculation system helps the engine coolant reach normal operating temperature more rapidly by circulating it around a section of exhaust pipe. This not only improves fuel efficiency by reducing the time needed for the engine to warm up, allowing the Lexus Hybrid Drive system to shut of the engine sooner, but also enables the 495 watt Positive Temperature Coefficient (PTC) heater to provide warm cabin air more quickly in winter.
Other energy saving features in the CT 200h include:
- LED Lighting. With available LED headlamps, up to 46 LEDs are used in front, eight used for the door mirror-mounted turn indicators and 35 in the rear, the CT 200h is equipped with no less than 89 external LEDs—the largest number yet fitted to a Lexus model.
- Lexus Audio System Amplifier. An available, energy efficient, Digital Signal Processing-integrated (DSP), eight-channel, full range class D amplifier makes its first appearance in the CT 200h. The new DSP unit consumes 50% less power than a conventional, analogue-powered amplifier and, with its weight reduced from 2.9 lbs. to 2.1 lbs., is 26% lighter.
- Bio-sourced Materials and Bamboo Charcoal Speakers. Improving its environmental performance, several of the CT 200h’s larger components including the loadspace deck sides, deck board and deck board trim have been fabricated from a bioplastic material containing 30 percent plant-based polyethylene terephthalate. The new full hybrid also benefits from an easy-to-dismantle construction, and recycle marks have been placed on the front, rear and tailgate trim to facilitate optimum recycling.
- A Lexus and industry first, both sound systems are equipped with unique, bamboo charcoal-based resin diaphragm speakers. Constructed using a complex compound combining bamboo charcoal, bamboo fiber and resin, the diaphragms are injection-molded to a thickness of only 0.008-0.01 in., and are some 10-15 percent lighter than a conventional speaker diaphragm.
My car gets 53 MPG on combined...and it's a diesel Audi A2
1.4 TDI dated 2003...there's something wrong on your way of considering an ecological car... maybe yours are too heavy, too big, too old on tech... maybe American's car producer are kiddin'you all...
The world don't need us and save itself despite of us.
We need world to save us...
Posted by: Federico | 13 September 2010 at 04:48 AM
"The world don't need us and save itself despite of us.
We need world to save us..." Japan is doing the best it can.
The A2 "Kerb weight 895 kg (1,973 lb) to
1,030 kg (2,271 lb)" (wiki) would certainty help get 53 mpg(US or British?)
Posted by: kelly | 13 September 2010 at 07:02 AM
Prejudice rears its ugly head even in the circle of "evolved."
Posted by: Reel$$ | 13 September 2010 at 08:33 AM
With all this new technology, shouldn't a Lexus 200 Hybrid do 50 mpg like its cousin Prius III? Where is the Lexus 200H losing 20+% fuel economy?
Posted by: HarveyD | 13 September 2010 at 09:17 AM
It sounds like a lot of good features, I would say the mileage is not as good because of weight and wind resistance.
"202V NIMH battery allows the new CT 200h to operate in EV mode"
They used enough NiMH batteries to allow EV operation. They do not say how far and at what speed. This SUV might attract some buyers and it gets much better mileage than conventional comparable vehicles.
Posted by: SJC | 13 September 2010 at 11:33 AM
Lame PR exercise. The Lexus buyer doesn't give a F about mileage, though they will easily pay a premium to appear "Green". But the 134 hp, 9.8 sec is way to pedestrian for this market segment.
Posted by: dursun | 13 September 2010 at 02:09 PM
Let’s compare with a BMW 320 Efficient Dynamics Edition. In the EU NEDC test, it has a fuel consumption of 4.1 l/100 m. This equals 57 mpg US (diesel; 51 mpg gasoline equivalent). It has 163 hp at 3250-4000 rpm and accelerates from 0 to 100 km/h in 8 s. Top speed is 228 km/h. For anyone else but HarveyD, this would be an interesting competitor to Lexus CT 200h. But, if you did not already guess, it is not available in the USA. For some strange reason I do not know, it does not (yet) have the option of a NOx catalyst as the 3-litre 6-cylinder engines have to meet Euro 6 (or corresponding US limits). However, it should be easier to meet these limits with a smaller engine (as well as a smaller car than the 7-series). The ultimate solution would, of course, be the 3-cylinder version of the engine currently in development (at 163 or 177 hp) combined with a hybrid drive system.
A reason for the low fuel consumption of the Prius is low resistance (tires, mass, drag, frontal area, etc.). When you put this drivetrain in a conventional car, fuel consumption will not be as impressive any more (oranges and apples…).
Posted by: Peter_XX | 15 September 2010 at 11:19 PM
CT200h is rated 57.3 MPG in EU combined test cycle running on gasoline with about 15% less energy than Diesel. NOx emission is a fraction of the Diesel.
Posted by: usbseawolf2000 | 18 September 2010 at 06:57 AM
Federico (aka Pendejo) spewed:
"My car gets 53 MPG on combined...and it's a diesel Audi A2
1.4 TDI dated 2003...there's something wrong on your way of considering an ecological car... maybe yours are too heavy, too big, too old on tech... maybe American's car producer are kiddin'you all..."
Stupid Europeans. Don't they ever learn?
1) Diesel has 20% more energy (BTUs) per liter than gasoline which means the tiny A2 is not particularly impressive except on the highway.
2) In the city, the hybrid will probably equal it or better it.
3) Diesel costs more per liter than gasoline so it's relative economic advantage is dubious.
4) The diesel engine itself will add significant cost to the car -- usually more than the hybrids. So you have to figure out how long it will be until you pay off the higher starting cost.
5) One barrel of crude oil produces roughly 10 gallons of diesel and 19 gallons of gasoline which means diesel is a better niche fuel and gasoline is better general purpose fuel. Exactly the way it works in the USA.
6) The only reason Europeans have so many diesel cars is because the governments of the EU have tax preferred diesel fuel and cars for years. The market prefers gasoline cars because they have more crisp acceleration overall and the fuel is cheaper especially when used in a hybrid.
The only thing in favor of diesel engines is the overall thermal efficiency of the engines which is something like 43% in a TDI and 36% in the Toyota Atkinson Cycle 1.8. But no one wants to pay the extra upfront costs for such a small gain and hybrids work better for fuel economy in the city so diesels become best as highway vehicles which is why they are popular for trucks.
Batteries are likely to get cheaper. The cost of building diesels is not. But thanks for the help, Europeans. You did so well in World War 2 without us.
Posted by: Ralph | 20 September 2010 at 02:26 PM
The comparison of gasoline hybrids and diesels needs to be done with more care than is shown in some of the comments for this post. The comments by usbseawolf2000 are meaningful because they compare the mpg for the hybrid and the diesel on the same EU driving schedule and accurately point out that the hybrid has much lower NOx emissions. Diesel fuel does have 11-15% more carbon per liter than gasoline, so if the diesel and the hybrid have the same mpg, then the diesel will emit more CO2. (This ignores CO2 produced in refining; most sources say this is about the same for gasoline and diesel).
With the right refining processes, one can choose how much gasoline vs diesel to produce from a barrel of oil, so there is no clear winner in that regard.
Within the context of U.S. emission laws, the comparison between the 2009 VW Jetta TDI and the 3rd generation Prius is probably meaningful. The Prius has better fuel economy (50 mpg vs 34 mpg)and less emission of pollutants. The Prius has technologies like electric water pump and electric steering assist that the Jetta probably does not have. If one took all the technologies of the Prius and added them to the Jetta, the difference in fuel economy might not be so great. The cost of the 2 vehicles is not too different, given the uncertainty in resale prices.
At a 2009 diesel conference in the U.S., most engineers were pessimistic about the prospects for diesel passenger cars in the U.S. The main concern was anticipated new pollution rules in California (which also apply to about half the U.S.) These would tighten up the requirements for hydrocarbon and NOx emissions. The engineers felt these would be extremely hard to meet with diesel powertrains. So I say - cheers to all the good engineers that are trying to improve hybrids and diesels. It will be interesting to see what is the best technology for each market.
Posted by: Cautious9 | 20 September 2010 at 06:25 PM