Trends: Air Powered Cars

As odd as it sounds, running a car on air is a reality. Proof of concept and prototype compressed air vehicles - commonly referred to as "air cars" - have been running around for a number of years.

How could it be possible to run on air? Consider the physical work that compressed air already does to make our everyday lives easier. Mechanics rely on air-driven pneumatic tools every day to turn nuts and bolts with authority in garages around the world. Pneumatic tools are powerful, even at a relatively low pounds per-square-inch (psi) pressure setting. They can free rusted-on lug nuts and separate metal from metal through an air hammer or pneumatic chisel. Crank the pressure up and compressed air is a force to be reckoned with, providing enough power to even propel a wheel driven car.

Perhaps that was the inspiration that led former Renault F1 mechanic Guy Negre of Motor Development International (MDI) to pursue compressed air propulsion for the auto industry. And what could be more environmentally friendly than a car with atmospheric air as its only exhaust emission? There's no combustion whatsoever. Power comes from compressed air sourced from special high-pressure compressors run by electricity from the grid.

MDI's design uses a pair of air driven pistons, one large and one small, to turn a crankshaft that produces a rotational force. The technology can potentially be paired in two, four, or six cylinder engine configurations and the design is quite inventive. Since there is no combustion and the only engine heat comes from friction, the engine can be made primarily from lightweight aluminum.

For those who want the technical details, here's the scoop: In MDI's air engine, the small piston has a conventional connecting rod for turning the crankshaft, while its neighboring larger piston utilizes an innovative rocker arm configuration with the connecting rod. This design allows the large piston to pause at top-dead-center for 70 degrees of crankshaft rotation while metered air pressure builds in a prechamber as the small piston keeps the crank turning during its power stroke. The large piston then turns the crankshaft with greater power as the pair combine to produce power over 270 degrees of crankshaft rotation. Got that all?

Prototype air cars are minimalist transportation that typically exhibit a top speed of about 70 mph and a range of approximately 125 miles on flat roads before requiring a refill. Compressed air is stored at 300 bar (4351 psi) in carbon fiber tanks mounted longitudinally beneath the vehicle floor. Refilling can be accomplished in a matter of minutes at a special high-pressure pump or in about four hours via a home refueling appliance or even an on-board compressor.

In 2007, Tata Motors licensed the rights from MDI for $28 million to build and sell Tata-branded air cars in India. Tata has not confirmed if it will build one of the MDI prototype cars or, more likely, install the MDI technology in one of its existing cars like the light weight Nano (shown here). The Nano is Tata's $2,500 "scooter replacement" people's car that recently made headlines. While sought after in developing countries, this inexpensive car clearly won't meet federal emissions and safety requirements in the U.S. and other regulated markets around the world. Still, the addition of air power to an already inexpensive and efficient model would be quite appealing in the Indian market and others where fundamental transportation is in demand, and air pollution could be a serious challenge as exponentially greater numbers of vehicles make their way to the highway.

In the United States, a company called Zero Pollution Motors (ZPM) has licensed the rights to produce the MDI design in a U.S. factory. Based in New Platz, New York, ZPM has an ambitious goal of rolling out a North American compressed air vehicle for $18,000 by 2010. The company most recently unveiled MDI's newest car at the Automotive X-Prize exhibit at the New York Auto Show. ZPM and MDI will field two entries - the U.S. production six seat, four door prototype in the mainstream class, and the three seat, two door economy-utility model in the alternative class.

Air cars haven't escaped the attention of mainstream U.S. automakers, too. For example, Ford has worked with an engineering team at UCLA to develop an air hybrid. In this application, the air hybrid builds air pressure using the engine as a pump while shut down during deceleration, and then utilizes the recaptured energy to launch the vehicle from a stop. Special electrohydraulic actuators in the valvetrain make the transition possible.

Air powered cars are not a new idea, and in fact the concept actually predates a viable internal combustion engine. In his book, "Paris in the 21st Century," Jules Verne foresaw a transportation system utilizing compressed air. Now, modern visionaries are striving to make that dream come true with the air car.

Active Fuel Management

Active Fuel Management (formerly known as Displacement on Demand) is a trademarked name for the automobile variable displacement technology from General Motors. It allows a V6 or V8 engine to "turn off" half of the cylinders under light-load conditions to improve fuel economy. Estimated performance on EPA tests show a 5.5%-7.5% improvement in fuel economy.
GM's current Active Fuel Management technology uses a solenoid to deactivate the lifters on selected cylinders of a pushrod V-layout engine.

BACKGROUND
                             High-powered multi-cylinder internal combustion engines may be necessary to satisfy driver demands for quick acceleration and/or heavy towing capacity, but during daily use they are generally operated at power settings of less than 25%. For example, at freeway speeds, less than 40 hp (30 kW) are required to overcome aerodynamic drag, rolling friction, and to operate accessories such as air conditioning.
However, when a gasoline internal combustion engine is operating under less than full load, the effective compression ratio is much less than the measured compression ratio. Under light load, the throttle is not fully open, and the cylinders receive less than a full charge of air on each intake stroke. The pressure and temperature generated at combustion are therefore less than under full load, and the thermodynamic laws which apply to all heat engines dictate that the engine will then be operating at less than its maximum possible thermal efficiency.
Thus, a high-powered, large-displacement engine is highly inefficient and wasteful when being used for normal driving conditions. This is the motivation for cylinder deactivation, to effectively spread the work load of the engine over fewer active cylinders which then operate under higher individual loads and therefore at higher efficiency.

SECOND GENERATION
                                              In 2004, the electronics side was improved greatly with the introductions of Electronic Throttle Control, electronically controlled transmissions, and transient engine and transmission controls. In addition, computing power was vastly increased. A solenoid control valve assembly integrated into the engine valley cover contains solenoid valves that provide a pressurized oil signal to specially designed hydraulic roller lifters provided by Eaton Corp. and Delphi. These lifters disable and re-enable exhaust and intake valve operation to deactivate and reactivate engine cylinders [1]. Unlike the first generation system, only half of the cylinders can be deactivated. It is notable that the second generation system uses engine oil to hydraulically modulate engine valve function. As a result, the system is dependent upon the quality of the oil in the engine. As anti-foaming agents in engine oil are depleted, air may become entrained or dissolve in the oil, delaying the timing of hydraulic control signals. Similarly engine oil viscosity and cleanliness is a factor. Use of the incorrect oil type, i.e. SAE 20W40 instead of SAE 5W20, or the failure to change engine oil at factory recommended intervals can also significantly impair system performance.
In 2001, GM showcased the 2002 Cadillac Cien concept car, which featured Northstar XV12 engine with Displacement on Demand. Later that year, GM debuted Opel Signum concept car in Frankfurt Auto Show, which uses the global XV8 engine with displacement on demand. In 2003, GM unveiled the Cadillac Sixteen concept car at the Detroit Opera House, which featured an XV16 concept engine that can switch between 4, 8, and 16 cylinders.

On April 8, 2003, General Motors announced this technology (now called Active Fuel Management) to be commercially available on 2005 GMC Envoy XL, Envoy XUV and Chevrolet TrailBlazer EXT using optional Vortec 5300 V8 engine. GM also extended the technology on the new High Value LZ8 V6 engine in the Chevrolet Impala and Monte Carlo as well as the 5.3L V8 LH6 engine in the last generation Chevrolet Monte Carlo SS and Pontiac Grand Prix GXP. In both designs, half of the cylinders can be switched off under light loads.
On July 21, 2008, General Motors unveiled the production version of the 2010 Chevrolet Camaro. The Camaro SS with an automatic transmission features the GM L99 engine, a development of the LS3 with Active Fuel Management which allowed it to run on four cylinders during light load conditions.

Active Fuel Management | General Motors

Active Fuel Management™ is the proprietary technology for General Motors' variable displacement technology, The technology was designed and implemented to conserve fuel during driving situations that require low power demands. The process works by switching off half of the cylinders in the engine until higher demand performance (such as acceleration) reactivates the dormant cylinders. According to EPA test drives, the technology effectively improves fuel economy by 6 to 8 percent.

Active Fuel Management is typically reserved for larger [[GM] vehicles with V6 or V8 engines. In vehicles with V6 engines, the technology temporary turns the vehicle into an inline V3 engine. V8 engines are momentarily reduced to V4 performance. The technology made its debut in Cadillac's ill-received 1981 L62 V8-6-4 engine. Due to unpredictable functionality, the technology was panned until the 2005 model year, when advancements allowed for more reliable performance. Originally known as Displacement on Demand in concept cars such as the Cadillac Cien and Cadillac Sixteen, the technology was officially renamed Active Fuel Management prior to being made commercially available.

Active Fuel Management - How it Works

The concept behind the technology of Active Fuel Management is that high-powered engines are excessively inefficient when high-demand power is not necessary. In fact, it is estimated that the average V6 or V8 engine only requires 25 percent of the engine's total power settings during the majority of everyday driving. Rather than install a smaller, more efficient engine and compromise acceleration and towing capacity, GM's Active Fuel Management system effectively deactivates unnecessary cylinders as needed to improve engine efficiency.

Generally speaking, the deactivation of cylinders begins by turning off the intake and exhaust valves. This is done through a solenoid control valve assembly that is signaled via pressurized oil to activate and deactivate hydraulic roller lifters. These lifters are the mechanism that physically close and open the exhaust and intake valves. Once both valves are closed, exhaust gas remaining in the cylinders expands in one cylinder as it decompresses in another. This compression adequately maintains power during low-demand situations. To initiate more power as needed, the exhaust valve is reopened to discharge the old exhaust gas and allow in a new cycle. On V8 engines, cylinders 1, 4, 6 and 7 are shut off during this process.

Due to the extreme precision necessary to create seamless operation of an Active Fuel Management engine, considerable electronic control is required. Advancements in vehicle system computing power, engine emission controls, electronic transmissions and GM's Electronic Throttle Control all contributed to the successful integration of Active Fuel Management technology in 21st-century vehicles.

GM Vehicles with Active Fuel Management

Presently, GM manufactures four different engines with Active Fuel Management technology. These four engines are the Vortec 5.3-liter V8, Vortec MAX 6.0-liter V8, 3.9-liter V6 and 5.3-liter small-block V8. Vehicles that are available with Active Fuel Management include the Chevrolet Avalanche, Chevrolet Impala, Chevrolet Silverado, Chevrolet Suburban,Chevrolet Tahoe and Chevrolet Trailblazer.

Competitor Equivalents to Active Fuel Management

Other automotive manufacturers offer similar variable displacement technologies. Mitsubishi was the first to offer an alternative to GM's technology, with the integration of Modulated Displacement (MD) technology in their 1982 1.4-liter 4G12 straight-4 engine. Like GM's first attempt in 1981, Mitsubishi's technology was discontinued shortly thereafter. The Japanese automaker improved and reintroduced the technology in 1993 under the moniker MIVEC-MD, only to be re-shelved in 1996. Mercedes-Benzintroduced Active Cylinder Control™ for their 12-cylinder engines in 2001, but discontinued the technology in 2002.

Currently, there are two variable displacement technologies that rival GM's Active Fuel Management system. Chrysler's Multi-Displacement System™ (MDS) was introduced in 2004 and is available in vehicles that feature a 5.7-liter HEMI V8 engine. Honda's Variable Cylinder Management™ (VCM) system uses i-VTEC technology to achieve similar results.

Acoustic Control Induction System

Acoustic Control Induction System, or ACIS, is an implementation of a Variable Length Intake Manifold system designed by Toyota.
Simply put, the ACIS system uses a single intake air control valve located in the intake to vary the length of the intake tract in order to optimize power and torque, as well as provide better fuel efficiency and reduce intake "roar"..
The engine control unit (ECU) controls the position of one or more air control valves based on input signals from throttle angle and engine RPM. The vacuum switching valve (VSV) which controls the vacuum supply to the actuator is normally closed and passes vacuum to the actuator when it is energized by the ECU. By energizing the VSV vacuum is passed to the actuator, closing the air control valve. This effectively lengthens the intake manifold run. By de-energizing the VSV, vacuum to the actuator is blocked and trapped vacuum is bled off of the actuator diaphragm. Toyota ACIS is an On/Off system. The valve (or valves in newer models with multiple valves to create more than 2 lengths) is either fully opened or fully closed. An example of early single-valve ACIS programming would be the 3.0L 3VZ-FE engine. The ECU actuates the VSV to close the valve when the throttle position is 60% or greater and engine speed is 3,900 RPM or greater.

HUMMER H3

The Hummer H3 was a crossover SUV/Sport Utility Truck from General Motors' Hummer division introduced in 2005 based on the GMT355 underpinning the Chevrolet Colorado and GMC Canyon compact pickup trucks. Produced at GM's Shreveport, Louisiana factory and the Port Elizabeth plant in South Africa the H3 was the smallest among the Hummer models, and the first to be built by GM. It was available either as a traditional midsize SUV or as a midsize pickup known as the H3T.

subaru forester

If you were hoping to see an all-new wrapper announce the arrival of this reworked engine, Subaru has news for you. It ain’t happening. The third-generation Forester debuted in 2008, and the vehicle’s face and roomy proportions are still quite fresh. To that end, there’s little to distinguish the 2011 model from its 2010 counterpart. Up front, the grille and swept headlights work together to create a cohesive look that draws your eye down the side of the vehicle. Details like large insets for fog lights, flared fenders and boxy side-view mirrors help give the Forester more of an SUV flavor than other compact high-riders out there, and while we miss some of the wagon aspects of older Foresters, we have to say this look is plenty becoming, especially when lined up against some of the other designs in the Subaru stable.

Inside, the story is much the same. Hordes of hard, yet well-grained plastics still abound, and while the decorative swath of silver trim helps to brighten the cabin, the cockpit is still a little dark for our tastes. The driver is treated to a well-sorted steering wheel with controls for cruise, hands-free calling and the stereo within reach, and the set of somewhat plain gauges are easy to read day or night. Things become a little muddled in the center stack, however. Our tester came with the optional TomTom navigation system, and its fitment looks aftermarket at best.

While most everything is well situated and logically laid out indoors, we did have to scratch our heads a bit over the placement of the switches for the heated seats. Located under the arm rest and on the driver’s side of the cupholder, passengers have no chance of finding the controls without instruction. While it makes for hilarious bun-warming practical jokes from the driver, a more centrally-situated location would be more user-friendly.

Of course, all of that could easily be said about the 2010 model. The real difference here lurks under the hood. Despite the deceptively similar numbers compared to last year’s model, the 2011 Forester uses an engine that’s considerably more advanced than its predecessor. The old engine’s belt-driven, single-overhead cam design has been replaced with a chain-driven dual-overhead cam setup for better efficiency. The change helped net the engine an extra one mpg in the city on the EPA’s cycle. Additionally, the four-cylinder uses a marginally larger bore and longer stroke, tweaking displacement from 2,457cc to 2,498cc and helping to deliver an extra four pound-feet of torque 300 rpm sooner than the old 2.5-liter engine.

Unfortunately, the new engine is still bolted to the same four-speed automatic transmission that Moses brought down from Mount Fuji. As a result, the new 2.5-liter feels very similar to the old one in terms of acceleration. The slight bump in torque is barely apparent low in the rev band, and the engine still runs out of breath on the deep end of the tachometer. Still, that’s not to say that the four-cylinder is identical to its predecessor. The engine is significantly quieter and a galaxy smoother than the last generation boxer four-cylinder. Whereas the 2010 Forester was saddled with the company’s characteristically tractor-esque rumble from under the rounded hood, the 2011 hums along with a fraction of the racket. To us, the improvement would have been worth building five factories to accomplish.

Otherwise, miraculously little has changed from last year’s model to 2011. The Forester still provides hilariously excellent driving dynamics given its lofty ride height thanks to a pile of DNA borrowed from the lovable WRX. Compared to metal like the Honda CR-V and Toyota RAV-4, the Forester is a grin-maker through any series of twists. Just make sure the groceries are tied down in the rear.

During our week with the Forester, we saw an average of 23.4 mpg in mild-to-aggressive combined driving, landing just a glimmer north of the EPA’s 21 mpg city and 27 mpg highway rating. While the Forester 2.5X Premium carries an MSRP of $23,495, our tester came equipped with the $1,095 option package that throws in the TomTom navigation system, heated front seats and windshield wiper de-icer. The archaic four-speed automatic transmission adds another $1,000 to the recipe, and a $725 destination charge brought our final figure to $26,315.

We’ve had a soft-spot for the Forester since the first generation debuted in 1998, and while we would have liked the third-generation boxer engine bring to bring a little more to the table, the quieter, smoother mill makes for a more pleasant driving experience altogether. For us, the five-speed manual transmission is the logical solution to the old four-speed automatic, at least until Subaru can come up with an automatic gearbox to keep pace with its new engine architecture. With its surprising poise, copious cargo room and ample passenger space, the Forester still makes an excellent alternative to hordes of Novocain CUVs out there.

If you are a huge fan of Subaru's SUV, the Forester, and live in North America, you will be glad to hear that Subaru is giving a little power upgrade to its 2011 Forester :

All-new engine for Forester 2.5X models (turbocharged 2.5XT retains current engine); new bore/stroke dimensions with slightly longer stroke; displacement slightly larger (2,498 cc vs. 2,457 cc); chain driven double overhead cam vs. belt driven single overhead cam before; 170 horsepower is same as before, at slightly lower rpm; torque is up to 174 lb.-ft. at 4,100 rpm (vs. 170 @ 4,400 rpm); fuel economy is improved: 2011 manual and automatic transmissions -- 21 mpg city / 27 mpg highway vs. 2010 20/27 for manual and 20/26 for automatic.

New 2.5X Touring positioned above Limited: features HID headlights (low beam) with automatic height adjustment; display audio system with backup camera; dual zone automatic climate control; silver finish roof rails; electroluminescent gauges, and side mirrors with integrated turn signals.

2.5XT models now include 2.5XT Premium and 2.5XT Touring, the latter replacing 2.5XT Limited as top Forester model.

2.5XT Premium gets new 10-way power driver’s seat.

Bluetooth® standard on all but base model.

Backup camera standard on 2.5X Touring and 2.5XT Touring as part of new audio system.

New standard audio system for 2.5X Premium and 2.5XT Premium: AM/FM stereo with single-disc CD player and six speakers; 3.5mm auxiliary input jack; Bluetooth® hands free calling and audio streaming; iPod control capability; USB port and Sirius Satellite Radio capability.

New optional TomTom Navigation System for 2.5X Premium includes removable 4.3-inch touch-screen portable navigation device; AM/FM stereo with single-disc CD/DVD player and six speakers; 3.5mm auxiliary input jack; Bluetooth hands free calling; iPod control capability and USB port. Also, a backup camera is available as an accessory with this system.

New audio system with rear camera for 2.5X Limited and Touring and 2.5XT Touring models: AM/FM stereo with single-disc CD/DVD player and six speakers; 4.3-inch display screen, Radio Broadcast Data System; 3.5mm auxiliary input jack; Bluetooth hands free calling and audio streaming; iPod control capability; USB port and Sirius Satellite Radio capability. (The backup camera is standard on 2.5X Touring and 2.5XT Touring and available as an accessory for 2.5X Limited.)

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automotive engineering

Modern automotive engineering is a branch of vehicle engineering, incorporating elements of mechanical, electrical, electronic, softwareand safety engineering as applied to the design, manufacture and operation of motorcycles, automobiles, buses and trucks and their respective engineering subsystems.

Some of the engineering attributes/disciplines that are of importance to the automotive engineer:

Safety Engineering: Safety Engineering is the assessment of various crash scenarios and their impact on the vehicle occupants. These are tested against very stringent governmental regulations. Some of these requirements include: Seat belt and air bag functionality. Front and side crash worthiness. Resistance to rollover. Assessments are done with various methods and tools: Computer crash simulation, crash test dummies, partial system sled and full vehicle crashes.


Fuel Economy/Emissions: Fuel economy is the measured fuel efficiency of the vehicle in miles per gallon or litres per 100 kilometres.Emissions testing the measurement of the vehicles emissions: hydrocarbons, nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2), and evaporative emissions.


Vehicle Dynamics: Vehicle dynamics is the vehicle's response of the following attributes: ride, handling, steering, braking, and traction. Design of the chassis systems of suspension, steering, braking, structure (frame), wheels and tires, and traction control are highly leveraged by the Vehicle Dynamics engineer to deliver the Vehicle Dynamics qualities desired.


NVH Engineering (Noise, Vibration, and Harshness): NVH is the customer's impression both tactile (feel) and audible (hear) feedback from the vehicle. While sound can be interpreted as a rattle, squeal, or hoot, a tactile response can be seat vibration, or a buzz in thesteering wheel. This feedback is generated by components either rubbing, vibrating or rotating. NVH response can be classified in various ways: powertrain NVH, road noise, wind noise, component noise, and squeak and rattle. Note, there are both good and bad NVH qualities. The NVH engineer works to either eliminate bad NVH, or change the “bad NVH” to good (i.e., exhaust tones).


Performance: Performance is a measurable and testable value of a vehicles ability to perform in various conditions. Performance can be considered in a wide variety of tasks, but it's generally associated with how quickly a car can accelerate (i.e. 0-60 mph, 1/4 mile, trap speed, top speed, etc), how short and quickly a car can come to a complete stop from a set distance (i.e. 70-0 mph), how many g-forces a car can generate without losing grip, figure 8, recorded trap lap times, cornering speed, brake fade, etc. Performance can also reflect the amount of control in inclement weather (snow, ice, rain).


Shift Quality: Shift Quality is the driver’s perception of the vehicle to an automatic transmission banana event. This is influenced by the powertrain (engine, transmission), and the vehicle (driveline, suspension, etc). Shift feel is both a tactile (feel) and audible (hear) response of the vehicle. Shift Quality is experienced as various events: Transmission shifts are felt as an upshift at acceleration (1-2), or a downshift maneuver in passing (4-2). Shift engagements of the vehicle are also evaluated, as in Park to Reverse, etc.


Durability / Corrosion engineering: Durability and Corrosion engineering is the evaluation testing of a vehicle for its useful life. This includes mileage accumulation, severe driving conditions, and corrosive salt baths.


Package / Ergonomics Engineering: Package Engineering is a discipline that designs/analyzes the occupant accommodations (seat roominess), ingress/egress to the vehicle, and the driver’s field of vision (gauges and windows). The Package Engineer is also responsible for other areas of the vehicle like the engine compartment, and the component to component placement. Ergonomics is the discipline that assesses the occupant's access to the steering wheel, pedals, and other driver/passenger controls.


Climate Control: Climate Control is the customer’s impression of the cabin environment and level of comfort related to the temperature and humidity. From the windshield defrosting, to the heating and cooling capacity, all vehicle seating positions are evaluated to a certain level of comfort.


Drivability: Drivability is the vehicle’s response to general driving conditions. Cold starts and stalls, rpm dips, idle response, launch hesitations and stumbles, and performance levels.


Cost: The cost of a vehicle program is typically split into the effect on the variable cost of the vehicle, and the up-front tooling and fixed costsassociated with developing the vehicle. There are also costs associated with warranty reductions, and marketing.


Program timing: To some extent programs are timed with respect to the market, and also to the production schedules of the assembly plants. Any new part in the design must support the development and manufacturing schedule of the model.


Assembly Feasibility: It is easy to design a module that is hard to assemble, either resulting in damaged units, or poor tolerances. The skilled product development engineer works with the assembly/manufacturing engineers so that the resulting design is easy and cheap to make and assemble, as well as delivering appropriate functionality and appearance.