Theory and principles of variable valve timing (VVT)

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There’s no doubt that engine specialists will begin seeing more variable valve timing (VVT) designed engines in their shops, as the generation of vehicles equipped with this technology begins to make its way into the service industry, writes Engine Builder’s Gary Goms. In fact, the current versions of VVT were popularly introduced into the US domestic production about 10 years ago.

The theory behind variable valve timing is simple. Imagine a column of air speeding through a two-inch pipe at 250 feet per second. Suddenly, the airflow is blocked off by a valve at the end of the pipe.

The kinetic energy of the air keeps it moving until a compression wave begins to develop at the valve. The optimum time to open the valve and achieve the greatest airflow is when this compression wave reaches its peak. In contrast, the best time to open the exhaust valve is when a vacuum wave develops at the valve.

These camshaft sprockets and timing gears are integral parts on this Ford application. The stamped steel plates are reluctors that allow the camshaft position sensor to sense valve timing. A conventional timing chain sprocket completes the set.

These camshaft sprockets and timing gears are integral parts on this Ford application. The stamped steel plates are reluctors that allow the camshaft position sensor to sense valve timing. A conventional timing chain sprocket completes the set.

Variable valve timing takes advantage of these pressure and vacuum waves to achieve a greater airflow through a given size of engine. Advancing valve timing increases low-speed engine torque while retarding valve timing increases high-speed torque. The powertrain control module (PCM) determines the valve timing position through data supplied by the camshaft position sensors or by valve timing sensors. Be aware of this terminology because some vehicles can use both types of sensors on a single engine.

Parts nomenclature
The part that actually controls the camshaft position and the valve-timing event is called a ‘phaser.’ VVT phaser design includes piston and vane-type configurations. In either case, the phaser uses engine oil pressure to push the piston or rotating vanes against a strong spring. With the vane-type phaser, a clock spring returns valve timing to a ‘default’ position during engine start-up or if the VVT system fails. Another part, called a valve timing solenoid, meters engine oil pressure into the phaser.

The VVT solenoid is supplied key-on voltage and the PCM momentarily grounds the circuit to meter oil pressure into the phaser until the valve timing reaches the desired value. The valve timing solenoid also includes a very fine-mesh screen to prevent sludge and debris from entering the mechanism.

Lubrication issues
Since correct lubrication is critical to the operation of the VVT phasers and solenoids, it’s doubly important that the correct viscosity of oil is used in a VVT engine.

Because VVT designs use a metered oil orifice to adjust valve timing, oil with a higher than specified viscosity can cause false VVT trouble codes to be stored in the PCM. In addition, the oil must have the correct additive package to keep the engine’s oil passages, phasers, and VVT solenoid screens clean.

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Low speed high load conditions: Under low speed high load condition, the engine should increase its intake advance angle in order to have a better dynamic performance. When the engine is running at a low speed, the air in the intake manifold has relative low inertia, backflow of cylinder gas into the intake manifold are like to occur at the end of intake phases due to the high pressure in the cylinder. VVT system closes the intake valve in advance to suppress this kind of backflow, as shown in Figure 1.

High speed high load condition: When the engine running under high speed high load condition, the air in the intake manifold has relative high speed and inertia, the VVT system postpones the close of the intake valve to magnify the amount of air that flows into the cylinder, as shown in Figure 2. This change in valve timing provides improves the engine’s dynamic performance.

Partial load condition: when the engine is running at partial load, VVT system raises the engine’s EGR rate to improve the emission performance. And the VVT system also minimizes the pumping loss during the intake phase to optimize the fuel economy. To achieve these two purposes, the VVT system open the intake valve in advance to create a bigger valve overlap, as shown in Fig-3

Low temperature start and idling condition: VVT system diminish the valve overlap during idling and low temperature start, as shown in Figure 4. When the engine is idling, the vorticity in the cylinder decreases. VVT system postpones the open of intake valve so there will be a bigger pressure difference between the intake manifold and the cylinder when the valve is opened. This results in better combustion in the cylinder. This is also the solution for low temperature start.

Everything old is new again!

 

An aluminum piston (left) and one of the new steel pistons (right)

An aluminum piston (left) and one of the new steel pistons (right)

 

In 1936, Mercedes-Benz became the first company in the world to launch a diesel passenger car – the 260D. Over the years, diesel automobiles became renowned for their efficiency and fuel economy. Now, the manufacturer is building on that success with the introduction of high-tech steel pistons.

The steel pistons will debut in the V6 diesel engine of the Mercedes-Benz E 350 BlueTEC. With the new pistons in place, the car will deliver the same engine output as would be achieved with aluminum pistons (190 kW/258 hp) yet will only use around 5.0 liters of fuel per 100 kilometers (47 mpg) – that’s an improvement of about three percent.

The use of steel pistons improves efficiency, as steel has a lower level of thermal conductivity when compared with aluminum, meaning higher temperatures are reached within the combustion chamber. This, in turn, leads to increased ignition quality, while the combustion duration is reduced. The overall result is lower fuel consumption and pollutant emissions.

An additional advantage of using steel is that it allows the piston to be smaller in size, while also offering a greater resistance to mechanical stresses. The use of steel has also allowed engineers to reduce the gap between the cylinder wall and the piston – resulting in the reduction of untreated emissions.

Steel pistons are already found in certain commercial vehicle engines, where they are combined with heavy cast-iron crankcases. Meanwhile, aluminum pistons are normally found in passenger car diesel engines. But the steel pistons developed by Mercedes-Benz will reportedly harmonize perfectly with a car’s much lighter aluminum engine housing.

Diesel engines have come a long way since the first Mercedes-Benz 260D. There was the introduction of turbo technology in the 70s, the first particulate filter system in 1985 and then the arrival of the common-rail diesel in 1997.

 

A ‘battery’ of old tyres

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There may soon be a new use for discarded tyres. Researchers from the US Department of Energy’s Oak Ridge National Laboratory have devised a method of harvesting the carbon black from them and using it to make anodes for better-performing lithium-ion batteries.

The process involves pretreating the tyres and then using pyrolysis – the decomposition of organic materials by heat in the absence of oxygen – to recover pyrolytic carbon black material from the rubber. Carbon black is similar to the graphite commonly used in battery anodes, although unlike graphite, it’s man-made.

When a lithium-ion battery with one of the carbon black anodes was tested in the lab, it was found to have a higher energy capacity than similar batteries with regular graphite anodes. This quality was attributed at least partly to the porous microstructure of the carbon black, which offers more surface area than that of graphite.

The Oak Ridge team is now working on a pilot project to scale up the process, with an eye towards ultimately licensing the technology to an industrial partner. Once the technique is commercialised, it is estimated that batteries made using it will actually be cheaper than conventional lithium-ions … plus, of course, the tyres will be diverted from sitting in a landfill. A paper on the research was recently published in the journal RSC Advances.

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Mazda gets behind the World Time Attack Challenge in Sydney

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Mazda Australia has thrown its support behind the World Time Attack Challenge in Sydney later this year, with the announcement that the Le Mans-developed 767B will feature at the annual event.

The #202 767B, which finished ninth at Le Mans in 1989, will enjoy track time at the event on Friday and Saturday along with some other iconic Mazda race cars. The 767B will also be on permanent display at a dedicated Mazda area with an assortment of other famous vehicles.

Newly signed Mazda ambassador ‘Mad Mike’ Whiddett, a professional drift driver from Auckland, will entertain the crowd as he performs in Formula Drift. Mad Mike is known globally and performs in ‘Madbul’ his naturally aspirated four- rotor Mazda FD RX7 and ‘Badbul’ a 20B turbo Mazda SP3 RX8.

According to Mazda Australia’s Alastair Doak, the World Time Attack Challenge is continuing to grow in stature and Mazda saw an opportunity to give event fans even more.

“We are delighted to showcase the stunning 767B in Australia. The development of the 767B led to the 787B which won the Le Mans 24-hour race in 1991, making it one of Mazda’s most important cars.”

Now in its fifth year of competition the Yokohama World Time Attack Challenge will bring teams from around the world to Sydney Motorsport Park (17-19 October) to compete for the ultimate automotive tuner trophy.

Myopic ‘Olympians’ battle it out over industry report

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If ever there were a myopic category introduced at some future Olympic Games, then the Victorian Automobile Chamber of Commerce and the ‘Stalinist-named’ Productivity Commission would be shoo-ins to represent Australia. However, they’re unlikely to make good roommates, especially following the VACC’s branding of the PC’s latest report on the automotive manufacturing industry, a ‘Clayton’s Review’.

What seems to have got right up the nose of the industry association, fresh from its recent success of persuading the Victorian government to continue burdening motorists with a set of useless and expensive vehicle tests, seems to be the reports recommendation on the phasing in of used car imports, or grey imports, as they are know in the trade. According to the VACC’s David Purchase, used car importation was outside the terms of reference of the review.

“As expected, the Australian Automotive Manufacturing Industry Report has proved to be a complete waste of time. It’s delivered little of substance, it’s out of touch with the industry and proved economists have a complete lack of understanding about the automotive industry. (…and just about every other industry these desk-bound dopes examine from their luxury accommodation in Collins Street).

“The VACC hopes the Abbott government will talk directly to the automotive industry and listens to our views, as we are the ones who really know what’s going on.

“With car making on its way out, it is time to focus on the majority of the automotive industry, the retail, service and repair sector where three out of four employees in Australia’s automotive industry, or approximately 320,000 people, work.”

The VACC’s own myopic list calls on the government to:

  •  Reject the phasing in of used car imports, which should not even have been considered by the Commission as it was outside the terms of reference of the review – it had nothing to do with manufacturing.
  •  The current restrictions on importing used cars from overseas markets work well and do not need to change.
  •  The consequence of relaxing used car importation, even progressively, from limited countries of origin and with new regulatory compliance frameworks, is likely to result in more unsafe vehicles on our roads
  •  Who is to say how long these so-called cheap cars will remain affordable and what are they cheap compared to? Australia will be flooded by unwanted vehicles dumped from overseas markets, and they will have dubious histories, questionable paper work and suspicious odometer readings.
  •  Consumers will face finance, insurance, spare parts and technical information issues making purchasing, maintenance, servicing and upkeep expensive.
  •  When dissatisfied buyers try to vent their frustration, they’ll do so, unfairly, on manufacturers, dealers and repairers, who will be able to do little to assist.
  •  Purchasers of used car imports face uncertain resale values.
  •  The Commission’s view that the relaxation of second-hand vehicle import restrictions should begin with vehicles under five years old, flies in the face of a recent decision by the Victorian government. Victoria is to maintain its state roadworthy certificate on transfer system because it recognises vehicle safety is not about age, but about the vehicle’s condition.
  •  The abolition of the Luxury Car Tax, with support from its national body, the Australian Motor Industry Federation, which said the LCT was ‘unconscionable’ and ‘served no purpose other than being a revenue raiser’.
  •  At first glance, the Productivity Commission’s view that the LCT should be removed appears to be welcome. However, don’t be fooled into thinking removed means abolished, because the PC recommends LCT is replaced with ‘more efficient sources of revenue’ in the Australian Government’s Taxation White Paper.
  •  VACC is concerned the replacement will be a worse option and calls for details of the alternative to be released immediately.
  •  Ken Henry must be wondering why he bothered making his LCT tax reform recommendation in the first place.
  •  Simply changing the name of something is not progress. The automotive industry wants the tax on luxury vehicles to be abolished completely.
  •  Consider LPG vehicle production proposal. A joint VACC and Gas Energy Australia (GEA) LPG vehicle initiative, re-employing skilled workers, revitalising car production communities and reinvigorating an important industry has been totally ignored by the Productivity Commission, which claimed it was ‘unnecessary’ and ‘unlikely to have an substantial effect on the industry’.

“This initiative is well conceived and has been presented to federal and state governments at a time when job opportunities in the automotive industry are at a premium.

“It is baffling that this viable plan has fallen on deaf ears and that a report into future of automotive manufacturing completely overlooks a sensible and practical proposition. The VACC and GEA will continue to promote the LPG proposal,” said David.

 

Audi upgrades to 48v electrical system

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Audi is to upgrade part of its vehicle electrical system from twelve to 48 volts in a move to facilitate the integration of new automotive technologies while increasing the power and efficiency of its vehicles.

The company recently showcased the scope of the 48‑volt electrical system with the technology demonstrators Audi A6 TDI concept and RS 5 TDI concept. Both models are fitted with an electrically powered compressor that acts like a supercharger from practically zero rpm to eliminate turbocharger lag, boosting both performance and efficiency.

It operates independently of the engine load and therefore fundamentally improves the acceleration performance. 48‑volt technology is also ideal for dynamic chassis control systems. In the current development version, a compact lithium‑ion battery supplies 48 volts as the energy source during engine‑off phases; a DC/DC converter integrates the 12‑volt electrical system.

 

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The lithium‑ion battery operates in conjunction with an alternator that qualifies the drivetrain as a mild hybrid. Within this concept there are diverse ways of starting, controlling and deactivating the combustion engine as needed. The alternator achieves an energy recovery output of ten kilowatts, far more than is possible at present, and adding a claimed saving of up to ten grams of CO2 per kilometre, equivalent to around 0.4 litres of fuel per 100 kilometres.

The current state-of-the-art technology has taken 12‑volt electrical systems to their very limits. Especially at low temperatures, all the various static‑load consumers can account for the entire power generated by the alternator, which can deliver up to 3 kW. The battery power is no longer capable of meeting the demands of new, dynamic‑load consumers such as high‑performance electric compressors.

The Audi solution is a second subsidiary electrical system running at 48 volts, to complement the 12‑volt power supply. The higher voltage means smaller cable cross-sections that translates into lighter cable harnesses with lower power dissipation.

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Continential Tyres adds augmented-reality head-up display (AR-HUD) system

continental-shows-its-augmented-reality-head-up-display-for-2017_1 As the name suggests Continental Tyres is all about putting rubber on the road. Well not quite! The launch recently of an augmented-reality head-up display (AR-HUD) system, offers a different picture…I know, it’s a lousy pun…of the company’s range of products.

HUDs mark objects directly in the driver’s field of vision and have usually been installed in upmarket models but are now finding their way into less expensive vehicles. AR-HUD can show the driver what vehicle sensors such as radars and cameras can see and what driving strategy the electronics have chosen as a result. Continental expects it to be ready for production in 2017.

Worldwide, ten automotive manufacturers currently offer a head-up display as an option in a total of 19 vehicle models. Continental estimates the global volume of installed head-up displays to be around 1.5 million units for the current year and the automotive supplier expects this volume to more than triple by 2018.

In addition to windshield head-up displays, which produce an image on the windshield that appears to float above the hood, Continental will be starting the volume production of combiner head-up displays in 2015. These are intended for mid-range vehicles and instead of the specially adapted windshield they use a small separate screen as a reflective surface.

The company expects the HUD market to split into two equal parts by 2018 – one for the windshield HUD and the other for the combiner HUD. Continental has implemented in a demo vehicle an advanced pre-development version of this new technology that reflects full-color graphics into the real road view in the driver’s field of vision.

The basis of the system is ‘digital micromirror device’ (DMD) technology, which is also used in digital cinema projects. The AR-HUD can display information from driver assistance systems, such as lane departure warning and adaptive cruise control, in the driver’s field of vision precisely and depending on the particular situation.

Joss Supercar back on the world stage

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Australia’s very own supercar, the Joss JP1, is taking another run at the world stage, according to a report on gizmag. With a mid- mounted all-alloy V8, a claimed top speed of around 340km/h and all of the current technical innovations expected in a modern day supercar, the Joss JP1 is the culmination of years of design and development work aimed squarely at producing a world-beating exotic machine.

Design work on the original Joss prototype, the JT-1, began back in 1998. The first prototype produced was the result of six years of hard work for its creator and founder of Joss Automotive, Matt Thomas, and was set to take on the best from the rest of the world in the supercar stakes. With a mid-mounted V8 engine, a claimed top speed of 300 k/mh (190 mph), and blistering acceleration, it was the epitome of a modern supercar.

Launched at the Melbourne Motor Show in 2004, the prototype created a storm of publicity and the adoration of many. However, once all of the hype died down, customers didn’t materialize. With such a small local market for supercars and potential buyers not willing to throw large amounts of money at a largely unknown vehicle and maker, the JT-1 struggled to find adequate backing and the project seemed destined to fade away.

Fast forward to 2014 and the re-emergence of Joss Automotive with the uprated JP1 version of their vehicle. Premised on the original layout, everything has been re-designed, re-assessed and redone to create a supercar for today, with an all new in-house designed DOHC alloy V8 to replace the existing pushrod version, a bespoke Albins/Joss transaxle, a chrome-moly space frame, carbon-fiber bodywork, and a host of other high-tech improvements and innovations.

 

Despite all of this engineering work, though, the Australian design regulations are amongst the toughest and most intractable in the world, and would take more money and time to comply with than is reasonably available to a boutique auto maker. The upshot of which means that the first five vehicles built and sold by Joss will only be available as track-day cars.

However, provided that that Joss can raise the necessary capital to fund its venture beyond this stage, the company will then apply for European limited-run approval where – particularly in the UK – the JP1 could actually be registered and used on public roads and compete against other niche builders, such as Caparo, Caterham and Noble.

To raise the necessary capital to take this approach, Joss Automotive has followed the lead of many of today’s entrepreneurs and gone down the crowdfunding route. Recently launched on Kickstarter, the JP1 project aims to raise AUD480,000 (US $446,000) to finish current work and produce the first of the new prototypes.

No official date has been given for a possible launch or impending production. Though, based on the proposed timeline and all going to plan, it would appear that it will be somewhere around two years by the time the first new prototype is produced.

The video below outlines a little of the history of Joss Automotive and shows the original JT-1 prototype in action.

Volvo launches ‘all-new’ XC90 SUV

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Volvo has released its new seven-seat SUV, the XC90, with the top-of-the-line model combining a two-litre, four-cylinder super and turbocharged petrol engine with an electric motor and around 400 [300kW] horsepower.

Volvo say that the vehicle offers the most comprehensive and technologically sophisticated standard safety package available in the automotive industry including a run-off road protection package and auto brake at intersection capability.

In such a scenario, the XC90 detects what is happening and the front safety belts are tightened to keep the occupants in position and an energy-absorbing functionality between the seat and seat frame cushions the vertical forces in an attempt to prevent spinal injury.

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The vehicle is also the first in the world with technology that features automatic braking if the driver turns in front of an oncoming car and detects cyclists and pedestrians in front of the car, both during the day and at night.

According to Volvo Car Group’s Lex Kerssemakers, the XC90 takes the first step towards self-driving cars with a new function that automatically follows the vehicle ahead in stop-and-go traffic, radically simplifying the semi-autonomous driving experience.

image113337_b“A tablet-like touch screen control console, which forms the heart of an all-new in-car control system, is virtually button free and represents an entirely new way for drivers to control their car and access a range of internet-based products and services.”

The XC90 is available with a range of accessories and two major exterior styling themes. The urban luxury package combines a colour co-ordinated body kit with polished stainless steel details, such as front deco frames, front and rear skid plates, side scuff plates and 21-inch polished wheels. Tech matte black exterior trim, stainless steel skid plates, illuminated running boards, integrated exhaust pipes and 22-inch wheels make up the rugged luxury kit

 CLICK TO WATCH VIDEO

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ZF start production of second generation eight-speed transmission

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ZF has announced the start of production of its second-generation eight-speedautomatic transmission, which it claims has been optimised for the requirements of modern engine technology. The new 8HP transmission has a focus on downsizing and downspeeding, as many engines are now turbocharged, have fewer cylinders and produce maximum torque at a very early stage.

The company claims a number of developments have helped improve the transmission’s efficiency by up to three per cent. Gearsets have been optimised and now have a higher spread, from 7.0 to 7.8, which is said to reduce speed by 50 revolutions per minute and fuel consumption by one per cent.

Internal losses have also been reduced by the introduction of new multi-disc separation strategies, with additional springs integrated into the multi-disc packages to ensure the friction shift elements are almost fully opened and cause less drag.

The transmission’s oil pump now operates with a reduced pressure, down from 5 to 3.5 bar, requiring less energy overall. An innovation of the 8HP is that the clutch is now fully opened during deceleration and when the vehicle is stationary, which ZF says means it is now no longer necessary to ‘brake against the drive’.

The transmission’s ‘coasting’ function, the uncoupling of the gearbox and simultaneous stopping of the engine, now operates at speeds up to 160km/h. ZF has also further optimised the stop/start function, with the engine now stopping immediately as the vehicle stops, rather than waiting 1.5 seconds as in the original eight-speed.

New advanced torsional vibration dampers claim to eliminate the vibrations that occur on the engine side, isolating them from the driveline and the body.

The second-gen ZF 8HP entered volume production in July, debuting in the BMW 520d as the 8HP50 version that is designed for torque outputs up to 500Nm. An 8HP75 version will join ZF’s portfolio in the future for torque outputs up to 750Nm. ZF says the transmission will eventually be rolled out in more than 1000 different automotive applications.