“Pumping Losses Can Be Practically Eliminated”

Interview COVER STORY INTERVIEW James Bearne © “Pumping losses can be practically eliminated” Cosworth has a long heritage in developing and building high-performance engines for motorsports as well as road- going applications. Nowadays, the UK-based company is utilising its knowledge more and more to support the development of highly efficient combustion engines. We sat down with its Managing Director Powertrain, Bruce Wood, to discuss the potential and technologies to further optimise gas exchange as well as supercharging systems. MTZ _ In a joint development project, very exciting results we achieved. At In this respect, we looked at several Cosworth and further partners have the beginning, Cosworth undertook an measures to minimise friction and fluid developed a highly efficient gasoline engine. extensive concept study to look at all circuit losses, but the greatest benefit The reduction of pumping losses was one the technologies available to reduce par- to giving a broad operating area of low major goal. Which measures have you taken? asitic losses within engines. The focus BSFC was through dethrottling. We WOOD _ I guess you are referring to the here was to provide our customers with considered several systems to achieve ME engine project we undertook in col- an engine that delivered excellent fuel this, such as Fiat’s Multi-air and BMW’s laboration with CEC / Haitec, for which consumption over a very broad operat- Valvetronic, but in the end decided to we have recently published some of the ing area. use the Pierburg UpValve system being 22 Interview Bruce Wood was born on 10 December 1964 in Amersham, Buckinghamshire, UK. After graduating from Brunel University with a Bachelor of Science in Mechanical Engineering in 1987, he joined Cosworth with the ambition to design his own racing engine. In 1996, he was promoted to the position of Chief Designer for the XD engine, which was used in the US ChampCar racing series. Afterwards, he oversaw the design, development and racing strategy of all products outside of Formula 1 such as CART, WRC, MotoGP and Le Mans sports prototypes. In the past decade, he has been key in transforming Cosworth from racing engine supplier to OEMs for engine technology. Having progressed to his current role as Managing Director Powertrain through different management positions, he will be cele- James Bearne th brating his 30 anniversary working for Cosworth this year. © developed by Rheinmetall Automotive. There are a number of alternative the energy released within the cylinder to This is a mechanical valve actuation systems being presented, including be extracted as useful work. The more system similar to the BMW Valvetronic mechanical-hydraulic systems such energy extracted within the cylinder dur- arrangement, but with fewer compo- as the Fiat Multi-air system. However, ing expansion, the less there is available nents and also capable of providing in our experience, the hydraulic sys- to power turbomachinery. If the situation cylinder deactivation. In this way, with tems give rise to quite significant losses with road cars where the drive profile is one valvetrain system, two methods through the need to pump hydraulic extremely dynamic is added, then the of dethrottling could be used, and the fluid through narrow passageways. reduced trapping efficiency that Miller compound and synergistic benefits of Also with these systems the work cycle systems suffer is also a significant both systems could be explored. done in opening the valve is lost, and handicap and compounds this effect. they can result in much greater net When you look at the current road car Variable inlet valve timing is currently in mechanical losses than with mechani- applications using the Miller cycle, the high demand to realise Miller timing under cal systems. ratio of compression to expansion used part load. Do you see any realistic road- Electro-mechanical valvetrains exist are certainly a lot less extreme than can going approaches other than mechanically- at the concept and prototype level, and be exploited in applications that operate actuated systems? provide useful tools for R&D activities. predominantly under steady-state con- Early- or late-intake valve closing can However they remain at a low TRL level ditions such as in power generation or be used to very good effect in control- due fundamentally to the cost, complex- marine propulsion. ling engine load through regulating the ity and weight of such systems. Correct turbo matching and ongoing trapped charge without throttling the development with turbomachinery to intake air. In this way, we have demon- get the most out of the exhaust enthalpy strated that pumping losses can be signifi- available becomes imperative to main- cantly reduced – although not entirely “Mechanical valve tain the required engine response. We eliminated – at light load. The degree to control systems have seen some very good development which this can be achieved depends on in recent years in reducing rotating iner- the extent to which throttling across the give the best benefit” tia and end-thrust loads, which can do intake valve can be avoided. a lot to improve the transient response The problem with mechanical actua- of turbomachinery and allow the boost tion systems is that the valve lift has to be In Cosworth’s experience, mechanical pressure to compensate for the reduced controlled together with duration in order valve control systems provide the great- charge trapping in the way that Miller to maintain acceptable dynamics, and est reliability and robustness, and the described. with early intake valve closing (EIVC ) weight and efficiency advantages give In this field, e-boosting offers some systems you reach a point where for very the best overall benefit. very good advantages. As with all low charge mass the valve lift reduces elec trical power systems, there is a to the extent that irreversible pumping Miller timing unfortunately places a high need to manage the electrical energy losses are incurred. Despite this, in our demand on boosting pressure in operating balance and to decide on how best experience these systems offer the best ranges where exhaust gas enthalpy is low. to utilise any electrical energy avai l- methods for providing charge control What is the most appropriate technology able – either through direct torque through variable valve duration. to solve this problem? or by exploiting the multiplier effect The whole concept of the Miller cycle is to of powering a boosting system. This Which challenges do you see in other system? improve efficiency by enabling more of depends on the application. MTZ worldwide 10|2017 23 COVER STORY INTERVIEW Pankl Turbosystems and Federal-Mogul Powertain have recently presented an electrically assisted turbocharger for 48-V power supply. Will this technology be the future of supercharging? In certain applications I think this is very likely. As with every electric com- ponent, there is a cost and weight pen- alty that needs to be justifiable, and the energy used has to be captured, stored and re-used with efficiency reductions during every step. Notwithstanding this, electrically assisted boosting systems offer a very neat and effective James Bearne solution to the problems of transient © response associated with extreme Wood describes that Pierburg’s UpValve system has been the enabler to utilise two methods of dethrottling downsizing and Miller cycle operation. within the ME engine project as it allows both valve actuation as well as cylinder deactivation In this respect it is likely that such systems will form a much larger part of automotive boosting systems in the future, especially as higher voltage over time. So overall the impact of the In terms of the technologies that are systems become more commonplace. RDE legislation in this area is not as most applicable to improving road-going In Cosworth’s experience, supple- severe as is sometimes portrayed. engines, there is a lot from our approach mentary turbocharger shaft power can The important thing always is to con- to producing lightweight designs that give a very good transient response in sider the most efficient package overall. can carry across to good benefit. We systems designed for up to 160 kW/l. If over a whole journey, less fuel is have derived some very good road-car Above this level, the benefit of electrical burned and less pollutants are emitted combustion systems from the high-effi- assistance becomes limited by the by using a more aggressively downsized ciency systems developed for motorsport, compressor surge boundary, and other engine with a slightly larger catalyst for- and these have proven to work very well forms of boosting are required to give mulated to cope with oxygen spikes, this in giving good stability and low emis- the required low-end torque. is better for public health and the envi- sions. Another area in which technologies developed for motorsport can be Scavenging has been an appropriate measure deployed to good effect in road engines to improve the low-end torque of engines “Motorsport offers a is in the use of plasma-spray technolo- with high specific power. With the upcoming wealth of knowledge” gies for lightweight, low friction cylinder RDE legislation … bores with very good thermal conductiv- … it is certainly true that the use of ity. These enable high compression ratios excessive over-scavenging during tran- ronment than the approach of not using and good downsizing ability. sient operation can short-circuit large any overlap and requiring the use of a amounts of unburned air directly into larger, less efficient engine to provide From your experience, are there also any the exhaust system, which overloads the the same performance. lessons learned beyond technology? catalyst with oxygen and reduces the Perhaps the greatest benefit that effectiveness of the aftertreatment unit Which technologies or methods from Cosworth’s heritage has given us is the to process NOx.

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