DieselMax at the FoS 2006
The JCB DieselMax's JCB444-LSR (land speed record) engines were signed off by Ricardo’s engineers this week after reaching their target power output of 750bhp each. The motors are at the heart of the speed record contender that will aim to propel Andy Green to speeds in excess of 300mph. The pencil-shaped machine starts testing in the UK next week.
Six LSR engines -- direct descendants of the JCB444 diesel engine that powers the company’s famous backhoes and Loadall telescopic handlers -- have been prepared for the record attempt at the world famous Bonneville Salt Flats in August.
JCB originally approached Ricardo -- which has also been commissioned by TVR to ensure that its Speed Six engine complies with Euro 5 (LEV II) emissions regulations -- in 1998 with a brief to design a totally new engine to power JCB products. The design targets called for robust construction; a long stroke to facilitate high torque at low engine speeds; reduced noise levels; and future proofing for the next steps in emissions legislation.
"These were worthy aims for an engine intended, among other things, to use its weight to balance a backhoe, but on the face of it some of them were contradictory to development of the unit as a racing engine," said Ian Penny, Ricardo’s global director of diesel engines.
It uses a standard block
Therein lies the technological fascination and validation inherent in the JCB DieselMax programme, which was built around the racing engine using the standard block, cylinder head and bedplate (albeit with some lightening) in order to showcase the extraordinary versatility of the standard engine.
"Our intention all along was to use a standard block, cylinder head and bedplate," said engineering director Dr Tim Leverton. "I wanted it to have exactly the same fundamental architecture as the JCB444 engine."
The standard engine – the only one of its kind in the world designed specifically for its industrial application – has already set new marks for power output and reliability in service. During the course of development of the LSR version, the standard engine showed it could cope with the very high cylinder pressures generated by the two-stage turbo-charging necessary to boost its 120bhp to the 750bhp needed to push the twin-engined JCB DieselMax streamliner beyond 300mph.
Engineering challenge
"The whole project has been a fantastic engineering challenge," said Penny. "Once we had defined the engine concept in January 2005, our effort then focused on validating and refining that concept. Initially we tried single and then two-stage turbo-charging, having taken the view to avoid more esoteric methods of boosting power. As a result we have advanced technology in the engine, particularly in the combustion chamber design where Ricardo has deep experience, that will filter through to JCB products, and to proprietary production cars, within the next five to 10 years."
Ricardo’s project director Matt Beasley, who has specific responsibility for the JCB444-LSR engine’s development, said: "The greatest challenge was how to get sufficient air and fuel into the engine to increase its power, and to manage that air and fuel flow and the associated heat generated by two-stage turbo-charging at 6 bar."
Besides the block, head and bedplate, the JCB444-LSR engine also uses the standard valve train, albeit with stronger springs and different exhaust valves. The crankshaft and camshaft are lightened, while the pistons and connecting rods are bespoke.
"One of the major areas of development has been the piston design," said Beasley. "The engine places very high mechanical and thermal loadings on the aluminium pistons, and we spent a lot of time refining the design. Aluminium normally degrades rapidly with such high temperatures. We experimented with a number of profiles. Since then we have focused on refining the other key areas – the lubrication and fuel systems. The former is totally new as the engine is inclined at 10 degrees from the horizontal for optimum installation in the car. There is a lot of oil flow, up to six times what you would expect in a normal diesel engine and the oil circulates around the engine every five seconds.
"The fuel system is also remarkable. We have achieved 750bhp after going to gold fuel pumps in place of the previous red pumps, and by very careful attention to the injection system. We are putting a tremendous amount of fuel through very small orifices in the injectors, and are doing so at massive pressure – 1600 bar – hence the magnitude of the engineering challenge in that area." Test ‘mule’ engines ran for as long as 12 hours during the development phase, and some were stressed to destruction in order to see where the limits of individual components were. "They were impressively high," Penny says.
Vital statistics
The definitive JCB444-LSR engine displaces five litres, weighs 382kg (dry), and produces 750bhp at 3,800 rpm on a relatively low 10.5:1 compression ratio and over 1,100lb-ft of torque at 2,200 rpm. "I am confident that the JCB DieselMax will easily be the cleanest and most efficient land speed record car ever built," said Penny. "The car has twice the power and more than four times the weight of an F1 car, yet half the fuel consumption.
"There is perfect synergy between Sir Anthony Bamford’s avowed aim of showcasing British engineering and Ricardo’s corporate ambition to promote the fuel efficiency and emissions cleanliness of diesel technology, particularly in the United States."
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