Diesel Speed Demon

JCB, the fifth largest manufacturer of construction equipment in the world, will make a land speed record attempt this August in a bid to earn its purpose-designed streamliner car the title of "World’s Fastest Diesel". To reach speeds of over 300 mph (480 km/h), JCB has developed the world’s most powerful automotive diesel engine, with a specific power of 150hp per litre.

The aim is to set a new record in excess of 300 mph. The current FIA mark stands at 235.756 mph to Virgil W Snyder and the Thermo King Streamliner, a record that dates back to 1973.

The JCB DIESELMAX streamliner will be driven by Wing Commander Andy Green, who set the first-ever supersonic world land speed record at 763.035 mph in ThrustSSC on the Black Rock Desert on 15 October 1997.

The innovative car has been designed by a team led by JCB Group Engineering Director Dr Tim Leverton. Richard Noble, the former land speed record-holder, has acted as a consultant to the project, and JCB has worked with long-term technology partner Ricardo plc to develop the JCB444-LSR engine.

The record attempt will be made at the Bonneville Salt Flats.

The Production Engine

The land speed record engine is based on the JCB444 production diesel which is fitted to the 4CX, 3CX and 2CX JCB backhoe loaders and Loadall telescopic handlers.

The JCB444 is a four-cylinder in-line mid-range diesel with four valves per cylinder and a 1.1-litre per cylinder design concept, hence the 444 nomenclature. With a bore and stroke of 103 mm x 132 mm, it displaces 4400cc and comes in a range of performance classifications, ranging from 74 and 84hp naturally aspirated up to 100hp turbo-charged and 125hp charge-cooled turbo-charged. Peak torque at only 1300 rpm is 320, 425, 525 and 620 Nm respectively.

The JCB444 Land Speed Record Engine

JCB’s purpose in creating the world’s fastest diesel automobile is to prove the versatility of the standard JCB444 engine, and to validate its inherent excellence in a totally different – and extremely demanding – engineering environment.

"Our intention all along with the speed record project was to use a standard engine block, cylinder head and bedplate," explained Dr Leverton. "I set that task at the very beginning. I wanted it to be the standard design block and have exactly the same fundamental architecture. It had to be recognisably the JCB444 engine."

But how do you take what is basically a bulletproof industrial engine and turn it into a record-breaking powerplant?

"The JCB444 has been designed with a very stiff bottom end. It’s designed to sit there for hours and hours and hours, chugging out the required horsepower. It’s an incredibly tough, long-life engine and therefore has the inherent strength to cope with the very high cylinder pressures generated when harnessing two-stage turbocharging to boost power to 750hp."

The land speed record engine develops almost 1500 Nm of torque at 2500 rpm, with a rev limit of 3800 rpm. Each engine will be laid over in the car - inclined at an angle of 10 degrees from the horizontal - to minimise the frontal area of the machine.

The DIESELMAX engines have been designed using Ricardo’s High Speed Diesel Race (HSDR) direct-injection combustion technology. Fuel is delivered via two parallel high-pressure pumps to a common-rail system delivering an injection pressure of 1600 bar. The cylinder head has been modified to enable the larger injectors required for the HSDR system. However, demonstrating the robust design of the original JCB444 engine, the valvetrain is carried over substantially in its original form, with the exception of high-temperature specification exhaust valves, up-rated valve springs and a modified camshaft profile.

A completely re-designed piston is used with a large, quiescent combustion chamber that has a reduced overall compression ratio and specific features to reduce the risk of thermal damage to the combustion chamber components. Piston cooling has been assured by doubling the size of the original oil-cooling jets and providing supplementary cooling jets, which together increase the cooling oil flow for each piston by around 600 per cent. A completely new, fully-machined connecting rod is incorporated, including a significantly enlarged small-end bearing to increase strength and robustness. While giving a longer stroke, the billet-machined crankshaft retains the main and big-end bearing sizes and bearing shells.

Ricardo calculated that for the speed record attempt, the two engines would require an intake airflow of almost five tonnes per hour. Moreover, this would need to be delivered at the 1300 metre altitude of the Bonneville Salt Flats, where ambient air pressure is 85 per cent of that at sea level. While the production engine requires a boost pressure of 2 bar, the two engines installed in DIESELMAX require 5.2 bar absolute at full power. The scale of this challenge can be appreciated in comparison with around 3 bar absolute for a diesel Le Mans racer, and around 4 bar for the turbo-era Formula 1 cars.

In meeting this significant air-handling challenge, Ricardo developed a two-stage turbo-charger system with both inter-stage and after-cooling, in order to deliver the required airflow across the engine speed range in Bonneville conditions. A water-injection system provides a further level of charge-cooling to protect the pistons and valves in this ultimate test of durability.

A radiator would have created too much aerodynamic drag, so Ricardo designed a cooling system based around a 200-litre water and ice tank in the nose of the vehicle. The system makes use of the latent heat required to melt the ice in addition to the low temperature of the water.

Each engine delivers peak power of 750hp and torque of 1500 Nm. This is over five times the power of the production version and, at 150 hp/litre, the engines exceed even motorsports applications as the world’s highest specific power diesel car engines.

The Car

John Piper, the project’s chief designer says: "In a Formula 1 team, efficiency is key. You spend a lot of money trying to provide the engineering to deliver that. The problem is that nobody has done this type of record car before, so you can’t walk down the pit-lane and go, ‘Ooh, that’s a good idea.’ And there are no regulations that guide you. There aren’t any markers anywhere. The only markers really are the laws of physics. That’s what makes it so exciting."

Aerodynamics

It’s not only the body shape of a record-breaker that needs to be highly aerodynamically efficient but also the underside, because the air flowing under the car accounts for about one-half of the total aerodynamic drag.

Project aerodynamicist Ron Ayers believes that the interaction between tyre and salt can significantly affect aerodynamic efficiency: salt and debris thrown up by the car’s passage slow it down. To minimise this drag, he has very carefully shaped not just the spats around the lower section of the wheels, but also the flow of air through the choke points between the wheels. Spray beneath the front of the car is deflected outwards, ensuring the rear wheels and tyres run on as clean a surface as possible.

For very practical reasons, all of the aerodynamics study was done via computational fluid dynamics (CFD), not in a wind tunnel.

"Even at the speeds we envisage," Ayers explained, "compressibility effects are beginning to become significant. Indeed, in the region near the wheel/ground contact points, the local airflow actually goes supersonic. We could not simulate such effects in a low-speed wind tunnel with a rolling road.

"The second reason is one of scale. To fit our long, slender vehicle into a tunnel with a rolling road would have meant restricting ourselves to a model scale of about one-sixth and the errors would have been too great."

The main changes as the shape evolved were to lengthen the nose and round it off, to lengthen the tail and to minimise the frontal area. At every stage Ayers had to achieve the optimal balance between aerodynamic drag, skin drag (the larger the surface area, the higher the skin drag) and downforce. If the car is envisaged as an arrow or a dart, it is the tail fin that acts as the flights to maintain stability at maximum speed.

The overall result is an outstandingly beautiful and effective car with a drag coefficient of 0.174 Cd and a CdA of 0.153m2 – extraordinary even by land speed record standards.

Tyres

Besides the aerodynamics and generation of sufficient horsepower, the other crucial area for any wheel-driven land speed record contender is the tyres. The thorny problem of sourcing them fell to David Brown, Project Chief Engineer.

"After the salt conditions, the tyres are the biggest challenge," Brown said. "It is critical to have the right rubber, because you cannot play Russian Roulette with a man’s life."

The technical data supplied for commercially available tyres made it difficult to assess their suitability for supporting a 2700 kg car travelling at 300+ mph. Tyre data should include maximum speed, load rating and running pressure; most proprietary Bonneville tyres come only with a speed rating and no indication of how that was calculated.

After investigating, and discounting, aircraft tyres (their performance was too difficult to predict) the team finally opted for 23 x 15 racing tyres, rig-testing them to ensure JCB DIESELMAX can run at 300 mph plus.

Structure

The general arrangement of JCB DIESELMAX places the front engine and its transmission ahead of the driver’s safety cell, and the rear engine and transmission behind.

This layout is attractive not just because of the optimisation of weight distribution but because it places the driver in the best possible position to monitor the behaviour of the car, and the safest place should there be an accident.

Chief Designer John Piper has opted for a 50 mm square-tube steel spaceframe chassis. This is the most cost-efficient way of producing a vehicle that must be both prototype and finished product, since it allows changes to be made much more simply than might be the case with a carbon-fibre composite structure (which, in any case, would not be allowed under the SCTA-BNI rules that govern Bonneville Speedweek). The cockpit cell is a bespoke carbon-fibre composite bathtub monocoque structure with mandatory SCTA steel tube rollover cage. The nine-litre, wedge-shaped fuel cell is located behind the driver’s seat.

A three-piece composite underfloor completes the basic structure, and is bolted and bonded to the bottom of the chassis to enhance stiffness.

Transmission

Two six-speed bespoke gearboxes are employed, one for each engine. The gearbox is mated to the engine using a JCB-designed stepper gearbox arrangement utilising oil-immersed multi-plate clutch packs from JCB’s flagship 3CX backhoe loader. A torque tube encloses the gearbox and connects the final drive to the rest of the driveline.

Gear-shifting in both boxes is synchronised and controlled electronically with shift actuation via steering wheel-mounted paddle switches.

Traction control will not be used, not just because it is outlawed by SCTA-BNI regulations, but also because the aim all along has been to keep the car as simple as possible. Because of the salt’s Mu factor (the coefficient of grip) – 0.6 – wheelspin will be the limiting factor in the car’s acceleration capability.

Steering

A conventional rack and pinion system provides steering to the front wheels. There will be no power-assistance and the ratio will provide seven degrees of lock and a likely turning circle of around a quarter of a mile. The plan at turnaround between each run is to lift the car and rotate it on a specially devised turntable.

Brakes

JCB DIESELMAX will employ a dual-circuit, triple braking system comprising friction brakes on all four wheels, driver-activated engine braking, and parachutes.

Using an innovative bespoke system, the carbon brake rotors are clamped not by conventional six-pot racing calipers, but instead by brake pistons mounted within the wheel upright. The pistons are activated by a torque tube which pushes them hydraulically into contact with a stator that clamps the wheel-driven rotor. The system provides enhanced swept area and effectiveness, and the aim is to provide a friction brake system capable of stopping the car in an emergency, such as complete failure of the twin-parachute back-up system.

John Piper pointed out: "The car is four times as heavy and almost twice as fast as a Formula 1 car, so there is a lot of mass to stop and a great deal of heat to dissipate. This system enables us to get as big a brake as possible within the 15-inch wheels, which will be turning at 5500 rpm, or twice the speed of rotation of a Formula 1 car’s."

Suspension

Conventional, heavy-duty wishbone suspension is used front and rear, with coil springs and hydraulic dampers.

To follow the record attempt go to www.jcbdieselmax.com/html/home.php

Technical Specifications

Engine: Two JCB444-LSR common-rail injection diesels, bored and stroked to 5000 cc, dry-sumped and inclined at 10 degrees.

Two-stage turbo-chargers with intercooling and after cooling

Ice tank cooling (capacity 200 litres).

Power: 750hp (560 kW) at 3800 rpm

Torque: 1105 lb ft (1500 Nm) at 2500 rpm

Fuel tank capacity: 9 litres

Transmission: Forward transmission and final drive connected to forward engine; rear transmission and final drive unit connected to rear engine.

Six-speed barrel-shift transmissions driven through torsional dampers and oil-immersed multi-plate clutches.

Steering: Rack and pinion, to front wheels

Brakes: Split circuit; unique design carbon rotors and twin stators.

Exhaust brakes for front and rear engines, manually operated.

Twin parachutes.

Suspension: Independent all round via twin wishbones,

coil springs and hydraulic dampers.

Chassis: Hybrid square steel tube spaceframe with

bonded carbon composite panels

Body: Aerodynamically designed (CdA <0.15); carbon composite materials

Wheels and tyres: 23 x 15

Dimensions

Length: 9091 mm

Width: 1145 mm

Height: 979 mm (to top of canopy, at run speed)

1337 mm (to top of fin)

Front track: 800 mm

Rear track: 600 mm

Wheelbase: 5878 mm

Weight: 2700 kg including fuel, oil, ice and water coolant and driver