Prodrive Unveils P2 Compact Sports Car

Motoring Channel Staff - 16/Jan/2006

Prodrive, an automotive company with interests in motorsport and automotive technology, presented the new P2 sports car at the Autosport International show, held in mid-January at the NEC in Birmingham, UK.

Prodrive explains that the P2 vehicle was the idea of its chairman and chief executive, David Richards, who wanted to create something that used the skills of every part of the business and demonstrated the company's capabilities.

Talking about the idea behind the tiny sports car, Richards said "What we created is P2, a unique two-seater sports car, which has gone from concept to reality in just nine months and which is the perfect manifestation of what happens when our inspirational ideas combine with our innovative approach."

First and foremost says Prodrive, the philosophy behind the design of the car was practical performance.

Weighing just 1100kg and with a power to weight ratio of more than 350bhp per tonne, the P2 is expected to reach 100km/h from standstill in under 4.0 seconds and carry on to 280km/h.

Yet, despite the focus on weight reduction, P2 has all the comforts of any modern car, claims Prodrive, with a 6-speaker stereo system, power assisted steering and electric windows.

The P2 uses a modified Subaru Impreza STi engine producing 260kW of power and 575Nm of torque, featuring an all wheel drivetrain, which incorporate two of its innovative technologies, which increase performance says Prodrive. They are the ALS (Anti-Lag System) and ATD (Active Torque Dynamics).

The 2.0-litre flat 4-cylinder engine is fitted with Prodrive's ALS, which the company says has been derived from the same system currently used on the Prodrive-designed Subaru World Rally Car (WRC), but modified for use on the road.

Simply put, ALS can keep the turbo on boost at low engine speeds, giving the car immediate throttle response and improved performance by using more engine torque throughout the rev range. The ALS on the P2 is based on the system currently used on Prodrive's Subaru World Rally Cars, but modified for use on the road.

Prodrive makes the claim that in tests, ALS has been shown to double engine torque at low revs, enabling a test car to accelerate from 50 to 80km/h (30 - 50mph) in the same time in third gear as it would without the system in second gear.

Turbocharged engines tend to run with a rich fuel mixture and, as a result, some of this fuel remains unburnt and ends up in the exhaust. At low engine speeds, when turbo-lag is experienced, the anti-lag system can introduce ambient air into the red hot exhaust manifold causing this fuel to spontaneously combust.

In turn, this reaction increases the manifold pressure, spinning the turbo back onto boost. In the Subaru World Rally Car, this gives Petter Solberg and Chris Atkinson instantaneous response throughout the Impreza WRC's rev range.

"Unfortunately, transferring the [WRC] system to a road car was not as straightforward as it might seem," said Prodrive powertrain engineer, David Hemming. "In a World Rally Car, our drivers are either fully on or off the accelerator and not concerned about how smooth the power delivery is. For motorists this is definitely not the case and an unmodified system would provide an unacceptable driving experience."

Prodrive spent six months developing the system on an engine on a transient engine dynamometer at its Milton Keynes test facility in the UK. During this time engineers managed to achieve closed-loop control of the turbo boost and make it work in a road car application. The system is so refined that it can control the turbo speed to within one per cent at almost any engine revs.

"The system is not ready for production yet, but it has shown great potential. It will make P2 far more flexible to drive as without the turbo-lag you don't have to drop down a gear to get the acceleration you want," said Hemming.

As well as enhancing the performance of turbocharged cars, in the longer term it could provide a solution to the downsizing of engines in cars and so help improve fuel economy and reduce emissions.

"With an anti-lag system, you could in theory replace a normally aspirated, 2.0-litre engine with a turbocharged 1.0-litre engine. This would typically reduce fuel consumption by about 25 per cent without any loss in performance," said Hemming.

Prodrive is already talking to an unnamed vehicle manufacturer about the application of this system.

To use this extra torque more effectively, Prodrive's ATD system is fitted to the P2's drivetrain. It uses an active centre and active rear differential to control the torque split between the front and rear of the car and across the rear axle to optimise the car's handling characteristics. For example, should the car begin to understeer while on power, then more torque will be pushed to the rear wheels, while if it began to oversteer then drive is sent to the front of the car, balancing it in all situations.

Prodrive explains that during the last five years, it has been developing the ATD system (Active Torque Dynamics) and has already built 12 demonstrators for a variety of vehicle manufacturers for different applications on four, rear and front wheel drive cars, ranging from large SUVs to supercars.

The principle of ATD is to keep a vehicle going where the driver wants it to go, by modulating the torque at the road wheels using active differentials rather than applying the brakes, as is the case with stability systems such as ESP.

Damian Harty, the chief engineer for dynamics at Prodrive said that the system has significant benefits compared with conventional brake-based stability programmes: "ATD is extremely responsive. It can predict the vehicle’s reaction to changes before it calculates the correction required, so can achieve the required wheel speed in around 70ms [milliseconds].

"Because it applies positive torque, working with the movement of the car, it also feels more natural, particularly to performance-orientated drivers. A brake-based stability system can not distinguish when a driver is deliberately pushing a car to its limits and when a driver really is in trouble. As a result, it has to always assume the driver is in trouble and so intervenes when driving hard so ruining the driving experience."

In addition to P2, Prodrive has two dedicated ATD demonstrators: an all wheel drive system, similar to the P2’s, on a Subaru Impreza and a front wheel drive system fitted to a Ford Focus RS which helps correct torque steer.

The P2's exterior and interior styling were created by Peter Stevens, who has worked with both Prodrive and many other marques on numerous road car and motorsport projects. His team produced a full scale clay model of the car to develop the styling and from this P2's composite body panels were formed.

The P2 chassis was originally based on a Subaru R1 (a 4-seat mini car), which was completely reengineered to give P2 its coupe styling and to accommodate the new engine and drivetrain.

Prodrive is quite chuffed that every part of its business has been involved in the development of P2 from its motorsport and automotive technology divisions. Prodrive's chassis, engine and drivetrain and electronics departments worked with its in-house manufacturing operation to produce the specialist parts and electronic systems. The company also called on the skills of a number of its partners to provide additional complementary technical expertise and specialist components, such as wheels, brakes and lighting.

While P2 is a fully working car, Prodrive itself currently has no plans to put it into volume production. However, should a vehicle manufacturer approach the company to do so, it is expected that it would have a retail price of approximately £40,000 ($A95,000).

P2 Specifications:

Structure
Front engine, all wheel drive
Steel monocoque chassis
Composite body panels

Performance
0-100km/h in under 4.0 seconds
Top speed 280km/h

Engine
2.0-litre DOHC 16-valve flat-four turbocharged (w/ALS)
Power: 260kW (349bhp)
Torque: 575Nm

Transmission and drivetrain
All wheel drive fitted with ATD
6-speed manual gearbox

Differentials
Front: open
Centre: active LSD
Rear: active LSD

Steering and suspension
Electric power assisted steering
Double wishbone front and rear
Adjustable coil over dampers
Front anti-roll bar

Wheels and brakes
Wheels : 19-inch x 8.5-inch
Front brakes: 355mm discs, 4-pot monobloc callipers
Rear brakes: 330mm discs 4-pot monobloc callipers

Tyres
235/35 ZR19

Dimensions
Length: 3910mm
Width: 1855mm
Height: 1310mm
Wheel base: 2500mm

Track
Front: 1530mm
Rear: 1590mm

Weight
1100kg