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Speed icon

10700 RPM


Power Icon

630 HP


Weight Icon

850 KG


About the concept



What happens when you take a race proven Sports Prototype chassis, a fire-breathing high compression, high-revving Naturally Aspirated 3.5 litre ex-Indy engine, a solid 6 speed semi-automatic Hewland transmission, add a pinch of OBR racing engine and power management, a touch of Cosworth steering and a sprinkling of Inconel harmonically tuned racing exhausts?
You have a recipe for the most aggressive, trackfocused, racing experience ever, short of a full-blown LMP1 or open cockpit F1 car, the XP-CR1 IRL delivers a visceral and audible onslaught to the scenes and provides the driver (and passenger) the full adrenaline fueled racing experience.

Design, Philosophy & Context

a light-weight mid-engined sports prototype

With the advent of premium track days, time-attack and club racing events opening the door for the adventurous and uniquely driven individual who understands that only the best will do, then the XP-CR1 IRL represents the very Nexus of excellence and individuality.
This car represents a three year journey to design and build the perfect track weapon and with over 630 HP and a fully loaded weigh of 850 kgs this car will set your senses ablaze.
The concept of a light-weight mid-engined sports prototype that would feature all the latest race bread engine management and power control systems along with state of the art pneumatic clutch and gearbox control led to the final presentation of this unique vehicle.

The Beating Heart

V8 3.5


The first stage of concept and design was to select a suitable engine.
Robust, Reliable and powerful!

This engine needed to deliver an explosive experience with a true racing pedigree and that path led directly
to the Indy Racing League. Regularly withstanding racing on pitched oval circuits for over 500 miles at WOT (wide-open-throttle) these
power-plants necessitated the highest degree of reliability while winding out to over 10,500 RPM of Methanol burning fury.

Enter the GM Developed 3.5 Litre GEN II IRL V8 – Racing Engine, the perfect choice and so the journey began.

These engines were highly successful, innovative race winners. Chevrolet engines swept the podium 13 times with 1-2-3 finishes, powered
88 percent of the top-five finishers, led 78 percent of the laps, and completed 61,781 racing miles. Chevy Indy V8 engines were the
choice of 75 percent of the starters and 80 percent of the finishers in the 2002 15-race series.

Whilst Peak-power is all-important on the high-speed ovals where the IRL series competes, a need to combine this with a good low-end Torque is essential for deriving the best result and extending the service life of the engine. The need to maximise power at the 10,700-rpm limit defined the Chevy IRL V-8’s camshaft timing, valve sizes, and port volumes. The Chevy IRL V-8’s all aluminium-alloy cylinder heads feature innovative design and are CNC-machined, port matched and blueprinted.  Four camshafts operate the 32 titanium valves directly through inverted-bucket lifters, while conventional dual-coil steel springs close the valves.

Chassis & Suspension

Featuring an aluminium Monocoque design

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The Chassis is of an aluminium Monocoque design, incorporating a fully triangulated TIG-welded 4130-N tubular steel space frame with stressed floor pan and firewall bulk-head. It features a Semi-stressed engine installation with sump casing and bellhousing joined by CNC machined aluminium alloy fittings, with the engine located on both sides and top by tubular steel “spiders”. The bellhousing is a fully stressed member, fabricated in ‘Docol 500’ high strength micro-alloyed steel. All suspension pick up points have detachable fittings, except upper forward wishbones, which pick up on integral reinforced anti-intrusion “cups”.

The suspension system fitted to the XP-CR1 IRL is of a fully independent double wishbone pull-rod type.  Innovative in design, it features symmetrically Non-handed fixed length elliptical section tubular wishbones with pressed-in spherical joints for ease of maintenance and repair, the suspension system comes as standard with Intrax™ 4-way adjustable external reservoir dampers developed specifically for the XP-CR1 IRL providing the driver with an almost limitless range of adjustability for every track and race condition.

4-Way Adjustable Suspension Options – Front Include:

Ride height adjustment on intermediate pushrod.

Corner weight adjustment on pull-rods.

Droop limit adjustment on damper.

Camber adjustment by shims without affecting toe adjustment.

Caster adjustment is available via shims on the lower wishbone pickup fittings.

Toe adjustment on tie rods.

4-Way Adjustable Suspension Options – Rear Include:

Ride height adjustment on pull-rods.

Corner weight adjustment on spring platforms.

Droop limit adjustment on damper.

Camber adjustment by shims without affecting toe adjustment.

Turnbuckle adjustable bump-steer (caster) on trailing arm of lower wishbone.

Toe adjustment on tie-rod turnbuckles

Aero Innovation

Le Mans Prototype Styling

Aero Innovation

The decision to use an existing mid-engined GT Sports Car chassis as the starting point of the aero design follows from the advantages gained in lowering the total frontal area – and in particular the greenhouse volume – that tends to be much smaller in mid-engined cars, leading to a reduction in overall drag.  Careful consideration is given to the cockpit profile that blends seamlessly into the fuselage becoming part of the same flowing teardrop design that tapers naturally to a point at the rear.

Alongside the fuselage, sit twin side-pods that house not only the rear wheels but also accommodate the high performance, ultra-lightweight racing battery, and additional oil-to-water radiators which benefit from the aerodynamically efficient airflow that can be captured in this area.  Meanwhile the roof-molded scoop provides an air supply to the Helmholtz resonantly tuned carbon fibre air-box sitting atop the mid-mounted IRL V8 Racing engine.

This concept evolves from the LMP1 GT Cars of the late 1990’s and early 2000’s with such iconic designs as the Porsche 911 GT1, the Toyota TS020 and Bentley EXP-Speed 8.

Porsche 911 GT1

Porsche 911 GT1

Toyota TS020

Toyota TS020

Bentley EXP-Speed 8

Bentley EXP-Speed 8


Hewland NLT


The GM Racing 3.5l GEN II IRL V8 is mated to a Hewland NLT-200 six speed sequential gearbox. The NLT gearbox is a transaxle unit, designed for mid-engined, rear wheel drive cars. The unit is produced with six forward gears, one reverse, and features an integrated Powerflow™ differential.

The gear selection mechanism is sequential, with a separate, mechanically interlocked reverse engagement mechanism.  The XP-CR1 is fitted with a SHIFTEC Paddle Shift and F1 style pneumatic Clutch Control system.

This Powerflow™ differential unit is designed with versatility as its major asset. Many factors will contribute to the settings required. A car with good traction and low power may require a completely different arrangement to that of a car with poor traction and high power.

There are 10 friction plates within the unit 4 (87) splined to the diff casing, and 6 (88) splined to the side bevel gears. Slip limiting is dependent on the friction resistance between these plates, and is affected by clamping the plates together.

Gear changing via the SHIFTEC pneumatic paddle shift system is effected through non-synchronising face dog-gears. An extensive range of gear ratios provides a wide range of gearing setups. For ease of maintenance, the gear ratios and differential assembly can  be changed easily without the need to remove the gearbox from the vehicle.


Custom Flywheel & Clutch Assembly

taking up the drive


Adapting the GM Racing 3.5l GEN II IRL V8 to the Hewland NLT-200 six speed sequential gearbox required extensive engineering.  This led to the re-development of a custom vanned flywheel and starter ring-gear to ensure timing events could be taken at the high rpm’s that this unit is capable of supporting.  Drive to the NLT gearbox is taken up via a Tilton triple plate carbon-fibre racing clutch.

Braking System

Alcon 6-pot racing breaks


The XP-CR1 IRL has been fitted with a set of Alcon 6-POT Racing Brakes both front and rear.  This design optimises breaking efficiency and reduces the total number of spares required to be carried for pit maintenance.

Key Features:

Differential piston diameters are used in all Alcon calipers in order to minimise pad taper wear.

Alcon uses top-quality materials throughout the range including billet aerospace-grade aluminium alloy and a hard-anodised surface treatment.

The use of high-temperature seals as standard.

Hard stainless steel wear plates protect the pad and caliper body in racing calipers.

Resonantly Tuned Airbox & Inlet Manifold

effective breathing – the key to all naturally aspirated engines


Careful consideration of the airflow through the GEN II IRL V8 has been made to ensure optimum results are maintained throughout the rev-range of this unit.  All modern engines with valve overlap will naturally develop a dip in the torque curve at about one-third to a half of the red-line rpm.

The custom fabricated carbon fibre airbox, specifically designed and manufactured for the XP-CR1 IRL, is engineered to act as a Helmholtz Resonant cavity thereby presenting the minimum resistance to air flow at exactly this cam-overlap rpm.  Through this and the careful matching of trumpet lengths and cam profiles (intake & exhaust), the dip in the torque curve is partially filled by the laminar airflow and the Naturally Aspirated engine can gain maximum effect from exhaust scavenging.

Custom Fabricated High-Flow Exhaust

from BTB Exhausts

The GEN II IRL V8 has been fitted with a custom exhaust system to meet the exacting demands of this racing engine.

The exhaust headers are of a 4-into-1 type featuring tuned length primaries flowing into a high-flow merge collector.  The system is constructed of Inconel to withstand the heat loading and vibrational stresses produced by this engine and is ceramic coated and insulated for maximum thermal isolation.

On a 180 degree, flat plane crank the exhaust manifolds can be treated as two independent four cylinder engines, and therefore no crossover is theoretically necessary for pulse tuning.  The XP-CR1 IRL, however, features a crossover tail pipe for sound attenuation and tonal quality reasons as this gives a higher pitch exhaust note.

As for silencing, the target dB rating is just 98dBA and every effort of design was aimed at not restricting performance (or adding unnecessary mass in the form of a very large silencers).  This was effected via two large transversely mounted oval silencers with a central chamber to allow for some noise cancellation between the banks.

Electronics & Control Systems

puts the driver in control

Cosworth CFW-277

The XP-CR1 IRL has been fitted with an array of sensors and telemetry capturing devices feeding into a state of the art engine management and power control system from Ole Bhule Racing (OBR).  Driver display and control are handled via a Cosworth CFW-277 Formula Steering Wheel and Driver to Pit Crew communications is provided via a Stilo: VerbaCom Pro Car to Pit System.

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