400bhp 3.6-litre supercharged Theon Design’s Porsche 911 964

400bhp 3.6-litre supercharged Theon Design’s Porsche 911 964

Destined for a new life in Belgium, this bespoke 964 from Theon Design debuts a numberof firsts for the company, including a 400bhp 3.6-litre supercharged flat-six...

Words Robert Smith

Photography Dean Smith


Theon Design’s supercharged 964 build.

400bhp 3.6-litre supercharged Theon Design’s Porsche 911 964

Founded in 2016, Oxfordshire-based Theon Design is headed by Adam Hawley, a car designer boasting more than two decades experience working for leading OEMs, including BMW, Jaguar, Lotus and Lexus. The Theon Design team — comprising experts in automotive design, engineering, engine and chassis development, as well as trim and overall vehicle assembly — is united around a singular objective: creating the ultimate air-cooled 911.


The company evolved from Hawley’s obsessive desire to build the perfect Porsche, one teaming the looks and driver involvement of an analogue classic with the comfort, drivability and performance of a modern sports car. “At Theon, our goal is to enhance the classic 911 formula, applying an OEM-like approach with computer-aided design, resulting in bespoke cars built to the highest possible quality and finish.”

400bhp 3.6-litre supercharged Theon Design’s Porsche 911 964

Above BEL001, resplendent in its coat of 356-inspired Aquamarine, is destined for a life in mainland Europe

Theon recently revealed its latest commission, a fully restored and enhanced 964, blending a number of exciting company firsts with Theon’s core values of world-class design and engineering. Destined for a discerning client living in Belgium, BEL001 is the first Theon commission to feature the company’s 400bhp 3.6-litre supercharged flat-six. Theon Design already offers customers a choice of three ultra-responsive, high-performance normally aspirated engine configurations (a 285bhp 3.6-litre flat-six, a 370bhp 3.8-litre unit or the option of a 400bhp four-litre variant), but this supercharged boxer is the company’s first foray into the world of forced induction. “We wanted to deliver additional performance, but also maintain the seamless delivery of a normally aspirated Porsche engine,” Hawley tells us. “This is why we opted for a Rotrex centrifugal supercharger, providing a wonderful, linear power delivery and instant throttle response without the delay or lag associated with turbocharged air-cooled boxers. It was also crucial to us that the Porsche flat-six sound remained undiluted. We’re very pleased with the results — the supercharger emits a subtle whine, but the bark of the flat-six stays front and centre, with wonderful added character.”

Above A huge amount of CAD modelling went into turning the 964 donor car into what Theon has labelled BEL001.

Above A huge amount of CAD modelling went into turning the 964 donor car into what Theon has labelled BEL001.


400bhp 3.6-litre supercharged Theon Design’s Porsche 911 964

The Rotrex supercharger chosen by Hawley and his team helps the engine deliver a broad, smooth power surge. It also offers excellent integration and compatibility with the Porsche flat-six engine, advantages Theon Design has further leveraged through its OEM+ philosophy. “As every Porsche enthusiast knows, there’s not a great deal of room within a 964 engine bay, which is why we located the supercharger in the space previously occupied by the factory air-conditioning unit,” he explains.


A highly focused six months was spent developing the optimum installation solution. The supercharger had to maintain the host engine’s character and Porsche’s original engineering values. To achieve this, the team utilised some of the existing air-conditioning system bracketry to support the Rotrex hardware, developing and designing additional mounts to mirror the design and materials used for the cam covers and other elements. Significant effort was undertaken to ensure this would provide solid and durable support for the supercharger, allowing for no movement or flex, no matter how extreme the driving conditions, whether a bumpy mountain road or a high-speed race circuit.


To maintain a clean look in the engine bay, Hawley decided to introduce a water-methanol injection system to proceedings, negating the need for an intercooler and avoiding the introduction of air intake apertures in the bodywork. “Injecting a water-methanol mix into the engine plenum not only provides the same cooling function as an intercooler, but also increases the octane rating of the fuel, boosting 98 octane petrol to 110 and improving performance as a result,” he says. The methanol supply system is fully integrated, with a 3D carbonprinted section to bridge the plenums, complementing a carbon-fibre engine and fan shroud.

400bhp 3.6-litre supercharged Theon Design’s Porsche 911 964

Like every one of Theon’s meticulously developed, sympathetically enhanced commissions, BEL001 was stripped to a bare metal shell and rebuilt from the ground up to its current exacting OEM+ specification. Honouring Stuttgart’s rich heritage and engineering ethos, the car benefits from a focus on CADassisted lightweighting throughout. The results are clear to see: BEL001 distils and enhances the essence of the aircooled 911, while incorporating modern innovations lifting performance into a new realm.


As mentioned, the first area of innovation lies in BEL001’s beautifully resolved engine bay. The 3.6-litre unit has been expertly calibrated to ensure it meets — and, indeed, surpasses — its owner’s performance and drivability brief. Despite the flat-six’s supercharged configuration, the team has gone to great lengths to ensure the Porsche feel of the motor is retained. With 367lb-ft torque, the power unit gives the best of all worlds: total tractability with accessible, lag-free supercharged torque, whilst retaining the spellbinding top-end surge of a motorsport-honed, normally aspirated Porsche flat-six. Breathing through a bespoke switchable stainless steel exhaust system with equal length headers, the motor’s distinct howl remains front and centre, with only a subtle aural hint of the forced induction at play.

As with all Theon powerplants, BEL001’s force-fed flat-six has been entirely rebuilt and re-engineered, benefiting from independent throttle bodies, flowed and ported heads, a lightened bottom end, motorsport-grade Mahle barrels and pistons, plus Carillo rods and custom-profile camshafts. The compact centrifugal supercharger in use was developed in close collaboration with its maker, Rotrex, and uses patented traction drive technology to deliver superior efficiency, reduced emissions and exceptional responsiveness.

400bhp 3.6-litre supercharged Theon Design’s Porsche 911 964

BEL001 also makes good use of chargecooling (essentially a reverse radiator, using water to cool the air, as opposed to an intercooler’s use of air as the cooling medium), with twin chargecoolers mounted on the opposite side of the flat-six to the supercharger, ensuring the arrangement of the engine bay remains symmetrical. The chargecoolers work in tandem the aforementioned integrated water-methanol injection system, the set-up delivering all the additional cooling requirements, while also boosting engine performance.

“We opted for chargecoolers because they negate the need for an intercooler, which is difficult to package in a 964 engine bay,” Hawley reiterates. “The avoidance of air intake apertures in the bodywork means we’re able to retain the super-clean look so important to us as a company.”

Such power and accessible torque in a car tipping scales at 1,265kg (with all fluids and a full tank of fuel) ensures delightfully muscular delivery and visceral, highly responsive performance. Driving through its original Getrag G50 manual gearbox — fully rebuilt by Theon Design to deliver perfect shift quality — and a new limited-slip differential, the driver is given total control of the enthralling air-cooled powerplant.

400bhp 3.6-litre supercharged Theon Design’s Porsche 911 964

As one might expect, with such an abundance of power, the team has gone to great lengths to deliver total dynamic control. The significant innovation here extends to the sophisticated suspension at work. Developed in partnership with TracTive UK, BEL001 features semi-active electronically controlled adaptive dampers. TracTive’s DNA can be traced back to celebrated Dutch motorcycle damping specialist, WP Suspension, a major player in top-flight two-wheel motorsport. In 2010, TracTive Suspension was established, promptly becoming an OEM development partner.

Thanks to efforts of the firm’s UK outpost, not to mention collaboration with many independent Porsche specialists and professional chassis tuners concerned with Stuttgart-crested road and race cars, TracTive possesses understanding of the unique damping requirements for Porsches on challenging British and European roads, hence Theon’s decision to equip BEL001 with a TracTive Road & Track Line Active Controlled Electronics (ACE) system, bolstered by RS front struts, Eibach Racing springs and monitoring real-time driving parameters, using lateral and longitudinal acceleration to observe behaviour on vertical, lateral and longitudinal axes.

Inside each ACE damper is a patented Dynamic Damping Adjustment (DDA) valve. This valve is controlled by a sensitive multi-axis g-sensor and advanced algorithms developed from decades of racing and road testing. A dynamic proportional valve operating as a bypass has capacity for a large range of damping adjustment. Users can adjust roll and pitch interference for stable braking, controlled corner entry and, after hitting the apex precisely, enjoy better acceleration out of the corner.

Little wonder a classic Porsche chassis, such as this, can suddenly feel very modern, particularly in terms of body roll and stability. Put it this way, even the electronic driver-configurable suspension system fitted to the new 911 GT3 RS doesn’t offer assisted roll and pitch. BEL001, on the other hand, very much does.

Response rates are between six and ten milliseconds. Consider the fact most humans react to visual stimulus at around two hundred and fifty milliseconds and you begin to realise what a game-changer TracTive’s products are when compared to traditional suspension systems — grip levels in all conditions are vastly increased, giving you the ability to push your car to limits you previously thought were impossible.

As intimated earlier, five different suspension maps can be created using the system software. Each setting can be selected by way of a rotary knob or an optional full-colour CANchecked touchscreen display. Maintaining an OEM+ look in BEL001’s pared back cabin, which we’ll come to shortly, is a specially developed and beautifully integrated metal rotary switch, calling the desired suspension mode into action.

The advantages are obvious: comfort and cruising for moving through regular traffic, as well as when travelling to and from a track, but within five clicks, an aggressive circuit set-up or fast-road option. A game changer? We think so, especially when different modes can be selected on the fly, adjusting the car’s behaviour to suit changing surface and weather conditions when on the move. For anyone used to crawling around on the floor playing with on-body damper adjustment knobs, or for those of you who regularly venture onto long tracks, such as the Nürburgring or Spa, where conditions can change from one end of the circuit to the other, this level of in-car damper control is the stuff of dreams.


BEL001’s five different driving modes were configured in partnership with Pete Leason and Chris Franklin at Atherstone-based chassis tuning outfit, Center Gravity, and were exhaustively honed over countless hours on the undulating roads surrounding Theon’s Deddington base, as well as on various race circuits. The enhancements continue with the body and construction. The classic 911 shape is enhanced by the appointment of Aquamarine, a stunning shade based on an early 356 colour. The lustrous paintwork is complemented by subtle tonal stripes, while yellow Porsche script adorns the lower sides of the doors and the engine lid, lending the exterior a motorsport-inspired edge.

The CAD-modelled bodywork pairs the ‘long hood’ of earlier 911s with the wider arches of a later model. Further aesthetic cues are lifted from Porsche’s historic motorsport machines. The bodywork itself makes extensive use of carbonfibre sourced from a leading Formula One supplier, representing one of the numerous technological partnerships made possible by Theon’s prime location in the heart of Britain’s ‘Motorsport Valley’. The carbon panels, as with all components on the car, were digitised and modelled in 3D design software to deliver an OEM-grade fit, working to the tightest possible tolerances.

400bhp 3.6-litre supercharged Theon Design’s Porsche 911 964 - engine

Above Supercharged 3.6-litre boxer chucks out 400bhp and is very neatly arranged in the car’s carbon-decorated engine bay.

The sympathetic enhancements continue beneath the carbon-fibre skin. The wiring loom, for example, has been replaced with a simplified modern solution, while the original air-conditioning unit is swapped out for a new, efficient, lightweight electric system. When the car left the factory, air-conditioning apparatus was mounted high up on the back of the engine.

The new parts are now positioned low-down in the front of the car, which helps achieve a near-ideal 50:50 weight distribution, front to back.

“Attention to, or even obsession with the detail is central to everything we do at Theon,” Hawley smiles. “My team goes to extreme lengths to ensure each commission delivers an exceptional driving experience. Every component is scrutinised and assessed with laser-like focus, then tweaked to deliver optimal performance, quality, and refinement. It’s how we deliver on our ‘OEM+’ philosophy.

With our use of 3D modelling, we can apply a forensic approach to enhancements throughout the car. This even applies to components hidden far from view — they’re all equally important to us. The carefully considered, incremental changes made throughout BEL001 add up to make a significant difference, delivering an ultra-responsive, highly sophisticated driving experience. It’s the manifestation of our ‘purity of purpose’ approach, which sets us apart and elevates the cars we build.”

The digital, ground-up design and modelling process enables Theon to carefully tailor each unique commission, working collaboratively with a client to deliver an entirely individual creation.

The personalisation potential Theon offer extends throughout each bespoke creation, from mechanical specification and exterior details to beautifully appointed interiors. Indeed, BEL001 features amazingly comfortable ‘touring’ front seats, based on Recaro frames and mechanisms, but modified with updated and customshaped foams, elevating comfort and support in equal measure. The seats are impeccably trimmed in soft tan leather. The rest of the interior is finished in matching hide with black accents, complemented by body-coloured elements on the dash, doors and rear quarter panels.

Ahead of the driver, the distinctive, easy to read gauges feature numerals picked out in the classic green made famous by early Porsche sports cars and are set against a black backing. The car’s centre console is constructed from carbon-fibre, then wrapped in leather, blending lightweight construction and hand-trimmed luxury. The Nardi steering wheel has been custom stitched to match the car’s interior by Nardi itself. Even the car’s ‘frunk’ is finished to the same exquisite detail as the rest of BEL001, wrapped in black leather, matching the leather-wrapped carbonfibre fuel tank. Theon Design has also fitted a 964 Carrera RS strut brace, which is also wrapped in leather. Tan, this time, thereby matching the bulk of the interior.

Surprise and delight features abound inside BEL001. A magnetic wireless charger — mounted behind the dashboard — allows a smartphone to be seamlessly attached, providing an immediate touchscreen control panel for the sound system and providing satellite navigation. Cable-operated heater controls, which have the beautiful, manual, tactile feel of those found on a classic 911, are also fitted, while the heater is, of course, a modern, highly efficient unit.

“We really are excited to be revealing BEL001 to the world,” Hawley beams. “This is our most ambitious, technologically advanced project yet. We are once again delivering on specific client specification, instilling the car with thrilling visceral performance, while using our design and engineering expertise to hone and evolve the 911’s distinct, captivating character, all to our OEM+ standards. BEL001’s innovations, both in terms of its thrilling supercharged motor and sophisticated adaptive damping technology, showcase Theon Design at its best — delivering beautifully resolved, exquisitely engineered enhancements, which in terms of both outright performance and pure driving enjoyment, elevate the air-cooled 911 experience to a whole new level.” We don’t doubt him, but how much do you need to budget and how long do you need to wait for a Theon-reimagined 911 of your own?

Commissions start at £380,000. Each car is a totally unique collaboration with its commissioning owner and takes eighteen months to build. It should be noted, this price excludes the donor 964 (which Theon can help source) and applicable local taxes. Not cheap, then, but a fraction of the cost of a car from Singer Vehicle Design and yours in a much quicker timeframe. Now, where did I put my cheque book?!

Above Rotrex supercharger occupies space in the engine bay previously taken up by the inefficient factory airconditioning system.

Above The most comfortable seats you’ll ever find in a 964? Highly likely.

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