Classic Retrofit recreates original Porsche 911R ignition

Original 1967 Porsche 911R coupes are few and far between, but that is exactly what Classic Retrofit was asked to look at for its latest ‘special projects’ prototype. Having already been brought in to create a period ignition for the exceptional 911 replica being built at EB Motorsport in the UK, we were well placed to help the owner of a genuine 911R who wanted to remove CDI boxes fitted to the R prototype sometime in the 1970s and replace them with proper spark boxes, as would have been on the car from new.

CDI technology was not introduced until 1969, so all factory cars prior to this date used earlier ignition systems. In the case of the 911R, the car relied on a High Energy Ignition (HEI) circuit to manage the ignition coils, running signals from the high-revving distributor through a circuit that stretched the ignition pulse, forcing the ignition coils to charge for longer. This system has a few shortcomings when compared to CDI, which is why most racers switched to CDI soon after it was introduced. However, for an original 911R, HEI ignition amplifiers are correct.

To recreate the original system, a genuine 911R HEI box was 3D printed and sent to us for reference. We scanned the printed replica and set about having new boxes created. While that was in progress, we created a modern HEI module to fit in the 911R units. Two original Bosch blue coils were sourced to complete the package.

The finished product is an impeccable recreation of the original Porsche equipment and a perfect example of what our special projects section has been creating for the rarest Porsche factory race cars over our three years in business to date.

“More than 200 CDI+ units are now in circulation and everyone who uses them is wonderfully impressed,” enthuses Classic Retrofit MD, Jonny Hart. “Working on unobtanium ignition units for rare race cars, including several Le Mans winners,  has been an illuminating spin-off from the exhaustive R&D programme that led to the continued success of CDI+. It’s a special service that we are delighted to offer clients and collectors all over the world.”

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About the Porsche 911R

Power-to-weight ratio rules all in racing. More power moving less weight delivers an exceptionally dynamic package, which explains how the compact 911R came to dominate production car GT racing in the late 1960s.

To achieve a weight of just 800 kilograms, Porsche built the 911R bodyshell using composite body panels including the doors, going so far as to reinforce the big plastic bonnet using simple strips of balsa wood. More weight was shaved using lighter front and rear light assemblies, plastic windows and simple plastic doorhandles. 

The power side of the all-conquering ratio came from a special flat six engine. Optimised magnesium crankcases enclosed a lightened and balanced crankshaft, titanium connecting rods and lightweight forged pistons. Big triple carburettors topped the flat six, powering the 2-litre engine to an astonishing 210 horsepower at 8,000 rpm. As discussed above, the sparks were provided by a twin-spark system, energised by twin Bosch coils and a pair of special ignition boxes.