Upgraded Bosch CDI Replacement from Classic Retrofit

One reason I’m bringing my 1976 Porsche 911 Carrera 3.0 out of long term storage is to try the Classic Retrofit CDI+ Bosch CDI replacement ignition unit developed by my very clever friend, Jonny Hart (he of the stunning Porsche 911 SC restoration featured on Ferdinand a while ago).

Jonny came up with the idea for a modern upgrade to the Porsche CDI unit when the time came in his 911 restoration to refit the thirty year-old Bosch CDI box to the 911 SC hot rod. The talented engineer runs an electronics firm building mission critical components for aviation and defence companies, so has a bunch of circuit designers and system engineers on staff. He diverted a few from designing guidance systems and set them to work making modern technology for the boss’s new Porsche.

The team spent almost two years developing their ideas, until eventually there was a plug & play prototype sitting on the bench. Then the real work began, as Jonny roped in a bunch of 911-owning friends to help with testing both the product and the upgradeable software (firmware) which runs the box and serves the two additional outputs. The cars were a mix of pre- and post-1973, as CDI+ is suitable for all 911s from 1969-1983 and 930/911 Turbo to 1989.

Porsche 911 Bosch CDI replacement Classic Retrofit 1

Bosch CDI boxes grow old disgracefully, delivering deteriorating performance over the decades and eventually giving up the ghost completely: one reason I always carry a spare CDI box in my car on long trips. Most CDI alternatives require changes to wiring looms and few add modern features such as mappable second spark. Ageing low-end replacements like PermaTune have a bit of a reputation for sporadic reliability. Up to now, ignition units have not been a very exciting topic.

Developed by a Porsche enthusiast who uses his 911 SC every day, the CDI+ box brings passion to this previously mundane arena. This is apparent from the minute you take the unit in your hands, as CDI+ ships in a smart hand-made wooden presentation box which should be used to store your original ignition unit (the idea being that CDI+ always has a value and can be removed to transfer to another car should this one be sold). Installation is simple: Jonny reckons he can fit it to my orange 911 (below) in less than ten minutes, so we’ll test that with a vid for the Classic Retrofit Youtube channel.

Porsche 911 Carrera 1974 1976 Ferdinand Magazine

In back-to-back testing, Neil Bainbridge’s engine dyno proved the CDI+ ignition to deliver notable improvements to torque on a 2.7 RS engine and all users report the new ignition as making the car feel much more alive. “Of the 98,000 miles I have done in my 1969 Porsche 911S, the 160 miles to Goodwood and back today (with my new CDI+ box fitted) were possibly the most enjoyable I have ever had,” is how how one satisfied customer put it. I am very excited to visit Jonny’s man cave and try this on my car.

CDI+ is available to buy direct from Classic Retrofit or US users can get one from Pelican Parts. Jonny’s Porsche 911 replacement fuse panels have already gained recommended upgrade status from Wayne Dempsey, author of 101 Projects for your Porsche 911, with hundreds of satisfied customers benefitting from the increased reliability of the new Porsche fuse boards.

Here’s a video of CDI+ being dyno tested on a 68k-mile SC, with the improved power and torque curves below. I am always impressed by my talented friends!

Classic Retrofit Porsche 911 Bosch CDI replacement dyno chart

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