Classic Retrofit CDI ignition for US BMW CSL race cars

Classic Retrofit has earned an enviable reputation developing modern ignition systems and replacement fuse panels for vintage Porsche 911s, but the UK-based Bosch CDI upgrade specialist has also used its expertise to improve the performance and reliability of many other classic sports cars.

The most recent examples were two classic BMW 3.0 CSLs, racing in the BMW centenary celebrations at Laguna Seca Raceway as part of the 2016 Monterey Motorsports Reunion. 

“Our first enquiry regarding Bosch CDI upgrades for BMW CSLs came from a satisfied Porsche specialist,” says Jonny Hart at Classic Retrofit. “BS Motorsport was about to run a newly-rebuilt CSL engine on an engine dyno in Florida and wanted to know if our CDI+ ignition unit could help deliver the same sort of power increase we typically see on old 911s. There was only one way to find out!

“We sent a unit to the dyno, where the test proved an increase in power using CDI+. No sooner had the test finished than we had a second CSL enquiry from America: this time from the team restoring the ex-Willi Martini BMW CSL for Monterey Historics. 

“With fresh dyno data to share, a deal was agreed. We sent another new CDI+ box out to the USA, only to receive a panic stricken call at the start of the Monterey weekend: a last-minute wiring error had damaged the unit and it was showing no signs of life. What could we do in the few hours available until first practice?

“Luckily, we have two US stockists within easy reach of Monterey. Lauren Beggs at 911 Design in Los Angeles had a replacement in stock, so that was sent to Laguna Seca later that day. The box was fitted the following morning without issue.

“While both cars performed well in practice, the Martini car did not race due to brake problems. Nevertheless, it was great to see pictures of the cars on track and satisfying to be involved with two great cars at such a famous event. Another box ticked for Classic Retrofit CDI+!”

Image by Erik Bonney: shared courtesy of