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Story by Michael Dennis

Appeared in Porsche Parade Magazine Winter 2009.

Any crucial equipment upgrade which involves non-factory modifications to our precious Porsches should only be considered after answering ‘yes’ to three questions - Is it necessary? Will it improve the driveability of my car? Is it the most cost-effective option? For owners of seventies and eighties Porsche 911’s the proposed upgrade ticks all these boxes. I am sharing my experience, both to alert you to a potential time bomb ticking away in your car and a viable solution. I wish to thank the technicians and suppliers mentioned for their assistance with the story, however I would also like to state at the outset that I have no commercial interest in this project.

THE ‘CDI’ PROBLEM: Capacitor-discharge ignition or ‘CDI’ is a solid state unit encased in a metal box somewhat larger than a cigarette packet, located on the left side panel of the engine compartment. Its function is to provide the actual ignition energy to the ignition coil. The Bosche CDI units in our mid-911’s employ technology from the seventies. While well engineered, between 20 and 35 years spent sharing a room with a hot flat six engine is causing them to fail, particularly if there is also a turbo in residence. When this occurs the car will stop without warning. Then, maybe five minutes or five hours later (or any random time frame), it may start and run for a day or a week before stopping again. This process can repeat itself ad nauseam, ruining your driving pleasure and leading to many a fruitless journey to your mechanic on a tray truck. The intermittent nature of the failure makes it hard to diagnose and equally frustrating for both owner and mechanic alike.


1. New Bosche CDI units (Part No. 930602702 00) once set you back just over $3,750 (inc GST), but as you might expect after all these years, were deleted from the Porsche catalogue some time ago. For the around the same price, Porsche Centre Melbourne offers exchange units with warranty (Part No. 930602702 X) ex-Germany. These can be ordered through their Spare Parts Division by phoning 9473 0917.

2. Reconditioned or second-hand Bosche units can be sourced through Porsche mechanics or parts dealers for between $500 and $1,000. They are hard to find and when you do it is a gamble – you either end up with a reasonable one or not. A unit I had installed failed within a year, leading to the dramas described above.

3. Aftermarket replacement CDI units are available for around $500, employ modern circuitry and come with manufacturers’ warranties. Their sensitivity to heat and moisture dictates that most must be positioned under the passenger seat, so there are additional costs in having an auto electrician fabricate a harness back to the engine compartment, plus a requirement to update the spark plug leads and the coil. I have heard about a US unit that clips straight into the original position, but reports indicate the engine environment affects both performance and reliability.


I decided on the third option and much research later settled on the ‘PRO-10’ under-the-seat CDI manufactured by an established Sydney company, M&W Ignitions. What impressed me was not only their claim to being the world’s premier builder of quality high energy ignition systems, their use of the latest CAD/CAM designed technology and their customer base in Formula 1, V8 Supercar, Daytona 24hr and Super Touring racing, but the fact that they supply special Porsche versions of the PRO-10 that replace the 3, 6 or 8 pin Bosche CDI units used on the 911. The general rule is 3 pin for engines less than 3 litres and 6 pin for engines 3 litres upwards (I believe the 8 pin CDI units are used on later model turbos). If you want to know more about M&W and the PRO-10, check out their website at


As we all know, before proceeding with such projects it is wise to talk to the people we trust with the wellbeing of our cars. After looking over the specifications, both Ben Faggeter at Weltmeister and independent auto electrics maestro Steve Varrasso both said it should work, but cautioned that I would be the first owner they knew of to fit the upgrade. I decided to ‘get in first’ before the next CDI failure drove me crazy. We mapped out how best to proceed, with Steve offering to collaborate on the project and devote the time required to explore the best installation options and sort any necessary technical modifications (hence the title of this story). Naturally you can use your own mechanic, but for the auto electrical stuff Steve has now acquired considerable expertise from actually completing a couple of installations (say no more). We also agreed that coordinating the upgrade with an annual service would save time and money, so here is how I went about it.


1. BOOK YOUR MECHANIC & AUTO ELEC - I phoned Ben Faggeter at Weltmeister on 9428 0662 and booked the car in for an annual service with a four-week lead-time. I requested that during the service Ben replace the ignition leads with new cables (to be supplied by me) and install a new ignition coil. I phoned Steve Varrasso on 9429 4988 and booked the car in for the CDI upgrade installation immediately following the annual service, alerting Steve that I would have the new CDI unit shipped to him well beforehand.

2. ORDER THE CDI – After determining whether I needed a 3, 6 or 8 pin unit (talk to your mechanic if you are not sure), I phoned Wayne Glasser at M&W in Sydney on (02) 9668 8481, ordered a 6 pin PRO-10 CDI and had it shipped to Steve Varrasso Auto Electrical, 23 Stephenson Street, Richmond, 3121. This set my credit card back around $575 (incl GST, freight and card fee).

3. ORDER THE IGNITION CABLES – I phoned Neil Fisher at Thundercord in Sydney on (02) 9604 9946 and ordered a set of Magnecor brand ignition leads with the necessary spiral wound inductively suppressed metal core. Neil has cable specifications for most 911’s and for this application offers either a standard 7mm set in black (which maintains the factory appearance) or an 8mm set in blue - check out their website at I chose the blue 8mm ‘Electrosports 80’ set and had it shipped to my local post office. My credit card charge for this was around $215 (incl GST, postage etc).

4. ORDER THE IGNITION COIL – When I booked the major service, I also asked Ben to replace the old ignition coil with a Bosche MEC 717 unit, which costs around $50 (incl GST). This coil handles the higher 450 volts that the PRO-10 operates at.

5. DROP THE CAR OFF FOR THE INSTALLATIONS – With a lot of the plumbing already removed from the engine for the service, Weltmeister installed the new cables I supplied and the new coil. The car was then delivered to Steve who made up a harness and installed the PRO-10 unit under the passenger seat. I won’t go into specific dollars here, but you are looking around an hour to install the cables and coil (it’s more complicated than you think) and Steve needs the car for a day for the auto electrical work, plus the cost of fabricating the electrical harness between the seat and the engine compartment. In my case, all this came to roughly $700.

6. LAZY BUGGER’S STEP – If you do not want to coordinate the project and order the parts yourself, I guess you can give Steve Varrasso the Auto Elec a call on 9429 4988. If you speak nicely to him he may arrange everything for you.


“So”, I hear you say, “Why should I outlay around $1,500 to replace something that is, well - still working?” Let us see - a modern high energy CDI unit that uses less current, more efficient ignition cables and a new coil - all for less than half the cost of a factory exchange unit. Then there is peace of mind from knowing you will never have to experience the ‘CDI failure blues’, your car will start first time every time and you have made some small gains in both performance and economy. How do I know? Well, I will let you in on a secret – the unit was installed way back in October 2007 and the car initially became more unreliable than ever! This nearly drove me insane and tested Steve Varrasso’s patience to the limit as he spent weeks looking for the electrical gremlin. In fact we shipped the PRO-10 CDI back to M&W in Sydney twice for lengthy bench testing sessions before a tiny flaw was finally detected in its circuitry. Wayne at M&W assured me that with hundreds of these units installed on Porsches in Sydney and the US, including the rare 959 owned by Bill Gates, a failure like this was unheard of (typically it seems, I just drew the short straw). With the unit back in my car by the start of 2008, I decided to give the PRO-10 the ‘mother of all product tests’ before I was prepared to recommend it to fellow members. Since that time, apart from everyday driving, the car has participated in 10 Club Sprint Days, 1 President’s Day and 10 Club Social Runs, including the demanding 2009 7-day Tassie Tour. During these 14 months the car has performed admirably and the PRO-10 never missed a beat. Oh yes, I nearly forgot – whether your old Bosche CDI is working or not, it is still worth at least a few hundred dollars from a Porsche used parts dealer, which helps to defray the cost of the exercise. Phone Stan Adler at Performance 9 on 9318 2848 or Dennis O’Keefe at aPorschaPart on 9587 5260 and haggle.


A ‘purist’ owner said to me recently, “Putting the CDI under the seat is a worry – the car is no longer original!” My answer was simple, “If it is good enough for Bill Gates’ master Porsche mechanic to stick one under the seat of Bill’s 959, it is good enough for my 930!” Humour aside, I know we are flirting with a recession and that $1,500 may be required for other priorities, in which case photocopy this article and stick it in your service book with a note “In case of CDI failure read this!” Despite the challenging economic environment however, you would be wise to consider getting a PRO-10 CDI installed sooner, before the old Bosche CDI gets you later!

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