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My Electric Boxster

Episode One: John Stonier picks the donor car for this electric car conversion project.

By John Stonier

Choices, choices. The first question I had to resolve -- after deciding I wanted to do an electric car conversion -- was which car to use.

Over the summer, after many months of considering a host of candidate cars, I made a decision and purchased a car. How I made that decision is the subject of this first installment.

In the course of my choice I put together a fairly complete list of possibilities of contemporary cars. I started my selection process with a list of objectives I wanted to achieve with this car.

To that criterion I collected information on a number of candidate cars and made some crude calculations using the dimensions and specifications available from various sources on the internet. As a primary ranking of the cars I was considering, I created a factor to approximate the efficiency with which the car moves through the air and the curb weight of the car. Right or wrong, I calculated the first factor by estimating frontal area by taking 70% of the width by height and then multiplying that by the coefficient of drag. I took that factor and multiplied by the curb weight, then dividing by 1000 to make the number range between 5 and 12. From that I ranked my candidate cars.

The Fourth criteria that I set for myself was simply this – what car would make me feel good to put a lot of effort (and money) into, and at the end of the day still be arguably worth the cost of all the inputs, and could also be considered a “show” car to raise the profile of EVs generally?

The fourth factor, for me, ruled out some very good and practical candidates for EV conversion. Among them was the Ford Probe that comes with a light chassis, leather upholstery and sporty features, excellent aerodynamics, and also a very low glider cost. While cruising Craig’s List (an excellent source for finding gliders) I came across the perfect situation – a 1993 car whose engine has died after years of faithful service - $500 obo. The other cars I liked for “show” car status included the Mini-Cooper, and the Nissan 350ZX, which also has an upscale cousin with essentially the same chassis and drive train – the Infinity G35 sport coupe. The Mini-Cooper was ruled out on spatial concerns for placing batteries, and its surprising heaviness for its size; and also – a horrible coefficient of drag.

I really liked the Nissan/Infinity options – both vehicles are rear wheel drive which provides the option for nestling a motor right into the transmission space if the proper final drive ratio can be obtained through the differential or through the insertion of a simple shifting 2 speed transmission inserted in the drive line. The issue for these cars was that their curb weight is approximately 600 pounds heavier than the Boxster.

After pondering all the criteria, I started test driving the Boxster, and it didn’t take long for me to feel satisfied with this choice, despite its pricey nature. The good thing about the Boxster is that it was launched in 1997, and since then has seen virtually no trim changes in the 10 years it has been in production. Thus my 1999 looks as up-to-date as new ones rolling off the lot today.

Before I leave the subject of candidate cars – one group of cars I didn’t consider where older models. Those didn’t meet my first criteria, but that doesn’t mean there aren’t some terrific candidates to choose from. Practically, many older cars can be found at bargain basement prices, and they are a natural for ground up conversions because many of the mechanical parts are now becoming difficult to find. One caveat you must watch is the amount of restorative work you need to do to the chassis and body to repair rust, dings and dents that may also come with such vintages. But there are some great classics that would and have made great electric conversions. Find one that was your favorite first car … and re-discover it!

Boxster Update
To date, I’ve removed the engine/transaxle and stainless steel exhaust system from the mid-engine compartment of the car. Early inspection and measurements show a very clean car underneath – no rust in this aluminum alloy chassis – and a number of opportunities to configure a drive line to mate the independent rear suspension axles (currently suspended by bungee cords to enable moving the car around at the moment). My (non-Porsche Dealer) Porsche mechanic estimated the engine/transaxle combination to be at least 800 lbs, which would bring my glider weight now down to the 2000 pound range prior to adding the new EV components. With the engine removed all other electrical devices apart from the engine appear to be working normally. Lights, hydraulic brakes, power windows, power top, radio, security, ventilation fans. I still have to confirm the status of a number of systems – I’ll report on this in future updates to this project.


Boxster engine compartment with gasoline engine removed

Next time – selection of components, sourcing key talent to assist with the various aspects of the project and some of the issues to be dealt with on the conversion.

John Stonier is a Chartered Accountant and EV enthusiast living in Vancouver, BC. He is a Director,and Spokesperson for the Vancouver Electric Vehicle Association and a Director of the BC Sustainable Energy Association. In his day job he is VP Finance of Day4 Energy Inc. a rising leader in photovoltaic products and technology.

Times Article Viewed: 35914
Published: 02-Oct-2007

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