1983 Porsche 911 SC Targa

Thursday, June 6, 2013

Impressions of the First Drive

After the last battery cell was connected and the controller was programmed, I could barely contain my excitement as I lowered the car from the four jack stands where the car has been perched for the last year.  My dad was visiting from out of town and I was proud to show him firsthand the project I’ve been talking about for more than a decade.  I backed out of the driveway with anticipation.  The first thing I noticed was the 8 kHz hum of the controller.  The squeal is audible in my video of the first drive and quickly becomes fatiguing.  I put the transmission into 1st gear and pressed the accelerator and the car moved forward.  The response to the throttle was rather weak, but with the controller set to limit the motor to 100 Volts and 400 amps, there was only 53 horsepower on tap, a mere 25% of what will be available when the motor limits are increased to 170 volts and 1000 amps.  The motor brushes need a chance to seat properly before handling more power.  But I was moving under electric power and the vibration free propulsion of the electric motor was fantastic.  The clutch worked, the transmission was fine, there was no smoke from the batteries, even the homemade tachometer was driving the stock gauge in the dash, and a sense of relief that there were no major problems was replaced with satisfied pride that the car was finally in motion.  A dream was finally becoming reality.
In the front, the car is sitting about an inch lower with the extra weight of the batteries.  The tires rub the fenders when I go over any bumps in the road.  The solution will be to install stiffer torsion springs in the suspension.
The controller has a quiet mode that uses a higher frequency to pulse power to the motor.  Luckily quiet mode is appropriately named, and now the hum of the controller is not detectable.
I noticed that after a few short drives that the motor gets hot – about 130 degrees F (55 deg C).  I think this could be a reliability issue over time, so I will be ordering a blower to force air through the motor and reduce the temperature rise.  
There is still a lot to be done to finish the car, but driving the car for the first time under electric power is a huge thrill and motivator to keep going.


  1. Great job Joey, I now know the sound of the gearbox is half the sound of a 911 :-)

  2. Hi Joey,
    I've been watching your blog almost since the beginning. I've always wanted to convert a 911, and it's been fun watching you make steady progress towards our goal. I've very excited for you, congratulations!

    As a long-time VW/Porsche nut, you may have another option for ride height. On VW torsion suspensions, the ride height can be adjusted by rotating the torsion bars relative to the spring plates. It's a little tricky, but probably no more difficult than getting the adjustment correct with new torsion bars. Of course, this advice is for VWs, so maybe the Porsche setup is completely different. Just an idea....

    I hope to start my own conversion in the next year. Rising prices on 911s has pushed me towards 924/944, or even BMWs like older Z3s. I got to meet and hang out with Tim Catellier and his awesome Z3, so I know they're great cars for conversions. Wish me luck!

    Alex Vieira
    Colorado Springs

    1. Hi Alex. Thanks for saying hello. I followed other blogs, too (like Tim's) for a long time before starting my own project. Please let me know if you start a build thread when you start your project. I would enjoy following along. My alternate choices for a car were the 944 and the predecessor to the BMW 3 series, a car from the 1970s called the 2002. I really wanted RWD. Just pick something you like, and you will be happy.

      The suspenstion has similar adjustments for ride height to what you described. I maxed out the adjustment range and only gained half an inch. An improvement, but I might as well take the oppertunity to go with a stiffer setup.

  3. Congratulations Joey! The first drive in the history books and no major problems. Well done.

    There's one thing that caught my attention, and that's the paragraph about the motor and cooling. When I was at EVCCON last year, I had a chance to talk with George Hamstra of Netgain Motors about cooling, and it was quite enlightening.

    Prior to that trip, I typically drove around town in 4th gear with the motor spinning at about 2250 RPM. But George stressed the importance of cooling and he explained that the fan in the back of the motor should be spinning far faster so that it sucks as much air as possible through the motor. He recommended that I keep the RPM above 3000, and preferably above 3500.

    The higher motor speed accomplishes three things. First, more air through the motor equals better cooling and second it helps to blow out the carbon dust produced by the brushes, preventing it from building up in the motor. The second item there is arguably the most important. The third thing is that the motor is slightly more efficient in that RPM range, though truthfully, I think the difference so slight I cant really see or measure it.

    So now, it's 3rd gear on the surface streets, and 4th on the freeway instead of 5th.

    Adding a fan is not only a great idea, I think it's perhaps the single best thing you can do to preserve and protect your motor. It will keep the motor cool AND blow out that carbon dust. George recommended a fan with over 160 CFM output. "Bigger IS better" to quote him.

    BTW, Christophe's first comment was insightful. You'll be surprised at how many things you hear in the car now; things that used to be masked by the sound of the ICE. You'll forever be hearing creaks and groans and thinking "wait, is that normal?"

    Well done!

    Tim Catellier

  4. Hi Tim, I am trying to keep the RPM above 3000. I start in 2nd and keep it there until about 40 MPH (4200 RPM). I shift to 3rd and it drops to 3000 RPM. I haven't had it above 55 MPH yet. I'm still trying to baby the brushes for as long as I can. I am so tempted to bump the current limit up and see what it will do. At 60% it has similar power feel to my ICE (Honda Accord). I'm going to get a force air blower installed.