Electric Porsche 944

Driving the Porsche 914

by on Aug.12, 2015, under Electric Car

ElectraFest 2015 was a great show, lots of interesting people and nice cars.  The majority of vehicles were OEM’s but there was a handful of conversions at the show.  The single most attractive feature that most people found with the 914 was the 200+km range.  This seems to be a mental threshold where all but a few people said “That would work for me.”  My 944 with 100+km range doesn’t get the same response with probably 50% of people saying that’s not quite enough.

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The lead up to the show was hectic and we actually left at the last minute not giving us much extra time.  The 914 is an old car and as I found out not all of the grounds are good.  I had reused a factory ground point for the inverter wiring and this turned out to be an issue.  I wasn’t getting a good enough ground for the inverter to call it “ground”, it was close but not close enough.  This caused the inverter to boot up, but the signal inputs (mostly grounded/floating) weren’t registering correctly meaning the inverter wouldn’t fully turn on.  This took hours of troubleshooting and wondering if something in the inverter itself had failed.  In the end I ran dedicated ground wires and all the problems went away.  The car runs great and after some software tuning the regen/shifting and throttle feel pretty good.  The potentiometer on the brake pedal gives a nice feeling of power brakes with the adjustable regen on the completely mechanical brake system of the 914.  The regen disable signal runs through both the clutch pedal microswitch and the center console regen disable switch.  There is a small amount of regen dialed into the throttle pedal when fully released to mimic engine braking.  When the clutch pedal is pressed it disables regen from the off throttle position and/or regen based on the brake pedal.  This makes shifting easy and the car is quite fun to run through the gears.  Starting in 2nd it feels really good with plenty of torque and is easy to shift to 3rd and beyond.  1st and reverse aren’t really needed, which is okay as they are somewhat segregated in the transmission requiring a firm push to the left against a spring plate to engage them.  2nd gear is good for forward or reverse using the electric forward/reverse switch in the center console.

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The cooling system is installed and being evaluated for both size and effectiveness, the Siemens Inverter seems to produce more heat than my DMOC645, but it does have a built in DC/DC converter as well.  The overkill cooling system in my 944 has a temperature rise of 3 degrees C over a 30-40 minute drive, depending on ambient temperature 10-20C is perfectly acceptable in the 914, however driving at highway speeds for more than an hour will have to stay within the thermal limits of the Inverter.  The pump and a single low speed fan run all the time, there are two higher speed and higher power fans that will be controlled by the Inverters fan output to assist in cooling when required.

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The stereo has been updated with a Bluetooth capable media player that can connect either to the tablet in the center console or a smart phone to easily accept phone calls and stream music.  The front factory speakers are in the kick panels which is close to the ideal location in most vehicles as far as imaging goes.  The aiming isn’t perfect but it’s not bad and works better than most door locations.  The problems came in the speaker mounting, the aftermarket coaxial speakers have a protruding tweeter that doesn’t allow the speaker to sit flush with the housing and mount the way the factory speaker would have.  Because of this the front and rear wave weren’t isolated so there was ZERO bass.  The solution to this was to design and 3D print speaker spacers that allowed the speaker to be sealed to the front of the enclosure as they were meant to be.  The sound is much better, but only as good as a 4×6″ speaker can be, I’ll do some testing with a small and lightweight subwoofer to augment the low end.

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The 3D printed spacer is visible through the grill and surrounding the speaker, printing in black ABS blends the part with the existing plastic housing.

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The Tachometer is connected and working properly, the existing set up was for the Porsche 928 which had a V8, the 914 was a 4 cylinder car so the output pulse count had to be adjusted.  This wasn’t too difficult to find in the software, F_out_Factor lets you change the pulses per revolution which was set to 4 for the V8 and needed to be changed to 2 for the 4 cylinder (2 pulses per revolution).  Although not completely intuitive the Siemens software is quite flexible and allows most important parameters to be adjusted easily.

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The dash and door panels had a few cracks from age (what car from the 70’s or 80’s doesn’t have a cracked dash?)  This is now a thing of the past and now looks quite exceptional thanks to a vinyl repair shop, they did some amazing work, recovering the tops of the door panels and fixing up the dash.  The car looks so good now I’m probably going to get a quote from them to fix my 944 dash, it has a couple of similar small cracks.  Between that and a new windshield my 944 can have a similar facelift.

Before:

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After:

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We’ve had the car out to a few shows now and the response is overwhelmingly positive, and the more I drive the car the more I love it.  It’s still a bit quirky, it is of course still a 1972 Porsche 914, but the driving experience is tough to beat!  Remove the top and cruise around on a sunny day and the EV grin multiplies.  The Siemens power system is perfect for a car this size and weight, there is plenty of torque and it accelerates very nicely, it cruises smooth and quiet and is simply a joy to drive once you get the hang of that 1972 gear box.  Yes it does take a little bit to get use to, it’s not quite the same as a modern manual transmission however it does work very well and shifts smoothly when you get the hang of it and where the gears are located.

The Porsche 914 next to it’s modern equivalent the 2010 Tesla Roadster!

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The to do list is getting shorter and shorter and the car is driving better and better every day.  It won’t be long till it’s ready for someone else to enjoy this beauty every day.

 

 


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