Electric Porsche – I can’t drive but I have A/C!

Since the coupler is on it’s way back for some rework with Charlie at evcouplerconnection the car is stationary, but I’ve been doing some testing with the Soliton1 off a ~50v battery pack.  I have the tach sensor hooked up and working (including rev limiter), I even tried the idle function in the Soliton, and it works very well, makes A/C testing a breeze (no pun intended).  After a few trips back and forth to the auto parts store I have my new A/C belt, it’s a goodyear gatorback “the quiet belt”.  Hopefully it lives up to it’s name.  The A/C compressor is mounted and working very well, and if my measurements are correct I should be able to leave the A/C compressor connected to the motor when I move it ahead to reinstall the coupler, making for fairly easy serviceability. I tested the vacuum pump, and although it’s pretty quiet it still makes some noise, I may or  may not put it in some sort of enclosure to reduce the noise a bit more.

Machining the A/C bracket:

 

As I test fit the Soliton1 mounting location I’ve decided to use more of the Bosch Rexroth extrusion because it’s so easy to work with, and also easy to mount accessories to.  A couple of years ago I built my CNC router almost entirely out of Bosch extrusion with very good results and very good reliability in a high vibration environment.

 

This happens to be the machine that I used to mill/engrave the motor mounting plate, A/C bracket, and the recently completed frame rail brackets to finish the motor mount setup.

The beauty of the t-slots and t-nuts that go in them is you can adjust and move the mounting location of something without leaving ugly holes behind.  So items are easily adjustable and movable/removable all with what amounts to built in lock washers everywhere.  There is a slight taper on the extrusion in the t-slot area so when a t-nut is tightened the extrusion acts like a spring (lock) washer.  Also being extruded aluminum it’s lightweight and very strong.   Pictures to follow next update.

 

I haven’t done any video on my blog because there simply wasn’t anything that a picture couldn’t capture.  Well the Warp11HV powering the stock Porsche A/C compressor is one of the first things that actually moves so it gets my first very lame video.

 

I did some testing on power usage of the A/C system vs the power to idle the motor.  With the A/C off, it takes about 250watts to idle the motor at 1000rpm, with the A/C on it took about 1300watts to run the motor, so all things being equal the A/C requires about 1050watts at 1000rpm (1.4hp plus a bit extra for the power used on the 12v side)  Not unreasonable for a car that will peak at about 270,000watts (362 electrical hp).   Sometimes it’s the smallest parts that take the most time.  Ever since my Evnetics hall effect throttle arrived, I’ve been wondering how I was going to attach my Porsche throttle cable to it.  I contemplated trying to find a way to attach the stock throttle cam onto the Evnetics throttle, but that didn’t seem appealing.  I thought of cutting off the stopper on the end of the cable and crimping on some sort of ring terminal that would attach to the Evnetics throttle arm.  I just wasn’t happy with any of these ideas, I simply wanted the stock throttle cable to attach to the throttle arm and be done with it.  Well it turns out that is easier said than done.

There is no question the Evnetics throttle is a nice unit, but the end user is left to come up with a solution on how to make it work with their vehicle.

This is one of those times that the CNC router shines.  I spent a couple of hours coming up with a simple design and making up the CAD/CAM files that would turn that idea into a real part (two parts actually, almost identical top and bottom).

The scrap piece of aluminum I was using was big enough to make three pieces, I did this just in case I messed one up, and sure enough I did mess one up, but still had two good ones that got used.

The final result is simple, and the machined aluminum matches the Evnetics throttle nicely.  Although it took 3-4 hours to simply hook the throttle cable up it’s something that I should never have to deal with again.

Since the car is stationary it’s a good time to do one of the last big jobs that I’ve been putting off.  Drop the transmission, remove the fuel tank, upgrade the transmission mount and install a set of locking CV bolts from Stage 8.  With a hoist and transmission jack this would be an easy task, however with a single garage and jack stands it takes a bit more work.  The transmission is out, but I’m too tired to take pictures, more updates to follow.

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