Electric Car Electric Porsche 944

9 Июн 2014 | Author: | Комментарии к записи Electric Car Electric Porsche 944 отключены
Porsche Electric Cars

Electric Car

A New Direction

From the start of this build there have been countless changes, and with the exception of the donor car every single component has been revised/updated/eliminated due to testing/learning or simply something new becoming available that just didn t exist earlier in the build.

I absolutely love the Warp 11HV and Soliton1 together, the torque is incredible and the car does 0-60 in 4.8 seconds.  I absolutely hate the brushes and brush dust in the 11HV.  (And the fact my 11HV requires repair/cleaning)   For this reason I finally have to agree with the OEM s that some type of brushless motor is required for a daily driven, low maintenance EV.  The series DC motors still have a place right now simply because there are no high power AC systems available to the DIYer at a reasonable price.

When Azure Dynamics went bankrupt last year I picked up a DMOC 645 AC Inverter as well as an AC24LS AC Induction motor.  I never really had a plan for the set, however the AC24LS would never be able to give me the performance I m looking for in the 944 without burning it up.  The motor that Azure Dynamics paired with the DMOC 645 was the Siemens 1PV5135 4WS14, an abnormally low voltage version of the typical Siemens AC Induction traction motor.

 This motor should give me decent performance for daily driving.  I won t have the 290-300ft-lbs of torque that I got from the 11HV but a more modest 220ft-lbs is still well above what the stock engine could produce.  The Siemens motor also rev s much higher, there is good power out to 7500rpm, and usable power all the way to 10,000rpm.

 I m not sure how well the stock 944 Turbo transmission would like 10,000rpm on the input shaft, so limiting it to 7500 should keep things safe.

A new motor means a new adapter plate and coupler.  As it turns out the length of the existing adapter plate is pretty close to ideal, I m going to add a 1/2 aluminium plate that will adapt from the 11HV bolt pattern to the Siemens bolt pattern.  The Siemens motor is slightly shorter than the Warp so the extra 1/2 does no harm.

 The coupler will be much simpler, smaller and cheaper.  There is a steel coupler available that normally mates either the Siemens motor or a Remy motor to the Borg Warner single speed gearbox used by Azure Dynamics (and others).  This coupler is only $72US, mine is in transit but apparently it s a good quality coupler.

 This is only half of the solution though, I can now mate to the splines on the Siemens motor, however the 944 input shaft uses a different splined shaft.  For this I am using the center portion of a stock 944 Turbo clutch disc.

After grinding off the flange that normally attaches to the rest of the clutch I m left with this small splined piece of steel.

The Siemens side of things is similar though a bit longer.  (image from the Vaxo website, click HERE to see more info from Vaxo)

The Siemens coupler is 40mm in diameter, the 944 clutch center is also 40mm in diameter.  I still need a pilot bearing, or to be more precise a piece to align the pilot shaft on the 944 input shaft, it doesn t need to turn as both shafts will be permanently connected.  I don t have a lathe, however I ve been able to get good results using my CNC mill to make round parts.

Above is the aluminium piece that I milled from flat scrap.  It has a 15.15mm ID hole for the pilot shaft to align.  It has a stepped OD, one size matching the ID of the clutch center and the other matching the ID of the Siemens coupler.  This piece will be used for alignment of the steel sections during welding and remain inside as the pilot bearing .

 It will also serve as a stop so that the coupler can not work it s way off of the Siemens motor and along the splined section of the 944 input shaft.

The two pieces fit together nicely, it s not quite as precise as could be done on a lathe, it would probably be better if there was a slight interference fit.  One day I ll get a mini lathe to go along with the CNC mill.

The DMOC 645 also has some challenges, it s CAN bus controlled meaning you can t simply attach a throttle and other things to it directly.  There are a number of VCU s in development from various people.  My favorite is in the final stages of development by Wolftronix.  This is a guy who is very familiar with both electric vehicles as well as Azure Dynamics/Solectria and because of this I believe his product will be the best first generation product out there.

 Others will play catch up and likely incorporate some of  the features that come out in his first product.

The above image is from the Wolftronix website and I suggest you check it out for more information.

The Siemens motor is also on route, it was purchased from Steve thanks Steve.  This picture is from his for sale listing and may or may not be the actual motor I m getting, he had purchased a lot (10?) motors from the Azure Dynamics auction.

If I didn t already have a DMOC I likely would have just purchased the pair from Jack at EVTV, I think his combo price is quite fair considering he includes the required cables/connectors to connect the motor/controller as well as the main IO for the DMOC itself.  I would also suspect the connector for the GEVCU will be included when that is available as well.  Jack is also working with various groups on their versions of the GEVCU, I m sure they will all catch up eventually but the feature set in the first generation Wolftronix is what I believe to be the best solution right now.

 Jacks price on a single item is less attractive and I m not sure if he would include any cables when only buying one piece.


In some respects this change could be considered an upgrade I ll have a water cooled maintenance free motor with regenerative braking.  Those are all significant pluses!  There is however a negative or downgrade .  The peak power of this system is rated at 118kw, the peak power of my Warp 11HV/Soliton1 right now is around 200kw, and could be higher when the remaining CALB cells are installed.

 I have no doubt that the system will still provide an exceptional driving experience, but it won t be a sub 5 second 0-60 car any longer.


I have more cells to install anyway, so range goes up, with the regenerative braking I will probably get a tiny bit more range.  I live on a bit of a hill so I should be able to recapture some energy on the way down instead of heating up my brakes.  More than anything, my peak power will be lower, which to a certain extent limits the amount of energy I can burn accelerating away from a stop sign or light.  With all of these factors combined I expect my Wh/mile to drop from 300-325 down to 275-300, not a significant difference but still a difference.  The DMOC also has a higher input voltage range, instead of 350v max like the Soliton1 it has a 450v max rating.

 It s nominal cell count is 105 where the Soliton1 s max cell count is 100.

I will have 100 cells once I add in my remaining CALB s, I also have a few more A123 s that could be installed if I have the room.  Each cell adds around 1km of driving range and I could easily go up to 110 or 115 cells providing I have the space to mount them efficiently, it s never been an option so I ve never actually looked into it.

Another small but interesting fact is my 944 will once again have a water cooled german motor.

It may be one of the hottest days of the year but I have heat!!

I ve had a bunch of posts over the years talking about heaters, some of them were planning, some were installing, some were testing, some were blowing up heaters.  I ve finally planned, installed and tested what I hope to be the final version of my 944 heating system.  Surplus components from Think EV s when they switched from the Mes-Dea RM3 fluid heaters to a ceramic or other PTC heater.

 The combo includes a 200-450v RM3 heater along with a high quality bosch pump.  During the removal at Think the HV power wires had been trimmed rather short.  These wires were replaced in a previous post, ready for installation.

New wires above, heater installed below.

Like most other systems in the car, it s very important to me to retain the stock look/feel/function of the original Porsche system.  I ve talked about it before, but a big thing for me was to NOT have a dedicated non factory switch to turn on the heater.  Some people have an aftermarket switch with some sort of label saying heater , this just doesn t do it for me.

 In the stock heating system there is a temperature dial, it s blue on one end, red on the other, and has numerical values in between.  The most intuitive method of turning on the heat would be to turn this knob from blue to red or some value between, we can all figure this out if we get into a new vehicle that we ve never driven before.  Why should it be any different in my EV?

 In addition to simple operation I also wanted to maintain the automatic climate controls that Porsche was using in 1986.  It s a simple system, it s mainly vacuum operated based on some simple analog electronics.  To make this happen I installed two microswitches, one in the heater control itself, it s basically a NC (normally closed) switch that only activates (opens) in the cold position on the temperature dial.

 The second switch was installed on the vacuum operated coolant valve that would normally restrict the flow of coolant from the engine.  I don t actually use this valve to restrict coolant flow, but the microswitch serves to turn off the heater.

The vacuum valve with added micro switch, and installed view below.

I haven t found a good program to create schematics but the system is quite simple:

Switched ignition +12v is connected to the NC microswitch on the temperature dial.  In any position above blue (cold) this switch applies power to a 12v relay which turns on the pump that circulates roughly 2L of coolant through the 4kW heater and stock heater core.  The same 12v out of the relay that powers the pump then goes to the 2nd microswitch connected to the vacuum valve that would normally limit coolant flow.  If the cabin temperature is lower than the temperature setting on the dial the valve is open and the NC microswitch applies power to the 12v terminal on the heater.  If the cabin temperature rises above the preset value the vacuum valve closes turning off the switch and removing 12v power to the heater.

 The heater itself also has built in thermal limits that attempts to heat the coolant to 70 degrees celsius.  Any of these various systems will turn off the heater which should reduce the amount of power wasted creating excess heat and allow me to dial in the amount of heat I need or want while driving.

With a 4000watt heater the draw on the main pack is 12-13A while it s on .  Only time will tell as to what kind of duty cycle I will end up with as the portion of time the heater is on vs off.  This duty cycle which will vary both with ambient temperature and the desired amount of heat and will ultimately determine the impact it has on my range.

I was going to make a short video on the operation and the various systems that control the heater however the ambient temperature this afternoon is too hot for the heater to even turn on.  There will be plenty of chances to do so in the coming months as the temperatures drop.  We have had some chilly mornings so time permitting I will demonstrate the system in action soon.

I still need to create some sort of indicator to make sure I know the heater is on and don t have it on needlessly wasting power if it s not required.

A weeks work on a lot of little (and big) things

I took a week of vacation to get some dedicated time to work on the car, I stayed busy the whole time and ticked a lot of check boxes off the to do list.  I also tackled a few things that weren t on the list and didn t imagine doing, but they are done and the car is better for it.

The week started with the manual steering rack, it turned out being a very simple and straight forward swap with no issues.  Since I had to remove the leaky rack I was up to my elbows in oily sludge which brought to my attention I was never able to pressure wash the motor bay before the install began years ago.

The other very significant difference between removing the rack from the 83 gas powered 944 and installing it on my 86 electric 944 is the access to all of the parts, I had plenty of room to work with easy access to where I needed to bolt things up vs the incredibly tight dirty and awkward process in the gas car.

Since the 83 is now just a parts car I ve started looking at pieces that I replaced to get it on the road for my wife, as well as parts that are still in great shape that can either be sold or kept as spares for my own use.  Since I had recently replaced the front strut inserts on the 83 and mine was in need I swapped the entire strut assemblies to the EV.  They are missing a couple of small clips that hold the brake wear sensor wiring but a zip tie took care of that.  The other good thing is that if I decide to buy performance struts and an adjustable spring kit I can install it on the original strut assemblies and then install the completed units back on the EV which could reduce down time.  (See how old this update is I already have the new Koni suspension installed)

After solving the dc/dc converter fan noise issue, the next loudest item in the car is the vacuum pump for the brake booster and hvac vents.  To solve this (or at least reduce it s annoyance factor) I milled a new mounting bracket that made use of the included rubber mounts on the vacuum pump as well as one of the unused motor mounts still in the car.

This new mount has significantly reduced both the vibration and noise created by the pump, but not eliminated it.

Porsche Electric Cars

One of the big things on the to do list was installing the heater.  Initially I had hoped to install it in an insulated box however the shape of the space I had to work with along with reduced serviceability forced me to reconsider.  Instead the heater is mounted out in the open on some simple brackets but I should be able to insulate the hoses/reservoir to hold in some heat.

Once again I was going to take some pictures to complete this post, but now it s getting old.

The heater is completely wired and integrated with the stock controls.  I would like to make some sort of indicator light to show that the heater is on however I m not sure where I would like that or how it should look.  Ideally it would be an indicator on the tablet and not require drilling a hole in the dash for an LED or something.

I also decided on the Momo Tuner 350mm steering wheel, again pictures needed!  The wheel is awesome and I found it for a very good price.  I was able to take the steering wheel adapter off of the 83 and modify it to work with the late steering column.

 The tab that kicks off the turn signal when the wheel returns to center is too short on the early version, otherwise it s exactly the same.  I used epoxy and a metal bar to extend it far enough to work properly again.

At the moment I m driving the Infiniti again, (not by choice) I had a Desaturation fault in the controller, so it s back at Evnetics getting repaired.  The people at Evnetics have been incredibly helpful and quick to respond to the problem.  I received an email back within 15 minutes on a Saturday when this happened.

 More info to come.

Gear ratio s and a possible transmission swap

When starting an electric conversion it s tough to know exactly what gear ratio will perform the best and feel the best when driving.  I was happy that my car had the turbo transmission installed since it would handle the extra torque from the 11 motor, however I really didn t know what the ideal gear ratio would be, but having a free box with 5 to choose from is a good start.

After driving the car for awhile on 300v I ve come to the conclusion that my ideal ratio wasn t included.  The car does drive beautifully and it s quite quick, however I wouldn t mind a few slightly shorter gears to choose from.

First gear is too short (too high a ratio) and 2nd is pretty close to ideal but could be a bit shorter for low speed driving and fun acceleration.  3rd gear is also close to ideal but is a bit tall for a 0-60mph run or spirited but not high speed driving.  What I feel might be ideal is a 2.5 gear, with a ratio about halfway in between my existing 2nd and 3rd gear.  As it turns out Porsche did make that transmission, it s has the tough internals like the turbo transmission to handle the hp and torque that I have, but has my desired 2.5 gear.

 It came in the later 944 s namely the 944S and S2.  It also has a 2nd gear that s shorter than my 2nd gear and would provide slightly better acceleration without being too short like my existing 1st gear which is too far in that extreme.

944 Turbo

1st 11.81    34.5mph @ 5500rpm

2nd 6.949 58.5mph @ 5500rpm

3rd 4.725 60mph @ 3830rpm

4th 3.490 60mph @ 2830rpm

5th 2.798 60mph @ 2268rpm (top speed 5500rpm 145.5mph)

As you can see from the above speed vs rpm vs gear ratio my existing 2nd gear is almost perfect for a 0-60 run, of course I would accelerate through 60 for the best time which puts the motor slightly above the recommended maximum RPM.  So for a safe 0-60 acceleration I need to use 3rd gear, which is a bit tall.

944 S2

1st 13.56    30mph @ 5500rpm

2nd 7.979 51mph @ 5500rpm

3rd 5.425  60mph @ 4400rpm

4th 4.007 60mph @ 3250rpm

The S2 info is above, and as you can see a 0-60 run in 3rd gear would take me to 4400rpm which happens to be around where the power starts to taper off anyway.  4th gear would also provide a nice RPM for highway cruising keeping the fan speed fairly high for good cooling.

I have many other things to work on first, but I ll keep my eyes open for a good used S2 transmission for a future swap.

In the mean time back to suspension and motor updates!

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