# Porsche 912E. Twin AC motors!



## Farfle (Jan 16, 2011)

Heya all, long time lurker here, with a few racing E-motorcycles under my belt over on Elmoto and endless-sphere. Team Farfle Racing

Anywho, my boss is converting a Porsche 912E. The car is in very usable, but not exactly pretty condition. The trans is in good shape, its got disk brakes and some mostly shagged yoko sport tires on all four corners. Paint is falling off, and the unibody needed some cut-and-patch near the front suspension member on the passenger front.

Here are the components going in:

Motors: AC24LS X2 re-terminated to delta

Controllers: Curtis 108V 550A x2

Batteries: 12s 3p Nissan battery modules. (technically 24s6p as each module is 2s2p of 30ah 4C NMC cells)

Drivetrain: Gates belt, 8mm pitch 40mm width.

Hopefully we should be able to make 80hp and hit triple digits. Its a nice slippery car, and we will be keeping the 4 speed trans. 


Here are some pics of the current progress:








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## Arlo (Dec 27, 2009)

I'M excited to see how this works out for you man.


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## steven4601 (Nov 11, 2010)

Looks tempting, but do you really want kind of mass that high above the wheels/axles?


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## Farfle (Jan 16, 2011)

steven4601 said:


> Looks tempting, but do you really want kind of mass that high above the wheels/axles?


The new motor plates bring both of them down to the level of the trans, and about 12" apart. The belt takes somewhat of a Z shape. Ill post up some cad files tomorrow.


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## MalcolmB (Jun 10, 2008)

Hi Farfle

This looks really interesting. I've been playing around with ideas for twin motors as well (DC in my case), so I'd love to see more photos. 

Shaft alignment and belt tensioning are obviously vital with a belt drive. I can't quite see from the photos how your arrangement works. You show two plates in the first photo. Will the outer plate carry outboard bearings to give additional support for the shafts. Does the belt run between the two plates? Is there a belt tensioner between the two motors?


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## Farfle (Jan 16, 2011)

Here is a better shot of how the setup will work, there are two plates, and each thru-shaft (motors and tranny) will have two bearings, one on each plate. 

We made some more progress, and most of the electric bits have arrived!


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## Farfle (Jan 16, 2011)

Finding the weight bias, looks like we will be able to keep the entire battery under the hood!


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## RIPPERTON (Jan 26, 2010)

With that much grunt you could have left the gearbox and diff out and belted each motor straight to each half shaft.
A bit like my Mira


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## Farfle (Jan 16, 2011)

RIPPERTON said:


> With that much grunt you could have left the gearbox and diff out and belted each motor straight to each half shaft.
> A bit like my Mira



Was thinking about it, but a 100mph gear, and a gear to get the rear end loose at 15mph aren't going to happen at the same time. 


Speaking of belts. We got parts! the belt is 8x30mm, and we have a 50t pulley for the trans, and two 30t pulleys for the motors.


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## Farfle (Jan 16, 2011)

Woo! The battery pack is assembled, and mounted. 88.8v nominal at 180Ah! Whole pack with buss bars and end plates is 221lbs! Fits like a glove in the gas-tank/spare tire area. That's only 16 lbs heavier than the full tank, spare tire and fuel pump that normally live there 

There will be a steel mesh screen that goes over the hole in the bottom to encourage airflow.


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## palmer_md (Jul 22, 2011)

Leaf pack? its starting to look like something.


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## Farfle (Jan 16, 2011)

Things have been rolling along quickly the past week until we found ourselves looking for a clutch to steal the splined bit off of for a motor shaft adapter. After giving up finding a used one (been casually searching for months), I was planning on ordering a brand-new clutch tonight ($300 :evil: ), BUT while removing the clutch depresser-arm-thingy today, I noticed it was splined... lo and behold, Its the same spline!! and a sturdy forging to boot!    . Probably going to buy a lottery ticket tonight.


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## DavidDymaxion (Dec 1, 2008)

I'm loving it! I have a 1977 Porsche 911 electric, down for lithium and motor installation that is taking forever! You can see it at http://ExplodingDinosaurs.com

Some of my comments:


Are you going to be pulling hard upwards on the tranny input shaft? I don't know how well the Porsche tranny input shaft will take to side loads. In the stock car all the tranny received was twisting force (torque), and a little bit of side load from the weight of the shaft, bumps, and cornering forces. How much tension do you need on the belt, and how does that compare to the weight of the shaft?
If the motors were on either side of the tranny shaft it would take 2 belts and two pulleys, but side forces would mostly cancel.
Thumbs up on keeping the tranny!
The stock clutch will likely slip. I used a Kennedy Engineering products pressure plate with triple the clamping force – no slip there! I am worried about the clutch cable and mechanism holding. The stock clutch cable broke but the replacement one has been holding up so far. If I were to do it again I would consider a racing clutch disk (like a copper one that you can't slip) or a small diameter multi-disk racing setup. Even with only 80 hp you'll have about double the torque of the stock 912 motor.

 Please keep the updates coming, this is exciting stuff!


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## Farfle (Jan 16, 2011)

We actually had a change of plans on the motor end of things. The AZD AC24LS motors will not make the horsepower we are looking for, (19hp per motor with the controllers we have) So we opted for a twin AC35, which is two AC35 motors in one can.
The end result of that is that we get much more horsepower, and lower motor heat. (with the 138v 650a controllers it is making almost 140HP ) ours are only 108v 550A controllers, so our motors should be making around 115ish hp between the two of them. Definitely enough to get into the triple digits club though.  . 

The guys on the 912 registry say that the trans can take the 257 ft/lb of torque this motor makes, but we will need to lock it out of first gear, because its making some insane 3600ft/lb of half-shaft snapping torque in 1st, and it will destroy the ring-and-pinion. with a 24" od tire, thats a 1.4 to 1 thrust to weight in 1st gear


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## Farfle (Jan 16, 2011)

I got the motor adapter and mount plates done up today. I figured a short video is better than a butt-load of pictures, so here ya go! More bracing yet to do, as the rear of the motor will be supported, and between the two supports will be the trays for the two controllers.


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## corbin (Apr 6, 2010)

Farfle said:


> I got the motor adapter and mount plates done up today. I figured a short video is better than a butt-load of pictures, so here ya go! More bracing yet to do, as the rear of the motor will be supported, and between the two supports will be the trays for the two controllers.


Cool project! I noticed you say Nissan batteries. Where did you get those out of? Pull them from a wrecked leaf? Are you going to have a BMS or anything of that sort in them? What type of C rating can they supply?

corbin


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## Farfle (Jan 16, 2011)

Made more progress today! Controllers are mounted, rear motor mount is done and the pot box is hooked to the throttle.


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## fb_bf (Jul 6, 2011)

WOW! Just WOW!. I want to see how it works. That is an amazing build so far. 

Frank


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## Bowser330 (Jun 15, 2008)

Really cool build and using the HPEVS AC35x2!!! 

PLEASE keep up posted with your updates.


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## Farfle (Jan 16, 2011)

The Porsche has moved from my shop to the bike shop, where all the final wiring will happen. There is a ton of wiring to do, but I was able to get both controllers programming taps to work, and was able to communicate with them  ancake: hopfully we will have at least one motor spinning today, we still need the encoder optoisolator to get the slave controller running, so we will be at 1/2 power.


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## JRP3 (Mar 7, 2008)

Farfle said:


> we still need the encoder optoisolator to get the slave controller running


It didn't come with one?


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## Farfle (Jan 16, 2011)

JRP3 said:


> It didn't come with one?


We ordered the motor separately from the harness, so there was a lil mixup. That being said, we got it running on one motor and WOOOOOOOOOOOT!!!! The 912 went for a frankendrive today! As per the norm, it was dark, snowing and foggy, there were no headlights, wipers or defrost. And there were burnouts involved.

It does straightline burnouts in 1st gear, AND WE ONLY HAVE ONE OF TWO MOTORS RUNNING!!! Needless to say, we were pretty stoked.


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## onegreenev (May 18, 2012)

Im interested in the battery pack. Looks great. Might not get as much life as you might like unless you got them for a real deal. Something I am looking to buy for my Porsche 914.


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## onegreenev (May 18, 2012)

I say that because my Leaf is not doing as well as I'd expected after only two years of driving. Its at the dealer right now for a serious checkup. Even with it being cold it should be doing better. Had I used any heat going to the dealer today I would not have made it and its only 43 miles away. Thats driving at 56 mph and no heat. Arrrrg.


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## Farfle (Jan 16, 2011)

onegreenev said:


> I say that because my Leaf is not doing as well as I'd expected after only two years of driving. Its at the dealer right now for a serious checkup. Even with it being cold it should be doing better. Had I used any heat going to the dealer today I would not have made it and its only 43 miles away. Thats driving at 56 mph and no heat. Arrrrg.



We only need it for super short trips, and sub 15 miles at racetrack pace. From what I have seen so far, the voltage sag has been absolutely minimal. At half amperage (550A) we saw a drop from 96v to 93.1 with 180ah. And that is with almost 12 feet of 00 cable, two connections and a contactor connecting it, the cable of which has a drop of 1v all on its own.


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## onegreenev (May 18, 2012)

Very nice. Excellent information to have. Mine will be mostly for shorter distances but I would use it for commuting for awhile. I will report on what the dealer says when I find out whats happening. 

Pete 

Did you take each metal can apart and re-configure the cells within?


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## Farfle (Jan 16, 2011)

onegreenev said:


> Very nice. Excellent information to have. Mine will be mostly for shorter distances but I would use it for commuting for awhile. I will report on what the dealer says when I find out whats happening.
> 
> Pete
> 
> Did you take each metal can apart and re-configure the cells within?


No, we left the modules in their stock 2s2p config. The pack is 24s6p of cells, or 12s3p of modules


And one more thing, these are cells from a 2013 leaf with 612 miles on it. (It was T-boned by a lifted F-350 at an intersection, car totaled, batteries unscratched)


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## DavidDymaxion (Dec 1, 2008)

I bow in your general direction! That is awesome you go it going so quickly (in two senses of the word!). So if 2 gears is about double the gear ratio, that means you'll be capable of 3rd gear burnouts with both motors! 

I like your idea of integrating the motor mounts and battery boxes.



Farfle said:


> We ordered the motor separately from the harness, so there was a lil mixup. That being said, we got it running on one motor and WOOOOOOOOOOOT!!!! The 912 went for a frankendrive today! As per the norm, it was dark, snowing and foggy, there were no headlights, wipers or defrost. And there were burnouts involved.
> 
> It does straightline burnouts in 1st gear, AND WE ONLY HAVE ONE OF TWO MOTORS RUNNING!!! Needless to say, we were pretty stoked.


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