# Thinking about 1975 Porsche 914 conversion



## Duncan (Dec 8, 2008)

Hi Luminary

Sounds like a good project
Comments
Lead is a bad idea - those conversions probably gave 20 - 30 miles in the real world
Regen is a good idea BUT - requires an AC system
An AC motor/controller with decent performance is ~ $18,000
A DC motor/controller with decent performance is ~$6,000

Do you need 100 miles? - battery cost is proportional to range! 
and so is battery weight


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## PThompson509 (Jul 9, 2009)

Howdy,

I also have a 1975 914, which uses AC. Mine *used* to have AirCon, but a PO took it out (fiberglassed the front trunk when doing so - major pain to fix). 

For better-than-stock AC performance, it is really hard to beat the AC50 (with the 650A curtis controller) combo. KTA-EV has it listed for $4725.

If you are careful with your conversion, you *could* get as low as 250 Wh/mile, but it could also be as high as 350 Wh/mile. When I was really trying hard to burn watts, I would be using 350, so let's use that for worst-case scenario. For 100 miles range, you need 100*350 = 35Kwh. Now add on the 20% padding the batteries require 35Kwh*1.2 = 42Kwh. 

Ok, so for a 42kwh pack, and the curtis' max voltage of 130v, you can use up to 36 batteries (CALB - less for Winston). This means you need minimum 120Ah (but those don't exist) - so let's assume 130Ah. I'm pretty sure you could fit those into the car without too much trouble, but you may have to give up at least one of your trunks.

If you don't want the regen, then going with the Warp9 motor and Warp Drive controller, you can go higher in voltage, and allow yourself to use 100Ah batteries.

Lots of choices to make for the motor/controller combo.

As for the suspension, beef it up as if you were going to autocross. You're going to add at least 300 pounds to the car.

BTW, I'm also on 914world. My blog is http://cruzware.com/peter/blog.

Cheers!
Peter


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## dladd (Jun 1, 2011)

PThompson509 said:


> Ok, so for a 42kwh pack, and the curtis' max voltage of 130v, you can use up to 36 batteries (CALB - less for Winston). This means you need minimum 120Ah (but those don't exist) - so let's assume 130Ah. I'm pretty sure you could fit those into the car without too much trouble, but you may have to give up at least one of your trunks.


that doesn't add up right. 36 x 3.2v x 130ah = 15kWh. You'd need 365ah cells to get 42kWh.


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## PThompson509 (Jul 9, 2009)

Ack. I should never do math before coffee. You are correct, of course.

So, since there are no 365Ah batteries, you'll need to go with the 400Ah monsters. Not so sure those would fit without sacrificing both trunks.

For example, I've got 108 60Ah CALBs in my car, for a 20Kwh pack. This requires the front trunk and engine compartment. Now, if I had gotten creative, I could have saved the rear trunk, but that's where all the electronics live - it's (mostly) watertight.

Cheers,
Peter


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## luminarycrush (Jan 13, 2011)

Thanks for the replies.

Peter, great blog, I'm going to read the whole thing before I post any more questions. I actually live in LA, but my 914 is currently parked at a friend's shop in Ramona where I have lots of room and access to all kinds of great shop facilities.

I'd love to check out your car sometime soon. I'll probably be heading down to SD within the next few weekends. Let me know if you'd be around and available to talk 914E...


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## PThompson509 (Jul 9, 2009)

I'll be around - however, we should connect via phone first to confirm actual physical presence.  

BTW, since your shop is in Ramona, you should get acquainted with the really nice folks at KTA-EV. WELL worth your time.

So here's a short version of the blog:

1) remove all the rust and 12v problems you can before you start the conversion.
2) take care of all paint issues before you start the conversion.
3) Have an expert look over the car for points #1, 2 and 3. 
4) Determine how far you need to drive on a day-by-day basis and then add on at least 10 miles for other activities, such as shopping. 
5) Run your plans past the experts on DIY - they will spot stupid things like math errors (see my posting this morning before coffee).
6) Have a firm budget (and then add 50% for mistakes and hidden rust).

I'll PM you with contact details.

Cheers,
Peter


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## luminarycrush (Jan 13, 2011)

Hey Peter, thanks for the reply.

I have the car down to the body now... actually, full disclosure: the 914 I was driving had rust problems that I wasn't going to be able to solve. I then found out a co-worker's husband had two 914s - the first he did a turbo Subaru conversion, the second was going to be a rally car... well he was forced to drop that project, and gave me his other 914, which had already been sandblasted and most of the bodywork done, complete with a rotisserie to hold the body while working on it.

I'm going to build the new, rust-free body up, use components from my rust-full 914 and spare parts he gave me to make it complete. I will probably install a completely new wiring harness... or maybe it's easier to just make my own at this point?

Regarding range, I have clients all over LA and some up in Santa Barbara, so I don't envision this car taking me everywhere I need to go on a regular basis - I have another car for that (unless there are some major battery energy density breakthroughs in the future). I would like to go as far as possible and still have a little room for a couple of small bags though...

I have no set budget and won't, which means I'll probably spend more than it would cost me to buy a new Leaf by the time it's all said and done (if it's possible to put a price on my time!). This isn't about saving money, it's about the journey. For example, my last project was to convert my Land Rover to diesel and run biodiesel in it (B100). I'd spend the next 15 years trying to get payback from the mileage increase if that was my goal.

However, if I can refine the design by picking the brains of you and other 914E guys before going one direction or another that will surely make this a lot less financially/temporally painful!

I finished reading your blog - when does the new motor go in? The problem you mention is exactly what I don't want to have - unable to zip past someone on the freeway. I might be one of those mildly aggressive drivers....

I figure if the design is solid and the motor is powerful enough, batteries will improve and I'll be able to upgrade the pack some years down the road to something with a much better energy density and range than the current LiPo state of the art. Then I can have my sports car cake and eat it for a 100+ miles, too.


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## EVfun (Mar 14, 2010)

PThompson509 said:


> 1) remove all the rust and 12v problems you can before you start the conversion.
> 2) take care of all paint issues before you start the conversion.
> 3) Have an expert look over the car for points #1, 2 and 3.
> 4) Determine how far you need to drive on a day-by-day basis and then add on at least 10 miles for other activities, such as shopping.
> ...


That is a good concise overview of the conversion planning process. I would only change #4 by saying "add 25% for other activities, heater in the winter, and not deep cycling the batteries every cycle."

I don't know what to expect for watt hours per mile with a 914 If you can manage 300 watt hours per mile then 50 miles +25% should be possible with 36, 180 amp hour LiFePO4 cells.


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## PThompson509 (Jul 9, 2009)

@EVFun - yeah, 300 Wh/mile would be good - provided the alignment was good, and the traffic wasn't horrible. However, he did mention he was in LA, so this will be "LA Freeway traffic"...meaning lots of nasty stop-n-go. I was working on worst case scenario. To be honest, I'd LOVE to have a 42kw pack, but I can't afford it right now.

@Luminary - I'm glad you have the right attitude for this - this is a journey, not an end. Zen like and all that. Just don't let your karma run over your dogma and such. 

The AC50 will do a decent job, especially with the 650A controller. If you need more performance than that, well, you have limited choices:

1) Warp9 running at high voltage
2) Brushless DC also at high voltage
3) Nissan AC motor and controller
4) Siemens AC motor and controller.

#1 is using something like the Soliton or Warp controller. Simple and direct - but no regen.

#2 is likely something like my motor and controller - from China with terrible support.

#3 is an 80kw motor - but you have to work with Nissan, and I don't know anyone that's done that. Yet. (A coworker REALLY wants to try this option, BTW).

#4 is just expensive. It works, but ouch.

So, there ya go. Don't expect miracles on the battery front, those are years out. I've got my ears on the R&D front, as do others, and nothing truely amazing is due anytime soon.

Cheers! Peter


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## Duncan (Dec 8, 2008)

_The AC50 will do a decent job_

Beg to differ - this is a Porsche! 
The AC50 would be OK for a small commuter car - in a Porsche it would be a case of a sheep in wolves clothing

AC50 - 60Hp -PEAK!

9 or 11 inch DC with 200v and a SolitonJr is 300Hp peak


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## PThompson509 (Jul 9, 2009)

Hi Duncan,

Yes, what you said is quite true. What he was asking for was regen, though, and the DC motor just doesn't supply that.

As for the AC50, well, I've driven a 914 with an AC50 in it, and it is definitely better than stock (again, what he was asking for). Heck, even my weak AC24 is better than stock, but I was starting with a lousy motor. :-D

The biggest problem is going to be the range, and how to fit in all the batteries to get 100 miles range. I just checked Richard's 914 (the one with the AC50 in it) and he gets from 210 to 250 Wh/mile. So that will help - he'll only need a 30kwh pack.



Duncan said:


> _The AC50 will do a decent job_
> 
> Beg to differ - this is a Porsche!
> The AC50 would be OK for a small commuter car - in a Porsche it would be a case of a sheep in wolves clothing
> ...


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## EVfun (Mar 14, 2010)

Duncan said:


> 9 or 11 inch DC with 200v and a SolitonJr is 300Hp peak


??? 200 volts nominal may be 170 volts to the motor (which is about you really want to do with a ADC or WarP 9) at 600 peak amps (Soliton Jr) is about 120 shaft horsepower.


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## Duncan (Dec 8, 2008)

EVfun said:


> ??? 200 volts nominal may be 170 volts to the motor (which is about you really want to do with a ADC or WarP 9) at 600 peak amps (Soliton Jr) is about 120 shaft horsepower.


I thought the junior was 600 amps continuous and 100 amps peak


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## Tesseract (Sep 27, 2008)

Duncan said:


> I thought the junior was 600 amps continuous and 100 amps peak


No, the Soliton Jr is rated for 600A peak and ~500A continuous at all duty cycles but it can run on a battery voltage of up to ~340V.

The WarP-9 needs to be limited to about 190V with 600A of peak current, but the official spec is 170V, so the realistic peak power to the motor would be in the range of 102kW to 114kW. Still more than twice the AC-50, but not quite 300hp...


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## luminarycrush (Jan 13, 2011)

This is where having the cake and eating it too comes in. Or not.

The Leaf motor is 80kWh right? That's not exactly a speedy car by reports, but the motor is more powerful than the AC50/AC55. Would that really be sufficient?

Some guys in the motor forum are talking about the Remy motor (HVH250), pulling the plant from wrecked SUV hybrids inexpensively, etc. Regarding performance, I should qualify that my 914 had a 1.8 with dual webers on it, so it wasn't so lethargic  ...probably around 100hp on a good day.

As for range, today was an unusually busy day - I had three meetings and put 115 miles on my car, so 100 miles would be useful most of the time (more if there were some charging stations handy...) but not always.

I read a lot of tech journal websites and hear about battery breakthroughs all the time - discoveries that boost density and discharge/recharge rates greatly, but who knows when will be productized. I think that we are poised for some exponential growth in solar and battery technology.

On the topic of solar, I'd probably make my targa top a solar panel, even if only for another feel-good item. Yeah, not much more than a big trickle charger, but perhaps with triple junction cells (efficiency 40+%) they might do something useful - prices on those are coming down.

Regarding suspension, I've upgraded to 5-bolt 911 suspension front and rear (well the rear was pretty custom). I'm guessing that, depending on which battery technology chosen, I'd still need heavier or much heavier springs. The 911 sway bar - inadequate? It handles pretty stiff as it is. The car has GT flares on it and rims/tires from a Boxster so it's got a wide footprint.


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## PThompson509 (Jul 9, 2009)

Sounds like you have the suspension already taken care of. The 911 sway bar is going to be more than adequate. 

The 80kw motor/controller from the leaf will do a nice job for your car - provided you can figure out all the details to make it work. Somehow I doubt that Nissan will make your job easy on that front.  One of my coworkers REALLY wants this motor for his BMW conversion. I'll keep you posted on any progress there.

I agree with you on the batteries - don't hold your breath for the New Stuff That Will Save The World (tm). 

Would be cool to have a solar panel on the roof, if nothing else for the talking factor. 

Oh - have printouts in the car on details for other interested people. I keep about 10 sheets in the glove box just for the Usual Questions.

Cheers!


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## luminarycrush (Jan 13, 2011)

Peter, any word on your new motor? When will you be installing it?


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## PThompson509 (Jul 9, 2009)

Hi Jason,

I met up with the machinist yesterday, and he has pretty much all the parts now. We will be installing the motor sometime this coming week, perhaps next weekend. 

I'm pretty excited about this - the rear battery rack is moving up 1.25", there's a new motor mount, and a whole new wiring arrangment. I'll be taking photos of the mounting, and the new wiring, and will post them on my blog later.

Cheers,
Peter


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## luminarycrush (Jan 13, 2011)

Peter, I haven't seen any updates on your blog in awhile - wondering how the new motor is working out.

You are probably having too much fun messing around with it to bother posting ;-)


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## PThompson509 (Jul 9, 2009)

Oh I wish I was too busy.  I only got the final motor parts picture yesterday (or was it friday). Spent Saturday and Sunday doing stuff like installing the 3rd brake light and the pump and coolant resevoir. Oh and making sure I had plenty of POR-15 on my skin - I'm not sure how this happens but I start out dabbling this stuff on rusty parts of the 914, and it ends up with me painting a LOT of the 914 and me. I have some big patches of the stuff on my skin and it won't come off. *sigh*

Anyways, I should have the motor mounted within a week, and soon can start testing the new configuration. The 12v system has tested out ok, so now I get the BIG SMOKE TEST as the next hurdle. 

Cheers,
Peter


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## Sun Motors (Aug 10, 2010)

Greetings lc,

I have a 75 914 basic dc conversion with about 12k miles on it now. I have about ideal driving conditions for my 55 mile round-trip commute and get about 205-220Wh/mi using about 11kWh depending on the temperature and wind conditions. The 42 x 160aH thundersky pack rests about 138v at 70-80 f and runs about 130-135v drawing 40-200 amps, but runs about 5v lower around 40 f.

I haven't weighed it yet but there is about 125 lbs over stock up front and it handles like my old 64 bug did when I put a couple of bags of cement up front -very grippy. I put stiffer springs in the rear and dialed-up the stiffness up front and it is quite fun to drive. We have taken it over 80mph with power to spare, and flooring it puts about 450a through the curtis controller. Normal driving at 55-60mph rides about 75-100a or about .5c, using about 15-20hp. 

Just with mild driving the controller gets hot after 20-30 minutes when the temperature is above 85 f. I am trying some fan action come summertime but I think I will get a liquid cooled one someday because of its location in the center of things.

http://www.diyelectriccar.com/garage/cars/283

Hope this helps. I think what you are looking for may be provided by the 11" motor and 1000a controller option. Then get about 25-30kWh of LiFeSo4, the best battery option today, and you should make 100 miles driving courteously, and accelerate like heck as you please. I figure you will use about 22kWh to go 100 miles with a 2500lb 914, then it is wise to have 20-25% more capacity remaining.


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## PThompson509 (Jul 9, 2009)

I agree that cooling is an issue. Especially when you putting a lot of amps through your system. The 914 has the unfortunate problem of bad airflow through the center of the car. There are a couple of ways of resolving this - but most involve adding airscoops either to the side or top of the car. I heard about using boxter airscoops but haven't seen any example yet. 

This is one reason I switched to the BLDC motor and controller - both are liquid cooled, so I can place the radiators where there is airflow. Oh, and all of the extra power of course. 

Cheers, Peter


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## luminarycrush (Jan 13, 2011)

When I still planned to rebuild the dino motor in my 914 I planned to use Boxster air scoops anyway (I was going to install a turbocharged engine and wanted the extra cooling) so I have them on hand for the electric system cooling issues.

Looking forward to hearing more about Peter's new motor before I start writing checks for the powerplant...


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## PThompson509 (Jul 9, 2009)

80kw BLDC is installed, but the cheap connectors have intermittent connections. I will have those replaced by this weekend, and drive tests then. When the connections were good, the response was REALLY nice. 

Downsides to the Greatland motor/controller - TERRIBLE factory response - none, very tight fit under the battery pack in the engine compartment. 

Upside - cheap. 

Hope to have some driving this weekend.

Cheers, Peter


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## PThompson509 (Jul 9, 2009)

I was right about the connectors. The 80kw motor is just so nice - I keep putting my foot into the accelerator just to feel the power. Now if I could just figure out how to hook up the tach and regen...

Cheers, Peter​


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