# Lightest builds completed- what donor car?



## toddshotrods (Feb 10, 2009)

I'm "in the process" with a street rod build that I am targeting a finished weight of 1200lbs. This is a real projection based on the component weights of everything that needs to be on it (plus a 10% margin for error), but also based on very expensive A123 battery packs. I'm using a direct-drive 11" GE forklift motor, solid rear end, independent front suspension, etc. The chassis is rolling now and the powetrain and body are being installed. So far, so good. I should meet my weight goal, if not beat it.

Under 2000lbs is achieveable with a regular street car, with careful planning. Either a fiberglass body over tube chassis, or a micro-sized unibody car, would be a good foundation to build on.


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## TomA (Mar 26, 2009)

Hi Chris:

I've been following your inquiry, and I replied to you on the EVDL.

I think your project is cool, and you are definitely in the very shallow end of the pool on weight. My vehicle will be about 400-450lbs empty. jmygann at Endless Sphere has a pedal trike with a full body at about 430lbs. Duxuk (Andrew) has a trike just finished at 725lbs. Both of these trikes could perhaps be somewhat lighter with Lithium instead of lead. Todayican (Tom) is building a trike that will be lighter than that, but its early in the fabrication stage. I'm not aware of any production vehicles in this class other than the Twike, which is just under 550lbs. Note that all of these are 3 wheelers. Most 3 wheeler kits, like the RQ Riley designs or Morgan SS variants, are far heavier- 1500lbs-2000lbs or so depending on batteries.

Four wheelers are even heavier. Yours is probably the lightest chassis out there. Even a Locost is much heavier. Sorry to say, there isn't a donor vehicle in your weight class, so you're really on your own. The principal problem is you really shouldn't be going over the original GVWR of the car after the conversion. Doing so will make it unregisterable in many states, and probably uninsurable if a carrier ever found out about it. The brakes, wheel bearings, tires and suspension are all limited by the max vehicle weight, and particularly on a 50+ year old design. This conversion is going to take some careful work, and may not ultimately be practical or satisfactory.

I actually considered a Berkeley for an EV conversion. If I were doing it, I'd either use an AC-12 or AC-15 motor with the Curtis 1236 controller. That package would be about 60 lbs, and use the existing TR or VR gearbox, unless an appropriate differential unit that weighed less could be found. I would use 30 TS/CALB 90Ah batteries, right at 200lbs. This would be a decent compromise, I think. The pack would be a little under 7kWh to 80% discharge, or about 7/8 of a gallon of gasoline equivalent. Since these cars got 45-50mpg, that should yield a safe daily range of 40 miles. Not bad, and hopefully still under the GVWR, even with the wiring, and composite bracing I would add for the batteries...

You could also go with two of the EnerTrac hub motors, as Mark from EnerTrac is already developing himself. This setup would be heavier, around 90lbs with dual controllers, and both more expensive and trickier to pull off, but it would have _much_ better performance than the Berkeley. Maybe too much...

Either of these powertrains would be really exciting in your Berkeley. You'd probably want to upgrade at least the front brakes, and maybe find out how the later factory Berkeleys have been adapted to use Mini drivetrain and suspension components. Changing to those bits (but not the Mini transmission) would solve a number of problems for you from weight and power handling capacity to basic availability and cost. 

Chris, the short answer to your question about 4 wheel conversions that are under 2000lbs is, well, there are likely extremely few. I don't know of _any, _and while I'm no old-timer EV guy, I've been studying super-light EVs for two years now. Yes, there are old Vanguards and ElCars and NEVs in this class, but their performance is terrible- and no one would do a conversion to get it! Besides, anyone that could have come in at such a light weight probably would add battery weight for range and/or performance instead, knowing that their original GVWR had the margin for it. This is exactly what I would do if I were converting, say, a Saab Sonett (<1900lbs) or Lotus Europa, (<1600lbs.) You are therefore very unlikely to find an 1800lb conversion, where the same car at 2100lbs would really be much more serviceable. Lastly, practical highway-capable conversions in this class have only really been possible since the prismatic LiFePO4 cells became available two years ago. Such vehicles are going to benefit from, if not outright require, the latest (lightest) drive packages, as well. Its no wonder there aren't many out there yet. The only ones I can point you to are Duane Ball's Electric Beck Spyder 550, and Jack Rickard's speedsters, both of which are on Beck kit car chassis.

Having said all that, you're in a class by yourself at 700lbs empty. Its actually a really cool place to start. Good luck and stay with it.

TomA


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## toddshotrods (Feb 10, 2009)

What's the project budget? If the budget can stretch for Headway, Kokam, or (ultimately) A123, cells...

It seems like the cost of a really high-end pack for such a small vehicle would be comparable to somone doing LiFeP04s in a medium-sized vehicle.

A little sports car like that with stock, or nearly stock, weight and the torque of an electric motor would seem to be really enjoyable to drive.


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## EVfun (Mar 14, 2010)

My EV buggy weighs in at 1420 lb. with 10 Optima yellow top batteries and onboard charger. This is a VW Beetle based kit car that weighed 1100 lb. before conversion (with VW Beetle engine.) It has about a 20 mile range with 10 good Optimas. It is tempting to go off board with charging and use a 100-120 volt pack of 60 amp hour TS cells bringing the road ready weight under 1200 pounds.


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## TomA (Mar 26, 2009)

EVfun said:


> My EV buggy weighs in at 1420 lb. with 10 Optima yellow top batteries and onboard charger. This is a VW Beetle based kit car that weighed 1100 lb. before conversion (with VW Beetle engine.) It has about a 20 mile range with 10 good Optimas. It is tempting to go off board with charging and use a 100-120 volt pack of 60 amp hour TS cells bringing the road ready weight under 1200 pounds.


 Wow, this vehicle makes my point exactly. Its _really_ light, but it has extremely limited range. I'm sure that works for you, Paul, but for me it wouldn't, and I'd be hanging batteries off the sides, bringing the weight up.

Great ride there, dude, and it would be a rip snorter with a small TS pack. While the 60Ah batteries would be great for you, I would go for more range. 36 SE 130Ah batteries would be 350lbs- you'd only lose about 75lbs, but the range would go way up- probably over 50 miles, which I think most builders would probably do if the car was to see routine use.

Either way, cool buggy...

TomA


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## dtbaker (Jan 5, 2008)

On the 'easy' side of small is the swift/metro. Mine weighs 2495# now with 12 x 8v. upgrade is planned to 38*100ah Li, which will drop 500# AND raise voltage from 96 to 120v.... should change performance from 'adequete' to 'fun'.


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## Bowser330 (Jun 15, 2008)

toddshotrods said:


> I'm "in the process" with a street rod build that I am targeting a finished weight of 1200lbs. This is a real projection based on the component weights of everything that needs to be on it (plus a 10% margin for error), but also based on very expensive A123 battery packs. I'm using a direct-drive 11" GE forklift motor, solid rear end, independent front suspension, etc. The chassis is rolling now and the powetrain and body are being installed. So far, so good. I should meet my weight goal, if not beat it.
> 
> Under 2000lbs is achieveable with a regular street car, with careful planning. Either a *fiberglass body over tube chassis,* or a micro-sized unibody car, would be a good foundation to build on.


tell me more about this tube chassis...

I want to replicate the frame of a standard donor's stripped unibody...

Wouldn't that be easier to replicate the dimensions rather than creating custom ones?

any ideas on approx cost? 

1000$? 5000$?


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## The Toecutter (May 30, 2010)

I've been working on my conversion on and off for the last 8 years(including the time spent designing it way back in high school). I obtained a Triumph GT6 for my purpose; it will begin its life as a lead acid conversion weighing in around 2,300 lbs with about 900 lbs battery weight(GVWR 2350 lbs), later to be upgraded with LiFePO4 and reducing weight to ~1,900 lbs. Glider weight is under 1,200 lbs, including weight reduction from switching to aftermarket seats and trim items.

My original design called for a lead acid conversion with 80 miles range to 80% DoD at 60 mph, 0-60 mph in 5.5 seconds, and a 140 mph top speed(with custom gearing to allow this). I had originally planned it to be a 300V conversion with Exide Orbitals and a zilla 1k, then changed the design to 192V of Deka 9A31 as the Exides increased in price and cheaper components entered the market that could meet my design goal(hadn't yet purchased a controller or battery pack at that point), but circumstance always had a way of eating away the money I had saved up for it. I'm finally now in a position to get it driving in some form, and can't wait!

I may start it off as a 72V PbA conversion with an Alltrax controller just to have it running, and upgrade it later; a 72V pack of Universal Battery UB4D batteries would theoretically give it 80 miles range to 80% discharge at 60 mph, 0-60 mph ~20 seconds, and 90 mph top speed with adjusted gearing(60 mph top speed without adjusted gearing). It would be a slow, but still very practical conversion.

If I go with the 72V setup, I will not buy the car another pack until I obtain enough for LiFePO4 batteries, although a Zilla 1k HV will probably be my first upgrade(even if in this application it won't increase performance except from 0-20 mph). I am intent on having LiFePO4 at some point in the car's life, and at least enough for 250 miles range at 60 mph and 120 peak horsepower from the motor.

My conversion is making extensive use of efficiency techniques such as aerodynamic modifications. The goal is 120 Wh/mile or less at 60 mph measured from the pack; Reverend Gadget has obtained < 120 Wh/mile from a Spitfire conversion that had no aerodynamic work other than a GT6 body, but did have the best LRR tires on the market and many other tricks to reduce rolling resistance. His conversion weighed in at 1,900 lbs with 15 Exide Orbitals, a Zilla 1k HV, and an ADC 6.7" motor, yielding a range of 24 miles to 80% discharge at 60 mph, 0-60 mph < 6 seconds, and a top speed of 120 mph, IIRC. The CdA of a GT6 MkIII body with no aerodynamic modifications appears comparable to a first generation Honda Insight 2-seater, *but* a converted GT6/Spit weighs less than a converted Insight if the same setup is used; the GT6 has a cast iron engine block that weighs 403 lbs by itself! With aeromods to reduce Cd to ~0.25, and due to very small frontal area(14.9 sq ft), the CdA of these conversions have the potential to be the same as or less than even the EV1!

Karmann Ghias also make excellent conversions if maximizing range per unit of battery weight is the goal. John Bryan's Ghia needed 100 Wh/mile from the pack in mixed city/highway driving, and had a lot of focus placed on reducing rolling resistance and some mild but significant aeromods like a bellypan and grill block(but nothing major like a Kammback). His 192V pack of Optima D750s gave him a real world ~50 mile range to 80% discharge! This is 50 miles usable highway range with a pack weight of only 720 lbs of _AGM lead acid_ battries! With more extensive aeromods, that car could have potentially had its highway range increased by 20% or more without increasing the pack weight!

That above mentioned Ghia's 1st pack of Optimas lasted more than 8 years last time I checked; I don't know if John still has the original pack in it or not.

Long range also has the pleasant side effect of reducing your typical depth of discharge, greatly extending battery cycle life! This in turn has an enormous impact on operating cost, allowing the EV to be much cheaper to run than a comparable ICE counterpart. Many conversions fail in achieving this because they are designed to be discharged 80% of more in typical use, and this leads to less battery life.

Efficiency goes a long way towards improving range. It really does.



EVfun said:


> My EV buggy weighs in at 1420 lb. with 10 Optima yellow top batteries and onboard charger. This is a VW Beetle based kit car that weighed 1100 lb. before conversion (with VW Beetle engine.) It has about a 20 mile range with 10 good Optimas. It is tempting to go off board with charging and use a 100-120 volt pack of 60 amp hour TS cells bringing the road ready weight under 1200 pounds.


Even though it has low weight, it's CdA is comparable to a sedan with two or three times its weight. It exemplifies the diminishing returns on reducing weight as a strategy for improving range.

It is an excellent conversion, however; I bet that thing can corner exceptionally, and most conversions will never have an efficiency comparable to this car at speeds below 30 mph(it must be very inexpensive to operate in city driving compared to most conversions, probably what it was designed for).

Lightweight EVs make excellent city commuters.


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## toddshotrods (Feb 10, 2009)

Bowser330 said:


> tell me more about this tube chassis...
> 
> I want to replicate the frame of a standard donor's stripped unibody...
> 
> ...


On one hand, it would take the guesswork out of what to put where - just do exactly what the factory did. That does save a LOT of time and energy. But...

A replicating a uni-body in tubes would be a serious project. Because sheet steel can be pressed into crazy shapes the chassis of a unibody vehicle kind of melts around the components. A tube chassis vehicle, on the other hand, normally has the compnents arranged to fit inside it; because there is a limit to how far the main tubes can be bent, twisted, and shaped. The closest tube chassis to a unibody would be a complete round tube chassis. If you have a fixture, the tools, skill, and time to do it yourself it's theoretcially feasible. To have one built at a shop to replace a unibody would be at least double your top figure, maybe as much as five times that amount, maybe more...

If you look around this site you can find pictures of the round tube chassis they build in some of the galleries. There aren't many up-to-date pics of the "Radical 69 Camaro" chassis in its album but they're doing what you suggested with it. There's nothing left but the external skin, and the tubes are being bent, almost unibody style, to recreate it. Probably a million dollar plus hot rod though.

The best option is a space frame. Lambo Countach and Diablo used them - not sure about the Murcie. It's a bunch of little sections of tubular material, heavily triangulated, and welded. You can use small square tubing and build a really strong, lightweight, chassis. With careful planning, you can come really close to the unibody.

As far as cost: You can buy most of the materials to build the frame structure, to do it yourself for $1000; you could probably get a chassis shop to weld up a nice base to build on, with the critical points in place, for around $5000. You may also be able to find a kit car tube chassis or space frame in that neighborhood. The rectangular-tube, ladder-style, tube chassis for hot rods start out around $5K for a roller. It's called a roller, but actually needs a lot of parts and work to roll under power though.


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## Bowser330 (Jun 15, 2008)

toddshotrods said:


> On one hand, it would take the guesswork out of what to put where - just do exactly what the factory did. That does save a LOT of time and energy. But...
> 
> A replicating a uni-body in tubes would be a serious project. Because sheet steel can be pressed into crazy shapes the chassis of a unibody vehicle kind of melts around the components. A tube chassis vehicle, on the other hand, normally has the compnents arranged to fit inside it; because there is a limit to how far the main tubes can be bent, twisted, and shaped. The closest tube chassis to a unibody would be a complete round tube chassis. If you have a fixture, the tools, skill, and time to do it yourself it's theoretcially feasible. To have one built at a shop to replace a unibody would be at least double your top figure, maybe as much as five times that amount, maybe more...
> 
> ...


Thanks Todd.

The space frame idea is what I was looking for. thanks for the ballpark estimates, I needed to ground myself on overall cost of the project.

Also as you mentioned, as long as the critical points match up, custom mounting brackets will probably need to be made anyway to correctly point a body panel.

any idea on how much a fully built space frame chassis weighs vs oem unibody chassis? Strength wise, i am assuming the space frame is stronger?


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## toddshotrods (Feb 10, 2009)

Bowser330 said:


> ...any idea on how much a fully built space frame chassis weighs vs oem unibody chassis? Strength wise, i am assuming the space frame is stronger?


I think that depends on who designs it and what their budget is. The modern unibody cars are pretty impressive in torsional rigidity. Someone just posted a chart showing that on this board, but I forget where. That's usually in the domain of major manufacturers though, with multi-million dollar R&D budgets. The engineering, and the tooling, to produce high-strength, stressed, sheet steel chassis isn't something that can be taken lightly.

On the other hand, space frames have been done by everyone from backyard builders to Lamborghini. The question is who did the design, and how good is it - with respect to the intended purpose. If it's designed properly it probably has the potential to be stronger, or high-end race vehicles would probably not use them.

Weight probably depends on design to tip the scales too. My Hondas have all been pretty light for their size, but feel pretty solid. In comparison, the Fieros I owned were really heavy for their size. They were claimed to have space frames, but it was actually unstressed plastic panels over a unibody platform. Two different approaches to the same method, different results. The same could be true with a space frame. The size of the tubing, wall thickness, etc, all play a part and are largely determined by the intended usage and design.

Any chassis starts with the questions: what are you going to do with it, and what are your goals?

Anoher thing you can consider is a reinforced unibody. That's what race cars based on unibody platforms do. Start with the lightest car available and add a roll cage that ties into all the critical points. Much less cost and time, a slight compromise on weight. You also have the option of incorporating weight saving parts and techniques that would otherwise compromise a unibody chassis.


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## TomA (Mar 26, 2009)

Bowser330 said:


> any idea on how much a fully built space frame chassis weighs vs oem unibody chassis? Strength wise, i am assuming the space frame is stronger?


There are no absolute answers to this kind of question, but there are some clear facts.

A tube frame from mild steel that _replicates_ a unibody (such that you throw the unibody away and do all the things the unidbody does with carefully shaped sheet metal panels, like sealing out wind and water, and crumpling on impact, with different structures like welded tubing and FRP,) is probably going to weigh a lot more than the unibody. Its really too much to ask of the materials, and the designer: like trying to replicate the performance of an egg shell with sticks and cardboard.

Unibodies are optimized for the strength and lightness properties of curved sheet steel, and they are remarkable efficient. Racers don't generally cut them up; they just brace them with additional material in certain spots that are taking loads beyond their original design parameters, and often enough they only really put in more structure because the rule book requires it (roll and impact cages.) NASCAR is a poor example to look at. There are many reasons these cars have tube chassis, not the least of which is they go _very _fast, and have huge forces to manage. They also weigh about a half ton more than the unibodies they replace.

The "stronger" question is equally thorny- yes, a well made tube space frame that weighs more than the unibody it replaces may well be stronger in certain modes than the original unibody, but I wouldn't bet on it. (I'm talking here about a modern car, not a '61 Chrysler, but I must say, those mid 1960's Ramblers were extremely tough.) Such a unibody was carefully engineered and is very, very strong, particularly for its weight. It also probably dissipates energy more evenly and effectively than its tube-frame replacement, making it safer on impact, and more resistant to structural failure. 

You'd have a hard time coming close to that welding up tubes in the shop. Programming them into the computer might significantly improve that, but if you don't know how to do it, its going to likely be a $15,000 chassis design project to buy. That isn't much, really, just 150 hours at $100 per, with getting all your unibody dimensions into the system alone being the biggest chunk of that time. I could see that figure doubling or even tripling, though, so its no surprise you don't see cars built like this at race tracks or car shows very often...

TomA


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## toddshotrods (Feb 10, 2009)

TomA said:


> There are no absolute answers to this kind of question, but there are some clear facts...


What he said. 




TomA said:


> ...like sealing out wind and water...


What is usually done there, for a street vehicle, is all the jambs and seals from the original car are preserved. Basically what is done in hot rods is skin the tube frame chassis with the exterior skins of the unibody car. Since the chassis carries all the loading and stress the remaining body panels are mostly cosmetic. This allows you to remove some of the double and triple wall sections the factories use to build strength. As Tom indicated though, it's usually going to weigh more.

Some vehicles end up around the same weight, or lighter than the original, but they were usually pretty expensive. The places where you can compensate are expensive and/or time-consuming.





TomA said:


> ...You'd have a hard time coming close to that welding up tubes in the shop. Programming them into the computer might significantly improve that, but if you don't know how to do it, its going to likely be a $15,000 chassis design project to buy. That isn't much, really, just 150 hours at $100 per, with getting all your unibody dimensions into the system alone being the biggest chunk of that time. I could see that figure doubling or even tripling, though, so its no surprise you don't see cars built like this at race tracks or car shows very often...
> 
> TomA


Anyone who has $15K (or even better double or triple that) ready to go, please send a PM to check out! I'll model it, test it, analyze it, until your heart is content! 

I see them all the time, but I will admit I normally only go to the high-end shows. Amazingly, quarter-million dollar and up hot rods have been flowing like water throughout this recesssion. At that level, the process starts with welding the body to a frame table, bracing, cutting the entire floor and firewall structure out, then building a new tube chassis. In the end, the original body skins are there to remind you what it was...


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## Bowser330 (Jun 15, 2008)

I appreciate the insight Todd and Tom, maybe I should be more forthcoming with my project specifics..

I want to convert a porsche 911, 996 models, the newer frame, started in 1998 and can be found in good/decent condition for 15,000$, im sure even less with a seized engine..

The plan is to bolt a 13" motor to an upgraded 6 speed transmission...I also will look into implementing a "max amps per rpm control", so my low rpm amps wont kill the transmission...example: @0-1000rpm motor amperage is limited to 500A, @1000-2000rpm motor amperage is limited to 750A, etc. That way, even if I go WOT (wide open throttle, max amps) I wont kill the transmission because it will be limited for safety reasons...

ANYWAY, point is, I want to use headways or A123s, I also will replace the body panels with fiberglass ones (body kit)...but I want to get the finished weight down to the 2XXXlbs range...i figured replacing part of or most of or completely the entire unibody was an option....

Due to racing regulations where Porsche's compete, unibody's have to remain untouched for the most part. So there is not a lot of people out there familiar with making space frames for 911 (996) models...

Maybe I could keep the center cabin unibody intact, and just tube the front and rear sections where the suspension/trunk (front) and engine/trans/suspension (rear) are in the 911? That way I could partially save weight while keeping the work/cost down...maybe...

what do you guys think? feedback?


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## toddshotrods (Feb 10, 2009)

Bowser330 said:


> I appreciate the insight Todd and Tom, maybe I should be more forthcoming with my project specifics..
> 
> I want to convert a porsche 911, 996 models, the newer frame, started in 1998...
> 
> ...


Honestly, my first thought was that's a pretty serious unibody chassis that has a LOT of engineering and investment to get it to the point it is. I wouldn't be so quick to cut it up. I'm not real familiar with 911s so any additional information, cutaways, technical drawings, chassis pics, you can find and provide would really help.

What I would be looking for are ways to safely lighten the factory chassis, probably starting with incorporating a cage. The money spent on a tube chassis would probably be better spent on composite replacement parts and higher energy density batteries (as you specified).

It would take a serious investment just to not go backwards regarding weight and performance, from the factory Porsche chassis.


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## Bowser330 (Jun 15, 2008)

good point...there has been a lot of engineering put into the 911 chassis.

Race weight 911s can get down to 1200kgs, but thats still 2600lbs...add the weight of the lithium and i will be lucky to stay under 3000lbs total...

not light enough if i want low wh/mile...


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## Duncan (Dec 8, 2008)

Hi Bowser

I like the looks of the Porsche - but for the amount of changes you are contemplating why not start with a "kit car"
I am thinking of a Stratos or an Ultima for the Porsche type looks or a speedster or (my favorite) a C type jaguar for an older look

Then you would have the tubular chassis and the lightweight body


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## TomA (Mar 26, 2009)

Bowser330 said:


> what do you guys think? feedback?


It comes down to what Todd said:

What do you want to do with this car?

Is it for racing? Road use? Daily driver? Street/Strip?

Fundamentally, a car is an appliance that allows you to do certain things. Until those things are defined, like the number of passengers, the performance required, the delivery date and the total cost, then it is just a juggle of possibilities. You really have to figure most of that out before you can start looking at what a car that could accomplish those things would look like and cost. Then the compromising and real design work begins. To do it the other way around is just an indefinite investigation, because every option is worth considering so long as you don't really have a budget or any firm performance, capacity or engineering goals. Fun, but not a project with defined requirements. 

Assuming you have a fair amount of those decisions at least provisionally made...

I personally wouldn't start with a Porsche for an EV, but I'm probably the wrong guy to ask. I just don't like them. Don't like the way they handle. Don't like the look, the road feel, the culture, the expense, the sound of the engine, (yes, I know that would at least be gone...) or anything about them, really. Not a Porsche guy. To each his own. I don't criticize other people's considered preferences, and some of mine are pretty strange, (I _really _want a 1959 Multipla...) so its up to you. If I were doing a Porsche EV, though, I'd use a Beck reproduction road car. Stronger, easier, etc.

I also think a 13" motor is too heavy at 367lbs, about 100 more than the Porsche ICE. A Warp 11 HV is a better choice- plenty powerful, and 140 lbs lighter. Headway or A123 cells are cool, but if you aren't drag racing or actually doing track days, you probably don't need the high discharge rate that is their primary benefit. By the time you connect and restrain them, I don't think there's such a huge weight savings over prismatic cells that the expense and trouble is justifiable for any purpose other than high-C discharges, but again that's one man's opinion. if your weight budget is 2999lbs, you'll probably make it with TS/CALB prismatics and a Warp11 in a 911. If its 2000lbs, you won't, so we are back to the project requirements discussion...

Anyway, that's what I think. It seems you have a fairly substantial budget if you are thinking about a Porsche roller, A123 batteries, a basically custom 13" motor, etc. If I were doing a project like that, which seems to have performance and "road race cool" requirements, I'd think seriously about a glider from these guys:

http://gtreproductions.com/

I would go for the M6 GTR, (even though Jim Hall is one of my heroes and I had a Cox Chapparal,) with the body modified to eliminate the radiator and engine-related slots and scoops, cleaned up front wheel wells, full rear wheel skirts, and an extended LeMans-style tail that came nearly to a point.

Such a car, with a Warp11HV, a Mendeola transaxle, a Soliton1 and 96 100Ah cells would really be something.

You asked...

TomA


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## toddshotrods (Feb 10, 2009)

TomA said:


> ...I also think a 13" motor is too heavy at 367lbs, about 100 more than the Porsche ICE. A Warp 11 HV is a better choice- plenty powerful, and 140 lbs lighter...


I didn't catch that one. Yeah, I wouldn't want a 13" motor hanging off the back. The Warp 11 would be much better. 140lbs may not seem like alot, but it is a huge difference for where it's located. The time-honered illustration of putting something heavy on a stick and trying to get it moving while holding the other end of the stick; then try to stop it once the inertia picks up. That's the 140lbs on the back of your car!  Polar moment.

Porsche has done a decent job getting that design to handle okay, but you don't want to upset the balance too much.

I've been toying with the idea of a siamese-9" Porsche 914, post Inhaler. My mental ramblings include a tube-chassis, with C5/6 Corvette suspension components. The body will pretty much be the outer skins and the door jambs, and I'd probably end up doing a carbon fiber front clip, doors, trunk lid, and targa top. Siamese 9s would allow me to tuck 335mm tires inside the quarter panels, and end up a really well-balanced true mid-motored car. With the right battery pack, I think I could end up between 2000 and 2500lbs. If money weren't an issue I would proabably go for 2500lbs and maximum range (after I got over the thrill of trying to smash my right foot through the composite floorboards!).


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## Bowser330 (Jun 15, 2008)

haha, Tom, you indeed are not a fan of the P-car...truly to each his own, like you mentioned...I like all those things about Porsche with the exception of the expense of them...which is why I would be getting one extremely used for a good price, relatively speaking.

I felt the headways were a good middle ground between the high discharge rates of the A123 and the low discharge rates of the SE bricks...even if it is a daily driver i would want some pep to it...So 1000A surges would be needed and would not only be demanded at low speeds, that's at least how i drive now..I like to drive, its fun, enjoyable...I would like to keep it that way with the transition to the EV...

The 13" motor hanging off the back has got me thinking...is swapping in boxster transmission an option...I wonder, because its mid-engine..the boxsters transmission faces the other direction...then the 13" motor would mounted more mid-ship rather than behind the rear axle...OR take out the entire rear-suspension and fab-in a ford 9" rear-end (white zombie-esque) both a bit probably cost prohibitive but would be needed for 13" weight and power....

Kit car, EXCELLENT idea friend...There are some kitcars I have my eye on..they are ferrari reproductions..but are FWD, so some modifications would need to be done to get them rear driven...also...I think a ferrari replica would be a little too much show...porsche is not at all seeing as i live in socal and everyone has a porsche it seems...

_I've been toying with the idea of a siamese-9" Porsche 914, post Inhaler. My mental ramblings include a tube-chassis, with C5/6 Corvette suspension components. The body will pretty much be the outer skins and the door jambs, and I'd probably end up doing a carbon fiber front clip, doors, trunk lid, and targa top. Siamese 9s would allow me to tuck 335mm tires inside the quarter panels, and end up a really well-balanced true mid-motored car. With the right battery pack, I think I could end up between 2000 and 2500lbs. If money weren't an issue I would proabably go for 2500lbs and maximum range (after I got over the thrill of trying to smash my right foot through the composite floorboards!)._

I will take one within a 911 body please! where do i send the check!?

Thanks again guys...I think this whole project needs more thought put into the right donor...

I mean all i wanted was to re-create john waylands white zombie using dennis breube's S10's concept of a single 13" GE motor..which also ran 11's in the 1/4 mile...John's estimating 100+ mile range with his ~25kwh pack and ~2250lb dastun510. I just wanted to shoe-horn all of that tech into a porsche 911 body...(granted, I cant spend THAT much on kokam batteries so headway's will have to do)


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## toddshotrods (Feb 10, 2009)

Bowser330 said:


> ...The 13" motor hanging off the back has got me thinking...is swapping in boxster transmission an option...I wonder, because its mid-engine..the boxsters transmission faces the other direction...then the 13" motor would mounted more mid-ship rather than behind the rear axle...OR take out the entire rear-suspension and fab-in a ford 9" rear-end (white zombie-esque) both a bit probably cost prohibitive but would be needed for 13" weight and power...


Renegrade Hybrids flips the diff and sets the 911 style transaxle up for mid-engine configuration - it ain't cheap though. IIRC, 2nd gear is the weak one in a Porsche transaxle. With the torque of even an 11-inch motor, let alone the big 13, and your desire to drive aggresively... Save up some pennies for a good rebuild. That can be done later though.




Bowser330 said:


> ...I will take one within a 911 body please! where do i send the check!?...


 Checkout line starts in my PM inbox! 


The most important thing that has been brought out here is the need to think things through. Always start with what your goals and needs are. Hang those on the wall, and weigh every idea against that foundation. It is so easy for serious projects like you're planning to get out of hand, and off track. The classifieds are full of them year-round. I can tell you firsthand that it's challenging enough to keep moving in the middle of these projects, without unnecessary distractions that serve no real purpose. People who don't keep a tight reign on the direction of a major project usually end up thinking, "what the heck am I going through all of this for?" The ones who do (including me with the Inhaler), are driven with each tiny little accomplishment, because we see the real goals coming to life.

I've been working on the Inhaler's forced-air system model for the past couple days. After seeing the rear mount machined, I get a doses of adrenaline with each little CAD piece of it that materializes on my screen. The primary goal of my project was to have a foundation to display my CAD work on. Every inch closer to that is like a freight train (diesel-electric of course ) driving me to keep going.

Sorry to babble, just trying to help you and anyone else who reads this thread to have a little better understanding of what it takes, from inside a major build project. It's not as simple as picking the right components (though that is critical) and slapping them together. You have to really plan it well and stick to that plan.


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## ewdysar (Jun 15, 2010)

toddshotrods said:


> Renegrade Hybrids flips the diff and sets the 911 style transaxle up for mid-engine configuration - it ain't cheap though. IIRC, 2nd gear is the weak one in a Porsche transaxle. With the torque of even an 11-inch motor, let alone the big 13, and your desire to drive aggresively... Save up some pennies for a good rebuild. That can be done later though.


I've spent a long time messing about with my Renegaded 914 with a Chevy 327 and have a decent idea of the torque limits of the various Porsche transmissions.

The 901 (914) gearboxes can take about 300 ft/lbs, so a WarP 11 @ 1000A is right at the limit. Later 915 (911) trannies are good to around 400 ft/lbs (I've got one flipped and geared to go into the 914 during its next major upgrade) which may or may not survive 1000A through a WarP 13. The real answer is the 930 (911 Turbo) transmission. They're built to handle 700 ft/lbs and should take a WarP 13 @ 1400A all day. The 930 and 915 trannies are configured for rear engines, but can have their ring and pinion flipped easily enough. A flipped 930 should cost around $10k, a flipped 915 around $5k and the Renegaded 901 (no first gear and taller ratios) is about $2k. My 914 with the Renegaded 901 feels just like a 4 speed late 1960's muscle car working through the shift pattern.

The last I read, Otmar's 914 uses a 930 transmission, the R&P are not flipped because he can spin the motor the other way, that's one place where electrics can save during an conversion.

Eric

edit: Porsche transmissions are often used in kit cars because they represent a good blend of high power capability and small volume for a reasonable price. There are other exotic RWD transaxles out there, but they are even more $$$.


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## toddshotrods (Feb 10, 2009)

ewdysar said:


> ...the R&P are not flipped because he can spin the motor the other way, that's one place where electrics can save during an conversion...


Oh yeah, I forgot about that - cool!  Do they get good lubrication just flipped, or are there mods needed inside for that as well?




ewdysar said:


> ...There are other exotic RWD transaxles out there, but they are even more $$$.


Like a Mendeola - drool and drain (your bank account)...

Great info and insight ewdysar.


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## ewdysar (Jun 15, 2010)

toddshotrods said:


> Oh yeah, I forgot about that - cool!  Do they get good lubrication just flipped, or are there mods needed inside for that as well?


For long distance track cars, the inverted 930 can use some additional oil cooling and external oil injection points, but that's for people running > 500hp continuous. They typically externally cool the non-inverted gearboxes too. Just inverting the box doesn't cause any daily use problems.

Eric


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## sunworksco (Sep 8, 2008)

I have talked with these fellows and the frame is very inexpensive along with the basic complete kit.You can customize the suspension to double wish-bones front/rear.The deluxe chassis is really for the ICE version , anyway.You can order the frame and create a rolling/ev chassis with the drive-train and bring it back to the factory for bonding the body onto the chassis.You can build this Spyder/EV with Life battery pack weighing only around 1300lbs.
Regards,
John
http://www.thunderranch.com/550two.html


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## ewdysar (Jun 15, 2010)

sunworksco said:


> I have talked with these fellows and the frame is very inexpensive along with the basic complete kit.You can customize the suspension to double wish-bones front/rear.The deluxe chassis is really for the ICE version , anyway.You can order the frame and create a rolling/ev chassis with the drive-train and bring it back to the factory for bonding the body onto the chassis.You can build this Spyder/EV with Life battery pack weighing only around 1300lbs.
> Regards,
> John
> http://www.thunderranch.com/550two.html


Nice looking car, but I can't imagine anyone converting an original Porsche 550 like the one in the pictures. Looking at the kit, if you throw in the VW suspension and other missing pieces, it looks like you're above $10K for a glider, more if you want to go with more exotic suspension. I noticed that, according to the kit's manufacturer, the finished car weighs 1150 lbs with a 200 lb VW engine. How small of a battery pack would you need to come in around 1300 lbs? The 8kW TS LiFePO4 pack for my sailboat weighs 200 lbs by itself. 

Eric


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## sunworksco (Sep 8, 2008)

The Spyder kit engine,trans,gas tank/parts,exhaust,all fluids weighs in around 375-400lbs.I would also recommend using Ducati 1098 brakes and wheels to save another 100lbs.This would give a 500lb. allowance for the batteries and motor.I would use the smallest lithium polymer battery pack that you could get by with and increase the size as batteries drop in price.
Those photos of James Dean are posted for a little history.
There are a couple of shops that can supply you with reproduction aluminum bodied Spyder roller but this would cost around $40,000.00.
Regards,
John


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## ewdysar (Jun 15, 2010)

sunworksco said:


> The Spyder kit engine,trans,gas tank/parts,exhaust,all fluids weighs in around 375-400lbs.I would also recommend using Ducati 1098 brakes and wheels to save another 100lbs.This would give a 500lb. allowance for the batteries and motor.I would use the smallest lithium polymer battery pack that you could get by with and increase the size as batteries drop in price.
> Those photos of James Dean are posted for a little history.
> There are a couple of shops that can supply you with reproduction aluminum bodied Spyder roller but this would cost around $40,000.00.
> Regards,
> John


Hi John,

It all sounds good. So what kind of suspension would you suggest, and how much would it cost? What kind of gearbox/drive would you use to connect the motor(s) to the drive wheels? How does one use Ducati 1098 brakes and wheels and how much do they cost? Is these bolt together components or would this take considerable fabrication? What the smallest lithium polymer battery pack that you would get by with? Everyone here knows that general ideas are pretty easy, but the devil is in the details. 

I'm a big Porsche fan, so the 550 is appealing. I can see that the Thunder Ranch kit is a good buy compared to a $40k alternative, but $10k is more than I want to spend for an incomplete glider.

Eric


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## sunworksco (Sep 8, 2008)

I would use http://www.palatov.com/products/suspension.html
The suspension is not inexpensive but very performing.
Complete suspension parts are around $5,000.00.The parts are very easy to adapt to the frame and Palatov will give you drawings.
This would include the Ducati 1098 custom hubs and Brembo brake parts.
The Ducati brake parts can be purchased used on Ebay for savings.
I do like the Vintage Spyder kit over the Thunder Ranch kit because the Vintage frame is more substantial and easier to adapt the Palatov suspension.Vintage will sell you a chassis as a partial kit,too.
I would use a front-wheel drive AC-50 from http://www.thunderstruck-ev.com/AC_drive_performance.htm with a belt drive 9-1 gear ratio.You can install around a 200lb. li-poly battery pack and increase the size as the battery packs come down in cost.Think of it as a lower capacity gas tank with optional increase in size upgrades in the future.


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## toddshotrods (Feb 10, 2009)

sunworksco said:


> I would use http://www.palatov.com/products/suspension.html
> The suspension is not inexpensive but very performing.
> Complete suspension parts are around $5,000.00.The parts are very easy to adapt to the frame and Palatov will give you drawings...


That's good stuff. Those uprights are about the same effective height as what's on the Inhaler now! Hmmm, serious performance upgrade potential there. The prices is cheaper than I can design and machine my own...


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## ewdysar (Jun 15, 2010)

sunworksco said:


> I would use http://www.palatov.com/products/suspension.html
> The suspension is not inexpensive but very performing.
> Complete suspension parts are around $5,000.00.The parts are very easy to adapt to the frame and Palatov will give you drawings.
> This would include the Ducati 1098 custom hubs and Brembo brake parts....
> ...


OK, now I'm getting an idea of how this might come together. What type of differential and driveshaft/cv joints would you use with the Palatov uprights?

We're closing in quickly on the $30k estimate with just the parts identified so far, and there are plenty of miscellaneous stuff not covered yet. So far I've got $10k for the basic car kit, $5k for the suspension, $5k for the drive and more than $5k for the batteries and management system. We still need to do the fabrication to combine the major systems, finish the interior and exterior of the car, add steering and brake controls, and get a charger, DC/DC converter, contactors, cabling, other instrumentation etc. etc. 

But this does look like a viable fair weather fun car, I wonder what the range would be with a < 10kWh pack... Unfortunately, while new batteries might come down in price, they probably won't get much better in weight in the near future and price hasn't been a limiting factor in this exercise so far. Another 200 lbs is a 15% increase in overall vehicle weight and would max out the LT suspension ratings.

Eric


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## sunworksco (Sep 8, 2008)

I would consider the DP3 chassis design with a BMW F-800 rear single-sided swing-arm for an economical ride weighing less than 1,000lbs..
By changing the design from 4-wheel to reverse-trike , this gives you more component space behind the seat.This would be a simple chassis to fabricate , as well.The bare chassis would cost less than $2,000.00.
Forget to add to the previous comment that the CV axles are Golf III type for the Palatov suspension setup.
Regards,
John


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## Duncan (Dec 8, 2008)

Hi Everybody

Just a comment about Kit car weights
I have found them to be VERY unreliable 
I seems to me that most manufacturers just make up a number

I am making a Locost type car - I am hoping to get under 800Kg 

Motor - 102 Kg
Batteries - 300 Kg

leaves me 400 Kg for everything else - I have been weighing bits as I go along

Trying to get below 1000 lbs - 459 Kg is difficult,

even a light weight motor and battery *for a car* will be 200 Kg - leaving 250 Kg for everything else 

If I was buying a kit car I would ask the manufacturer how he knew the weight and I would weigh the bits

You could visit the manufacturer with a mate and two bathroom scales


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## sunworksco (Sep 8, 2008)

The weight figures are real honest ones.
Regards,
John


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## Duncan (Dec 8, 2008)

_*The weight figures are real honest ones.*_
_*Regards,*_
_*John *_


Trust But Verify

I would still take the scales!!


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## TomA (Mar 26, 2009)

Duncan said:


> I seems to me that most manufacturers just make up a number
> 
> If I was buying a kit car I would ask the manufacturer how he knew the weight and I would weigh the bits


This is a real problem. The plain fact is, most kit car mfrs don't actually weigh the bits. Everybody who builds one uses rather different bits to begin with, so it would really be impossible for them to spec the weight of an average build. They also don't want to do that for marketing purposes anyway, so what I think they do is quote the minimum possible values for the essentials like (all billet) suspensions and such, and then they completely ignore a whole range of things from weatherstripping to carpet glue to paint and primer (which can easily be 25 lbs...)

I am finding this a major challenge, and I just have to smile every time I see weights tossed around. I'm on a TOTAL weight budget of 400lbs, and I have gone through two or three iterations with most of the parts I'm using. It is a very, very tedious process and actually gets to be an expensive game to play.

BTW, even the OEMs fail at it. Don't forget Mercedes-Benz having to sack the chief engineer of the A-Class car when it came in not only overweight, but with a Cg so high that the production car flipped over in the moose test. Weight creeps in. People don't like to talk about it. Most kit cars have super-heavy bodies and a chassis that is far heavier than any _real _racing tube frame of the same size.

You just have to weigh everything and be ruthless and focused about dealing with it. Hell, the damn stereo probably adds 25 lbs to most cars... 

TomA


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## sunworksco (Sep 8, 2008)

The original Porsche 550 Spyder is 1200-1300lbs.
The Thunder Ranch chassis is the original design and weight.
The Palatov suspension is lighter than the original Porsche .
The Ducati 1098 wheels/hubs/brakes are 100lbs. lighter than stock.
You can still buy aluminum or fiberglass seats.
There are many lightweight parts available now for the Spyder.
You can even install a polycarbonate windshield.
Regards,
John


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## DavidDymaxion (Dec 1, 2008)

Responding to older posts:

The Porsche 6 cylinder is pretty heavy -- around 400 lbs.

I think it would be challenging to cut up a Porsche 911 too much and greatly modify it. The tranny, suspension, and rear seats are a very tight fit. If you flip the tranny to mid-engine, that would involve a total redesign of the rear suspension. You'd also have a challenge to get a shift linkage back there, and still have room for both front seats -- it would almost force a single ratio. Rear motor is not a liability for an electric, you can balance it by putting batteries in front.

I'd suggest looking in the back of Porsche magazines and Porsche boards for used 911 race cars. Then you are already gutted, have the lightweight windows and seats, roll cage, etc., and you can often negotiate for minus the motor, or see the motor separately yourself.


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## jeff mccabe (Feb 23, 2010)

Hi Guys,
New to this forum. I saw the thread and couldnt resist.
My conversion is a 928 Porsche that weighs 2,765lbs(25kwh Lithium). verified on scales.
It orginally weighed 3,500lbs. with a 21kwh pack in it. 
I was quite happy with the amount of weight I was able to remove from it.(over 1,600lbs...no really )
I have had a lithium pack in it a year now and use it dailly. I have put nearly 10,000 miles on it since last august.
Now the real fun is just starting . I purchased an unfinished Factory Five Roadster(Cobra) a few months ago and I am in the process of converting this.

http://www.evalbum.com/736

Thanks,
Jeff McCabe


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## ewdysar (Jun 15, 2010)

jeff mccabe said:


> Hi Guys,
> New to this forum. I saw the thread and couldnt resist.
> My conversion is a 928 Porsche that weighs 2,765lbs(25kwh Lithium). verified on scales.
> It orginally weighed 3,500lbs. with a 21kwh pack in it.
> ...


What on earth did you take out of it lose 45% of the original weight?

I'm astounded!!

Eric

edit: I misunderstood, you were saying that it weighed 3500 pounds as a prior 21kWh conversion. I thought that you meant 3500 pounds as the original 928. Still I'm surprised that you could get a 928 under 2000 pounds as a glider...


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## sunworksco (Sep 8, 2008)

Great build,Jeff!
I always thought the Porsche 928 was a very special under-rated car!There are a number of these cars languishing in a garage with sick engines ripe for conversion.The Porsche 944 is a good candidate,as well.
The fender skirts work very well on this car!
Do you have a close-up image of the charging port?
Regards,
John


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## jeff mccabe (Feb 23, 2010)

ewdysar said:


> What on earth did you take out of it lose 45% of the original weight?
> 
> I'm astounded!!
> 
> ...


Eric,
The car weighed just over 3.500lbs. with 1/3 tank of gas befoe conversion. It weighed the same after the conversion with 1.300lbs of lead.
The 928 really made it easy getting rid of all the weight. Remeber I started with a v8 engine, that was over 800lbs with all the accesories. Their was 200lbs of sound insulation on the floor boards and firewall alone. Gutted gear box with just 2-3rd gears left, removed the limited slip rear gear for an open diff. out od an automatic. Just these items were over 1.100lbs.
After I got rid of all the heavy bitts, I was left with a car with aluminum doors hood and fenders. Anyway the list is long and it is late.
Good night !
Jeff

p.s. the charge port is hidden under the aluminum cake pans that used to have the popup headlights(another 35lbs removed)


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## ewdysar (Jun 15, 2010)

jeff mccabe said:


> Eric,
> The car weighed just over 3.500lbs. with 1/3 tank of gas befoe conversion. It weighed the same after the conversion with 1.300lbs of lead.


Then I'll go back to my first question. What on earth did you take out of the car to get to a 1600 pound weight reduction?

Eric


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## jeff mccabe (Feb 23, 2010)

sunworksco said:


> Great build,Jeff!
> I always thought the Porsche 928 was a very special under-rated car!There are a number of these cars languishing in a garage with sick engines ripe for conversion.The Porsche 944 is a good candidate,as well.
> The fender skirts work very well on this car!
> Do you have a close-up image of the charging port?
> ...


 John,
Check my Flikr album, it has most of my build photos. Also has some of my new project.

http://www.flickr.com/photos/[email protected]/

Jeff


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## jeff mccabe (Feb 23, 2010)

ewdysar said:


> Then I'll go back to my first question. What on earth did you take out of the car to get to a 1600 pound weight reduction?
> 
> Eric


Eric,
The car weighed just over 3.500lbs. with 1/3 tank of gas befoe conversion. It weighed the same after the conversion with 1.300lbs of lead.
The 928 really made it easy getting rid of all the weight. Remeber I started with a v8 engine, that was over 800lbs with all the accesories. Their was 200lbs of sound insulation on the floor boards and firewall alone. Gutted gear box with just 2-3rd gears left, removed the limited slip rear gear for an open diff. out od an automatic. Just these items were over 1.100lbs.
After I got rid of all the heavy bitts, I was left with a car with aluminum doors hood and fenders. Anyway the list is long and it is late.
Good night !
Jeff

p.s. the charge port is hidden under the aluminum cake pans that used to have the popup headlights(another 35lbs removed)


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## aeroscott (Jan 5, 2008)

Jeff , welcome , I've been talking about your conversion for a long time . We met at the airport (eaa ) , we talked about A8 and the 928 . looking forward to many more details of your super car . john


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## DavidDymaxion (Dec 1, 2008)

I bow in your general direction! That's awesome weight reduction, and awesome you came in at the same weight with that much lead! My Chevy's V8 weighs 650 lbs, amazing the Porsche one was so much heavier. The 911 six is around 400 lbs, pretty heavy for an air cooled motor of its size.

Why did you go to an open diff? Doesn't that lead to 1 wheel tire destruction?


jeff mccabe said:


> Eric,
> The car weighed just over 3.500lbs. with 1/3 tank of gas befoe conversion. It weighed the same after the conversion with 1.300lbs of lead.
> The 928 really made it easy getting rid of all the weight. Remeber I started with a v8 engine, that was over 800lbs with all the accesories. Their was 200lbs of sound insulation on the floor boards and firewall alone. Gutted gear box with just 2-3rd gears left, removed the limited slip rear gear for an open diff. out od an automatic. Just these items were over 1.100lbs.
> After I got rid of all the heavy bitts, I was left with a car with aluminum doors hood and fenders. Anyway the list is long and it is late.
> ...


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## jeff mccabe (Feb 23, 2010)

DavidDymaxion said:


> I bow in your general direction! That's awesome weight reduction, and awesome you came in at the same weight with that much lead! My Chevy's V8 weighs 650 lbs, amazing the Porsche one was so much heavier. The 911 six is around 400 lbs, pretty heavy for an air cooled motor of its size.
> 
> Why did you go to an open diff? Doesn't that lead to 1 wheel tire destruction?


David,
I went with the open Dif. because it weighted 10 pounds less and rember that is rotational mass, so it worth 4-5 times as much. But it didnt count it that way for the overal weight reduction.
As far as one wheel spinning. that hasnt proved the case. In straight line burn outs it leaves two strips and when cornering fast both wheels usaully spin. I guess Porsche just designed a good unit. 

Jeff


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## aeroscott (Jan 5, 2008)

Jeff , I was thinking of your great numbers on watts / mile (160 w/m ) . The aero drag (c/d ) must be really good .It sure looks good . If a car like yours had a pmac drive and transverse transmission ( Honda or VW ) , Do you think a 15 to 25% reduction could be acheaved (128 w/m). that would be getting into the Aptra numbers almost .


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## ewdysar (Jun 15, 2010)

aeroscott said:


> Jeff , I was thinking of your great numbers on watts / mile (160 w/m ) . The aero drag (c/d ) must be really good .It sure looks good . If a car like yours had a pmac drive and transverse transmission ( Honda or VW ) , Do you think a 15 to 25% reduction could be acheaved (128 w/m). that would be getting into the Aptra numbers almost .


According to the specs that I can find on Porsches, the various 928 models all have a Cd around 0.34, but because of the larger size the CdA (in sq. ft.) is 7.13, about 15% worse than many 911s. Even with the impressive weight reduction, Jeff's glider was around 1900 pounds, so I doubt that it's efficiency can compete with CRX's (CdA = 5.71) or a '93 RX-7 (CdA of 5.61). A CRX is considerably lighter too. I believe that a 914 has a CdA less than 6.0, but I'm having a hard time getting the measured frontal area, so I might be mistaken.

That said, the 928 CdA of 7.13 is very respectable, you have to search carefully to find anything under 6.7.

Eric

Edit: The Nissan 240SX and Toyota MR2 both have CdA values under 6.0 also.


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## aeroscott (Jan 5, 2008)

stock cd's are not going to tell much once spoilers are removed , belly pans ,fender skirts , etc. are added .


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## jeff mccabe (Feb 23, 2010)

aeroscott said:


> Jeff , I was thinking of your great numbers on watts / mile (160 w/m ) . The aero drag (c/d ) must be really good .It sure looks good . If a car like yours had a pmac drive and transverse transmission ( Honda or VW ) , Do you think a 15 to 25% reduction could be acheaved (128 w/m). that would be getting into the Aptra numbers almost .


John,
The way I acheived the efficiency of 165-175 wh/m was through lowering the car,aero, drivetrain, rolling resitance and reducing brake drag. It will never get close to the aptera numbers though. 
An AC system would be nice. I did consider the AC Propulsion setup untill I got a qoute.
I have been looking into loosing the transmission all together and installing a 11" GE, direct drive setup. That would improve efficiency a bit on the highway, but hurt some at lower speeds.
Jeff


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## ewdysar (Jun 15, 2010)

aeroscott said:


> stock cd's are not going to tell much once spoilers are removed , belly pans ,fender skirts , etc. are added .


Since we're talking about a 928 that is starting with a Cd of 0.34, how much do you think you could reduce that?

I didn't get the impression that Jeff had done all of that to improve his aero. And while you might work on improving the stock Cd, not many people significantly reduce the frontal area. Typically the only thing that one can do for that is to cut off the roof and windshield. That's more than most owners will do to their street drivers.

Eric


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## jeff mccabe (Feb 23, 2010)

ewdysar said:


> According to the specs that I can find on Porsches, the various 928 models all have a Cd around 0.34, but because of the larger size the CdA (in sq. ft.) is 7.13, about 15% worse than many 911s. Even with the impressive weight reduction, Jeff's glider was around 1900 pounds, so I doubt that it's efficiency can compete with CRX's (CdA = 5.71) or a '93 RX-7 (CdA of 5.61). A CRX is considerably lighter too. I believe that a 914 has a CdA less than 6.0, but I'm having a hard time getting the measured frontal area, so I might be mistaken.
> 
> That said, the 928 CdA of 7.13 is very respectable, you have to search carefully to find anything under 6.7.
> 
> ...


 Actually the glider weight was just under 1,700lbs but who's bragging. Two of the biggest aero improvements were the full undertray and the udjustable rear airfoil. Im able to change the angle to reduce the rear turbulance. I also changed out the brakes to Willwood four piston brakes which geatly reduced brake drag. This really improved how long I can glide.
Jeff


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## aeroscott (Jan 5, 2008)

The high price of ac systems is daunting . My poor mans ac system is the Prius motor/trans with a industrial motor controller (Allen Bradly 98kva) . ditching the hypoid rear end would be 10% and 10-15% for the motor . check posts in controllers, Allen Bradly 98kva motor controller . Aptras watts/mile is 100 w/m if i remember ?


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## Jesse67 (May 12, 2009)

1992 Dihatsu Hijet Jumbo cab 4wd. 

- 1500lbs original weight
- weighed in at 1000lbs with un-needed parts removed
AC 50 and 24 x 100AH TS cells along with the on board charger etc should bring it back to ~1500lbs.

Shooting for 100kmph top speed, 50km range at city speeds. A few pictures here, more to come.

http://jessetufts.wordpress.com/the-electric-mini-truck/

Its got terrible aerodynamics, ~24ft^2 frontal area and about a 0.45 CD but its about the lightest 4wd truck you can find. And it has about 1000lbs of payload capacity! 

Cheers,

Jesse


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## aeroscott (Jan 5, 2008)

Very nice, great to see the other side of aero eff. your weight is so low , + 1000 lbs for more batteries and /or load . It would be very interesting to see what would happen to the c/d with faring in the back to a tear drop , that could removed to hall big loads . I was looking at running sheet material from the top of the cab of a pickup to a sharp end at the back end . then add a belly pan .


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