[askme233]

New here, reading the Wiki, and looking for ideas and suggestions:

I am looking to convert a garaged, but non-functional 912 into EV. I would love ideas and suggestions, especially on likely costs involved. A few points first:

Your skill level with auto mechanics and fabrication: low to moderate. Repaired Porsches in a garage as a kid. Handy, but haven't done any real auto work since.

The range you are hoping to get (how many miles/charge). I am East Coast, so a 100 range would be plenty to get to major locations.

What level of performance you are hoping to get. 912's were not really that fast, but I'd like to get something faster than your average minivan. So, I see that as looking to go one step faster than "normal"

How much money you are willing to put into your project. Competing options for the money run about $30k, and I may need to put $10 into just paint, body, brakes, suspension, etc. Looking to this sub for help validating the rest.

What parts you've already considered, if any. When I looked at individual components, this AC50 kit seemed reasonably priced and already worked out, but I would love your view on how it will meet the expectations above.
http://www.evwest.com/catalog/product_info.php?products_id=221

batteries seem to be the limiting factor for budget vs performance and range.

 

[brian_]

What level of performance you are hoping to get. 912's were not really that fast, but I'd like to get something faster than your average minivan. So, I see that as looking to go one step faster than "normal"

As a minivan driver, I see frequently see comments suggesting that minivans have terrible performance. In reality, my decade-old ordinary Toyota Sienna can accelerate more quickly than is ever required on the road, can cruise all day at beyond the legal speed limit on any road in the country, and can haul a couple tons of trailer up a mountain grade at highway speeds. It is vastly more capable than an original 912 in everything except cornering response. So, perhaps a more objective target would be helpful.

What sort of acceleration times would you consider "one step faster than normal"?

While I'm sure a stock 912 is fun to drive, it's not fast: 90 to 100 hp in a one-ton car puts it on par with the most basic econobox currently available. A 1969 Car and Driver test showed 0 to 60 mph taking 11.4 seconds; my minivan takes 7.8 seconds for that run. So what's the target? Better than 11.4 s for 0-60? Better than 7.8? Some other measurement?

 

[askme233]

As a minivan driver, I see frequently see comments suggesting that minivans have terrible performance. In reality, my decade-old ordinary Toyota Sienna can accelerate more quickly than is ever required on the road, can cruise all day at beyond the legal speed limit on any road in the country, and can haul a couple tons of trailer up a mountain grade at highway speeds. It is vastly more capable than an original 912 in everything except cornering response. So, perhaps a more objective target would be helpful.

What sort of acceleration times would you consider "one step faster than normal"?

While I'm sure a stock 912 is fun to drive, it's not fast: 90 to 100 hp in a one-ton car puts it on par with the most basic econobox currently available. A 1969 Car and Driver test showed 0 to 60 mph taking 11.4 seconds; my minivan takes 7.8 seconds for that run. So what's the target? Better than 11.4 s for 0-60? Better than 7.8? Some other measurement?

lol, I wasn't dissing minivans, but referencing a quote I have heard a number of times about older sportscars. Something along the lines of, "it was considered damn fast in its day, but would be smoked by a modern minivan". e.g. even a car not designed with speed as a goal is faster.

I was just looking at new SUV's. They all listed sub 6sec 0-60 times. Those were sports car times when I growing up.

If I am gonna dump money in a custom EV, I will spend a few $k extra to get to something that could at least feel like it is at the level of modern performance.

EDIT to add:

So specifically, I am trying to work out likely performance with the planned AC50 motor and various Battery configs, or wondering if I need to do what they did in the recent 911 conversion and go with dualAC34's. It is a bit more money and seems to be more complicated. So if I can get the 912 (a bit lighter than the 911 used) doing a decent 6/7 0-60 with the AC50, I'll stay with simplicity. Top speed is less important to me as I am unlikely to aver see north of 90mph (even that would be worrisome in an older suspension).

 

[Moltenmetal]

Sub 6 second 0-60 may or may not be possible with an AC50 depending on what batteries you use and how much they weigh.

With dual AC34s it should be no trouble at all...that's tons of torque and power.

Of course a big DC motor would also do the job if performance is most important to you. AC gives you higher reliability, regen braking for a 10-15% range boost and the feel of power brakes without any of the mechanical complexity, and of course no brush dust and associated maintenance to worry about. But it does give you considerably less grunt for your dollar, even though the total number of dollars spent for a single motor application are similar unless you build your own DIY controller.

I haven't measured the 0-60 time in my Spitfire with its AC50- it may be under 6 seconds but probably isn't- when you are that low to the ground, everything feels fast! The grunt it gives you immediately off the line is really fun too- the most fun, actually. That's with a gearbox and a clutch- you'll need the former for sure. The clutch is optional but helpful for quick gear changes without wear and tear on the synchros in your tranny.

 

[askme233]

Sub 6 second 0-60 may or may not be possible with an AC50 depending on what batteries you use and how much they weigh.

With dual AC34s it should be no trouble at all...that's tons of torque and power.

Of course a big DC motor would also do the job if performance is most important to you. AC gives you higher reliability, regen braking for a 10-15% range boost and the feel of power brakes without any of the mechanical complexity, and of course no brush dust and associated maintenance to worry about. But it does give you considerably less grunt for your dollar, even though the total number of dollars spent for a single motor application are similar unless you build your own DIY controller.

I haven't measured the 0-60 time in my Spitfire with its AC50- it may be under 6 seconds but probably isn't- when you are that low to the ground, everything feels fast! The grunt it gives you immediately off the line is really fun too- the most fun, actually. That's with a gearbox and a clutch- you'll need the former for sure. The clutch is optional but helpful for quick gear changes without wear and tear on the synchros in your tranny.

Thanks. I wasn't looking at sub-6 sec, but a bit slower. If I went to a newer BMW 328, they spec at 7.3sec 0-60 with a big step up for the 330 at 5.5sec (with 70 more HP). SO I would be quite happy with 7 sec-ish 0-60 as in line with a modern car, even if not the very fastest.

I will say that a Spitfire would be my other all time fav's and the lust of my youth. Can you point me to what you have done in terms of motor, batteries, etc? How much did it all weigh?

 

[askme233]

I think I have some of my answer.

This site talks about using the AC50, Curtis controller, and lithium batteries in a professional conversion in a 356 replica and getting 11sec 0-60 but about 130mph top speed.

http://www.electric-cars-are-for-girls.com/ac-electric-motors.html

I have to imagine same motor will have similar performance in a 912 (or at least not better)

 

[Moltenmetal]

Go to the Garage and search for the E-Fire- there's a link to my whole thread in there, plus the vital specs. I figure the car is about 150lbs heavier as a result of the conversion, but don't have an accurate weight.

 

[Moltenmetal]

I don't know my top speed either, but know that on the flat at 60 miles/hr (100 km/hr) I'm drawing 150 A, and I could draw up to 650A for up to about 2 minutes before the Curtis would start to cut back.

 

[onegreenev]

The metal body 912 will not have better performance than the fiberglass versions. It will be good but will not have Porsche Performance. If you want some good performance you need to go with a dual motor setup or a larger motor/inverter from someone else than HPEVS.

Check out this setup. I'd use the AC51 at 144 volts. It is considerably more expensive but would have much greater performance.

Pete



http://www.evwest.com/catalog/produ...ucts_id=441&osCsid=dokr59nn97vfs2d5o23t9ff932

 

[brian_]

lol, I wasn't dissing minivans, but referencing a quote I have heard a number of times about older sportscars. Something along the lines of, "it was considered damn fast in its day, but would be smoked by a modern minivan". e.g. even a car not designed with speed as a goal is faster.

I was just looking at new SUV's. They all listed sub 6sec 0-60 times. Those were sports car times when I growing up.

If I am gonna dump money in a custom EV, I will spend a few $k extra to get to something that could at least feel like it is at the level of modern performance.

We're on the same page about performance trends!

A current vehicle typically has two to three times the power of an equivalent from 40 to 50 years ago, although it's also heavier. A light sports car like the 912 is now expected to have at least 200 hp: the lighter Mazda MX-5 at 160 hp or the slightly heavier Subaru/Toyota BRZ/86 at 200 hp are great to drive, but get flak from many people for being underpowered; most "sports" cars are heavier, but have 300 hp or more... which you can get from the V6 in that minivan.

This makes achieving modern sports car performance with battery-electric power over significant range while maintaining 912 agility a tough combination. Perhaps settle for that performance only at lower speeds, so the peak power requirement is not so high?

So specifically, I am trying to work out likely performance with the planned AC50 motor and various Battery configs, or wondering if I need to do what they did in the recent 911 conversion and go with dualAC34's. It is a bit more money and seems to be more complicated. So if I can get the 912 (a bit lighter than the 911 used) doing a decent 6/7 0-60 with the AC50, I'll stay with simplicity. Top speed is less important to me as I am unlikely to aver see north of 90mph (even that would be worrisome in an older suspension).

What if you aimed for the same rate of acceleration as a typical 0-60 in 6.5s car, but settled for less acceleration at higher speed? Just wondering... it depends on the circumstances in which you want to use the performance.

 

[brian_]

... The grunt it gives you immediately off the line is really fun too- the most fun, actually. That's with a gearbox and a clutch- you'll need the former for sure.

That makes sense to me as the way to get performance at low speed, by keeping the motor speed up in the range where it produces maximum power, yet not over-revving the motor at higher speeds... particularly with motor and drive voltage combinations which don't have the speed range of the setups used by modern production EVs.

Since adapters for VW/Porsche transaxles are readily available for common DIY motors, and the motor would be well placed for mass distribution and packaging, using the original transaxle makes sense to me... even if it doesn't work so well for some other vehicles.

 

[brian_]

This site talks about using the AC50, Curtis controller, and lithium batteries in a professional conversion in a 356 replica and getting 11sec 0-60 but about 130mph top speed.

http://www.electric-cars-are-for-girls.com/ac-electric-motors.html

I have to imagine same motor will have similar performance in a 912 (or at least not better)

I've seen that web site before, and found it not worth reading through to get at solid technical information... but I'm sure there's good stuff in there. Accepting the data as quoted...

Given that the top speed is much higher than required, much shorter gearing (with the same motor and voltage) would be suitable, and better for performance at sensible speeds. Assuming that the 11-second time was obtained using the gearing available appropriately, that means you would want a shorter final drive.

 

[askme233]

The metal body 912 will not have better performance than the fiberglass versions. It will be good but will not have Porsche Performance. If you want some good performance you need to go with a dual motor setup or a larger motor/inverter from someone else than HPEVS.

Check out this setup. I'd use the AC51 at 144 volts. It is considerably more expensive but would have much greater performance.

Pete



http://www.evwest.com/catalog/produ...ucts_id=441&osCsid=dokr59nn97vfs2d5o23t9ff932

It seem not that much more expensive (20%), and presumeably would be a direct swap for the AC50 as opposed to the dual AC34 at twice the price. I did read on HPEVS site that the AC51 is just modified to push the torque band out. I don't know enough translate that into how it changes things.

That link was for the a dual motor setup. Were you suggesting dual AC51s?

 

[brian_]

I will say that a Spitfire would be my other all time fav's and the lust of my youth. Can you point me to what you have done in terms of motor, batteries, etc? How much did it all weigh?

We have a Spitfire which needs an engine rebuild; considering an EV conversion was what brought me to DIY Electric Car. Since the car is now relatively obscure, I was surprised by the number of Spitfire EV conversion projects, and I built a very incomplete list:

In DIY EV

• Planning a new ev from a triumph spitfire
• gerd1022's "Spitwire"
  • DIYElectricCar: Spitwire Build
• ClintK's "Bumblebee Transformer"
  • '78 Spitfire Electric Conversion
  • DIYElectricCar: Bumblebee Triumph Spitfire Build Thread
• Bottomfeeder
  • no known build thread
• Moltenmetal
  • E-Fire '75 Spitfire conversion: 1st build!

Other

• Ralph Goodwin's DC 203-06-4001A

The Spitfire and 912 have some similarities: both are sporty variants of an earlier small sedan, both were mechanically outdated by the 1970's, and both even have similar rear suspension. The Spitfire is a bit smaller, which means it should need less power, but it certainly has less space for battery packs. In the 912 you could sacrifice the rear seat for lots of battery space (in addition to the front fuel tank location), but in the Spitfire most builders seem to need to resort to piling a mass of battery in the nose, well ahead of the front axle.

 

[Moltenmetal]

The Spitfire has a full-on chassis with a bolt-on body bucket, which makes it easy to restore. The only component which actually bears on the body bucket is the radius arms of the rear suspension- everything else bears on the chassis. The chassis is a bit of a weird shape, but it's still a useful platform to build on.

That, plus a decent suspension design for the time, and many consider to be quite a nice body design, make the thing quite attractive as a target for engine swaps of all kinds, and electric conversions too. As one guy put it, the Spitty is basically a road-legal go-kart...

The Porsche is gorgeous too and has its advantages.

The AC-51 is intended for use in trucks- more grunt at lower speeds unless I misremember.

Again I think the AC-50 is likely underpowered for what you want, and that if performance is your main goal, a big DC motor is your cheapest bet. Dual AC-34s are very expensive but will give a lot of fun factor...assuming you have a pack capable of meeting their current demand safely.

 

[brian_]

Sorry... missed a significant recent build thread from my list, above

• Baratong's "Thistle"
  • DIY Electric Car:'79 Spitfire Conversion

... and the Garage has a couple of pages of Spitfires, including the ones that I've specifically listed.

 

[Duncan]

Brian
I had not realized that you were thinking about "doing" a Spitfire

Have you seen the Hurricane?

It's a fiberglass body kit for the Spitfire - as in a complete replacement body!

But it looks awesome!

 

[brian_]

Brian
I had not realized that you were thinking about "doing" a Spitfire

Have you seen the Hurricane?

It's a fiberglass body kit for the Spitfire - as in a complete replacement body!

But it looks awesome!

Yes, I saw the Hurricane a while ago, while looking for information about the Spitfire. In addition to the (presumably) intended use to revive a Spit with a rotten or crashed body (not for me - ours is pretty good), this could be a really interesting basis for an EV, using a custom frame and modern suspension bits (Miata?) instead of working around the limitations of the old Triumph bits... but keeping the size and style of the Spitfire. Too much time and money for me, though...

For someone wanting a small car like the Spitfire with a similar style, but wanting to use a custom powertrain, and willing to use a kit... there's the Catfish. It's strictly a roadster (no roof, not even convertible) and doesn't even have doors (you jump in over the side), but it looks like it could make a great small open sports car. Of course, that's even more time and money...

(No, I don't know why anyone would take marketing photo of their product against that background!)

Duncan, it seems to me that someone wanting to use the configuration of your Dubious Device could use a Catfish with a custom tunnel (to suit their chosen motor) and the Miata chassis bits for which the kit is intended, with almost all of the design work done for them. But maybe that's not what the original poster is looking for.