German Supertuner RUF Building an Electric Porsche

[Joseph]

Something to add.

I know it sounds odd that electric motors are more efficient at high rpms. My understanding is that at lower rpms, the current (amps) vs. voltage proportion is higher than it is at higher rpms. So basically, low rpms use more current but less voltage and higher rpms use less current but more voltage.

High current and low voltage is less efficient. I don't know why, but I know for certain that is true. A wire containing 100 amps at 50 volts will create much more heat that 100 volts at 50 amps.

Also, there's nothing wrong with transmissions. They improve performance a whole lot, but the problem is reliability. Super high rpm and super high torque puts too much stress on the transmission. Plus, it's a disaster on the clutch because the "engine" can't wind down quick enough. A gas car will lower rpms in an instant, allowing for a smoother shift; but an EV spinning at 14k rpm will still be spinning very quickly when you shift it.

 

[TEG]

...Also, there's nothing wrong with transmissions...

Turning more gears hurts overall efficiency. Tesla realized a range improvement when they went from 1.0 to 1.5...

 

[stopcrazypp]

I think there's a balance in terms of efficiency. Is the efficiency that you gain from having the option of the lower lower gear greater than what you have lost from having a transmission?

The biggest positive I see from the transmission is just the option to have a higher top speed. But using the existing transmission on the car is something I expect more from homemade conversions than a professional tuner. If it's like other conversions I have seen, you can't actually switch gears easily while driving. So we still don't have a true manual multi-speed transmission for EVs yet.

 

[TEG]

...The biggest positive I see from the transmission is just the option to have a higher top speed...

I have said a bunch of times that I think EVs shouldn't be geared for high top speed. It just shows off their shortcomings. Limited energy storage results in very short ranges at high speed. EVs are a lot about efficiency, and wind resistance starts to cut into that big time at speeds > 90 MPH.
Besides, look how the Roadster didn't fair so well when the German auto journalists took them out on the Autobahn. The eMotor started to get too hot and reduced top speed back down to something closer to 100MPH. Tesla needs to gear the Roadster for brief excursions to 125MPH top speed because they sell a product that has to have a decent 1/4 mile time for image reasons. For something not aspiring to be a "supercar" (of sorts) an 85MPH top speed could be much more reasonable. Why complicate things when a high rev AC motor can get you up to US Freeway speeds with only 1 gear. Direct drive all the way, thank you very much.

 

[Joseph]

Transmissions are not necessary by any means, and are completely impractical for efficiency and reliability reasons for a normal production car. However, if you're building some unique, oddball EV (sorta like Ruf's EV Porsche) keeping the transmission has its merits. You sacrafice reliability, (clutch, gears wear out) usability (EVs don't shift gears well) and efficiency (all those extra gear will nock off about 5-10% of your range) BUT you get a higher top speed.

For the automotive enthusiast who has enough time and cash to waste going after this EV Porsche, that's all that matters.

 

[doug]

However, if you're building some unique, oddball EV (sorta like Ruf's EV Porsche) keeping the transmission has its merits. You sacrafice reliability, (clutch, gears wear out) usability (EVs don't shift gears well) and efficiency (all those extra gear will nock off about 5-10% of your range) BUT you get a higher top speed.

For the automotive enthusiast who has enough time and cash to waste going after this EV Porsche, that's all that matters.

This was pretty much my point in mentioning the transmission above. Having 6 gears is overkill, seems you could skip half of them, and I really doubt top gear is all that useful. But my main point is that this is a fine shortcut for an enthusiast conversion project, but seems like a poor effort from "professionals."

 

[TEG]

Yes, well, as Tesla can attest it takes real money to make your own gearbox!

 

[bill]

I have said a bunch of times that I think EVs shouldn't be geared for high top speed. It just shows off their shortcomings. Limited energy storage results in very short ranges at high speed. EVs are a lot about efficiency, and wind resistance starts to cut into that big time at speeds > 90 MPH.

Good Point..!!
Your last mail about "It's the battery, stupid" really drives home the message. Before we invest in gearboxes, we need the battery performance. Top speed can wait. From what I read here, it seems most of us who are buyers, or future buyers won't be on the track looking to drive 200MPH. The single speed box is a Super Asset for us.

 

[DaveD]

When Tesla announced that they were dropping the two-speed transmission, and going with a single-speed gearbox, I was personally very happy with that decision. Simple to operate and more reliable. Mind you, I don't like automatic transmissions; I've never owned a car with one, and I never want to. But I'll happily take a single-speed gearbox any day.

 

[dpeilow]

eRuf Model A (electric Porsche 911) - First Drives | Reviews | MSN Cars UK

 

[graham]

Porsche Buying a Tesla Roadster to Study It

Tesla spokesperson told Inside Line, "A Porsche senior engineer actually came over a few weeks back, and he was seriously analyzing the car in every detail." The spokesperson said that Porsche will have to wait a little while to get a Tesla, as the automaker is "pretty far down on the list of current orders."

Separately, a German source has told Inside Line that Porsche is none too pleased with the recently tested eRuf , created by tuner Ruf and California expert Calmotors using a 997 911 Carrera chassis and body packed with lithium-ion units. No one is detailing exactly why Porsche is unhappy with the car — which Inside Line tested and will report on soon — but Porsche is known to be working on its own lithium-ion-powered prototype.

 

[doug]

What this means to you: We suspect this is a case of Porsche engineers simply being upset over the "not invented here" aspect. They'll get over it and build the best lithium-ion racer ever.

I suspect is has more to do with having their brand associated with the (relatively) low performing and kludgey eRuf vehicle.

 

[just-an-allusion]

German Supertuner RUF Building an Electric Porsche | Autopia from Wired.com

Personally, I am not surprised with Porsche's interest in the electric/hybrid car technology since they did manufacture the first electric/hybrid car 100 years ago:

Porsche Had World's First Hybrid 100 Years Ago

Surprise! The first hybrid car is a 100-year-old Porsche! The car had in-wheel electric motors and an onboard gas engine to recharge the batteries. This makes the car a serial hybrid (only one engine drives the wheels) like the Volt, instead of a paralell hybrid (both engines drive the wheels) like the Prius. And the car, on the whole, was quite a breakthrough at the time.
The in-wheel electric motors were an absolute stroke of genius as they significantly increased the vehicle's efficiency by removing all mechanical parts. Unlike the Volt, the 1901 Porsche hybrid could only be charged by its onboard engine. Unlike its all-electric predecessors, it didn't have a plug.
Unfortunately, Porsche didn't see any reason to continue development of these hybrid vehicles, as gasoline became exceptionally cheap, and the extra electric motors were prohibitively expensive. And now, 100 years later, the last thing Porsche is concerned with is efficiency. Porsche will have one of their antique electric cars on display at this week's Los Angeles Auto Show. They're using it to promote their new green initiative. Unfortunately, there's no real story there, as Porsche seems to be more interested in luxury SUVs than plug-in hybrids.

Porsche Had World's First Hybrid 100 Years Ago | EcoGeek - Clean Technology

 

[dpeilow]

Porsche 911 EV unveiled by German tuner RUF

Some interesting specs here. That is a very heavy battery but at 3000 charge cycles should last a while.

 

[TEG]

http://www.gizmag.com/porsche-911-ev-ruf/10548/Some interesting specs here. That is a very heavy battery but at 3000 charge cycles should last a while.

That is basically what you get if you use Li-Fe-Po cells instead of Lithium-Cobalt based cells.

• No need for Tesla's complex heat management system.
• Higher cycle life.
• Lower energy density so you end up with a heavier pack.

http://www.autobloggreen.com/2007/1...ng-iron-phosphate-batteries-for-the-roadster/

 

[graham]

Geneva 2009: Ruf Greenster evolves the electric Porsche concept

The battery pack system has been improved and is now 30 percent smaller in volume, restoring the front trunk space that was lost on the original. The battery pack now has greater power capacity allowing it to release and absorb power faster, enabling more regenerative braking capacity. The battery can apparently be charged in only one hour from a 400V outlet. The next iteration will switch to a twin motor setup and the company is planning a small series production run in 2010

 

[vfx]

Geneva 2009

A lithium powered RUF 911

Quote:

Last fall, Porsche high performance tuning specialist Ruf announced it had built a prototype electric sports car called the eRuf, which was essentially a lithium ion battery-powered 911. That was just the beginning of the story, as the company has brought the Greenster here to the Geneva Motor Show. The Greenster is a targa top 911 in the old style with a chopped speedster-type windshield. In the back sits a 270kW Siemens electric motor with 695 lb-ft of torque. The battery pack system has been improved and is now 30% smaller in volume, restoring the front trunk space that was lost on the original. The battery pack also has greater power capacity allowing it to release and absorb power faster, enabling more regenerative braking capacity. The battery can apparently be charged in only one hour from a 400V outlet. The next iteration will switch to a twin motor setup and the company is planning a small series production run in 2010.

 

[dpeilow]

Porsche R&D says electric 911 possible, needs more development

In an interview with the German magazine Motor Zeitung, Porsche's R&D director Wolfgang Dürheimer discussed the possibility of electrification of the iconic 911 sports car. Legendary Porsche tuners Ruf first showed a prototype battery-powered 911 called the eRuf last fall and then revealed a second-generation version (pictured)at the Geneva Motor Show in March. The eRuf Greenster was a major improvement over the original and Dürheimer praised the achievement of the smaller company.

 

[vfx]

Yeah that will go well.

Anyone remember the change from air to water cooling?

 

[TEG]

Gas Turbo Porsche=contender for Autobahn top speed king.
Electric Porsche=limited top speed, and rather short range at 100MPH+

Germany is trying to lead the way in all things "green", but I still don't see this as the place to emphasize battery technology. A country with 65MPH speed limits is better suited.