[BillR]

I know that Lyle got to drive one of the Chevy Fuel-Cell Equinox's in the recent past. For his video, see this link:

http://www.youtube.com/watch?v=uqo7zDRLZGI#

Well, this is significant, as both this Equinox and the Volt have the same motor and power electronics. See this link:

http://www.greencarcongress.com/2007/01/gm_introduces_e.html

"The Volt uses the same electric motor as used in the Equinox Fuel Cell vehicle in its electric powertrain: a 120 kW peak machine that develops 320 Nm (236 lb-ft) of torque."

These values are also consistent with the numbers listed under "Full Specifications" on the home page.

http://gm-volt.com/full-specifications/

The Green Car Congress article also mentions the following:

"Furthermore, GM leveraged its experience with the EV1 in the design of both the E-Flex System and the Volt. The use of the range extender in the Volt design, for example, originated with feedback from EV1 customers about not wanting to have to plan their lives around the next charge, according to Tony Posawatz, GM Vehicle Line Director."

I made some projections regarding this in the Design section of the Forum:

http://gm-volt.com/forum/showthread.php?t=197

Now for many of those asking about the motor and the power electronics, I would first suggest reading some info from the Tesla website. Apparently some of the engineers that worked on the EV-1, have also worked with Tesla. See the attached link:

http://www.teslamotors.com/blog2/?p=30

As you can see, the EV-1 had an AC motor with a variable frequency drive.

For more information on the efficiency of this motor/inverter system, see the following link:

http://www.acpropulsion.com/technology/gen2.htm

Be sure to open the PDF specification sheet at the bottom of the page, as it has the performance curves attached.

So now, it appears that the Volt is a stretched EV-1 with a Li-Ion battery pack and an ICE. The drive motor/system is the same as the Fuel-Cell Equinox. For a rendering of the Equinox electric drive, see page 20 of the document at this link:

http://www.gmstc.com/courses/ChevEquinFuelCell.pdf

Now compare this with an assembly drawing for the Volt (from Lyle's Gallery):

http://gm-volt.com/galleries/album/72157603653293621/photo/2172216375/Chevy-Volt-2007-Chevrolet-Volt-Concept-Chassis.html

Note the similarity, only in the Volt, the power inverter module is tilted towards the front of the vehicle, probably to allow more room for the ICE.

Now comes the questions for Lyle. The following link describes the driving experience for the 4,430 lb Fuel-Cell Equinox to be "mundane". They also go on to say "The 94 kilowatt (126 horsepower) electric motor deliver 236 pound-feet of torque to the front wheels almost instantaneously. The electric motor offers nice torque but not much top-end, so there isn't much on tap beyond 40 mph. That's why the zero to 60 time is a glacial 12 seconds. Still, the Equinox is quick enough to get you onto the freeway without any trouble, and GM says its top speed is 100 mph - although we didn't get to test that claim." Not what you would classify as a "performance" vehicle?

Another review had this to say " We learned a lot on our 45-minute drive. The vehicle was quick to accelerate and actually, surprisingly slow to stop. In other words, the brakes needed a little fine-tuning. To maximize energy capture, the regenerative braking system is unusually aggressive. And that made the brakes hard to modulate. We hear GM is working on the creating a more natural brake feel. Chevy claims the Equinox FC goes from 0-60 in 12 seconds, but under our well-calibrated backside, it seemed a lot quicker. Much of that sensation is probably due to the characteristic common to many cars with an electric motor—instant low-end torque. In fact, the FC pulled strong all the way up to the 60-70 mph range."

That link is here:

http://www.popularmechanics.com/automotive/new_cars/4228264.html

Now we know the Volt should weigh in at about 3200 lbs, (versus 4430 for the Nox) and it will have less aerodynmic drag than the Equinox, but what will it be like to drive?

Lyle, it seems to me that no one on this forum is in a better position to answer that question than you. We have seen the video, now can you tell us more about the Equinox drive train and its characteristics, and how much different to you think it would be in the Volt?

Thanks again for being our test pilot!

 

[BillR]

Missing Link

Sorry, I forgot to add this link that mentioned "mundane".

http://blog.wired.com/cars/2008/03/we-drive-the-ch.html

 

[nasaman]

Estimated Volt 0-60 Time

.....The following link describes the driving experience for the 4,430 lb Fuel-Cell Equinox to be "mundane". They also go on to say "The 94 kilowatt (126 horsepower) electric motor deliver 236 pound-feet of torque to the front wheels almost instantaneously. The electric motor offers nice torque but not much top-end, so there isn't much on tap beyond 40 mph. That's why the zero to 60 time is a glacial 12 seconds.....

Thanks, Bill, for this EXCELLENT & interesting bibliography of articles on the FC Equinox, whose drive train is very similar to the Volt's!

One of the recurring (BURNING) questions our members keep raising is what the Volt's 0-60mph time might be. Based on your references, I can't help but make an admittedly simplistic prediction.....

(3200lbs/4430lbs)x(94KW/120KW)x12sec = 6.79 sec

....which is very close to Frank Weber's answer at Volt Nation of 7 sec, and which almost puts the Volt into a "performance car" class.

Of course, my simplistic scaling here neglects several factors such as motor torque ratings and gear reduction ratios (FC Equinox vs Volt), but even from this back-of-the-envelope calculation it's clear to me that GM could reduce the Volt's 0-60 time to under 6 secs by simply reducing its top speed somewhat ....which I personally think would be a very wise marketing decision! And since the Volt's drag coefficient has improved by ~30%, this would likely have little or no effect on top speed --which I would expect to be ~120mph even with a 0-60 time under 6 secs!

 

[Lyle]

Those are some brilliant analyses guys

As you may know, I am not an engineer.

I was told by the Volt's engineers that the electric motor being developed for the Volt is actually different than that used in the Equinox..I don't know the specifics, they are keeping those quiet for now.

If you look at my video, you will see I gunned the fuel cell Equinox from stop to 55 on the West Side Hwy in NYC. I didn't count the seconds, but the instantaneous torque was profound and felt awesome...I didnt notice a late decay.

The Volts curb weight is also not being disclosed publicly. Also there may be some accelerative governing to prevent discharging the battery too much.

I expect the drive experience to be out of this world though

 

[NZDavid]

Great post Bill, well researched. Lyle, it must be tricky, maintaining the site to reflect the new systems as they arrise.

Nasaman, thanks for bring this to my attention.

Kind regards
David

 

[KariK]

There seem to be several items wrong on the full-specifications page. Maybe someone (Lyle?) could go over it and get it updated so newcomers to this site would not get confused.

 

[DaV8or]

Also there may be some accelerative governing to prevent discharging the battery too much.

And this is where the after market can tap in and maybe build a more sports version of the Volt.

 

[BillR]

Further Speculation

Those are some brilliant analyses guys

As you may know, I am not an engineer.

I was told by the Volt's engineers that the electric motor being developed for the Volt is actually different than that used in the Equinox..I don't know the specifics, they are keeping those quiet for now.

If you look at my video, you will see I gunned the fuel cell Equinox from stop to 55 on the West Side Hwy in NYC. I didn't count the seconds, but the instantaneous torque was profound and felt awesome...I didnt notice a late decay.

The Volts curb weight is also not being disclosed publicly. Also there may be some accelerative governing to prevent discharging the battery too much.

I expect the drive experience to be out of this world though

One tidbit I have noticed recently is that the torque for the Volt's drive motor has increased (different from the Equinox and the original Volt concept, as you mention, Lyle). Apparently it has increased from 236 ft-lb, to 273 ft-lb. See the attached link:

http://www.nationalpost.com/life/driving/story.html?id=436590

Looking at this motor at 273 ft-lb of torque, the power at 4000 rpm equates to 155 kW (208 hp). Therefore, the fact that the 155 kW may be the maximum power, means the power electronics must control the current draw to limit the power between 4000 and 7000 rpm to 155 kW, thus the "accelerative governing" as mentioned by Lyle.

To illustrate this, I edited the motor/inverter curve from AC Propulsion to show this performance. Also, for simplicity, I assumed a reduction gear ratio of 7.595. This is because the tires indicated in the above article (P215/55R17's) will turn approx. 790 revolutions per mile, so this gear ratio provides 60 mph with 6000 rpm on the motor. Therefore, all speeds are readily calculated as motor rpm/100. The Volt's proposed maximum speed of 120 mph comes at the motor's max speed of 12,000 rpm.

The modified curve is attached.

Note the torque is steady at 273 ft-lbs up to 4000 rpm, where power max's out at 155 kW. Power is steady at 155 kW until 7000 rpm is reached, where power then begins to decay.

I added another curve to the graph. It is the estimated power to overcome drag at a steady speed for the Volt. Since we have discussed 0.200 kWh per mile, at 60 mph, this equates to 12 kW. The power to drive the Volt at higher speeds should be proportional to the cube of the speed, and the lower curve approximates that trend.

Note as we near 120 mph, the drag forces essentially equal the power produced by the electric motor (max speed, drag limited).

The EV-1 had a motor that produced 110 ft-lb of torque. The reduction gear ratio was 10.946, so the torque at the driveshaft
was 1204 ft-lb. For the Volt, given the above assumptions, the torque at the driveshaft would be 273*7.595 = 2073 ft-lb.

If any of this is near correct, this could be a fun little car to drive.