What you missed was that Marmaduke faked a quote from you that contained all that about leaving GM and the H4. You never wrote it - at least in any post I saw. He was impersonating you.

I hope I'm not on the banned list either. I've tried to be supportive even though I started off with a different opinion. You make convincing arguments, and I'm fascinated by the insider view.

 

DaimlerChrysler have the lithium-ion / diesel powered plug-in hybrid Sprinter van.

They are the only company with a genuine plug-in hybrid in public hands in testing on US roads today. DC's Mercedes are planning several passenger car hybrid models too.

 

There seems to be some confusion about this:
The rolling resistance comes from the tires, bearings and moving parts of the differential and transmission. For the most part, this drag can be treated as a constant.

The coefficient of drag is a function of the shape of an object and the force is proportional to the cross section (aka., the size) and the velocity squared. Both the rolling resistance and aerodynamic drag are the forces that try to slow the vehicle down. If we multiply the drag times the speed, we get the energy, the power required to keep the vehicle moving at a steady speed down a flat road.

To compare the Volt, Hummer, hybrid or any other vehicle, all we need are:

• rolling resistance
• coefficient of drag * cross section

DRAG = ROLLING_R + ((COEF_OF_DRAG * CROSS_SECTION)*(V**2))

HP = DRAG * SPEED

You can quickly plot the power required as a function of speed and this determines how much power is needed (take care to use the right units.) The only part missing is the source of this power.

The specific fuel consumption is the power generated as a function of fuel burn. If you combine the specific fuel consumption with the power-speed chart, you can generate a maximum, MPG vs. mph curve (see chart at end.)

One of the functions of a good transmission is to match high efficiency power bands of the ICE to different speed ranges. The use of "overdrive" gears and "lock-up" mechanisms help to improve ICE efficiency and reducing internal transmission losses. However, often the high efficiency ranges are different from the high power ranges. I understand Martin has experience in this area.

One way of looking at a hybrid part of our vehicles is they are sophisticated transmissions that have an energy storage and source that reduces the peak power required from the ICE. This allows use of a smaller ICE and one with very high efficiency that might not be very good in traffic.

Ultimately, I'm looking at hybrid electric vehicles with such highly optimized engines that the engine only operates at one speed but very efficiently at that speed. The traffic power demands would be handled by the hybrid transmission system. So the Volt's three cylinder ICE like the Precept's earlier three cylinder ICE makes a lot of sense.

Personally, I'd like to see a two-cycle, turbo-charged diesel with topper systems to recover every bit of heat energy available. This power plant provides energy to the hybrid drive system that handles everything else including the 'creature comforts.' This advanced engine system would be sized to provide the enough power for a speed-limit climb of 98% of the longest grades in the USA with 120% of maximum vehicle load. Then I would be one happy engineer.

These last two are really aimed at how fast the vehicle can accelerate to speed. Personally, I find my NHW11 Prius has enough so I've never felt at risk. Others aren't happy unless they can double the Prius acceleration. I don't know that there is a minimum given we share the road with semi-trailer trucks whose loaded acceleration is quite enjoyable, to me.

Hopefully that clears things up.

Bob Wilson

ps. The following chart shows this exercise for my NHW11 Prius:

 

Bob, please indulge someone who's just starting to learn about the intricacies of automobiles...hybrids specifically...

but is your chart saying your experimental datapoint can be higher than theoretical (mpg efficiency)? I am I missing something here?

 

Seems like today's Lithium batteries can charge/discharge at 10C (heck if I remember how to explain what 10C really means - I think that means like 10 times the rated power of the battery). That's why Altair Nano and lithium from A123 claims charge time of 6-10 min for 35kwh battery! That's A LOT of energy to squeeze into a chemical reaction in 6-10 min! I think that's more than enough to handle all that energy from a 2 ton object stopping from 40mph or more.

 

Actually the theoretical model was based upon two assumptions:

• 31% thermodynamic ICE efficiency
• 121 MJ per gallon of gas

The thermodynamic efficiency came from a 533 mile highway trip on hilly, I-81 taken in October of 2006. This was before I'd mapped the specific fuel consumption charts of my ICE. On that trip, I simply used cruise control and recorded the data. Spreadsheet analysis gave the 31% efficiency. But I now realize that many of those hills pushed the ICE into inefficient rpm ranges.

The data points that show up above the curve are from my trip from Texas to pickup the car. That was along I-20, which from Fort Worth Texas to Birmingham AL is about as flat as it gets. Even on cruise control, the car stayed in a fairly narrow and efficient rpm range. I was probably getting better than 31% ICE efficiency and might have avoided ethanol in the gas, thus getting more energy per gallon. But I didn't have instrumentation until later.

It is not trivial to gather fundamental vehicle engineering data. But it is the only way I know to get reproducable results. I just wish we could get similar data for all vehicles instead of these nearly useless MPG estimates from Asia, the Americas and Europe.

Bob Wilson

 

Nope. You're on my "Pay attention to this guy" list.

Thanks for the kind words. My primary objective for being active on this site is to actively discuss issues with open minds and in the process open up a few more minds. Overall, I'm pretty satisfied with the way things have shaped up. I don't think you guys (at least the most visible / vocal of you) treat me that bad. This past week has been a trip through the Twilight Zone" but we've weathered through it.

Peace,

Martin

 

And talking about people on my "Pay attention to this guy list", Bob you are yet going to make me uncrate and study my undergrad engineering principles books. I sure as heck am not gonna nit-pick anything in your previous two posts.

The only thing I'd point out in your post is that the 3-cylinder ICE in the Volt provides no tractive effort. It's sole purpose is to replenish the batteries. Remember, my criticism of the EV-1 is that it has an inherent recharging problem. The Volt allows you to take the recharging system with you, in a manner of speaking, eliminating the infra-structure problem that cursed the EV-1.

Peace,

Martin

 

Agreed and that is why I see it as a better solution than even the Prius I drive today. Some call the Volt a series hybrid because it decouples the thermal engine from the drive. The motors and batteries become the 'transmission' and the whole system is much simpler. Heck, a 4-wheel drive with superior traction capabilities (aka., the mini-hybrid) becomes possible with a substantial reduction in noise and vibration.

Bob Wilson

 

Why not have a system with solar cells on the roof to trickle-charge while parked?