I think hybrids are only one way of thousands that we can impact the enviroment positively. It's not just the fact that they get better gas mileage. That's only one reason and conservation and making the most effective use of all natrual resources is also important. It's a total shift in thinking that should have taken place MANY years ago........regardless of how expensive gas has become. The fact is all of our natural resources need to be used and resused as though they are a precious commodity. Because all of them are. Hybrids are only one way of many ways to do that.......and if we apply the same thought process to all aspects of energy and resource use.........we will all be headed down the right path!!

Going back to the original question, I use a simple "figure of merit," which is the ratio between the electric (or hydraulic) motor to total power. This simple ratio gives the following "figure of merit:"

• 141hp / (141hp + 147hp) = 49%
• 50kW / (50kW + 57kW) = 47%
• 70kW / (70kW + 90kW) = 44%
• 15kW / (15kW + 69kW) = 18%
• 10kW / (10kW + 48kW) = 17%
• 12kW / (12kW + 125kW) = 9%
• 2.4hp / (2.4hp + 285hp) = 1%

I have have not identified the specific makes and models. But every one of these vehicles has the word "hybrid" used to describe them and were tested at the Dept. of Energy, Idaho National Laboratory as part of the Advanced Vehicle Testing Activity:

http://avt.inl.gov/hev.shtml

The lower ranked hybrids are no longer being sold. Although extreme weight reduction works, it has not been emulated. The "figure of merit" has been the greatest indicator of hybrid success. Calling a vehicle a hybrid without paying attention to the "figure of merit" except for extensive weight and aerodynamic modifications, has not worked in the market place.

Wiki reports the GM two mode transmission has "two 100kW (133 hp)" motors. The architecture allows both motors to power the vehicle for a battery limited, period of time. We do not know if the two-mode hybrid has a mode that flows power between the motors to put the ICE in more efficient, power generation modes (aka., electric overdrive, a good thing.) Regardless, this gives a figure of merit:

• 133 hp / (133 hp + 332 hp) = 28%

This is between the 18-49% of existing, successful hybrids. Now if it could be fitted into a 200 hp, rear-wheel drive, GM vehicle, the figure of merit would be 50% and substantially competitive.

Bob Wilson

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There are three ( at least ) very different forces at work now in the 'enviro-efficiency' discussion.

1) The most well known is the 'greenie' movement which holds demonstrations seminars and generally is for reducing our output of GHG among other environmental goals.

2) The most personal is the kitchen table calculation , rarely done accurately, as presented by the auto writers and finance pundits about whether the hybrids are 'worth it'. These 'analyses' are at best shallow in order to be understandable to the lowest common denominator in the population. At worst they are intentionally wrong in order to promote someother goal.

3) The least well known, because it's being ignored in most cases by us the driving public, is the 'supply is limited and this may override all other considerations very shortly' discussion. These are the reports of academia, industry, intelligence and other governmental offices that our way of life as based on petroleum is at risk - soon.

These three forces may have nothing to do with one another.

1) Is the T/Y 2-M good for the environment? Not as good as a Corolla or an HCH that's for sure. 2) It may or may not be economical personally. 3) But it does save more fuel as a hybrid vs an ICE than either a conversion of a Corolla to a Prius or a Civic to an HCH.

I didn't see the HCH-II in that list, but if I follow you correctly, the HCH-II should be low on the scale:

12 / (12 + 70) kW = 15%

What about torque? It also gets you moving, even when horsepower is lacking. The HCH-II's IMA contributes proportionately more torque than horsepower, but it's still low compared to the engine.

I don't understand what the "figure of merit" tells us.

Both Honda hybrids, the Civic and Insights, are in the middle of the scale. In the case of the Insight, the vehicle was unusually small, light weight and used lean-burn technology. The Civic has a slightly higher figure of merit and continues to be sold (I used 69kW for the Civic ICE power.)

What the figure of merit tells us is the ratio of electric power. Vehicles with a higher values are able to handle more of the vehicle energy demands in electric mode so when the ICE is off:

1. at a stop - the 1% vehicle
2. while moving and decelerating - lower limit is ~15%
3. accelerate and sustain speed w/o ICE - lower limit is ~30%(*)

The 30% figure comes from what little we know of the GM two-mode hybrid specifications. The others are from hybrids that have been in service for sometime.

Adding more electrical storage to a hybrid in the 50% range makes it into a plug-in, hybrid electric vehicle (PHEV.) With enough storage, it can use grid power for a substantial fraction of the short range trips. Adding electrical storage to the lower ratio hybrids can not make them into a PHEV.

You are correct that the additional torque significantly improves the HCH performance. One significant weakness of internal combustion engines is the problem of low torque and power at low rpm. The IMA solves that problem.

Bob Wilson

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I get you. It's electric motor power above all other considerations. But it doesn't tell the whole story. Succes in the market place or not, I'm sure you would agree with me that Honda's i-VTEC with IMA is more efficient and cleaner than Toyota's Synergy drive (including, but not limited to, emissions of Tier 2 Bin 2 vs. Tier 2 Bin 3). Where the Toyota solution can evolve into a plug-in HEV with potentially no engine contribution, Honda's solution is paired with possibly the cleanest consumer engine available today.

I think I know where the market success lies, and why more manufacturers are anxious to get hybrids in their lineups: Toyota/GM can license their hybrid drive to anyone and make the licensee look good because it essentially disregards (or disguises) the performance of the engine. Be it efficient or sloppy, the engine has more leeway when paired with the electric motor/battery. I don't know if that's such a good thing in the long run, considering what is more environmentally responsible.

Correct because the electric motor dilutes the tailpipe emissions. But it also has another advantage by allowing more efficient engines to be used.

A clean engine is important but combining a motor and engine allows more efficient engine cycles. For example, the Honda IMA uses the motor to solve an engine specific, low-end torque problem. But with more electric motor power, the car can run during the warm-up cycle at a very low rate of fuel consumption with improved efficiency over an engine alone.

If we wanted ultimate, low emissions, we would use an external combustion engine. But their size and non-existant throttle response makes them impractical. However, if they feed power to a battery pack and electric motor, the motor provides the throttle response and the battery pack the energy storage needed for an efficient and responsive vehicle.

I'm primarily interested in total vehicle efficiency and the electric motor, especially one large enough to handle vehicle loads, allows inefficient engine modes to be minimized, like low rpm, warm-up and partial power. Furthermore, large electric motors open the window for engine cycles that could never work as primary vehicle propulsion. For example Sterling and combined Rankine cycle engines. IMHO, the Volt (even without LiON batteries) is the end game.

Today, our engines achieve efficiencies of mid-30s but future engines can and should reach the mid-40s. For our 50 MPG vehicles, we would be seeing 63+ MPG. Add running gear and aerodynamic improvements and we're looking at 70 MPG all the time.

For me, the environment that needs to be preserved are the remaining reserves of fossil fuels by more efficient vehicles and systems.

Bob Wilson

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My other 1500 cc car:

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Okay Bob, help me out here. Are you saying existing engines are 30% efficient, being 30% of the energy goes into propultion and the rest is lost as heat? I am guessing that is what you are saying.

And are you saying that the 30% effiecient vehicle today that gets 50 MPG, would get 63 mpg by the improvement to 40% propultion efficiency?

Also, what is an external combustion engine? Is that like a turbine engine maybe?

Thanks in advance.

Correct but there is considerable variability depending upon the type of engine. The worst case is generating say 10 hp with a 300 hp Otto cycle engine. Typical efficiencies would be terrible. Although a Diesel cycle is 'less bad,' it is still burdened by all of the mechanical parts thrashing about.

It turns out that many engines have one speed and power output that is closely tied to the maximum and that is the efficient speed and power range. Going slower or generating more power causes the efficiency to drop off. So this is the trick the hybrid drive pulls on the engine.

A Toyota/Ford/GM hybrid simply runs the engine in a more efficient range and then, shuts it off. The stored energy is then used to maintain speed and the storage-return loss is much less than the loss of running the engine in an inefficient power/speed range.

The other trick, something the HCH uses, is to fill-in the torque range so the engine appears to have a wider, high efficiency range. The stored energy that extends the range came from the ICE running in a high efficiency mode.

The external combustion engines have some nice features including better combustion control. They don't need catalytic converters. However, they have abysmal throttle response. But take one of these engines and tie it to a hybrid transmission to handle the variable power load and 'voila' high-efficiency engine with infinitely variable power from the hybrid system.

Yes, it could be a turbine with a heat exchanger, something that captures waste heat from the exhaust to pre-heat the compressed air before combustion. However, there are still challenges with building an efficient turbine. But as part of a compound engine, one that combines different heat cycles, you can achieve some pretty impressive results.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

Humm, I would rate a turbine as an internal combustion engine, based on my power mechanics courses. The combustion occurs in the "closed" combustor at higher than atmospheric pressure. The expanding exhaust gases then push the blades.

The classic external combustion engine is a steam engine. An external fire heats the water. The definition I've read has always been the burning must occur at atmospheric pressure, not enclosed.

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