http://www.iop.org/EJ/abstract/-sear...326/2/1/014003

A little technical, it is a good survey report with interesting data for predicting future hybrid performance numbers.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

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Indeed, this gives a little credence to Honda's 3 year old statements that HEV technology offers significantly diminishing returns in fuel economy for larger platforms - which soon begin to erode the benefits of the technology.
Until now, this corollary has not been proven wrong even with the latest HEV and the soon to be released models (2-mode included) from the GM consortium.

If this remains true, then the question then becomes what is the "sweet spot" in terms optimal FE and size that a platform must have in order to maximize the benefits of the HEV tech?
At the moment, I believe the Prius II is closest to offering the perfect balance of size and FE.

Cheers;

MSantos

You've asked a very good question:
One possibility is the peak efficiency point is not at some given vehicle weight and power combination but actually is achieved at one end of the scale. It might have been the lightest hybrid, the Insight, achieved that spot.

Now there is another metric, the payload vs. efficiency, and that might move the scale up towards higher weight vehicles. But I don't think they really addressed that question (future paper???)

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.

It depends if you are talking about % increase in fuel economy, or absolue fuel economy.

An 1800 pound Insight ( hybrid ), will easily average 60 MPG.
I'll bet an Insight car, without hybrid IMA would still get 50 MPG.
So the Insight's "hybridness" is only a gain of about 20%.

Now take a Ford Escape V6 vs. a Ford Escape Hybrid, at 3800 pounds.
A V6 Ford Escape will average 18 MPG.
A Ford Escape Hybrid will average 31 MPG.
The Escape "hybridness" is a gain of about 70%.

Denver was the first U.S. city to purchase and put into use a fleet of hybrid electric vehicles.
Starting as early as 1996, Denver put a small fleet of Hybrid buses in lower downtown.
These buses never exceed 30 miles per hour and have to stop every city block, and navigate congested traffic.
The older buses, carried 75 people with standing room taken, and got 1MPG from diesel fuel.
The new hybrid buses are articulated in the middle, double long, and carry 125 people when standing room is taken.
The Hybrid buses get 4 MPG.
For a city bus, the "hybridness" is a gain of 400%.

Sounds to me like the bigger the better, and the Insight is the clear loser.

-John

If you take into account the ridership capacity it is closer to a 665% gain.

I find that people who don't compare apples to apples don't get the concept even if it's explained to them to the nth degree.

Equally annoying are members that compare apples to oranges for a more impressive mpg number. For example, we have members here that say they are saving tons of money because their Hummer they replaced only got 8mpg and their current hybrid is getting 40+ mpg. Ignoring the fact that any econo box car can get 30+ mpg.

Well they are saving two tons of $ with certain hybrids versus maybe only one ton for "any econobox" - but lets not split tons

Moving away from a Hummer tends to be a good thing.

Yeup... and buying any econo car proves that.

My point is that if you are going to compute savings from your prior vehicle you should compare what a comprable non-hybrid equivalent can do in mpg vs the hybrid you bought.

ex. A hummer gets 8mpg (not sure what it gets but let assume it does).

A civic ex gets 35mpg (again, assume it does)
A civic hybrid gets 45mpg (again, assume it does)

your saving should be the difference between the comprable car and not the original car.... both cars are saving from the original.

But if you replaced your hummer with the civic ex, wouldn't you compare your civic ex's gas mileage to the hummer?

So why can't someone who buys a hybrid compare the hybrid's gas mileage with the hummer they replaced with it?

Are you saying they can only compare the civic hybrid with a car they never owned (the ex)?

That doesn't sound very fair to me! (or realistic)

08FEH