http://www.evworld.com/view.cfm?sect...le&storyid=887

the article talks about an interesting limitation that the prius has at higher highway speeds that effectively prevent it from being purchased in europe. i'll leave it up to you to read. the comments at the end are a bit technical but interesting.

from the article:

" Some time ago, Mercedes identified in public the 'Achilles heel' of the current HSD, namely the losses that occur at higher speeds, with the generator needing to supply power to the motor via the controller even when the battery is effectively out of the picture. This has been one of the reasons why DaimlerChrysler has joined with General Motors to develop an alternative which is more efficient at freeway speeds. "

from the author's comments:
" Of course the Hybrid Synergy Drive (to give it its proper name) is efficient at urban speeds, and also when running various governments' so-called 'highway' cycles (US average speed 48 mph); that's what it was designed to do. The issue is the increasing losses at steady cruising speeds, particularly at 70 mph and above. The problem is that the MG2 vector torque must be CONTINUOUSLY maintained during cruise, and the torque must be greater the higher the road speed, to allow increased engine torque to be fed through the single stage planetary gearbox to the road wheels. This can only be achieved by generating more electrical energy the higher the cruising speed, with the associated losses in the generator, controller and motor increasing as a consequence. Why else would they all need to be water cooled? A relatively trivial issue at urban speeds becomes significant on the freeway, as more than a few Prius owners (and Honda, Mercedes and GM) have all noticed. I am equally sure that Toyota has been aware of this limitation all along, and (correctly, in my estimation) judged it to be irrelevant in Japan and acceptable in California. Let's see if the Lexus GS 450h has an HSD, or something a little more suitable for Europe. 19/Aug/2005"

 

It's interesting how the technical pundits at Daimler Chrysler, GM, and other places can come up with all these technical reasons why HSD is suboptimal.
The bottom line is though that the Prius II gets better mileage at any speed, than any of their gasoline cars, period.

 

GM has not actually implemented their hybrid system on any vehicels yet, and will not do so it seems until 2008. Based on the description, the transmission does seem to be somewhat better suited for fast highway cruising:

http://en.wikipedia.org/wiki/Advanced_Hybrid_System_2

one thing I immediately noticed is that unlike the Toyota system with a single planetary gearset, the GM/DC system has two planetary gearsets. This allows for both the torque-blending CVT technique of the prius, and the ability to actually switch from a "low" to a "high" gear. The problem with the Toyota transmission is that it is essentially a fixed-gear, that must adjust the appropriate level of torque using generators and electric motors. This wastes a lot of energy at fast steady speeds. GM/DC's system does this as well, but with the addition of a true high gear for the highway. In "low" mode, it's essentially the same as the Toyota HSD transmission.

 

I have also seen articles (in the prius forum) speculating that the prius doesn't
get high enough mpg to compete with Europe's small diesels either. The
turbo diesel Beetle (non-hybrid) can get hwy mileage close to a prius.

Toyota is designing their 2007 Prius to get 94 mpg (and slightly more power)
to make it more competitive in Europe.

https://www.greenhybrid.com/discuss/...sted.6897.html

I wonder how Honda will respond to a car like that?

It is going to be very cool to watch the hybrid wars heat up, with gas around
$3.20 here now (up .35 from a month ago) there is lots of incentive.

 

Kurt,

My understanding is that those specs are for the 2009 Prius (due out in 2008), not the 2007 Prius (due out this summer).

I'd love to see something really concrete on this, mostly I've seen tons of postings that all trace back to the same rumor from a UK car show. Though I can understand Toyota not wanting to make a huge announcement about the Prius III, because its basically saying, "Don't buy a new Prius for the next two years. Wait until the 94mpg ones are out in 2009!"

Personally, that's my dilemna. I just paid off my 2001 Accord, which I absolutely love. I'd like to buy a hybrid to save on gas, but I'd like not to put myself back into debt, so I've been putting aside $100 a week into a savings account. I figure that between my trade-in, the money I'm saving, and hopefully some decent interest (4% at INGDIRECT) I'll be able to buy a new hybrid by the end of 2008. If the 94mpg Prius isn't vaporware, that'll work perfectly for me. Hell, if they had a diesel/electric plug-in hybrid that I could fill with B100 I'd be in heaven (though I doubt that'll happen).

But the more I read these fora, and the more gas prices rise, the more I want to run out and get my hands on a Prius or an Insight or an HCH RIGHT NOW!!

 

Does it seem odd to anyone that hybrids are being criticized for not being able to sustain 70 MPH? Given that wind resistance takes more energy to overcome after 40 MPG, and we've all seen data on how inefficient things get at 50, 60 ,70+, seems a tad contradictory to call the hybrid inadequate to perform a task that is directly counter to it's efficiency goal. Isn't that like buying a pair of dress shoes then complaining that they hurt your feet when you jog?

If you want to go blasting down the highway, buy something suited to that purpose. Don't blame the Prius.

 

All of the current hybrids are important interim steps to a better future as far as fuel efficient vehicles, including mine. There is nothing wrong at looking at true weaknesses in current systems in order to develop better ones.

 

Don't be so defensive. The simple point is that there are no speed limits on Germany's autobahns and Italy's autostrada. People routinely drive 100 MPH over there, and they don't want cars that can't reach such speeds. If Toyota wants to sell Prii in Europe, and I'm sure they do, they must address the issue.

 

Only 35mpg at 85mph!Wow,that is pitiful.Let me trade my Prius for one of those European wonder diesels. I bet the Euros have a huge choice of vehicles with 70" behind the front seats(enough for an adult human ,and one very leggy 75 lb greyhound,and one somewhat smaller mutt).Help me here,let's name all the 175" x66"wide vehicles with 70x45" behind the front seats that easily beat 35 mpg at 87mph?
Give up?I don't think the Euros have a comparably sized car that will get 35mpg at 85 mph.The Volkswagens TDIs we get here sure as heck won't-and they are dogs-12+seconds 0-60 mph.
Now , a properly sized TDI in a Prius sized car should be able to beat a Prius in a high speed, no braking hy trip MPG.However ,we don't have that properly sized TDI here,and I have my doubts that the Euros do.A 115 hp 4cyl TDI in a 3000 lb car won't accelerate as well as a Hybrid with electric motors.This is why the HH(4400 lbs) is so quick-7.4 0-60 while having just 268 hp.
On a 90 mpg Prius in 2008-that is absolute BS.It will be about as much better than the 2004 as the 2004 was better than the 2003.The Prius would have to drop 900 lbs to get a 90mpg city rating.It will probably be 4 mpg better real world.Don't wait the 2 years in the hopes of that sort of improvement.LucK,Charlie

 

There are a few other mis-statements in the article.

The U.S. Prius has no EV mode? Where did he get that?
And the thing about the dangers of driving a silent car (in EV mode) - give me a break. I drove a Toyota RAV4-EV (pure electric) for three years and never had a problem due to the lack of engine noise.