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OK, Don... My main beef was with those who initially claimed that ~25hp would be enough ICE power when they saw charts that said that is all that is needed to maintain highway speeds.
GM ended up using a more Prius sized ICE, and 53kWh is probably enough nearly all of the time with that healthy battery assist for occasional passing requirements. I am content to wait and see if any Volt owners complain about long hill climbs or not. It might be acceptable, but time will tell.
Yes, I have a Synergy drive vehicle myself.Originally Posted by donauker
Toyota does call it a CVT.
Prius Glossary
By the way, for whatever reason, Toyota has decided to increase ICE size for the 2010 model:CVT is a type of transmission with an infinite number of gear ratios that are always changing depending upon the relative speed of the vehicle and the engine rpm. There are several types of CVTs. Hybrid Synergy Drive® uses an electronically controlled CVT (ECVT) which integrates a planetary gear set into the drivetrain.
Toyota's 2010 Prius breaks cover
...The move from 1.5 liter to a larger and more powerful 1.8 liter Atkinson-cycle, four-cylinder engine should significantly improve the power to weight ratio and the performance of the Prius. The current 1.5l Prius has always scored well in city driving due to its regenerative braking but it has been noticeably lacking in highway performance due to its small engine capacity and the additional weight of a battery pack compared to vehicles with similar engine capacity. Contrary to conventional wisdom, the larger engine actually helps improve highway mileage. By making more torque, the new engine can run at lower average rpm on the highway. When operating at lower rpm, the new engine uses less fuel.The 4 cyl VVT-I puts out 98 hp (72 Kw) @ 5,200 rpm with 105 lb/ft (142 Nm) @ 4,000 rpm compared to 76hp (57 Kw) and 82 ft/lb (111 Nm) in the current model.
Slightly related discussion:
High revs uphill - GreenHybrid - Hybrid Cars
Prius and steep inclines - PriusChat Forums
I must say, my experience on the grapevine was slightly different. It was one of the only two times that I felt my car wasn't quite powerful enough. Don't get me wrong, the Prius is a great car and handles everything nicely. It's just occasionally you might wish it had a little more oomph.
Anyway, onto the story.
I was headed southbound and all was fine. There was enough power, I had enough to noticeably accelerate with, too. That is, until the the last couple miles or so on the final uphill stretch. I was slowly falling behind traffic (which was cruising around 72 mph...but increasing!) and I found myself pressing the accelerator lower and lower. Finally, with the pedal floored I was going 76 mph with cars continuing to pass me. Even highway patrol decided to go around me. Needless to say, I was a little disappointed -- for the first time -- not because I couldn't keep up (I could, just barely) but rather I had no margin for safety. I was literally maxed out.
If you're wondering when the only other time was, it was southbound on highway 5 (ironic that it's the same freeway) somewhere near the Oregon-California border. Although this time the car was loaded with people and luggage. Again, it wasn't that I couldn't keep up, it was just the fact that I didn't have anymore room for a "just-in-case boost."...Avoid...I'm beginning to think that some running algorithms were changed
around '06 to manage the pack charge a little differently when
moderate to heavy power is asked of the engine and a larger
throttle opening is necessary at higher altitudes. My '04 took the
SOC down to one pink bar [from only 3 or 4 blue!] on the way over
Vail and Loveland in CO this summer [11000 feet or so] and with
nothing left in the battery, I was on the engine alone and having
to push it right up to 4000 or 5000 RPM to match "normal" traffic.
At 78 HP or less that is a bit anemic for the weight of the car, but
I was perfectly fine with climbing more slowly and waiting it out
like any loaded semi would.
Do You Regularly Drive in Mountains?
The Prius will not climb very steep hills indefinitely. One aspect of the vehicle's design that drastically improves economy and reduces emissions is that the engine is not sized for the peak power demand. When heavy acceleration or steep hill climbs are called for, MG2 provides a boost to meet the performance needs using power from the battery. Although heavy acceleration can't go on for very long and the battery gets a chance to recharge, in some parts of the world you can find steep hills long enough to drain the battery to its lower limit. At this time, you have only the ICE power to run with and you'll be forced to slow down. You'll still make it to the top. People have driven to the top of Mount Washington, which averages a 12% grade for more than seven miles. But, after the battery power is gone, the maximum speed (according to my calculations) will be about 40 m.p.h. Not being able to climb Mount Washington at 60 m.p.h. is, of course, no reason not to choose a Prius. But, if your daily commute happens to be over the California coastal range or some other long steep hill, joining the trucks in the extra slow lane might wear a bit thin after a while.
Nice explanation of Toyota's Synergy Drive "power split" device.
(yes, eCVT is a bit of a misnomer, but Toyota does use it too).
How much power to maintain speed?
...
22 HP to maintain 55 MPH
...
50 HP will maintain 55 MPH up a 6-7% grade.
......Also going up even a 1% incline will change the results as well...
rolling resistance will be reduced by 1% as the normal force against the road is no longer the whole weight...
so ~6.57 Watts less rolling resistance... but you traded it for gravitational force acting against you... which means ~1% of the gravitation force of the car becomes a counter force... or about 834*9.8*0.01= ~81.732 N * 13.411 = ~1,096 Watts = ~1.1kW of gravitational resistance to even a 1% incline......Gravity:
as you go up an incline your normal force for the rolling resistance will be decreased.
So a 1% incline will reduce your rolling resistance to 99% of the 0% incline rolling resistance.
while at the same time adding 1% of the vehicle weight as a pull against you... 834 * 9.8 = 8,173.2 * 0.01 = 81.732 N
...
Yes, this is the single best source of information on the Synergy Drive I have ever seen. Oddly enough it was this site that several years back started me down the road to electric.
Being a techno geek all of my life and a computer programmer most of it, I was intrigued by the complexity/simplicity of the Synergy Drive. After studying all of Graham's writing's in depth I just had to have it and purchased my Lexus 400h. The brief periods of electric only drive lead me to trying to maximize electric mode which of course became frustrating in how limited it was. After a few months with the Lexus I decided any new personal vehicles I would purchase would need to have a plug and a substantial electric only range.
Same story for me basically.
My wife's Highlander Hybrid (same drivetrain as the 400h) sits in the driveway next to my RangerEV, which was the most I could afford to get myself a plug in vehicle with decent range, and batteries that will last more than a few years.
The Highlander will be our long trip car, and hopefully the RangerEV gets replaced by a "BlueStar", SmartEV, MiEV, or some such affordable EV once the Ranger eventually wears out. Perhaps "Model S" if something miraculous happens, but I am not holding my breath on that right now.
He is a different and much more knowledgeable Graham, just in case there was any confusion!
Just a quick (probably uninformed) question .... but it seems like the issue with the Prius on hills/mountains is primarily due to the relatively small battery that drains too quickly to provide any useful impulse on a hill. With the Volt, the battery is substantially longer and should be able to provide full power on a hill ... provided that the hill is not too long (many miles of mountain/hill driving) or the battery is not too fully depleted when starting.
Question: Couldn't the problem be substantially addressed by a toggle switch for the driver to let the car know to keep the battery nearly fully charged. i.e. if you know you are driving up to Mammoth Mtn, then tell the car, and it will maintain the battery at full charge state. A fully charged battery plus the engine should be able to last quite a while -- 40 miles of mountain, minimum, by definition.
Similarly for a range-extender on the Tesla: if you turn on the range extender when you start driving, then even a small range extender should be able to get you quite a distance. i.e. 250 miles nominal electric mode + (3 charging hours while you're depleting your electric range * 25HP) + (whatever time that buys you * 25HP). I expect the result would extend the range out to ~500 miles...
Dan.
Or include an inclinometer in the car and in a setup menu tell it what angle you want to kick in the ICE,
Last edited by doug; 03-09-2009 at 05:36 PM. Reason: fixed broken quote syntax
The world loves to be deceived.
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