Last post on Jul 28, 2013 at 8:39 AM
You are in the Toyota Prius
What is this discussion about?
Toyota Prius, Hybrid Cars
#3591 of 7508 quote from www.fueleconomy.gov (EPA and DOE)
Jan 16, 2004 (11:32 am)
"The test used to determine the city fuel economy estimate simulates an 11-mile, stop-and-go trip with an average speed of 20 miles per hour (mph). The trip takes 31 minutes and has 23 stops. About 18 percent of the time is spent idling, as in waiting at traffic lights or in rush hour traffic. The maximum speed is 56 mph. The engine is initially started after being parked overnight. Vehicles are tested at 68 F to 86 F ambient temperature."
EPA ran that course in their lab on 04 Prius and marked down the result by 10% for the published espitmate of 60 MPG.
The city MPG's we have seen reported here are nearly all in the 40's, about 25% to 33% lower than the estimate on average. My city and highway MPG's of a conventional car (93 Eagle Summit Wagon, same as Mitsubishi Expo LRV) were about 10% better than EPA estimates in summer when the car was new and 10 years old. These MPG's precisely matched their lab numbers.
A Toyota Rep at 1-800-331-4331 told me on December 17, 2003 that their engineers were working on it and there would be an answer by mid Jan 04. But there was not a published solution so far, another Rep told me yesterday. "I would be concerned if it was my car", the Rep said.
We, true Prius owners and possibly dealer's agents here, need to face the issue.
Jan 16, 2004 (1:32 pm)
> And you said your's is 43? Your claim is false.
That's not what I was referring to at all. It was a LA owner on the Yahoo forum, contributing far more detail then what's available here, hence the confusion. And now, I don't even remember what the heck the original topic was anymore. Apparently, summarizing doesn't work either.
Plain & Simple: stop & slow sub-30 MPH traffic is the worst. 70+ MPH highway cruising is nasty. 35 to 55 MPH suburb driving with occasional stops is the best. Cold weather lowers efficiency (and I have 4 years of winter data to clearly showing that).
#3593 of 7508 So the definition of City Mileage is not Accurate!!
Jan 16, 2004 (2:15 pm)
Toyota should re-define what they mean by City and Highway driving...John stated that Suburb driving (35-55) with occasional stops is best...
I would define CITY driving as 0-35mph with many stops or holds (stop lights as well as heavy traffic in which you must stop regardless of lights).
HIGHWAY would mean cruise speeds of 65-70 mph with minimal or no stops.
So the Pruis in heavy traffic behaves the same as any all combustion vehicle...and you don't get the opportunity to regenerate in stopped traffic (all power plants now equal at this point) ...regeneration only occurs during the braking...grabbing the kinetic energy during the stopping process, once you stop this energy of motion is gone ... so is the regeneration!
Jan 16, 2004 (2:30 pm)
> 35 to 55 MPH suburb driving
Except I made a mistake... it's actually 35 to 50.
55 MPH is still better than 60 though.
Sorry about that.
#3595 of 7508 Driving Styles Effect MPG
Jan 16, 2004 (3:15 pm)
Maybe it's the WAY everyone drives that most affects MPG. My 30 mile commute is at 0-30 mph for about 15 of it and 65-75 for the other 15. I am getting about 48 mpg here in warm L.A. I'm not a leadfoot although I do accelerate quickly to keep up with traffic, a necessity in LA traffic. I imagine the posted "estimates" are done under very strict and easy conditions. No testing can meet all qualifiers.
#3597 of 7508 braking is not necessary
Jan 16, 2004 (4:07 pm)
> if you just cruise down the highway then you are not
> braking and thus regenerative energy is not recovered
Braking is not required for the recapture of energy.
I prove this routinely. Without touching the brakes at all while just going with the flow on the highway, I earn "leaf" symbols on the Multi-Display indicating how much was regenerated.
Any excess kinetic energy can be reclaimed, any minor decline will cause this.
It is amazingly easy for the Planetary-CVT in Prius too. Rather than using the 50kW motor (MG2) like it does for braking recapture, it instead uses the 10kW motor (MG1) since that is ALWAYS spinning while the engine is providing thrust anyway. The switch-over from generating electricity from the engine to from the wheels completely seemless, since everything is already moving. The electric flow doesn't even change. All that actually happens is the sensor detects thrust coming from the wheels instead of going to them and eases up on the engine RPM.
#3598 of 7508 Fundamentals....
Jan 16, 2004 (4:11 pm)
Nothing in life is free!
Regenerative braking slows the vehicle down. If you intended to stop or slow for some reason anyway that is all to the good. But the use of regenerative braking while cruising down the highway would simply defeat the purpose.
Just suppose that Toyota was smart (or devious) enough to start the DOE/EPA mileage test series with the batteries "full" and end with them empty?
Who's to know?
I rather doubt if the rules and regulations cover that issue yet.
#3599 of 7508 So now....
Jan 16, 2004 (4:14 pm)
Regenerative braking so as to not overspeed on a decline (assume downhill run) isn't regenerative braking at all.
So, John, just what do YOU call it then?
Or you assuming that since your braking foot is not involved it should be called recovery of kinetic energy?