Speaking of the Prius... Real world expierence.

[DarkBlack]

Here is an EXCELLENT 2011 article explaining in great depth what I'm talking about.

Google "Understanding the Challenges in HEV 5-Cycle Fuel Economy"
for the PDF research from MJ Meyer

It's a long interesting read. If not, In the summary:
"As of 2011, the fuel economy labels for EVs and PHEVs are calculated using some form of the MPG-based estimation equation, which was not specifically designed to work with these types of vehicles. Future testing work will need to consider how EVs and 58 PHEVs respond to full 5-cycle testing procedures. It has not been demonstrated with test data whether the MPG-based estimate for EVs actually produces results similar to the full 5-cycle method. The testing burden is automatically doubled for PHEVs since they have to be tested in both charge-depleting (CD) and charge-sustaining (CS) modes. That is, electric and fuel consumption are determined for operation where the battery is being depleted, and then fuel consumption is measured under operation once the battery has been fully depleted.

An even more complex decision facing regulators is the finalization of rules regarding fuel economy of other advanced technology vehicles such as battery electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs). These vehicles already require much longer test procedures by needing to repeat cycles until a battery is depleted (at least to a degree to make extrapolations). The industry-standard test methods for PHEVs are also addressed in the Society of Automotive Engineers (SAE) J1711 standard that is referenced in this thesis for testing of hybrid electric vehicles like the Toyota Prius. A standard for EVs is defined in the SAE J1634 recommended practice. As of 2011, the fuel economy labels for EVs and PHEVs are calculated using some form of the MPG-based estimation equation, which was not specifically designed to work with these types of vehicles.
"

 

[milkman]

I see I'm still loosing you on this one. I'll re-word for a final try:
The EPA approved city/hwy #'s posted/advertised by car makers have only accounted for the liquid (gasoline) fuel consumed during the tests.
It's been that way for years.
Since a hybrid also has a second fuel source (large battery)+electric motor, that fuel was not being reported. This allowed Hybrids to start the EPA fuel efficiency tests with a pre-charged battery, that got it's energy from a plug in charger. The tested hybrid car then finished the EPA mandated 5 cycle routine, but at the end it had discharged it's battery and this "pre-paid for" energy was not required to be converted to equivellent gallons of gas it would take toi charge it back up.

This is a big part of hybrid owners getting less MPG than advertised.
Fortunetly there is enough consumer pressure that the EPA and car makers are being shamed into changing the 5 cycle fuel economy testing rules to account of this false advertisement

I'm not lost, you are obviously talking about the Plug In Prius, no one else in this thread is talking about the PIP. The Prius hybrid does not have a plug in to use any other power source than the gas engine and the battery that is charged by the engine or regenerative braking.

 

[DarkBlack]

I'm not lost, you are obviously talking about the Plug In Prius, no one else in this thread is talking about the PIP. The Prius hybrid does not have a plug in to use any other power source than the gas engine and the battery that is charged by the engine or regenerative braking.

No. It applies to both models. The standard model discharges a battery to help city mpg #'s during the test and it's computer controlled recharging of the battery can fall outside of the test times. This is unaccounted gas using engine load that would be required in normal driving to bring the charge back up.

From the same paper: This part is regarding specifically a 2010 standard model:
" Chapter 4 discusses the general testing procedures for considering battery energy change, including several possible metrics, which are required for HEV testing. As a result of the synthesis of results from individual drive cycle phases, the battery energy changes that occur in the course of each drive cycle phase will affect the fuel economy label results. Testing of the 2010 Toyota Prius shows that significant battery energy changes can occur on individual phases even when the overall cycle is charge-sustaining and that these changes do affect the fuel economy result for each phase."

 

[milkman]

No. It applies to both models. The standard model discharges a battery to help city mpg #'s during the test and it's computer controlled recharging of the battery can fall outside of the test times. This is unaccounted gas using engine load that would be required in normal driving to bring the charge back up.

From the same paper: This part is regarding specifically a 2010 standard model:
" Chapter 4 discusses the general testing procedures for considering battery energy change, including several possible metrics, which are required for HEV testing. As a result of the synthesis of results from individual drive cycle phases, the battery energy changes that occur in the course of each drive cycle phase will affect the fuel economy label results. Testing of the 2010 Toyota Prius shows that significant battery energy changes can occur on individual phases even when the overall cycle is charge-sustaining and that these changes do affect the fuel economy result for each phase."

You wrote in post #67 "This of course requires plugging it in to an outlet that may be fed by a coal fired electric plant, and this isn't factored in."

How does above post apply to the 2010 or any Prius that is not a Plug In, that has no provision to be plugged into anything that is coal fired to generate electricity to charge the battery? The MPG rating includes the gas used to propel the car and recharge the battery, where's the cheating?

 

[houstonscott]

The testing should clearly start with an empty battery. If it doesn't they are bogus. HS

 

[dave1949]

No. It applies to both models. The standard model discharges a battery to help city mpg #'s during the test and it's computer controlled recharging of the battery can fall outside of the test times. This is unaccounted gas using engine load that would be required in normal driving to bring the charge back up.

From the same paper: This part is regarding specifically a 2010 standard model:
" Chapter 4 discusses the general testing procedures for considering battery energy change, including several possible metrics, which are required for HEV testing. As a result of the synthesis of results from individual drive cycle phases, the battery energy changes that occur in the course of each drive cycle phase will affect the fuel economy label results. Testing of the 2010 Toyota Prius shows that significant battery energy changes can occur on individual phases even when the overall cycle is charge-sustaining and that these changes do affect the fuel economy result for each phase."

I can see what you are getting at. The test sounds over-engineered to me, or really wrong for these types of vehicles to begin with.

If, like Egon said, you begin with a full charge and end with a full charge, the gas engine in a non-plugin will automatically be penalized when it recharges the battery--has to happen somewhere in the test. You gain some here, lose some there.

 

[milkman]

The testing should clearly start with an empty battery. If it doesn't they are bogus. HS

Can't start with an empty battery, the small 12v battery powers up all the electronics and the HV battery starts the engine.

 

[DarkBlack]

milkman- read the article. I'm done trying to explain it to you, and I have no interest in you trying to drag me into a straw man argument.

 

[DarkBlack]

Hasn't that correction already been made?
===============
From:
http://www.autonews.com/article/201...s-mpg-test-holds-up-for-hybrids#axzz2lmzCSUtK

That test was revised in 2006 for the 2008 model year, in part because early hybrids were performing far better on the agency's test than in real life.

With those changes, the fuel economy of the Toyota Prius plummeted from 51 mpg highway and 60 mpg city to 45 mpg highway and 48 mpg city.

Actually while that article is about the loophole of allowing "similar" cars reports to be used for another car there is a mention of the other issue I've been posting about:

"Meanwhile, despite the urging of Consumer Reports, the EPA doesn't intend to rework its five-cycle fuel economy test. That test was revised in 2006 for the 2008 model year, in part because early hybrids were performing far better on the agency's test than in real life."

 

[Egbert]

While the mpg debate is interesting, I'll just say that my 2010 prius is averaging just over 49mpg for 30K miles. It is superior quality, runs great and handles great. A little bit ugly ... but, you can't have everything