Carbon measured as a part of EPA mpg Test
#1
07-11-2005, 02:20 PM
Join Date: Jul 2004
Location: Phoenix, AZ
Posts: 1,430
Carbon measured as a part of EPA mpg Test
Something I never knew:
http://www.thecarconnection.com/Shop...241.A8895.html
So the EPA test is even MORE flawed for Hybrids in part because they measure the carbon from burned fuel, which is not produced when in EV mode....
I never made that connection before.....
Why do such discrepancies tend to be more pronounced for hybrids? Basing fuel economy upon the amount of carbon exhaust that's emitted by a vehicle's tailpipe automatically favors gas/electric-powered vehicles. Since some of a hybrid's power comes from an electric motor that automatically produces zero emissions, these figures tend to skew higher than simple miles-driven/gallons consumed computations would otherwise indicate.
So the EPA test is even MORE flawed for Hybrids in part because they measure the carbon from burned fuel, which is not produced when in EV mode....
I never made that connection before.....
#2
07-11-2005, 02:50 PM
Re: Carbon measured as a part of EPA mpg Test
Hi Lars-ss:
___The Bag test is the only true way to measure an automobiles FE after either the FTP75 city or HWFET highway federal tests. There is just no way possible to get an exacting measurement of gallons consumed from a beaker to fill any particular automobiles tank up and then measure what is consumed afterwards.
___In regards to the differences after the test is performed, it measures exactly what it is supposed to (how many gallons consumed via the CO2 calculation over a given test cycle) and there is no advantage or disadvantage for a hybrid vs. a non-hybrid. If you were to run your HCH when it was brand new through the exact same acceleration/deceleration, max/min speed, exacting stop and go, temperature controlled, Hot start or Cold start depending on which test is being performed, exact door rated tire pressures, and exact break in oil’s for the particular FE test cycle on a treadmill and the % reduction applied afterwards, it would come darn near what Honda tested it to be and what the EPA would if they have in fact tested that particular years HCH as equipped w/ a stick or CVT. The manufacturers are the ones that give the EPA the actual FE data and if there was a question, the EPA could run the test themselves to verify. They (the EPA) does not verify each and every vehicle but runs enough of them through their own lab(s?) to make sure the manufacturers are being honest about performing the exacting Federal test(s) as written to the letter before posting FE ratings on the Mulroney stickers as the automobiles hit the lot. If you want to dig deep into this monstrosity, take a look at the CFR 600’s on the FTP75. It is a monster to verify all the qualifications are exact before you even think about placing a new car on a treadmill let alone run the test and measure the bag’s contents afterwards.
___Good Luck
___Wayne R. Gerdes
___Waynegerdes@earthlink.net
___The Bag test is the only true way to measure an automobiles FE after either the FTP75 city or HWFET highway federal tests. There is just no way possible to get an exacting measurement of gallons consumed from a beaker to fill any particular automobiles tank up and then measure what is consumed afterwards.
___In regards to the differences after the test is performed, it measures exactly what it is supposed to (how many gallons consumed via the CO2 calculation over a given test cycle) and there is no advantage or disadvantage for a hybrid vs. a non-hybrid. If you were to run your HCH when it was brand new through the exact same acceleration/deceleration, max/min speed, exacting stop and go, temperature controlled, Hot start or Cold start depending on which test is being performed, exact door rated tire pressures, and exact break in oil’s for the particular FE test cycle on a treadmill and the % reduction applied afterwards, it would come darn near what Honda tested it to be and what the EPA would if they have in fact tested that particular years HCH as equipped w/ a stick or CVT. The manufacturers are the ones that give the EPA the actual FE data and if there was a question, the EPA could run the test themselves to verify. They (the EPA) does not verify each and every vehicle but runs enough of them through their own lab(s?) to make sure the manufacturers are being honest about performing the exacting Federal test(s) as written to the letter before posting FE ratings on the Mulroney stickers as the automobiles hit the lot. If you want to dig deep into this monstrosity, take a look at the CFR 600’s on the FTP75. It is a monster to verify all the qualifications are exact before you even think about placing a new car on a treadmill let alone run the test and measure the bag’s contents afterwards.
___Good Luck
___Wayne R. Gerdes
___Waynegerdes@earthlink.net
#4
07-11-2005, 03:13 PM
Join Date: Jul 2004
Location: Phoenix, AZ
Posts: 1,430
Re: Carbon measured as a part of EPA mpg Test
Originally Posted by EricGo
That is the same as saying "the test is skewed because in EV mode, no gasoline is burned." It is a nonsensical statement.
This all comes about from the arguments I have had on Edmunds with people about how the EPA tests are flawed.
I have always thought the test was "just as flawed" for ALL cars, but now I think it is "more flawed" when it comes to HEVs, because the car is being propelled with no GAS being burned, i.e. producing no measurable carbons, when the electric motors are in use, which will give an INFLATED mpg number.
So yes, that means to me that the test is MORE flawed in the HEV testing. Which is shown in part I think by the Prius having a 60 EPA and only averaging 48 at GH.COM, while the HCH, which CANNOT be propelled by EV alone during the test, has less of a discrepancy. The Prius in the test is running on electric far more than in real-world driving.
Last edited by lars-ss; 07-11-2005 at 03:23 PM.
#5
07-11-2005, 03:25 PM
Re: Carbon measured as a part of EPA mpg Test
Hi Lars-ss:
___You are mixing some items up … While being propelled in EV mode, the dyno is registering distance traveled but the bag is not receiving any CO2 because the ICE is off. When the ICE starts back up (on fuel) it charges the pack back up to ~ the same condition it was in when the test was started. This charge comes from the excess fuel being consumed to both propel the Prius II and charge its pack back up. The charge to drive the Prius II in EV mode is not free as it appears you might be thinking.
___Good Luck
___Wayne R. Gerdes
___Waynegerdes@earthlink.net
___You are mixing some items up … While being propelled in EV mode, the dyno is registering distance traveled but the bag is not receiving any CO2 because the ICE is off. When the ICE starts back up (on fuel) it charges the pack back up to ~ the same condition it was in when the test was started. This charge comes from the excess fuel being consumed to both propel the Prius II and charge its pack back up. The charge to drive the Prius II in EV mode is not free as it appears you might be thinking.
___Good Luck
___Wayne R. Gerdes
___Waynegerdes@earthlink.net
#6
07-11-2005, 03:31 PM
Join Date: Jul 2004
Location: Phoenix, AZ
Posts: 1,430
Re: Carbon measured as a part of EPA mpg Test
Wayne, do you mean to say that regen braking has no impact on the test at all? It MUST have an effect - that is energy transplanted back into the HSD system which is not fuel burned, and thus not measured by the bag carbons.....Right?
#7
07-11-2005, 04:47 PM
Re: Carbon measured as a part of EPA mpg Test
Originally Posted by lars-ss
Wayne, do you mean to say that regen braking has no impact on the test at all? It MUST have an effect - that is energy transplanted back into the HSD system which is not fuel burned, and thus not measured by the bag carbons.....Right?
Don't forget that what's on GH is real averages of people driving their cars with SUVs barrelling down blasting their horns behind them etc... The Prius has decent power, plus it's easy to activate since it's fully automatic, so I think real world MPG average is less than EPA tests because of how people really drive versus the tests. What should be noteworthy in the discrepancy is the way people drive the Prius (taking advantage of it's power, rather than it's economy modes of operation) on average, much like the HAH with it's even beefier engine people are getting less MPG because it's so easy and 'fun' to blast away.
What's important is if the Prius (and others) can actually get what the EPA tests show it can get, and indeed it certainly can, given the data here, it can even far exceed what the EPA says it can get.
#8
07-11-2005, 05:06 PM
Re: Carbon measured as a part of EPA mpg Test
I don't understand why everyone is so perplexed by the EV mode producing no emissions. This is exactly what happens in real life! Unless the test is so short that the engine is never used at all or the battery is not at the same level at the end as the beginning, this should not make hybrid results less accurate.
#9
07-11-2005, 05:22 PM
Re: Carbon measured as a part of EPA mpg Test
Hi Lars-ss:
___It doesn’t matter about regen either. The energy the pack receives back from regen is initially given to you from the gasoline consumed that accelerated the car up to speed. Non-hybrid’s give this up as pure heat at the pad/disc or drum surface and that is the way it is. If you were thinking that its regen that gives the Hybrids such good numbers, it is a part of the overall higher FE but remember, the initial energy still came from the fuel and no where else.
___Good Luck
___Wayne R. Gerdes
___Waynegerdes@earthlink.net
___It doesn’t matter about regen either. The energy the pack receives back from regen is initially given to you from the gasoline consumed that accelerated the car up to speed. Non-hybrid’s give this up as pure heat at the pad/disc or drum surface and that is the way it is. If you were thinking that its regen that gives the Hybrids such good numbers, it is a part of the overall higher FE but remember, the initial energy still came from the fuel and no where else.
___Good Luck
___Wayne R. Gerdes
___Waynegerdes@earthlink.net
#10
07-11-2005, 05:30 PM
Re: Carbon measured as a part of EPA mpg Test
Hi Jason:
___I don’t see anything to be perplexed about either. If a PHEV were in the test and ran the entire FTP75 or the HWFET tests in EV without the EPA accounting for the pack charge (infinite mpg), then we would have a problem but the Prius II’s pack was supposedly pretty close to the same on each side of the test the last I had read. I thought at first it wasn’t given the sky high numbers but read in an Edmunds forum post a few months ago that it was a 4 or 5 bar at the beginning and the end of the test.
___Good Luck
___Wayne R. Gerdes
___Waynegerdes@earthlink.net
___I don’t see anything to be perplexed about either. If a PHEV were in the test and ran the entire FTP75 or the HWFET tests in EV without the EPA accounting for the pack charge (infinite mpg), then we would have a problem but the Prius II’s pack was supposedly pretty close to the same on each side of the test the last I had read. I thought at first it wasn’t given the sky high numbers but read in an Edmunds forum post a few months ago that it was a 4 or 5 bar at the beginning and the end of the test.
___Good Luck
___Wayne R. Gerdes
___Waynegerdes@earthlink.net
