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zero miles / 1 gallon = zero MPG
zero miles / 50 gallons = zero MPG :surprise:
It never goes negative.
Maybe if you coasted downhill in reverse? :P
That's due to the torque converter being bypassed the majority of the travel time and the aforementioned fuel cut technique. The Automatic's ECU can shift down sequentially 4 times or more to sustain minimal engine RPM doing coastdowns. Can you imagine any stick driver being consistently attentive enough to do all those downshifts and at precisely the right time...just before the engine RPM gets to low...?
Personally I find that I sometimes fail to "properly" upshift into top gear, 6th in my case, unless or until I happen to notice the tach indication.
Longer term, the 03 TDI 5 speed manual is ahead of the automatic by easily 5-7 mpg. (app 17%) And either of these is considered a fuel miser @ 46.5 average vs 39.7 mpg
Wrong again. Your "instant MPG", as you called it in post 6703, NEVER "goes" negative.... it goes to zero. That will reduce the average over time. Which will. as you said, " 'negatively' impact MPG computations". But that is just putting spin on the original misstatement.
Perhaps that was your was of admitting that you were in error?
I think the biggest factor driving this is gearing. In most cars whose AT variants use less fuel than the MT versions, the AT has a very tall overdrive that allows for very low RPM at highway speeds, while the top gear on the manual is shorter and the engine turns higher RPM at the same speed.
On a side note, gearing is also why there are a lot of cars where the highway mileage penalty of going to the bigger/more powerful engine is very small, or nothing. The version with the bigger engine gets an extra gear, or a taller top gear. Check out the MPG on a Toyota RAV4 with the V6 vs the 4-cylinder.
Can you imagine any stick driver being consistently attentive enough to do all those downshifts and at precisely the right time...just before the engine RPM gets to low...?
I don't think that saves as much fuel on coastdowns as just pushing in the clutch.
No, it was the OBC programer's choice, or program spec. writer's choice, to not have the computation continue beyond zero. Your instant gas mileage does in fact go negative at those times just as reflected in the continuing declination of average mpg computation.
Or maybe it was/is a simple display shortcoming, no ability to display a minus sign.
Did you by chance flunk math...? I got all the way to algebra II before flunking out, bailing out, actually.
Just pushing in the clutch will still require enough fuel to not only keep the engine idling, at the same time power must be provided to the the A/C compressor, the alternator (ENTIRE electrical system), the power stearing pump, the water pump, and the oil lubricating pump.
Have I missed anything, maybe that 300 watt stereo..?
Some time ago some marque (MB, BMW..??) began installing a higher than normal size 12 volt battery and then, up to a point, only allowed the alternator to be functional during coastdown periods. Regenerative braking in its simplest form.
With an automatic in coastdown fuel cut mode all of that power is provided via the drive wheel traction. Think of it as REAL-TIME regenerative braking without the HV battery.
NO, it goes to zero. While you sit at a light, or whatever, you are using some amount of fuel, and traveling zero miles, thus an instantaneous zero MPG.
Please explain to the room how you can travel negative miles.
Whatever, Bye.
"If you take a look I think you'll find that modern day automatics on the highway are outperforming stick shifts by a goodly amount."
When I said "classic", I should have said, "classically incorrect". While there are a few (as in very few) automatic transmissions out there which turn in better EPA estimates than their otherwise identical sibling with a manual transmission, I don't believe there is even one example that shows a margin of more than one or two miles per gallon; so much for a "goodly amount". The flip side is that in the majority of cases, the manual transmission equipped cars equal or better their automatic equipped stablemates.
Don't believe me? Cool, look it up.
Then there's the whole "EPA estimate" thing; anecdotal evidence suggests that cars equipped with manual transmissions have a much easier tiime consistently besting the EPA estimates by relatively huge margins while the automatic world has a difficult time even matching said estimates.
I have - same result
What I can't figure out is why he didn't simply state this.
Yes, it adversely affects miles per gallon. Of course.
No, you cannot accrue actual negative MPG. It goes no lower than zero. If you were tracking gallons per hour instead-- for argument's sake, pretend your Porsche is an aircraft or something
The other major argument over the past few days was in regards to fuel consumption while coasting. Of course the engine when coasting is still consuming some fuel. If it were not, the engine would cease running. Try this with a very low tank and you'll see. Just as you cannot idle without fuel, you can't coast without it either. The fact that the throttlebody isn't open means nothing. All fuel injected engines have idle circuits just as carburetors had before them.
That's the crux for me, and at least in an automatic, coasting keeps the engine turning allowing the fuel to completely shut off. So it's more fuel efficient to coast downhill at 70 mph than it is to idle at a stop light. And it's more fuel efficient to coast in drive than in neutral.
People report that their factory manual says that fuel injection shuts off under deceleration. Others say that the fuel injectors will only go to zero pulse if the catalytic converter is hot enough, and perhaps if the engine is going at least 1500 rpm while coasting.
Or so the theory goes.
The hypermilers are all out with their Scangauges figuring out how fuel efficient their cars are in various gears, whether their car's ECUs actually allow the injectors to completely shut off, comparing coasting in gear with coasting in neutral, shifting manually through D-3-2-1 to keep the fuel shut-off turned off, etc.
I think also with the push in the new 2012 35 mpg fuel standard for those engines in those cars that do not have a SOLID place in the new scheme/schema/pecking order, there will be a constant improvement effort from minor tweeks to all out effort (spare no expense) to boost mpg. "No fuel draw" downhill or at rest throttle position is one "minor" one.
So for example, the idle shut off option that the Toyota Prius has (and for years) will probably become more common place. I understand that the oems have for years been putting them in selected models in Europe. So depending on how much one idles, it can range from .5 mpg (barely measurable) to 1.5 mpg (my swag).
In the overall picture, "the sword is dangling over the head" of the (SLUSHBOX) automatic transmission. 1% to 17% better mpg (with the older than the hills. 5/6 manual transmission with engine management and gearing tweeks) are really very hard to ignore. So for example, the population bearing the DSG (better mpg than the slushbox and lesser than the 6 speed manual transmission) is almost not measurable. Hybrids with their almost EXTREME price premiums, offer a only an app 20% mpg advantage. However again it truly depends on the conditions you find yourself driving in. Hybrid population is est @ less than 2% and that is after more than a decade of policy support and full court media press.
So for example VW went from a slushbox to a DSG (-7 mpg off the 5 speed manual) and essentially the EPA mpg is @ par with the 6 speed manual (30 C / 42 H) In mpg terms that is a pretty good solution. As I have said before in real world terms the mpg on the 6 speed manual can be STILL up to 17% better than the DSG.
Another hard to ignore issue is the 20-40% better fuel mileage of a TDI ( and mated to a 6 speed transmission).
When you put the various factors together with higher mpg as a goal, the results can almost be astounding. So for example, 03 VW Jetta the gasser 1.8 with automatic gets real world 24.1 mpg. The 03 TDI with 5 speed manual gets 46.5 mpg. The mathmatical translation: mpg on the diesel with manual transmission posts 92.9% better. From the diesel side the 1.8 gasser with automatic is 48% worse.
The one's "driving" an automatic have a rather easy time of it. On the other hand the ones "driving" the stick shifts must be CONSTANTLY ATTENTIVE in order to have the car in the absolute PROPER, most OPTIMAL, gear ratio throughout the driving simulation.
Now, just what percentage of the public owner/drivers of stick shift will be that constantly attentive...?
Never happen, based on what I've read here over the past several weeks.
Let me call your attention to the 2004 Toyota Prius EPA bru ha ha. Toyota advertised 60 C and 50 h mpg. While this is a swag, there were a lot of NON Prius owners who bought where mpg was a high priority.
UPSHOT this small small small minority of folks (dissed and pissed Prius owners) was able to change the EPA test which had existed for 3-5 decades to change the tests in favor of ... hybrids (Prius). Even at that, Toyota took easily 5 years to get back to even 50 mpg and it took a HOST of redesigns and modifications to do so.
Indeed one has to be WAY more attentive driving an AUTOMATIC transmission than stick owners to get the advertised mpg in the favored vehicle PRIUS.
Let me put it another way. If I drove the Prius the way I drive my TDI's I would get FAR less mpg than the Prius !!! If I drove my TDI's like you have to drive the Prius to even come close I would get far better mpg than the Pruis !!!!
Given that just a few years ago now automatics were falling far short of stick shifts in this area.
The core, fundamental, differences between automatics and manual transmission have been the losses associated with the torque converter and ATF pump in the automatic.
About 10 years ago now the constant pressure, ATF line pressure, was done away with in favor of a new "real-time" ATF line pressure control design. There is no substantive level of ATF line pressure unless the transmission is in the process of shifting from one gear ratio to another.
The second development was the result the adoption of a more robust torque converter lockup clutch. Nowadays the Torque converter need only be in the drive line if the road speed is such that the traction load would stall the engine.
As you can see, it is likely that these 2 developments alone brought the automatics FE up to a par with the stick.
Then there is the need for constant attentiveness on the part of the driver, the inadvertent biasing toward the stick, and the practical, REAL-WORLD, FE comparison suddenly becomes questionable, VERY.
The icing on the cake comes from the adoption of the fuel cut technique. Even if done on the stick shifts it will forever remain dependent on the whims, constant attentiveness, of the driver to match the newer automatics.
The future of the stick shift will now go the way of RWD.
Only of use/desire in the sporting, sports use, world.
We also talk about cutting consumption, green, etc.. However, consumption has NEVER been higher !!! The end (REAL) goal, as consumption GROWTH grows slower (104% to 103% to 102%), year over year is that prices of per gal fuel will RISE !! That is on no less an authority than PO's energy secretary. If I may paraphrase him. WE/They have to find a way to get the price up to European prices @ app $10.00 US. If and when that happens (unless they have by then an automatic transmission that can out perform a manual transmission) you will actually see an upward M/T trend. Europe is upwards of 90% manual transmission.
Never happen, based on what I've read here over the past several weeks.
You are right. One may as well argue with a fence post. :sick:
As for Mr West's assertion that negative MPG exists: the only way to do so would require either negative fuel consumption or negative miles traveled; hence my earlier joke about coasting downhill in reverse to achieve the negative 99 MPG that he claimed at idle.
It's really not that difficult to understand.
WHAT? I am going to bias my results on something that makes my car cheaper with lower transaction prices and lower profit margins? Riiiiight.
In the meantime the low sales, high profits, CAFE contribution, are all to the good. Sales only to the manual transmission affectionotoes who are not likely to complain about the FE disparity, or even take notice, apparently.
2020 Acura RDX tech SH-AWD, 2023 Maverick hybrid Lariat luxury package.
I think it's the way you name the systems that had me confused.
There is no AWD Sienna 4 cylinder.
There is a FWD Sienna 2.7l 4 cylinder.
I read F/awd as "Front or All Wheel Drive". Now I'm thinking you meant them as one in the same, i.e. a system that switches between those two modes.
6th is taller than 5th on the 5 speed manual. The auto is geared much taller than either of the manuals.
You get good throttle response on the highway, but I still think 6th should be a tall cruising gear.
But you see plenty of manuals in the compact and sub-compact segments.
What amazed me more was that the Scion tC I bought (with the torquey lump of a 2.4l camry motor) was geared darned near as short. Probably doing close to 2900 at 60 in 5th gear. And absolutley no reason it needed to be that short. Now, if it had a deep overdrive 6th gear too, it would have been fine!
2020 Acura RDX tech SH-AWD, 2023 Maverick hybrid Lariat luxury package.
2011 Edmunds' Inside Line Readers' Most Wanted Awards
Let's see here automatic versus manual pricing:
Acrua TSX: same price
Aston Martin DB9: Automatic $5,300
Audi A3: Automatic $1,480
Audi A4: Automatic $1,300
BMW 1-Series, 3-Series, and 5-Series: same price (new as of this year)
Buick Regal: same price
Cadillac CTS: Automatic $1,250
Chevy Aveo: Automatic $925
Chevy Camaro: Automatic $1,170
Chevy Corvette: Automatic $1,250
Chevy Cruze LS & Eco: no automatic availability
Chevy Cruze 1LT, 2LT, & LTZ: same price
Dodge Challenger: Manual $995 (includes LSD, engine, steering, and trim changes)
GTB Fiorano Coupe: same price
Fiat 500: Automatic $1,000
Ford Fiesta: Automatic $1,095
Ford Focus: Automatic $1,095
Honda Accord Coupe: Automatic $800
Honda Civic: Automatic $800
Hyundai Accent: Automatic $1,000
Hyundai Elantra: Automatic $2,250
Infiniti G Coupe IPL: Automatic $1,900
Kia Forte: Automatic $1,000
Lotus Elise: no automatic availability
Mazda Mazda3: Automatic $800
Mazda Mazda6: Automatic $1,000
Yeesh! I could go on but you get the idea.
So, let's look at this list; there is one (yes, count them, ONE) car where the manual transmission is an extra cost option, and that option includes extra goodies not on the Automatic trim. Call the Dodge Challenger a wash price wise. With this one exception, where are all of the cars with stick shifts which "are now a higher priced option?"
'Nuff said!
Right next to all those "automatics on the highway [that] are outperforming stick shifts by a goodly amount."
Automatics, in addition to hybrids, are also the reason that EPA dumbed down all its numbers in 2008, so that buyers of auto-equipped cars couldn't squawk as much about how their cars weren't meeting the fuel economy standards displayed so prominently on the window.
So now we have this ludicrous situation where automatics are finally achieving fuel economy that is in the range of the EPA numbers, while manuals are now wildly exceeding them at all times. Me, I just take the highway number and add 5 to know what my average fuel economy will be, and I'm always spot on. ;-)
2014 Mini Cooper (stick shift of course), 2016 Camry hybrid, 2009 Outback Sport 5-spd (keeping the stick alive)
If I may add to your Honda example/ issue, they have actually done pretty well in the equalization of EPA mpg (M/T vs AT). So for example, on my Civic the epa difference between M/T and A/T is minus -1 mpg as I recall. I would also swag in a M/T, far better than the 38-42 mpg I now get with the A/T.
Gee, I know some grandma's who are comfortable and safe cruising @ or close to xxx speeds. (hard to make it to grandma status, if grandma kills herself in a car wreck) I hope you are not hanging around a bunch of folks who had their licenses pulled (or close to it) because of age related health issues, and ...STILL drive.
In my 5MT WRX only the steepest parts of the big hills allow me to coast in 5th. All moderate hills just slow me down if I leave it in gear and then I have to add throttle defeating the purpose. 2L/100km is the lowest the computer will read out for fuel consumption, so I have no accurate idea of whether coasting in gear on the really steep sections is better or not. I do know that there are only a couple of places I can do it. There are some very shallow hills I drive all the time, and with pulse to 35mph I can glide in N (or clutch pedal in) for 1/3 mile, and show lowest consumption. In 5th with clutch engaged maintaining the same speed, consumption registers 2-3 times higher, and I slow down if I don't use the throttle.
As to the premise that AT do a better job, our Suburban coasts downhill in gear on the bigger hills, but if I swap between N and D, the fuel consumption is 1L/100 km better in N than D.
Of course, this is using the computer read-out, and not a scan guage, but it should be internally consistent in both cases.
Would you believe the folks at popular mechanics?
How about Jeremy Clarkson?
'11 GMC Sierra 1500; '98 Alfa 156 2.0TS; '08 Maser QP; '67 Coronet R/T; '13 Fiat 500c; '20 S90 T6; '22 MB Sprinter 2500 4x4 diesel; '97 Suzuki R Wagon; '96 Opel Astra; '11 Mini Cooper S
God forbid you drive a manual and have to put down your Starbucks Latte and cell phone....
Oh! And I hate coffee, Starbucks included. :P
2014 Mini Cooper (stick shift of course), 2016 Camry hybrid, 2009 Outback Sport 5-spd (keeping the stick alive)
This all helps to keep oil imports lower, thankfully! Hoo Rah!
If WW's and others misinformation were true about fuel being required during coastdown, the world & laws-of-physics would indeed be different and posterior porcine aviator egress would be rampant everywhere !
In truth, the zero-fuel-use-coastdown mode is equally useful/used/unavoidable regardless of diesel vs gas, or manual vs automatic. Many people find zero-fuel-use-coastdown counterintuitive - perhaps they are ignoring the energy input from the wheels being turned by the road.
in the thought experiment world, try this one, it's fun:
make the vehicle weigh 100,000 lbs and have it turn an electric generator on the way down that loooooong hill.
then with an onboard tesla coil or a really long unreeling extension cord or traintracks third-rail-in-reverse, you could power a whole town with the energy, as well as powering all the car electronics/etc, all with zero fuel use.
A good/analogous question for the train/subway buffs is whether trains regenerative braking can apply power back into the third rail to power cars going up a hill further down the track? Why not? Probably no manual transmissions in trains, huh? (don't make me go find one example of a train with a manual transmission just to make it relevant to this forum, ok?)
Also, don't try to run a modern car downhill or any other way zero fuel in the tank! Many of them have fuelpumps cooled by the fuel itself. With no fuel and empty tank on your long downhill zero-fuel-use cruise, your fuel pump will cook itself trying to maintain fuel pressure even though no fuel is being injected...
All the electronics will run fine at 13.8 Volts DC all the way down the hill, powered by the alternator which is turned by the road/transmission/gears/etc.
cheers - see you all in a few weeks - keep up the manual transmission talk/clamor/demand and let's all clamor for the 2013 CHEVROLET CRUZE DIESEL with 6-SPEED MANUAL TRANSMISSION !
My Accord confirms this. I get about 300 mpg coasting down hills at 70 mph (on scanguage).
General rule of thumb is you get about 4 times your speed in mpg if you coast in idle. So 30 mph = about 120 mpg. 15 mph = 60 mpg. Obviously the slower you go the less advantage to coasting in idle.
BTW I would love a Cruze diesel with 5mt. Especially if they gave us the wagon/hatch or a little more leg room in back.