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blacksmith37 (Materials) (OP)
8 Dec 11 15:10
Theoretically there should be a 3% loss of MPG when going from gasoline to 10% ethanol. I have recorded every tankful MPG for 115,000 miles. A few yrs ago our rural was required to add 10% ethanol (to buy corn belt votes), so I have 70,000 of MPG with real gasoline and 65,000 miles with 10% ethanol. ( Same driver, same driving pattern, modern state -of -art fuel inj 5.6L Nissan V8). By inspection (have not mathmatically averaged data) it looks like a change from 16.8 MPG to 15.2 MPG, or about >10% loss due to ethanol.
Is there a reason why 10%ethanol would reduce MPG by more than 3% ?   
Toddr8541 (Mechanical)
8 Dec 11 15:19
Ethanol has less BTU's per gallon.  Therefore to maintain the same power output the engine requires for fuel.   
patprimmer (Publican)
8 Dec 11 15:51

Quote:


Ethanol has less BTU's per gallon.  Therefore to maintain the same power output the engine requires for fuel.   

That is what the 3% loss mentioned in the OP is about. The additional 7% is the question.  

Regards
Pat
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dgallup (Automotive)
8 Dec 11 15:58
Starting at a 70,000 mile baseline?  Perhaps you have lost compression, partially plugged cat, etc.  Bigger tires?  Not a direct comparison so no way for us to know.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
 

patprimmer (Publican)
8 Dec 11 16:05
We could blame climate change, or even claim it is evidence of climate change.  winky smile

Seriously, a variable such as listed by dgallup sounds likely. A change of tyres can be significant. A change of brake pads or even accumulated dust or corrosion may have resulted in minor brake binding

Regards
Pat
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swall (Materials)
8 Dec 11 16:15
Perhaps the btu content of the baseline gasoline has dropped from the time blacksmith37 did his baseline with pure gas compared to the current trials with E10.
jmw (Industrial)
8 Dec 11 17:12
Perhaps a more reliable measure would be to see what the EPA says.
The EPA is supposed to run tests on additives and is that not what this is?
OK, its a mandatory requirement in some areas and because it is likely to be more widely used than the many additives and after market bolt on goodies like "fuel harmonic dingbats" , surely more pressing that it is properly evaluated and reported.  

JMW
www.ViscoAnalyser.com

 

blacksmith37 (Materials) (OP)
8 Dec 11 17:20
Trust me , Nothing obvious has changed. I am retired, nothing changed in drive pattern ; still like to burn some rubber once a week (entering the interstate).Vehicle is a 2004 Titan, in 7yr, about 4 on gasoline and 3 on 10 %, so weather should not be a problem. 3 sets of tires which I selected primarily on max O.D. (all pretty close), plus I have included 0 to 1% speedo/odo error (depending on tire O D).Presently 10,000 miles since last oil change(I know its overdue) NO apparent oil consumption (Castroil 5W20). I interperate this as the engine showing no wear. With the plugs buried between each heads twin cams, pulling plugs to measure compression is difficult.
JSteve2 (Automotive)
8 Dec 11 17:25
The ethanol could also be causing something in the system to change, like a temperature somewhere in the system, that causes a different fuel map to be utilized.
blacksmith37 (Materials) (OP)
8 Dec 11 17:26
I would not necessarily believe ANYTHING the EPA says. I did work 30 yr in Amoco R&D; not in engine lab ,but I often read their internal reports. So I am aquainted with some considerations.
jmw (Industrial)
8 Dec 11 17:40
Damn, does that mean these fuel economisers that magnetise the fuel might actually work?

JMW
www.ViscoAnalyser.com

 

mattsooty (Automotive)
8 Dec 11 18:58
Although the energy per volume of fuel suggests a delta of 3% - this does not take into consideration the different heat releases characteristics of the two fuel blends.

MS
hemi (Automotive)
8 Dec 11 19:05
This thread boils down to an experimentally observed 10% variation, with 3% of the variation accounted for as a controlled variable (fuel BTU content).  The question is: is the observed 7% anomaly statistically significant, or can it be accounted for by noise?
That can only be answered by making a series of trials, with all controlled variables held constant.  The results can be statistically analyzed to determine the "noise" in the experimental method.  One shortcoming in the procedure, already pointed out by dgallup, is the observations were not randomized temporally (relative to unleaded vs E10), so there is much potential for a systematic error.
 
patprimmer (Publican)
8 Dec 11 21:29
Also I at least don't know the ECU strategy for handling the requirement for a slightly richer mixture and possibly different timing requirements.

The base map tunes will not be optimised for E10, but knock sensors and oxygen sensors will react differently and attempt to modify the tune at least in closed loop. I doubt different heat of vaporisation will have an effect as it will be very small, and will mostly have its effect in the port away from intake charge temperature sensors.

Regards
Pat
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jmw (Industrial)
9 Dec 11 7:02
That's an interesting thought Pat.
It suggests that when legislating for 10% madatory ethanol content, the legislators should also make provision for peoples vehicle sot be modified to handle the fuel.
I presume that as far as they got was that "there are no mechanical modifications required".... but no one seems to have mentioned the engine mapping.

It suggests that some of the green savings will be eroded by inefficient burn of the fuel (oops!) and if 10% is a semi-typical figure and not the 3% they first thought of, then they have a problem because a great many people may simply not bother to have their engines re-mapped.
If this is the case then I guess the legislators now have to find some way to fund remapping everyone's ECUs....without succumbing to the temptation to meddle more with the maps than is necessary to optimise efficiency.  

JMW
www.ViscoAnalyser.com

 

SomptingGuy (Automotive)
9 Dec 11 7:10
I thought pump gas in the US varied during the year, with ethanol content higher in the colder months to promote starting.

- Steve
 

swall (Materials)
9 Dec 11 7:46
Ethanol inhibits cold weather starting, which is how the E85 came about--the 15% gasoline content is necessary for cold starting.
1gibson (Mechanical)
9 Dec 11 9:29
Tire pressure?
IRstuff (Aerospace)
9 Dec 11 10:26
Certainly, in California, the gas mix changes twice a year, based on the start and stop of "smog" season.  However, many states don't have that, since they don't even have emission controls on the gas nozzle.

If nothing else, an off-optimum gas mixture relative to mapping would result in higher emissions, so the next generations of ECUs will nno doubt have automatic sensing of the mixture change and adapt the mapping to suit the mix.

TTFN

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dgallup (Automotive)
9 Dec 11 11:22
E10 mandate is pure pork barrel politics, nothing more, nothing less.  The billions given to ethanol producers are a total waste of tax payer money.  The ethanol producers would all close up shop if they did not have a mandated market for their product.  Hence the attempt to force E15 down our throats.  With the decrease in fuel usage in the USA due to the recession and consumers driving less the ethanol suppliers were in danger of having excess capacity.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.
 

ornerynorsk (Industrial)
9 Dec 11 14:34
70,000 + 65,000 = 115,000 ??????  Why, there's your loss and then some!

(sorry, couldn't resist)

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

blacksmith37 (Materials) (OP)
10 Dec 11 10:58
As a norski curmudgeon myself, I am so embarassed by my arithmetic.
Tire pressure has always been "high"; 45 to 60 psig.
Can anyone suggest an easy to use (for a computer illiterate) statistical software. Real averages and std deviations could make me honest.
The only way ethanol even starts to look "green" is if the corn field work ,plowing etc, is done with solar power tractors; I haven't seen any working TX fields.
blacksmith37 (Materials) (OP)
10 Dec 11 11:10
IRStuff; In the old days there were 4 gasoline blends : high and low altitude, summer and winter. Today a refinery may make a dozen blends, as many legislators are now chemical engineers and define fuel requirements in local municipalities.
Old guy story : Oil corps used to monitor each others gasoline, Amoco would have meetings to decide if they should match (say Shell) in the Denver regeion because Shell was 0.2 octane higher than Amoco in that region.They worried a lot about "octane giveaway" like that.
dicer (Automotive)
12 Dec 11 4:01
I agree Dgallup, along with other not so apparent things as well.
Along with 10% alcohol, in the gasoline supplys, what percentage is the water emulsion, that will be displacing more gasoline, upsetting tune etc. I would say that is the major contributor to a variance in what a proper heat value calculation is and the actual measured MPG or power output. If this ethanol is so wonderful as a motor fuel and does all these nice things advertized how come the major airlines aren't using it?  
patprimmer (Publican)
12 Dec 11 6:09
Very small amount of water may be dissolved in the alcohol, but I never saw enough to separate out or form an emulsion. There will not be enough water absorbed to displace anywhere near 7% of fuel.

Aircraft have to travel long distances without refuel and weight is much more critical, so it is the same reasons behind WW11 aircraft not using alcohol vs top alcohol cars using it, ie mpg and consequential fuel load is more important in an aircraft.

Regards
Pat
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Tmoose (Mechanical)
12 Dec 11 12:39
Maybe one of those analyzers that access the OBD II port and can report real time mpg would provide some useful info
DigitalGT (Military)
12 Dec 11 16:00
Tmoose,

The computers that plug into the OBDII port and report fuel consumption are only as good as the information they are provided. I have one called the ScanGauge II and it does a reasonable job of reporting mileage. It requires very deliberate refueling in order to correctly report to the unit what the car has just burned for fuel. Keep in mind these things only look at injector pulse width and fuel rail pressure (if available) along with the number of cylinders and do rough estimates of consumption based on what you tell it the engine it just burned (aka how much fuel was in the most recent fill up). If you don't fill up the tank every time and you don't do it the same way, or for that matter at the same pump, the numbers get skewed. Most of the ones also only have 1/10th of a gallon resolution. So you can't tell it you pumped 1.05 gallons, you have to tell it you pumped 1.1

If the vehicle has a non-return style fuel system where the ECU varies voltage to the fuel pump to keep the rail pressure at a desired value AND the scan gauge can't read fuel rail pressure (such as in my case) the numbers will be all over the place. Even though the gauge can read pulse width, if the ECU commands a high rail pressure during WOT and a lower one for part throttle duty the gauge gets left in the dark and is only really able to report an accurate average based on the previous tank's worth of driving.

They're nifty gadgets and I've used mine several times to diagnose problems. The built in DTC scanner it worth it alone. But I wouldn't use one and quote it's findings as empirical data. If anything I would only trust one to show me an overall trend over several tanks of fuel.
patprimmer (Publican)
12 Dec 11 16:21
If you know your fuel pressure and you know it's stable, pulse rate should be a fair indicator of instantaneous fuel use, but is fairly useless at calculating broad usage averages. total amount added to the tank vs mileage covered over a long period of time is still the best way, It would be better if the variable being measured was swapped around at regular but long intervals, say like once every month, or once every ten tank fulls to eliminate a variable that might have changed at the same time the fuel changed by coincidence.

Regards
Pat
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hemi (Automotive)
12 Dec 11 17:55
Apropos WWII aircraft engines, some did use alcohol injection as an additive, in a surgical manner when it was needed most, "wartime emergency power", was one of the appellations, I believe.  The Germans were onto this as well as the US, IIRC.  Not sure about the Brits.
patprimmer (Publican)
12 Dec 11 18:39
The Brits also used water/alcohol injection as a detonation suppressant, not as a fuel. I think the main reason for the alcohol was as antifreeze.

Regards
Pat
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hemi (Automotive)
12 Dec 11 21:04
quite right on both counts, same with the Yanks and the Jerries!  I understand that there are some subtle advantages of alcohol vs straight H2O as a detonation suppressant (in terms of net power), but I'm far from an expert on the topic.
dicer (Automotive)
12 Dec 11 23:59
Reason old piston aircraft can't and won't use it is corrosive issues.And same as the modern aircraft below.

Reason any modern aircraft won't use it is because, of the lack of power or the increase in the amount of fuel needed to get that power.

And the reason it is used for our the motoring publics cars is, it makes our cars use more fuel. ie reduces the MPG.  
patprimmer (Publican)
13 Dec 11 2:25
Your not paranoid if they really are out to get you.

Regards
Pat
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dicer (Automotive)
13 Dec 11 14:08
Not at all paranoid, just check out the pump prices. It is reality.
drwebb (Automotive)
13 Dec 11 14:28
The airlines are looking at biodiesel for their renewables strategy, and flight tests have been conducted to establish feasibility running 1 of twin engine craft on blends.

10 years ago when I was in the fuel additive game, EPA only required 'testing' of additives that contained elements other than C, H, O, (or N?).  So Ethanol and MTBE were not regulated as additives, although I'm pretty sure they got scrutinized for emissions control compatibility.

An Excel spreadsheet is about the easiest way to handle averages, standard deviations, and plotting the data as well that might be useful for spotting trends that may be significant.
 
jmw (Industrial)
13 Dec 11 17:21
Shame the guys at CRU can't use Excel... but maybe that's why they think the planet is cooking off and why we have to have biodiesel in the first place (despite the data coming in showing biodiesel is less good than fossil fuel).

JMW
www.ViscoAnalyser.com

 

patprimmer (Publican)
13 Dec 11 19:40
I do check pump prices and buy the cheapest I have confidence in re suitable octane and cleanliness.

If it is E10, I calculate the value for money at 3% extra fuel consumption. It seems to work OK generally. Pricing mainly favours E10 here by a small margin.

I don't do accurate MPG checks, I simply zero the trip metre at every refill and get a feeling for distance travelled vs gauge movement and distance to empty and how much it takes to refill. Typically range is reduced a few miles on E10, but not so much compared to variations due to manner of use. Highway cruising is the only reasonably consistent manner of use as it is constantly at 110kph 99% of the time due to speed limits.

Corrosion is not normally an issue for E10. It certainly is an issue for E85 or methanol blends or 100% ethanol or methanol fuels unless the system is designed to handle it.

Fuel flow capacity is not normally an issue for E10 It can be an issue for E85 or straight alcohol fuels.

Tune correction for E10 is not normally an issue for E10, although how accurately that is handled might impact on fuel economy to give a different result to the 3& expected. It is a major issue for E85 or straight alcohol fuels unless the system is designed for it.

Fuel weight to cover a specified distance is greater for alcohol or alcohol blends. The more the alcohol in the blend and the lower the molecular weight of the alcohol (presuming only one OH group per molecule) the heavier the fuel load.

Aircraft will always be more concerned with weight of fuel to distance covered and with possible engine failure from using the wrong fuel where alternatives are available and there is a potential for confusion. If someone refuels a car from the wrong bowser, it might stop and cause some lost time and inconvenience. If an aircraft is refuelled with the wrong fuel. it might cause a crash. It ain't exactly rocket science and frankly I wonder why it needs this much explaining to someone qualified to be here.  

Regards
Pat
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NickJ67 (Mechanical)
20 Dec 11 16:33
Returning to the OPs question, I'd like to throw another thought into the ring:

As E10 has stochiometric ratio of 14.1:1 rather than the 14.7:1 of petrol, in an engine fed by carburetor or open loop injection, changing fuels will cause it to run a bit lean.

Obviously modern engines (including the OPs) have closed loop control and will self-correct based on the signal from the O2 sensor.  However, as ethanol also contains O2, could it be that this is throwing the correction off and actually leading to over-correction, causing the engine to run slightly rich and thus use a bit more fuel than expected?

Seems to me that given the fairly large sample mileages here 7% should be well outside the noise band.  I would also tend to think that a nice big, low stressed engine like that will be barely getting into its stride at these kind of mileages - even to the extent that it quite likely used more fuel in the first 20 - 30k or so as it was still completing its "freeing-off".  I know that I'm getting better mileage figures from my 230k mile Audi TDI than I was at 115k when I got it.

As an owner of other, older, petrol powered vehicles I'm not appreciating the other problems caused by ethanol addition such as failing hoses, loosened deposits leading to (repeated) blockages, O-ring and seal issues, diaphragm failures and so on.  People are also reporting strange happenings on vehicles left standing for 2 or 3 months (winter layup) possibly caused by separation.  Here in the UK we are only at 5% addition so far with 10% threatened.

Regards

Nick
Helpful Member!  patprimmer (Publican)
20 Dec 11 20:19
The O2 sensor measures FREE oxygen in the exhaust and will not double count the oxygen already combined with the carbon or hydrogen.

Regards
Pat
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Hotrodrobert (Automotive)
28 Dec 11 8:34
I deal with performance street cars in North Carolina, USA.  The E10 is a problem to any hoses, diaphrams, etc.  We constantly have to replace hoses, fuel pumps, carburetor accelerator pumps, and fuel inlet control valves.  Water and corrosion is a small problem, more so in the fuel tank of cars that sit.
For performance, a richer mixture is necessary because of the alcohol.
I also build very high performance engines just for E85.  The fuel system MUST be built for the alcohol with proper hoses, pumps that can flow enough-you need at least 60 percent more flow, etc.
The higher octane of the E85 allows higher compression, boost, etc. to make much more power.  You cannot EVER go back to gasoline without major modifications.  Carburetors need major modifications.
Many vehicles have "Flex Fuel" which passes the fuel going to the engine through a sensor that changes the programming for the amount of alcohol it detects.  These engines have larger injectors, etc. than non flexfuel engines.
Talk by the politicians is they want E20 now.

 
dicer (Automotive)
1 Jan 12 14:37
My hint was, simply, if the thing burns more fuel, someone makes more cash, that is number one reason for the alky being added.
I liked the excel comment above.  
patprimmer (Publican)
1 Jan 12 16:39
Wouldn't that be related to the relative amount of fuel burned times the relative cost of that fuel. I mean it's primary school maths. No need to be an engineer or even a technician to figure it out. Basic 10 year old child literacy levels are enough.

Regards
Pat
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drwebb (Automotive)
5 Jan 12 10:08
For those interested here is a handy reference map of US gasoline requirements:

http://www.mobil.com/USA-English/GFM/Files/US_Gasoline_Map.pdf
dgallup (Automotive)
5 Jan 12 11:04
Interesting, that's changed a lot since the last time I saw it.

Any idea what "No 1 psi EtOH Allowance" means?

Everywhere I've been that is in the white "Conventional" areas has up to 10% ethanol blends at 99% of the pumps.

----------------------------------------

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JSteve2 (Automotive)
5 Jan 12 12:40
Ethanol is more volatile than standard gasoline, and in many areas is allowed to test at a higher vapor pressure. I think those must be places where the allowance is not in place. If you can get your gasoline with ethanol to test within the standard, it can be used in those places.

This map is more about relative strengths of lobbying groups than anything fundamental about gas formulations.
swall (Materials)
5 Jan 12 13:58
Ethanol has a Reid Vapor Pressure of 3, pure gasoline ranges from 5-15 and E10 is around 18. The increase that occurs when ethanol is added to gasoline is attributed to ethanol being polar.
Duwe6 (Industrial)
5 Jan 12 16:35
I actually have not seen any mpg loss running E10.  It will be acting like the old-time water-vapor injection that gave a small, but significant mpg increase.  Ethanol is VERY hygroscopic, so it will always be 'wet'.  The small ammount of water in the E10 blend will flash to steam and give you that 1,600x expansion and cool the exhaust gasflow.  Puts more energy into the motion of the pistons, and less energy being blown off as hot exhaust gas.  Internal combustion engines are heat driven.  Every bit of heat you can keep at the pistons increases mpg.

E85 is a whole 'nother case.  I see at least a 10% drom in mpg, and evaluate the price accordingly.  Thus, E85 is seldom a bargain.
patprimmer (Publican)
5 Jan 12 17:26
E10 theoretically gives about a 3% drop in fuel economy. Various aspects of tune and EMS can impact on that in a positive or negative way. Most people cannot really measure to 3% accuracy.

E85 if it is actually 85% ethanol theoretically uses about 30% more fuel. It is inconceivable that tune and EMS and measurement by any competent person could reduce that to 10% unless something was really wrong with the tune for the 100% straight hydrocarbon, alcohol free fuel

Regards
Pat
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hemi (Automotive)
5 Jan 12 21:22
Pat, I agree 100%.
pontiacjack (Electrical)
6 Jan 12 2:06
Where should I go to learn the terminology seen on that map?
fermjohnp (Mechanical)
20 Jan 12 17:38
patprimmer,

Does it then even make sense to put E85 in ones tank if we are on aveage losing 30% efficiency?
Helpful Member!  berkshire (Aeronautics)
20 Jan 12 17:42
fermjohnp
Only if you can get it 35% cheaper.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them.  Old professor

patprimmer (Publican)
20 Jan 12 18:28
Gee whizz berkshire, who would have thought on a site dedicated to working engineers with engineering work related problems to discuss, that anyone here could have done that mathematics so quickly.   winky smile

Regards
Pat
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hemi (Automotive)
20 Jan 12 18:54

Quote (berkshire):

fermjohnp
Only if you can get it 35% cheaper.
... or are willing to pay a premium and have the skill & tools to take advantage of the higher performance potential! upside down

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