MPG loss with 10% ethanol--- 2

[blacksmith37]

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]

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

 

[patprimmer]

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
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[dgallup]

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.

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

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]

We could blame climate change, or even claim it is evidence of climate change. ;-)

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
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[swall]

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]

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

http://www.ViscoAnalyser.com

 

[blacksmith37]

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]

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]

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]

Damn, does that mean these fuel economisers that magnetise the fuel might actually work?

JMW

http://www.ViscoAnalyser.com

 

[mattsooty]

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

 

[Lou Scannon]

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]

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
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[jmw]

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

http://www.ViscoAnalyser.com

 

[SomptingGuy]

I thought pump gas in the US varied during the year, with ethanol content higher in the colder months to promote starting.

- Steve

 

[swall]

Ethanol inhibits cold weather starting, which is how the E85 came about--the 15% gasoline content is necessary for cold starting.

 

[1gibson]

Tire pressure?

 

[IRstuff]

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

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[dgallup]

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.