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Old 05-06-2011, 10:30 PM   #1 (permalink)
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Quantifying ethanol effect on mpg - list your results

I've done some poking around and found estimated mileage drops from using fuel with ethanol added of anywhere from 2% to 30%. I'm sure a number of people here have done semi-rigorous testing, and I think it would be good to have a thread where people post their findings so we can aggregate the results and hopefully identify some trends.

Pleast post your findings here, and if possible include:
  • Vehicle type
  • Detailed engine information
  • Percent ethanol used
  • ABA test results
  • Description of your test process

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Old 05-06-2011, 10:32 PM   #2 (permalink)
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Old 05-07-2011, 06:56 AM   #3 (permalink)
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Quote:
Originally Posted by justjohn View Post
. . .
Pleast post your findings here, and if possible include:
  • Vehicle type
  • Detailed engine information
  • Percent ethanol used
  • ABA test results
  • Description of your test process
Ok:
  • 2003 Prius
  • 1.5L 1NZ-FXE
  • E10 vs E30
  • indeterminate as within the margin of error
  • Test protocol - fill a 1 gallon spare can with straight gas. Run the car until all fuel burned and add spare gallon. Drive directly to station recording the amount of fuel burned. Add ratios of fuel to achieve targeted ethanol ratio. Then drive to a 525 ft., 8% and conduct a maximum acceleration, hill climb while recording engine torque, rpm and fuel burn. Calculate the BSFC. Repeat process with a different ethanol ratio.
For full technical details:
Yahoo! Groups

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Old 05-08-2011, 10:42 PM   #4 (permalink)
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Sounds good, any chance of a link that doesn't require a signup?
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Old 05-08-2011, 11:12 PM   #5 (permalink)
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Sorry, here is a cut-and-paste assembly:

Quote:
Originally Posted by Jun 7, 2009

I can not rule out that E30 has similar fuel consumption rates as straight gas:

speed(mph), E30(MPG), expected(MPG), comment
61, 52.1, 53, Close
71, 44.0, 47, Close considering normal drop 70-75 mph is 49-39 MPG

I also ran a hill climb test:

speed(mph), E30(gal), Expected(gal), comment
55, .0738, .0720, Close

The problem is these differences can easily be explained by temperature
differences. If there is a difference, it is easily within the margin of error
for MFD based testing.

From a practical point of view, mixing E30 in the tank is a pain. There is a
small economic benefit:

E30 = E85@$2.15 + 2.75*E10@$2.35 (local prices)

I am not sure I will pursue this investigation until I improve my NHW11
instrumentation. The benefit appears to be marginal and we're looking at
fractional changes. I really want to find a metric that I can correlate to using
E30 versus straight gas, say spark advance. We do have a variable valve
mechanism but measuring it is not trivial.

I'm putting further investigations aside for now. I'm switching back to straight
gas since I'll need an accurate baseline before proceeding.
Quote:
Originally Posted by Jun 7, 2009
. . ..
>
> From a practical point of view, mixing E30 in the tank is a pain. There is a
small economic benefit:
>
> E30 = E85@$2.15 + 2.75*E10@$2.35 (local prices)
>

My apologies. I'm fighting a cold (I hope) and didn't explain this well:

3.75*E30 = 1*E30 + 2.75*E10 # Mixture ratio if E10 and E30 are available

So doing the cost for prices a couple of weeks ago:

$2.15/gal = E85
$2.25/gal = E10
$2.22/gal = E30

So for saving $.02/gal, a 1% cost savings, have I recovered more than a 1%
improvement in performance OVER E10? But to make such a judgement call, I need
very accurate measurements over longer periods of time. Plus, I have to be
willing to put up with the dual fill-up and carry a small "topper" container.

A "topper" container is used to top off the tank after filling most of the tank
with fixed ratios of E10 and E30. A smaller, spare can, when it is empty, I fill
it with the fixed ratio and then complete the tank filling. But there is a
fundamental question: Is it worth it?

I want to know but in the meanwhile, I'm going back to straight gas. I'll need
to improve my instrumentation and methodology. In particular, I don't want to
have to carry fuel in the trunk. So I'm thinking of a running fuel log.

By accurately recording each fill-up of straight gas and keeping an accurate
fuel burn record, I can add 1 gallon of E85 when the fuel level is low enough to
make an E30 mix. The advantage is a 1 gallon (or a set of 1 gallon containers)
of E85 can be stored safely in a remote shed at our home. There will be a couple
of days during the burn-down while the straight gas dilutes the E30 until there
is enough space in the tank for 1 gallon of E85 to bring the mix back to E30.
However, I can use these intervals to track the vehicle fuel trim and spark
advance.

With these changes, I should be able get the accurate data needed to evaluate
both the fuel burn and economic impact. But these are small values.
Quote:
Originally Posted by Jun 7, 2009

>
> We appreciate all the investigations you have pursued
> and information you have posted, but I wonder whether this
> test can yield any conclusive result. We expect a very
> small difference with a large number of variables
> involved. It would be difficult to even identify all
> the significant variables.

I gain much more from the peer review. Unlike other forums, I know a serious
posting is likely to have serious answers ... the occasional joke aside. But
seriously, the path to understanding is to share what is being done and using
the feedback to tweak the experiment.

> Some of these variables can be controlled or measured. Some
> cannot. We could probably make a large list including
> barometric pressure, wind, temperature of air, tires,
> transaxle, etc., but how to determine which can be ignored.

Using vehicle MFD, I agree. Fortunately, I have a Graham mini-scanner and many
of the metrics eliminate the problems of MFD metrics.

>
> It is one thing to experiment on a dynamometer in the lab,
> where fuels can be quickly switched while other parameters
> are nearly the same, but comparing road tests at different
> times can be very difficult. I suppose the initial question
> will be how repeatable are your results over a significant
> number of runs with straight gas. If the data looks promising,
> you could repeat the same test protocol with a different fuel
> and, with sufficient data, develop some probability estimates
> of the results. I'm not a statistician so can't help with
> the details.

I can record up to six metrics and my thinking is:

1) ICE rpm
2) injector timing
3) MG1 torque
4) spark advance
5) MG2 rpm
6) ICE temp

The first three allow tracking the brake specific fuel consumption, the amount
of fuel burned per engine shaft power. The spark advance is the most likely trim
function and MG2 provides speed. The ICE temperature helps eliminate cold engine
effects.

> It is an interesting experiment, but I agree with questioning
> "Is it worth it?"

I've seen E10, ethanol blamed for a number of MPG drops of different amounts.
But I don't think anyone has done a Prius specific study and this may be the
first. It will take time and it will be limited to the NHW11/NHW20 models.
However, it may give some insights.
Quote:
Originally Posted by Jun 7, 2009
> OK, I'm too lazy to do the math, about how much E85, do I add to Gasolene with
10% methonal to get the E30?

1 part - E85
2.75 parts - E10
Quote:
Originally Posted by Jun 7, 2009
> Would it not be simpler to just add straight metholated
> spirits (100% ethanol) to straight petrol and be sure you got
> the right figure. ? Or 47,5% rum. They say the exhaust
> smells better.

It is easier to use one of the traditional gasoline stations.
Bob Wilson
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Last edited by bwilson4web; 05-08-2011 at 11:19 PM..
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Old 05-11-2011, 10:13 PM   #6 (permalink)
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Nice find Bob. It would behoove him to also monitor the Air:Fuel ratio if possible, to check and see if it maintains stoichiometric throughout the test. But I see those posts were from '09.

I'm pretty sure that people will want to see this test completed using Gasoline without Ethanol. I for one would like to see some "poor man" scientist spell out this issue so it can stop maligning Ethanol. But good and bad, people will see results how they want.

Justjohn, we've had a member try to quantify the difference. I've forgotten his name, silly me, maybe Neryls? I remember that he succeeded in getting straight Gasoline and E10 and was seeing a big difference in his cars MPG but it was over tankfuls. His post should still be here.
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Old 05-12-2011, 10:51 AM   #7 (permalink)
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Quote:
Originally Posted by Allch Chcar View Post
Justjohn, we've had a member try to quantify the difference. I've forgotten his name, silly me, maybe Neryls? I remember that he succeeded in getting straight Gasoline and E10 and was seeing a big difference in his cars MPG but it was over tankfuls.
That was Nerys.
Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Profile: Nerys
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Old 05-12-2011, 11:55 AM   #8 (permalink)
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Quote:
Originally Posted by Allch Chcar View Post
. . .
Justjohn, we've had a member try to quantify the difference. I've forgotten his name, silly me, maybe Neryls? I remember that he succeeded in getting straight Gasoline and E10 and was seeing a big difference in his cars MPG but it was over tankfuls. His post should still be here.
It would be interesting to see his methodology and results. I'll look around but I had done similar testing last year, straight gas vs E10, and I remember the results were a modest difference. I'll try to post my method and numbers later this evening.

Bob Wilson
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Old 05-12-2011, 12:01 PM   #9 (permalink)
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I looked up his stuff and his theory is that there is a small difference on newer cars and a large difference on older cars. Bumped his thread to see if he ever got direct comparison numbers.

These are the things I'm hoping to find out. If we can get enough data we can start to identify trends.
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Old 05-12-2011, 01:34 PM   #10 (permalink)
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E10 15.2mpg 30 tanks
E85 12.4mpg 35 tanks (-18%)

1998 Dodge Stratus, 2.4 auto, preliminary data, in order they were collected this earlier spring. (assumed E85 was 85% could have been 70%, drops blends about 5%) SGII of no value as has to be recalibrated so tank to tank is only way to check mpg.

E30, 2 tanks back to back, 28.4 mpg (-11%)
E0 2 tanks back to back 31.9 mpg
E10 3 tanks back to back 30.5 mpg (-4%)
****replaced all of rear brakes*******
E25 1 tank* 33.5 mpg
E44 1 tank 30 mpg
E0 1 tank 35 mpg, best tank ever but E44 still cheaper per mile

* - Fluke tank maybe, but I'm driving better and warm outside.


Last edited by roosterk0031; 05-26-2011 at 11:15 AM.. Reason: Updated 5-25
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