Hotrod on AWDPirates wroteWhere can I buy E85?
Distribution is currently a problem, it is most available in the mid western states, but there is a concerted effort to get an ethanol
fueling infrastructure built, it just takes time, and recognition by the gasoline vendors that there is a market. Marathon oil has
already added E85 to their formal product line so things are moving in that direction.
Current high fuel prices can only help that process, as will lots of people calling up gas stations and asking them when they plan on
pumping E85 for FFV's.
E85 already contains inhibitors and such to minimize corrosion, and most of the problems with ethanol usage were solved 20 years ago
when most of the country moved to ethanol addition to gasoline following the oil crisis in 1973 and high oil prices that continued
up until 1981.
For information on distribution points check out:
http://www.e85fuel.com/
How about fuel mixtures for E85 what is needed ?
The one interesting thing to note is that the stock pig rich mixtures at WOT on the stock ECU of the WRX are very close to max
power mixtures on E85 blends. If you play with the blending ratio to find your magic number you can take advantage of this by giving the
car a fuel blend that is max power rich at stock ECU WOT mixtures. *** just take your time and work up the blend slowly ***
After a few folks have dyno runs on various blends we can probably pick out a "best starting point" blend that will get you very close.
We could also work out the other supporting mods to make best use of E85 for minimum cost.
It basically takes about a +30% increase in fuel flow to get the same equivalent mixture with E85 that you had with gasoline.
For example an adjustable fuel pressure regulator can increase your effective injector flow to partially compensate for the fuel
changes.
As mentioned above, lean is still a bad thing, and with alcohol fuels due to the higher power levels a serious leanout is more
lethal. With conservative mixtures alcohol actually burns so cool that on E85 FFV there is some concern about getting the cat to light off.
If you sneak up on a fuel blend slowly you should be just fine. I would venture to say for the near stock folks, up to 30% is probably
safe as long as you give the ECU a few miles to make the major part of the fuel trim accomodation before you start beating on the car.
You'll know when the ECU starts to get happy as the midrange torque is noticably better.
I also strongly suspect that a well tuned car with no cats can probably pass the emissions sniff test on high E85 blends.
How does ignition timing change on E85 ?
Timing on ethanol blends will not change very much. MBT timing for both gasoline and E85 are very nearly the same at light to moderate
engine loads. At high engine load the E85 will want just slightly more advance. The big difference will be fuel/air mixture. The E85
will give improved torque with much richer mixtures than gasoline. Both gasoline and E85 will give best thermal effeciency at about 15%
rich of stoich, so the equivalent of 12.78:1 on gasoline would be about 8.5:1 on E85, but E85 will continue to give better torque
numbers up to about +40% rich of stoich or 7:1 mixtures, so on a utec you would want to richen up your WOT high load cells and add a
tweak of timing to get the most out of E85 from what I've read.
Question
Are you sure you don't mean that E85 will allow more advance?
Just passing on what I've found in the various sources. Logically you are correct, but one source says simply that MBT timing is the
same for E85 and gasoline, and another report says at low loads the E85 and gasoline like the same MBT timing but at high loads MBT
timing for the E85 is slightly more advance.
I suspect this is due to them not running ideal max power mixtures but cannot confirm it. Burn speed for E85 changes quite a bit with
mixture, so if they were just a little bit lean or rich of ideal the burn rate would be lower.
Lots and lots of variables not well covered in some of the sources and in general they are focusing on emissions issues not max power
torque so that would incline them to use less than best power timing advance. In a couple of the reports they also had limited control
authority over timing and may not have explored the extremes very thoroughly.
Just about a year ago (2003), I was finding conflicting information on alcohol fuel burn speeds and contacted The National Renewable
Energy Lab here in Denver, they did a search and could only find a couple of references on it, one that showed ethanol fuels burn
faster, so the literature is not very rich in data on the subject. Most reports are not entirely applicable to our needs like tests on
lawnmower engines and alcohol fuels have some significant limitations
Still digging for info but that is my best information at the present time.
The report that mentioned the slight increased advance requirement on heavy load E85 fuels was :
"Final Report Control of Exhaust Emissions from Small Engines Using E-10 and E-85 Fuels"
http://www.michigan.gov/cis/0,1607,7-15 ... --,00.html
http://www.michigan.gov/documents/CIS_E ... 7915_7.pdf
On page 12 it says :
"Tests were conducted to assess the impact of MBT ignition timing on fuel economy and exhaust emissions. The spark timing was varied
until the least advanced timing was achieved for the maximum torque for a given setting of the engine throttle. The A/F ratio was
adjusted to achieve near stoichiometric operation. ... " The MBT timing for E-85 fuel was a few crank angle degrees advances compared
to E-0 fuel when the engine was delivering high loads, typically 100 - 75%. Not much difference was observed at lower engine loads."
I'm assuming that this explains the timing change as they were using what would be closed loop fuel mixtures on the WRX. So in load cells
that would continue to use closed loop fueling you would want to have slightly more ignition timing than you would with gasoline. In
the case of WOT open loop fueling where your running a max power rich fuel mixture, I very strongly suspect the fuel burn speed would
be noticably faster, and you would use less ignition advance than on gasoline and reap the benefit of less negative work on the late
stages of the compression / early period of combustion prior to TDC.
In a power point presentation presented by the EPA at the SAE Government and Industry Meeting in Washington D.C. on May 13, 2003
titled:
"Ethanol-Gasoline Blends: Fuel Economy and Emissions Benefits"
http://www.epa.gov/otaq/presentations/g ... 051303.pdf
On page 9 of the presentation is a nice chart comparing laminar burn speeds of gasoline and Ethanol.
It shows the following burn speeds:
Mixture fuel/air---- 1:1 ------------ 1.1:1
Gasoline --------- 26 cm/sec ------- 30 cm/sec (max about 31 cm/sec)
Ethanol ---------- 41 cm/sec ------- 45 cm/sec (max value)
Clearly at +10% - +15% rich mixtures where ethanol shows max thermal effeciency it burns significantly faster than gasoline. Which could
be quite important to a very over square bore engine like ours!!
what is the ideal fuel air mixture for E85
If you are tuning with a wideband O2 sensor you will want to switch it to Lamda mode to get valid fuel air mixtures with blended fuels.
Here are some comparisions of stoichmetric fuel mixtures for different fuel blends:
======== stoichmetric AFR ===== max power rich AFR
Gasoline ---------- 14.7:1 -------------------12.5
100% E-85 ------- 9.73-9.8:1 ------------- ~ 9:1 - 8:1
100% fuel ethanol - 9:1 ------------------- ~ 7.2:1
One source specifies that the proper fuel tune (stoich) for a VW Golf running 22% ethanol was 12.7:1 (this reference was probably
from the Brazil tests)
Ethanol reaches max torque at richer mixtures than gasoline will.
Using a 99% ethanol mixture MEP increases with mixtures up to 40%
excess fuel where with gasoline MEP is reached near 20% excess fuel. Over all thermal effeciency for both gasoline and ethanol is reached
near 15% excess fuel.
E85 burns faster than gasoline at best mixtures so it is an inherently more effecient fuel. It also produces more exhaust gas
for a give weight of fuel air mix giving higher average cylinder pressures inspite of lower EGT's. With streight E85 in a properly
tuned car its good for about +5% power / torque increase. I suspect on a turbocharged car the benefit is larger.
My source lists stoich for E85 as 9.8:1 ( "Burn rates and emissions from ethanol gasoline blends" )
http://www.engin.umd.umich.edu/research ... 04.doc.pdf
Here's a little reference chart I whipped up when I was working out my dyno numbers.
Fuel AFRst FARst Equivalence Lambda
---- ----- ----- Ratio -----
=======================--====================================
Gasoline stoich 14.7 0.068 1 1
Gasoline Max power rich 12.5 0.08 1.176 0.8503
Gasoline Max power lean 13.23 0.0755 1.111 0.900
=======================--====================================
E85 stoich 9.765 0.01235 1 1
E85 Max power rich 6.975 0.1434 1.40 0.7143
E85 Max power lean 8.4687 0.118 1.153 0.8673
=======================--====================================
E100 stoich 9.0 0.111 1 1
E100 Max power rich 6.429 0.155 1.4 0.714
E100 Max power lean 7.8 0.128 1.15 0.870
=======================--====================================
Estimating fuel required on E85
Fuel injector, carburetor jet sizing, and fuel pump requirements can be estimated by using the following rules of thumb as a starting
point. For a naturally aspirated (NA) engine (carbureted) on gasoline most need a brake specific fuel consumption (BSFC) for
gasoline of 0.50 lb/(hp·h). On E85 the same NA engine would need a BSFC of about 0.65 lb/(hp·h).
Turbocharged engines typically need BSFC fueling of about 0.60 lb/(hp·h), a reasonable first guess for fueling required on E85 would
be 0.77 lb/(hp·h).
For a simple conversion to replace gasoline with E85 take the current "flywheel horsepower" as a reference point. With E85, power
should increase by about 5%, so the estimated E85 fueling would be:
(BHPgasoline x 1.05) x BSFCe85 = Estimated E85 fuel requirements.
What is your test history to date (6/2005) with E85 ?
I just tallied up my usage over the last 2 years, (the first year I was very cautious and did not use very much). I've put about 500
gallons of E85 and 100% fuel grade ethanol through the cars tank --- that's some where around 40 fill ups, or around 9,000 miles or so on
high ethanol (ie greater than 10%) blend fuels.
I am intentionally running the E85 with no special fuel system modifications. In a few years or when ever problems crop up, I'll
pull things apart and see what has happened. So far I have absolutely no evidence of ANY kind of degradation on my 2002 WRX.
The only non-stock component I'm running in the fuel system at the current time is a walbro 255 L/hr pump, so I cannot absolutely tell
you how the stock pump likes the stuff.
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