Thread: E85 fuel FAQ
View Single Post
Old 07-08-2005, 10:53 PM   #2
hotrod
Scooby Specialist
 
Member#: 14141
Join Date: Jan 2002
Location: [email protected] @ 5800 ft on 13T
Vehicle:
2002 Impreza WRX

Default

Part 2
Where 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.

Where can I buy E85
For information on distribution points check out:
http://afdcmap2.nrel.gov/locator/FindPane.asp



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.

Quote:
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.

what data is available on combustion speed for E85?
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...0064--,00.html
http://www.michigan.gov/documents/CI...E-_87915_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/presentation...mjb-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 efficiency 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 Lambda mode to get valid fuel air mixtures with blended fuels. If you can only get gasoline AFR's, simply divide the gasoline AFR's by 1.5 to get the true AFR for 100% E85. If running a partial mixture you can make proportional changes based on the percentage of E85 in the mix.

Here are some comparisons of stoichiometric fuel mixtures for different fuel blends:
======== stoichiometric 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 efficiency 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/resea...5-2004.doc.pdf

Here's a little reference chart I whipped up when I was working out my dyno numbers.

Code:
 
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    0.10235    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 


=======================--====================================
Detail discussion of E85 tuning can be found at specialty E85 web forums such as www.e85forum.net/forum where they have assembled people with lots of first hand experience tuning with E85 in high performance situations.

E85 fuel ethanol content seasonal changes

E85 fuel blends change content seasonally just like all gasolines blends change with the seasons. This seasonal change in blend for E85 is primarily to improve cold weather starting, where the changes in gasoline during cold weather is to improve cold weather starting. In the summer months, gasoline must be blended to reduce vapor lock and to reduce evaporative emissions.

The recommended dates for changing E85 fuel blends are listed in a chart in the E85 handbook on page 22, which is in the "E85 Fuel Specification" tab.
The Volatility class specifications are broken down on page 10.

Volatility class 1 --- minimum ethanol 79%
Volatility class 2 --- minimum ethanol 74%
Volatility class 3 --- minimum ethanol 70%




As you can see each region has a different start date and recommendation for seasonal blends depending on local weather climate.

Here on the high plains east of the rockies in Colorado we run the class 1 fuel blend from mid June -- mid Sept, run class 2 fuel from mid Sept -- mid Oct and run the class 3 fuel blend from Mid Oct -- mid April, then back to the class 2 blend from mid April to mid June. The standard only specifies a minimum ethanol content, vendors can run higher ethanol content if it is economical. If it is cheaper for the fuel blender to add more he can. Ethanol content is bottom line driven by local weather conditions, and cold starting problems for local drivers just a gasoline blends are modified to give easier starting in cold weather.

In the Southern part of Texas they would never go to a class 3 blend, and in Wisconsin, they would only have the class 1 blend for about 2 months in the summer. In Florida they would be on class 1 almost all year long and in North Dakota and Wyoming and Montana, they would be on class 3 almost all year long.

Power available on E85

Many sources make a big deal about E85 having less thermal energy per gallon that a gallon of gas. They frequently draw the false conclusion that you cannot make more power on E85 than you can on gasoline. E85 actually has a higher specific energy at stoichiometric fuel air mixtures than gasoline, and at proper max power mixtures releases more thermal energy in the cylinder for a given amount of air to burn. Since an internal combustion engines power output is primarily air supply limited this means you can make 5% to nearly 30% more power on E85 than you can on gasoline.

(edit 6/10/08) Current experience shows turbocharged cars like the WRX and DSM families can run upwards of 30 psi boost on E85 tunes without knock. The only case I know of where knock was logged was on a 500+ whp DSM running 35-39 psi boost!

Ethanol specific energy at stoichiometric fuel air mixtures is actually higher than gasoline allowing a higher release of energy per lb of air burned than gasoline.

Typical gasoline Thermal energy 19,000 BTU/lb max power fuel air mixture 12.5:1
Typical E85 Thermal energy 13,475 BTU/lb max power fuel air mixture 6.975:1
Typical ethanol Thermal energy 12,500 BTU/lb 6.429:1

If you are consuming 100 lbs of air, lets see how much fuel energy you release for each of these fuels using gasoline as the base 100% reference.
100/12.5 = 8 lbs of gasoline @ 19,000 BTU/lb = 152,000 BTU = 100%
100/6.975 = 14.337 lbs of E85 @ 13,475 BTU/lb = 193,189.9 BTU = 127% more heat energy
100/6.429 = 15.555 lbs of Ethanol @ 12,500 BTU/lb = 194431.5 BTU = 128.9% more heat energy

Typical fuel energy contents:
gallon of gasoline = 125,000 Btu
1 gallon of ethanol = 84,400 Btu
1 gallon methanol = 62,800 Btu
1 gallon of gasohol
(10% ethanol, 90% gasoline) = 120,900 Btu
1 gallon of E-85
(85% ethanol, 15% gasoline) = 90,500 Btu
1 gallon of kerosene or light distillate oil = 135,000 Btu
1 gallon of middle distillate or diesel fuel oil = 138,690 Btu


My long term average on gasoline was 24 mpg, my mileage on the same setup on E85 was 22 mpg, my current mileage on gasoline is about 22 current mileage on E85 is 18 mpg.

Current setup upgraded turbo-
gasoline mileage 22 mpg = 5682 BTU/mi
E85 90,500 Btu /gallon / 18 mpg = 5028 BTU/mile (daily driving with periodic high boost acceleration)
E85 90,500 BTU/gallon/ 19.3 mpg = 4689 BTU/mile (driving mostly off boost as daily commuter)

Old setup stock turbo -
gasoline mileage Gasoline 125,000 Btu/ gallon / 24 = 5208 BTU/mile
My old setup, @ 92% of gasoline milage or 22 mpg
E85 90,500 BTU/gallon/22 = 4114 BTU/mile

A 5% increase in engine power is common on NA engines with minimal conversion changes, and much higher numbers are possible if compression or boost is used to take advantage of E85's higher fuel octane.

Last update 6/10/08)
* Registered users of the site do not see these ads.

Last edited by hotrod; 04-01-2011 at 11:51 PM.
hotrod is offline   Reply With Quote