I'm learning about E85. Why is it that fuel trims lean out going from winter blend E85 to summer blend E85 and get richer going from summer E85 to winter E85. Sorry if this sounds dumb just wanting to know. Got this from a statement from ebrisol. I just would like to know why

 

so basically your asking what the difference between winter and summer blends is, and how to tune for the winter blend when your on summer?

 

ya and just the reason why this happens or what is making this happen

 

As far as my understanding goes...
Gasoline has Stoich Air Fuel ratio of 14.7:1
E85 (85% Ethanol, 15% Gasoline) has Stoich Air Fuel Ratio of 9.7:1
This means you require more fuel when using E85 for the same "Amount of Energy" to be released.

But, again E85 has a much higher Octane Rating than Gasoline which is NOT a measure of the Amount of Energy Contained in the Fuel, but a measure of how Controlled the Fuel will burn.
Usually, higher octane fuels have Lower Amounts of Energy Contained within the fuel but they burn much more Controlled and thus you can advance the Timing Farther and Safer than on Lower Octanes (This is where the added power comes from using High Octane Fuel, Also associated with this is a need for increased fuel supply).

But, E85 is not always (85% Ethanol, 15% Gasoline). In the summer this is true (85% and 15%) but in the winter the mix can go as low as 70% Ethanol, 30% Gasoline.
This obvously changes the Stoich Air Fuel Ratio value and the Octane Rating.
This results in a car tuned for Summer E85 to run rich on the Winter E85 Fuel.
Vica-versa, A car tuned of Winter E85 will run Lean o Summer E85.

I plan on tuning in the summer on Summer E85, it seems to be safer to richen up in the winter than lean out in the summer. The richening effect seen in the winter can also be offset slightly by the increase in Air Density from the COLD Winter Air. (I live in Colorado and this plays a big role in how the car performs).
Another option is Multiple E85 Tunes for each mix of fuel or Maybe just run E85 in the summer and switch back in the Winter?

Hope that helps, If I have any facts wrong please correct me and disregaurd my mistakes.

 

or if your maf was tuned properly and your injectors settings were inline you probably could just adjust the stoich value.

 

Exactly. If you knew the % of methanol then you can either not tune your maf or tune it very little between the blends.

 

if you set your afr to 9.7 for e85. you're an idiot.

 

 

stoich afr that is.

 

Yah I got that.

Area, "you" do change your stoich right?

 

yulp, that i do. my truck does it on it's own.

i say that for a reason. the smartest man in the fuel injection industry i have ever spoken with did massive research on it from day one of inception. variations in blends from day to day float on percentages. if you set it to 10.4 you wave the variations and drop it to a smaller percentage of error. from my own personal logs on the truck this is very true.

why? same station i get e85 from blends their fuel in the ground. it is not shipped in like 90% of the country. the stoich afr changes from 10.3 to 10.5 every time i fill up. this could range from twice a day, to once a week. how does the truck know? more **** behind the scenes than i care to go into detail about.

 

Nice work!

I have messed around with my tune and have gotten to a 10.6 stoich with little error, but that was before my MAF felt like taking a **** "so I thought". It is actually a whole in the intake that, I hope, is causing the problems. Anyway, from what I have learned (from you and a few others) is to not "rape" the MAF and to change the stoich.

You may not agree with the stoich from your findings but this is what I have come up with due to trial and error. I had my tune within 1% before I went E85 and it changed to about 8-10% when I had it set to 9.7.

 

sorry I'm new to this what does stoich mean for a/f ratios

 

Air-fuel ratio - Wikipedia, the free encyclopedia


SC, i personally wouldn't set it at 10.6 thats just me. .2 is going to make or break you in terms of power.

 

Ok. I will try setting it to that stoich when I get my intake totally fixed. Thanks for the tip. Some of that findings of what stoich my car "seemed" to like may have been skewed from my intake problems. Some quick steel will patch that up and be a temp fix till I get another one. Lol

 

Just twincharge it already that turbo is getting dusty

 

I know man I want to so bad. Just need to be patient.

 

marriage, who needs it LOL

 

lol yah, once those bills are paid (obviously by the wedding they will) I will purchase the remainder of parts and start the build. I may have valve guide issues, gotta check it out this weekend. Oh and I have a whole in my intake... I just love when things come in pairs.

 

wow that sux thank for the help in understanding

 

when he said it changes the stoich what does he mean does it get highier more closer to gas. Is stoich ratio different then redular a/f ratio. What happens when setting your stoich value. What is that doing

 

Isn't changing your stoich to 9.7 the easiest way, apparently these people think it is the more appropriate way to tune for e85, E85 people step in. - HP Tuners Bulletin Board

now I'm totally open, I don't have a side in this..so don't flame me

 

setting it to 9.7 is setting yourself up for headaches down the road. not every single station is exactly 85%

some are higher, some are lower. this can change DAILY.

 

I fill up from the same station each time, and run 14.4 as my stoich afr.

Why? Hess uses UP TO 10% ethanol in their fuels. E10 stoich = 14.0-14.1, so by using 14.4 that sets the stoich value somewhere in the middle. Works for me.

Note: This is for 93, not e85. 42's and e85 won't work well. heh

Area, do you think this is a good idea, or should I switch it back to 14.7?

 

I get it know that makes sense. It kind of tell the car this where you should be at. Because it is not a 85% of the fuel all the time. SCcobaltss we in AZ only have what to different blends right. I mean it isn't real cold here. The coldest it getts is like what 45 degrees