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Old 01-05-2015, 02:59 PM   #2826
Glocknurse
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I'm getting an e85 tune this Wednesday and had a qquestion. The tuner says they have e100 at the shop and will tune it on that if I Ihoose not to bring my own gas. My question is, will getting tuned on e100 and then running e85 be bad?
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Old 01-05-2015, 03:32 PM   #2827
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Quote:
Originally Posted by Glocknurse View Post
I'm getting an e85 tune this Wednesday and had a qquestion. The tuner says they have e100 at the shop and will tune it on that if I Ihoose not to bring my own gas. My question is, will getting tuned on e100 and then running e85 be bad?

It won't be accurate. Most e85 pumps put out e70-e85. So if you have e70 on an e100 tune, you would be rich and have too much timing.

Better to tune on the fuel you are actually using.


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Old 01-05-2015, 03:34 PM   #2828
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If your tuned specifically for your setup for example 06wrx, vf39, turbo inlet, uppipe, stock injectors on an e-tune,.... How much if any of a blend of e-85 would be safe to run? 10%? Will the ECU adjust any even with the reflash tune that is set up for 93oct?


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I've run a gallon of e85 on a full tank. Saw no benefit. Didn't scan everything but watched knock. I think their 91 octane was pretty crappy so it watered it down.


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Old 01-10-2015, 10:02 PM   #2829
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Ok so I've seen mixed answer's on this subject. I know you need a tune, fuel pump and bigger injectors to run e85. But what's the process in swapping between e85 and 93? Is it something you can do between maps? Do you have to run the car empty to switch?

Looking to run it in a stage 2 08 sti.
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Old 01-11-2015, 09:09 AM   #2830
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Quote:
Originally Posted by never_finished View Post
Ok so I've seen mixed answer's on this subject. I know you need a tune, fuel pump and bigger injectors to run e85. But what's the process in swapping between e85 and 93? Is it something you can do between maps? Do you have to run the car empty to switch?

Looking to run it in a stage 2 08 sti.

Probably depends most upon your maps and setup.

If u have a 93map and e85 map logically you'd want to run a tank of e85 as far to empty as possible them fill with 93 and switch your map to 93. If you have enough residual 85 in the tank it could very well effect the ignition timing of the mixed formula that is now making it into the cylinders. Based upon some research on these forums running as close to empty as possible will help to make that negligible as possible.

If u were to have a setup with maps that take into account 93 only, e85 only and a 93 e85 mixture I'm sure you'd be experiencing something different but the principle remains the same in that your map is setup on timing for a certain type of burn.

Then there are the flex fuel conversations. Where maps are created for various levels of e85 concentration and switched and scaled based upon pre-ignition cycle fuel concentration using sensors in the fuel lines.
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Old 01-11-2015, 01:54 PM   #2831
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There's more leeway when switching from E85 to 93 than switching from 93 to E85. For the former, the worst that can happen is that you run a little rich for that first tank since it has a higher ethanol content when you're expecting none. However, for the latter you'll potentially run leaner since there's less ethanol content when you're expecting more.
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Old 01-11-2015, 05:04 PM   #2832
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Actually you have that completely backwards in every respect. You run LEAN going from E85 to 91 and have to be very careful because there is excess ethanol which raises your effective AFR!

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Old 01-11-2015, 05:27 PM   #2833
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Originally Posted by Jubathoph View Post
Actually you have that completely backwards in every respect. You run LEAN going from E85 to 91 and have to be very careful because there is excess ethanol which raises your effective AFR!

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Huh? No. Most people with access to only 91 will actually mix a gallon or two of e85 in with their normal fillup in order to gain a bit more detonation resistance. This is much safer than running an e85 map which is "watered down" by 91 or 93.
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Old 01-11-2015, 07:21 PM   #2834
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Originally Posted by Jubathoph View Post
Actually you have that completely backwards in every respect. You run LEAN going from E85 to 91 and have to be very careful because there is excess ethanol which raises your effective AFR!

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Uh...no. If what you're saying is true, then it's safer to run the E70 winter blend on an E85 summer tune, which is absolutely NOT true. You can run more ethanol on a tune that expects less (for detonation resistance like Jonnyfive said), but you should definitely not run less ethanol on a tune that expects more.
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Old 01-11-2015, 08:20 PM   #2835
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With all due respect you have no clue what you are talking about. If you run more E85 than your tune expects you will run lean which is dangerous. I know from experience. You have your understanding of lean/rich effect of ethanol backwards. I have switched back and forth numerous times and by far the most critical is going from E85 to regular gas. The reason is residual e85 in the tank throws the mixture slightly lean. The car runs like **** until fuel trims can catch up. The slight increase in octane does not protect against knock in that diluted state. Consequently you can get knock if you push the car before fuel trims even out.

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Old 01-11-2015, 08:25 PM   #2836
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If you dont understand that excess e85 on a tune meant for regular gas makes you run lean you need to do some more reading on the subject!

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Old 01-11-2015, 08:38 PM   #2837
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E85 = leaner < gasoline. That is why, bigger injectors are needed. The car ecu can only fix -14 to +14 of the enrichment. Ask your tuner for a safe in between gas/E85 tank, map. Thas what I do for my costumers.

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Old 01-11-2015, 08:38 PM   #2838
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Herp.

Last edited by fiatlux; 01-11-2015 at 08:57 PM.
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Old 01-11-2015, 08:40 PM   #2839
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Derp.

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Old 01-12-2015, 06:58 AM   #2840
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i think it's important to remember what we're measuring here.

"afr" is a calculated value based on lambda.
lambda is determined via leftover o2 levels in the combusted exhaust gas.

pure gasoline contains no oxygen atoms. ethanol, being an alcohol, does, as does mbte, and methanol, etc. all are considered fuel oxygenates as a result.

displacing pure hydrocarbons with oxygenates will cause your o2 sensor to read greater levels of leftover oxygen. this is interpreted as running "leaner."

however, in the case of purely open loop fueling (ie, no feedback-loop based trims in play) the injector on time will be the same in both cases, which means the same volume of fuel is being squirted into the chamber.

a decade ago i experimented with dumping methanol into my fuel tank. at around 20% concentration what was indicated as a 11.5 on 93 w/10% mbte "leaned out" by a full point to 12.5. that's the effect of reduced hydrocarbon density and increased oxygen content due to the methanol. car ran very strong (ie increased power) and never knocked, with no tuning changes. in order to really take advantage of the meth ignition advance had to be increased.
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Old 01-12-2015, 09:30 AM   #2841
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Sounds made up, but plausible if you don't know any chemistry. I call BS. Your O2 sensor reads just that, free O2. The O2 sensor does not read atomic Oxygen. The OH- group in alcohol based fuels is very reactive and readily combusts to form H2O. The OH ion does not form Free O2 during combustion nor is it read by the O2 sensor as free oxygen.

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Old 01-12-2015, 10:13 AM   #2842
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who the **** said it read atomic oxygen?
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Old 01-12-2015, 10:17 AM   #2843
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let me break it down for you, with little words and easy concepts:

you put more oxygen into the combustion process, you get more oxygen out of the combustion process.

you're free to make yourself look like a neanderthal by arguing this point.
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Old 01-12-2015, 10:57 AM   #2844
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Derp. Keep dumping crap into your gas tank without understanding how it burns or affects your engine. I have been running E85 with proper tunes for over a year, and switched back to 91 on several occasions. My point is its dangerous to run lean with more E85 than you're tuned for. I Dont think a lot of educated people would argue this. BTW I studied combustion chemistry as part of my BS in mechanical engineering from UCLA, so feel free to use big words if you know how ;-)

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Old 01-12-2015, 12:41 PM   #2845
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More E85? So, >85% ethanol?
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Old 01-12-2015, 12:54 PM   #2846
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Moar than you are toon'd for I.e. Bubba who is pouring his moonshine in with his gas to make his car run more gooder.

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Old 01-12-2015, 12:56 PM   #2847
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For simple reference to the name, 85% is 85%. So... More E85 is E85.
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Old 01-12-2015, 01:56 PM   #2848
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I concur doctor. In reference to my aforementioned post, "more E85" referred to people who are adding E85 to regular gas without a tune. So their ethanol % going from say 15% to something higher like 30-40%. I am trying to communicate that when you add E85 to regular gas without tuning for it your engine runs lean while fuel trims catch up to the changing fuel mixture. It is also possible to exceed the allowable fuel trims (14%) and throw a CEL or worse.

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Old 01-12-2015, 02:58 PM   #2849
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I was poking fun as I have had people tell me their cars were tuned on E85, but it was more like E30 due to what you have just explained.

Yes, the more ethanol content you have, the more fuel you'll need to squirt in.



I do think some of the confusion with this is that there is no reference on switching maps, nor to specifics of a map. I say this as when I saw it quoted, I had to trace back up the thread to pull the context (which also didn't actually reference a map). I understand how it works, just pointing out where some of the confusion may be coming from.

Quote:
Originally Posted by Jubathoph View Post
Actually you have that completely backwards in every respect. You run LEAN going from E85 to 91* and have to be very careful because there is excess ethanol which raises your effective AFR!
*when running map for straight 91 with a fixed percentage of ethanol


For the most part, if you run it nearly dry, fill it up with desired fuel, change map, drive responsibly for a couple tanks of fuel... Worry less.

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Old 01-12-2015, 05:43 PM   #2850
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You are right; I have had no issues when draining the tank to near empty before switching fuels/maps. I will also let it idle for some time to get things stabilized before hitting the road. No matter how empty I get the tank, I do see my fuel trims go +/- 3-4% for the first tank on that map. By the second tank things are back to normal!

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