E85 diary
#82
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Ahh, no. At least in California, it's required to be at least 75% ethanol (at least where I fill). In reality, there's so much safety margin with a sub-300whp E85 setup that you can just ignore it. For those of us looking for more, it's not hard to fill cans and measure the ethanol content (and then compensate by adding E100 in correct amounts).
#85
Brilliant.
For methods to measure E content without getting your hands dirty. I've seen two methods that OEM's have used to measure E content for flex fuel cars. 1 is obviously the flex fuel sensor. They work great, but they're expensive and the ones I've seen go inline in the fuel return line and can only flow a limited amount of fuel. So if your fuel pump flows too well you will have idle issues.
2nd method is a lot more sneaky. They let the car run in closed loop till the long term fuel trim evens out after filling up and then you know how much fuel you needed to add or subtract and you know the stoich of the fuel previously in the tank, so you can determine the stoich of the fuel in the tank. OEM's actually have a look up table for it in the ecu. And with either option in a flex fuel car it will interpolate between the e values (could tune to either e85 or e98) and the gasoline values for commanded lambda, timing, etc. Of course for the straight gas to e85 switch you'll need fuel trims with sufficient range. And if you're using this method manually, dear god stay out of boost until you compensate it.
For methods to measure E content without getting your hands dirty. I've seen two methods that OEM's have used to measure E content for flex fuel cars. 1 is obviously the flex fuel sensor. They work great, but they're expensive and the ones I've seen go inline in the fuel return line and can only flow a limited amount of fuel. So if your fuel pump flows too well you will have idle issues.
2nd method is a lot more sneaky. They let the car run in closed loop till the long term fuel trim evens out after filling up and then you know how much fuel you needed to add or subtract and you know the stoich of the fuel previously in the tank, so you can determine the stoich of the fuel in the tank. OEM's actually have a look up table for it in the ecu. And with either option in a flex fuel car it will interpolate between the e values (could tune to either e85 or e98) and the gasoline values for commanded lambda, timing, etc. Of course for the straight gas to e85 switch you'll need fuel trims with sufficient range. And if you're using this method manually, dear god stay out of boost until you compensate it.
#88
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You're just wasting fuel. I was tuning to ~12.2:1 on E85. Actual AFRs are somewhere in the 8-9:1 range, but my head works in gasoline AFRs so I don't bother switching the wideband translation.
#91
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I'm not sure how much fuel is wasted between 11.6-11.8 and 12.2 but I'd guess not that much.
And you're right, I'm probably being too conservative staying in the 11's but better safe than sorry. (esp if there is a swing/variation in batches of e85)
(and yes most my tuning is on Scoobs)
And you're right, I'm probably being too conservative staying in the 11's but better safe than sorry. (esp if there is a swing/variation in batches of e85)
(and yes most my tuning is on Scoobs)
#92
So you tune for 12.2 and I tune for 11.8 (just check my fxt maps) and you're saying that .4 afr is the difference between dumping buckets of fuel and a non-sloppy tune? LOL ok.
I'm not arguing with you, its just you're bashing my targets when the difference isn't even significant....And on cars that love to run richer.
Thanks for the input. I actually do plan to experiment with much leaner mixtures on my current miata.
I'm not arguing with you, its just you're bashing my targets when the difference isn't even significant....And on cars that love to run richer.
Thanks for the input. I actually do plan to experiment with much leaner mixtures on my current miata.
#96
In his defense. Tuning subies rich is common practice. You'll see tunes that people pay good money for commanding as rich as 10.5:1 on 93 octane tunes. I think they're being silly and its way to rich. BUT the fuel mixture thats going to make the most power depends on a metric **** load of factors like combo chamber geometry for example. People think you've built a grenade if you've tuned leaner than 11.
#97
In his defense. Tuning subies rich is common practice. You'll see tunes that people pay good money for commanding as rich as 10.5:1 on 93 octane tunes. I think they're being silly and its way to rich. BUT the fuel mixture thats going to make the most power depends on a metric **** load of factors like combo chamber geometry for example. People think you've built a grenade if you've tuned leaner than 11.
dumbass
Even with miatas there's a whole bunch of peopele on here who pulled out pistons scorched and melted around the ringlands/tops from lean mixture.
#98
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I apologize for jacking this thread. My posts must seem non sequitur. I know, I should start my own thread that has useful E85 information, mea culpa.
Here is a baby bottle that requires no math:
Echecker - E85 Fuel Test Tube
Here is a baby bottle that requires no math:
Echecker - E85 Fuel Test Tube