01-31-2015, 01:38 AM #1
Running 30% E-85 As an "Octane Booster"?
I have been researching my hi octane options recently, and have found a Sunoco 260gt 100oct station, and a four E-85 stations all local to me. I know the Sunoco 100 is all that, but is just too expensive. The pump E-85 is only 2 bucks a gallon. If I can run 30% e-85 to gain a few points above my 93oct, then I would be good to go
If this is a viable option I would quality test for % at the pump, and add exactly 5 gallons with every 15 gallon fill (or adjust slightly depending on e-85%), to try and run a consistent 30% final ratio. If need be, I could also drop down to 20% of straight E-85 mixed in - to offset the inherent E-10% already present in most 93oct pump gas.
I know it may require a different target afr, and greater injector & fueling requirements. I am running an Aero340 pump with my rrfpr & injectors for around 35psi base pressure currently. So figure I could already support the increased needs. This is all running a R3 reflash, and not a stand alone ecu.
Could anyone please chime in as to whether they are already going this route, or any input or opinions good or bad would be appreciated as well. Target afr's, approx bump in octane, effects on ss braided fuel lines, etc..
Last edited by WP3223; 02-01-2015 at 03:22 AM.
01-31-2015, 07:51 AM #2
I experimented with this on a twin turbo bmw 335i I had a few years ago. I enabled auto tune in my tuning program and logged every mix. The knock sensors were very sensitive and was direct injected so we were squeezing every bit of power out of it just under knock conditions. The fueling automatically increased to its appropriate stoich for every mix by the way. Two theories were made and were in fact observed. Boost and timing would increase. And so would injector duty cycle. Base fueling was e10 and targeted boost was 14psi and 24 degrees timing. With e30 target went up to 16.2 psi and 27 degrees. E50- 17.4 / 28.5. E70 18.6 / 29.8. E84 (as tested at pump) - 20psi / 30.4 . All the values were established after 4-5 wot runs for auto tune adjustment. Overall e85 and boost go together like pb and j.
01-31-2015, 07:54 AM #3
Also I want to add the fuel pump did not like anything above a e50 mix. It went out on 2nd tank. I backed the mix down to e50 and the pump and myself lived with it until I sold her.
01-31-2015, 11:04 AM #4
- Join Date
- Jan 2008
- Currituck, North Carolina, United States
people here are tuning carbs to run E85 at drag way guess its cheaper than VP fuel we use
01-31-2015, 01:08 PM #5
E85 is great fuel for making power in NA and FI. The key is testing as its very irregular mixed at the pumps we have found. Either purchase in 55 gallon drums (consistent mix from vp or Sunoco) or you could test at pump with a kit and add fuel or ethanol to it to bring it to your spec. Don't assume anything . It's not a big deal to test.
01-31-2015, 02:38 PM #6
- Join Date
- Jan 2008
- Currituck, North Carolina, United States
01-31-2015, 09:48 PM #7
Thanks for your real deal experiences with the "boost juice". I did know there can be huge variances at the pump, so figured I would take the time to test each batch & always adjust ratios to stay consistent.
I am also aware of the big negative impact on fuel economy when running straight E-85, so I'm wondering if a 30% mix is enough to be a factor with a ski's already limited range. Not sure if this quote is actual/factual, but it may be a good sign-
Blending ethanol and gas
"For most vehicles, E10 (10% ethanol) yields worse mileage than gasoline without ethanol. What many people don't know is that E10 is probably the worst blend and for many vehicles, 20-30% ethanol will give you similar mileage to gasoline with no ethanol."
So far it's looking all good, and maybe if others could post up if they have gone this route with skis, turbo sleds, etc.. To see how well it works in our application. My goal is to have a cost effective way for running into the lower side of mid 20's for boost - without a tick, tick, boom.
And I do like's me some pb&j
Last edited by WP3223; 02-01-2015 at 01:40 AM.
01-31-2015, 10:55 PM #8
Here is something I just came across -
They are listing an "E-35" blend to equal 97oct, when starting with 93oct. That would be right on the money for my needs. Now just gotta know what kind of adjusted target afr's would be safe/ideal??
Some more fuel I found for the fire -
If tuning for full-power WOT, use the table’s full-power ratios instead of the stoichiometric ratios. For example, to calculate the max-power rich A/F ratio of your 20/80 E85/gasoline blend:
Caution! What most A/F ratio devices actually measure is really the amount of residual oxygen (for lean mixtures) or unburned hydrocarbons (for rich mixtures) contained in the exhaust gas. Reflecting this, many consumer-level wideband sensors read out in Lambda (λ) values instead of the A/F ratio. Regardless of the fuel or fuel blend, the λ value at the correct stoichiometric A/F ratio for any fuel or fuel blend is always equal to 1.00—therefore with rich mixtures λ is less than 1.00; for lean mixtures λ is greater than 1.00. If tuning for a specific mixture ratio other than stoichiometric, the λ number would then be:
Blend A/F ratio = (0.20 × E85 Rich A/F Ratio) + (0.80 × Gas Rich A/F Ratio) = (0.20 × 6.975) + (0.80 ×12.5) = 11.395
So if you need to know what λ is for the 20/80 E85/gas blend at its max rich power A/F ratio:
λ = (Desired A/F ratio) ÷ (Stoichiometric A/F Ratio)
Conversely, if your meter reads out only in A/F ratios, it is probably calibrated just for pure gasoline. If running a different fuel or fuel blend, it will therefore report the A/F ratio inaccurately (since it is measuring residual exhaust oxygen or hydrocarbons, not the actual ratio). This calls for a meter-correction factor, and that’s where the λ number again comes into play. Using the previous equation, simply multiply the meter’s calibrated stoichiometric gasoline A/F ratio of 14.7 by the λ Value for your blend or different fuel’s real-world target A/F fuel ratio. Again, using the 20/80 E85/gas mix as an example, if tuning for the previously calculated max power rich 11.395:1 ratio:
λ = 11.395 ÷ 13.713 = 0.831
In other words, if your meter reads out only in A/F ratios and it’s calibrated for standard gasoline—in this example, when you tune for the true 11.385:1 A/F max-power-rich ratio for the blend under discussion—the meter would actually display 12.22:1.
Meter Correction = 14.7 × Target λ Value = 14.7 × 0.831 = 12.22
Last edited by WP3223; 02-01-2015 at 05:41 AM. Reason: Optimum afr settings??
02-01-2015, 09:26 AM #9
Sounds like you are on right track Wayne. Later today I will try to crunch some numbers as well. As a side note another interesting observation was the specific heat removal affect. Like it's cousin, methanol, when atomized ethanol does remove a decent amount of heat. I happened to be running on the stock intercooler at the time and when compared to other guys with aftermarket intercoolers we found that the gap did indeed narrow the higher we went up with the mix. And this was direct injection!! Standard rail/intake runner systems will see even more heat removal. This attribute alone makes ethanol blends superior to octane equative Dino fuels....
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