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 Difference in tuning characteristics of straight gas vs. E10 
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Joined: Wed Dec 18, 2013 2:23 pm
Posts: 118
I'm curious if there are typical differences in the tuning characteristics for running straight pump gas vs. an E10 blend of the same octane. The recent D. Vizard Holley book has charts indicating how much more jet area for fuel is required based on certain % blends for both Ethanol and Methanol, and an E10 blend was +3%, IIRC.

For a Holley-type metering system, would you apply the same thing to other circuits such as increasing the area the IFRs, reducing the area of the emulsion air-bleed circuits by 3% to richen the mixture, etc.?

I've generally not taken into account the difference in the fuel blends in the past, but am attempting to take a more refined approach to my fuel curve tuning, including having purchased a wideband O2 setup to add to my car when it's back on the street & track.

Thoughts? Suggestions? Experiences?

Thanks. - Brad

Sun Mar 30, 2014 2:46 pm
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Joined: Sat Feb 09, 2013 10:46 pm
Posts: 250
I've tested both the Shell and Sunoco 93 octane down here. Both were at the 5% ethanol range.

Having said that, it would be difficult in my estimation to throw a jet size at a combination and expect it to be spot on based on a formula of some sort.

I started out in my car with 93 octane so I had no prior data to start with. So it was with a 92 holley jet and went from there. I'm at about a 95 now. About a 11% increase. This does not take into consideration float level, main circuit air correctors, emulsion stack, timing, or plug choice. It's a bit more than what was in the book. I've run this 93 octane thing to hell and back. I think I'm where I need to be. OH, BTW I run 3 circuit stuff. That's a discussion for another thread.

We don't know what your calibration is now or what you're going to run that carb on. I'm guessing if you've read this forum enough your calibration is close to what seems to be working for everyone here.

I'd start with what you have now. You have the instrumentation and the ability to read plugs so that would be a good start.

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Sun Mar 30, 2014 3:58 pm

Joined: Wed Dec 18, 2013 2:23 pm
Posts: 118
Booster wrote:
I've tested both the Shell and Sunoco 93 octane down here. Both were at the 5% ethanol range...

That brings up a really good question as to how much the local pump fuels actually contain for ethanol. We've had the "Contains up to 10% Ethanol" stickers on the pumps for so long now that I've always assumed the had the max amount blended in. :ummm?:

Tue Apr 01, 2014 8:36 am

Joined: Sun Jun 23, 2013 1:41 pm
Posts: 375
Location: Phila. Penn.
I'm pretty sure I've seen kits for sale on-line.
- Matt

Tue Aug 26, 2014 6:00 pm
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Joined: Thu Mar 28, 2013 6:09 am
Posts: 728
I Run E85 in my race car and cause Bruce has tested some pump gas down there I have done the same here..I test every time I buy E85 and it's always above 85%, had it at 92% once. As far as testing pump gas I did have it at one time 8% at the local Sunoco station and the local Shell station it been as low as 4% and as high as 8% but I have never seen it at 10%..
Honestly I don't think it is going to make any difference at all...But I may be wrong :roll:

Thu Aug 28, 2014 7:52 am
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