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Those running flex fuel get in here :)

Speedy!

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#1
I've started playing with Flex Fuel a bit now that I have a more beefy fuel system with the dual pump drop in kit. I'll be limited on boost to where I'm at now, which is a Litens 2.72 and I see about 16.5 - 17.5 pounds of boost depending on weather. I'm running ID1000 injectors.

With the dual pump system I have quite a bit of fuel system over head with injectors at 50% DC max and fuel pumps at about 65-70% max DC. Fuel pressure is healthy at about 83psi at WOT.

I'm hoping I can start to play around with the timing a tid bit when I add E85 to the tank.

I'm curious what you guys see for alcohol content on standard 93 octane pump gas. Our local pumps claim "up to 10% ethanol". However I've found some brands of 93 octane read as high as 23% like Racetrack for example where Shell 93 will read 4% in 500HP mode and 11.5% in 707HP mode. I thought that was kinda interesting as well.
 

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#2
Haven't really data logged it on pure 93. I can get some logs next time I fill up with 93. Right now I've been running a blend. Basically when I get to half a tank, I fill up with the opposite of whatever I already have in the tank, so for example if I had started with a full tank of 93, when I get to half a tank, I fill up with E85, then when I get to half a tank again, I fill up with 93, and then I just keep repeating the process. This gives me a blend which typically works out to E40-E50 which is more than fine for daily driving on a 2.85 pulley.
 
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Thread Starter #3
Thanks. I'm trying to get a sense for how accurate the readings are.
 

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#4
Using the factory wideband O2s right? I'll let you know. Tank is currently half full but it might be another week before I can log since I still have a half tank of blend in now that I'll have to run that out and then add 93 to check it.
 
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Thread Starter #5
Yep factory O2s.
 

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#6
What are you using to read the ethanol? Hptuners?

With the "inferred" patch that is used, it takes 5 mins or so of driving for things to "change" when you add in a different fuel.

I haven't had pure 93 in the tank in 2 + years....
 
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Thread Starter #7
Yeah HPT. Been going on 30 minute drives
 

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#8
5 minutes is probably a safe bet but I've seen changes on the in-car AF/lambda gauge start within 1-2 minutes.
 

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My understanding of it is it’s generally within 10-15 percent on flex fuel and it does take up to around 5 minutes of driving and around 8-10 miles , when I switch back to flex fuel the last time I raced I new I had above 75 percent but the logs showed 63 and stayed there several days and right befor I added 11 gallons of shell 93 it actually showed 78 percent now it shows 55 percent and I’ve put about 80 miles on it
 
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Thread Starter #10
So three whole people running flex on this forum, interesting. I figured there'd be more.
 

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#12
Slow is a matter of interpretation.

I'm on the flexible Curtsauce. IE Gasohol. FIC1200's.

I also test every new station prior to going on the E. Today's fill was E76. Dont have my laptop with me but it's usually within that 10% margin. The "flex" tune is slightly soft compared to his E85 only kill tune for that reason.
 

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#13
I should add that most 93 measures right around the 10% threshold for me even on the inferred flex tune.

When in the CTS-V with a direct content sensor I'd see anywhere from 5-12%
 
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Thread Starter #14
Cool, I think we're on the right track then and yes flex tunes aren't usually set to kill like an E85 tune since there is a little margin of error. This will be street use for me, so a little soft on flex will be much more than 93 and I'm good with that, plus it's a chance to learn something new which is fun for me.
 

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#15
I’d love it if we could get 100% gasoline and 85% E85 at fuel stations instead of whatever % isn’t on the pump.
 

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#16
Cool, I think we're on the right track then and yes flex tunes aren't usually set to kill like an E85 tune since there is a little margin of error. This will be street use for me, so a little soft on flex will be much more than 93 and I'm good with that, plus it's a chance to learn something new which is fun for me.
I've been running Curt's flex tune for over 2 years without issue on pump E85. I realize its not a full kill tune and probably a little soft but Curt has already told me for those customers that want bleeding edge performance, he will typically create two tunes, one for daily driving and one strictly for the track using proven Ignite E85, E98, etc...which seems like a fair compromise compared to those having 3-4 tunes and having to swap between them depending on fuel and pulley.
 

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#17
I've been running Curt's flex tune for over 2 years without issue on pump E85. I realize its not a full kill tune and probably a little soft but Curt has already told me for those customers that want bleeding edge performance, he will typically create two tunes, one for daily driving and one strictly for the track using proven Ignite E85, E98, etc...which seems like a fair compromise compared to those having 3-4 tunes and having to swap between them depending on fuel and pulley.
That’s exactly what I have , flex for every day driving and I have a E85 tune for racing that works well with all my pulleys
 

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#18
In the V series most of the benefit was found going from 10% ethanol up to about 50% ethanol. From 50% to 85% did not make nearly as much difference. There is still power to be had but that was the point of diminishing return.
 
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Thread Starter #19
That makes sense and I've read the same in research.
 
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Thread Starter #20
Ok, weather permitting I'll be adding my first few gallons of Ethanol to the tank tomorrow. Fingers crossed.

It looks like there's a couple thresholds that can be set to basically turn on when it's using flex fuel tables in terms of alcohol %. Where do you have your set? It's a percentage value. I was think 20% would be a good number? Anything above that and it starts using the flex fuel tables for timing and what not. I'm still learning about this, but I think it uses a multiplier and as more Ethanol is detected you get more from those tables. So it detects 30% ethanol you get 70% of your 93 tables and 30% from the Ethanol tables for example.
 
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