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Old 01-28-2009, 10:05 AM   #1
rjrutzky
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Default 10% ethanol 93 vs no ethanol 93

Hopefully this can stay here since this is where all the dyno tuners post. Now I know if I am mapped with straight 93 and then fill up with 10% ethanol 93 my car will run worse (I've seen it on my knock threshhold map). Question is with a new tune would I be able to get more power out of 10% eth since 10% would need to be richer (like the quenching effect of E85)? It would help me out too because it's easier to find than eth free 93.
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Old 01-28-2009, 10:29 AM   #2
OkieSTI
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All I know on both my Harley motorcycle and my 08 STI, the difference between normal 91 octane gas and 10% ethynol is a big hit on gas mileage (at least 10% or more) so I'm sure your performance will suffer as well.
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Old 01-28-2009, 10:58 AM   #3
jays05
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I am interested to know this too... my car was tuned on E10 93oct, and now I found a place that has ethanol free 93oct.
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Old 01-28-2009, 11:01 AM   #4
Phatron
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is there a difference between cali 91 and az 91?

on my recent trip back to phoenix my knock and egt's were less on az 91 than on cali 91.
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Old 01-28-2009, 11:16 AM   #5
JSarv
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I believe the power increase would be unnoticeable since 93 E10 is what it is, a 93 octane after 10% ethanol, meaning its somewhere around 91 octane but the added ethanol content brings its pump rating up to 93. Yes Alcohol does burn way cooler and has a way higher knock threshold (higher than MBT) but its such a small amount that it wont be noticable.

I run E85 and only had the choice of 93 E10 prior, my fuel trims were always off about 7%, which I believe is the result of 10% ethanol.

I don't think you will see a performance increase, rather a mileage drop if anything. Your IDC will be a bit higher with E10 (if your tuned for it)


just my .02

-Jerod
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Old 01-28-2009, 11:21 AM   #6
juanmedina
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The mileage should go down a little but you should get a little more power on the 10% ethanol 93 oct. I think this what Buschur uses to push 30 PSI on pump gas, is less prone to knock.
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Old 01-28-2009, 11:33 AM   #7
Element Tuning
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I never found out exactly what the fuel difference was but I will tell you an interesting experience I had. A customer came to me from a rural area of PA and my base map from Wash DC burbs was way too rich. A number of years ago we had a winter blended fuel and a summer fuel but it's been consistent over the last couple years with +10 ethanol. I leaned out the car and finished what I could on the dyno before verifying everything on the road.

Since the gas was too low I had the customer fill up locally and then during the road test it ran about .5-.8 AFR leaner (it's normal to see about a .2-.3 change during real world tuning). This left me scratching my head so I checked for any mechanical issues and I could find nothing. I started leaning things out and the fuel map headed right back to where I had the Element Tuning base map. At this point I knew I was dealing with a gas issue so I sent the customer home with two maps (the dyno tuned map on his fuel, and the road adjusted map for our fuel).

When he got home, filled up on his fuel, and ran a data log for me as we suspected it was .5-.8 richer. He then switched to the map I tuned on his fuel and it was exactly how I tuned it here. The next time he came to see me for tuning he came with extra fuel from his local stations

The bottom line here is don't assume your local gas is indicative of all gas everywhere. This is the reason you never get a perfect base map because we have to add a calculated amount of slop to deal with these variations in fuel.

Thanks,
Phil
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Old 01-28-2009, 11:46 AM   #8
rjrutzky
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Yeah I always bring my local gas, just wasn't sure if I should bring the local 10%.

I actually came 10 hours to see you, Phil, with 5 gallons of Tennessee gas and 5 of 110. I need to come back again. It was worth the drive.

I'm probably gonna do 10% this time just because of it's availability. Any power increase will just be bonus.
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Old 01-28-2009, 12:08 PM   #9
Element Tuning
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Quote:
Originally Posted by rjrutzky View Post
Yeah I always bring my local gas, just wasn't sure if I should bring the local 10%.

I actually came 10 hours to see you, Phil, with 5 gallons of Tennessee gas and 5 of 110. I need to come back again. It was worth the drive.

I'm probably gonna do 10% this time just because of it's availability. Any power increase will just be bonus.
That story is probably why I told you to bring gas
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Old 01-28-2009, 12:34 PM   #10
blowbyu24
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Quote:
Originally Posted by Element Tuning View Post
The next time he came to see me for tuning he came with extra fuel from his local stations

Thanks,
Phil
www.elementtuning.com
hahah i was already planning on doing that for my next tune coming up, getting down there with enough fuel from the shell i always get my gas and then bringing 5gal container with extra just incase...


to answer the op's question, if indeed the fuel is making the car run rich it could possibly rob the motor of some power
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Old 01-28-2009, 02:59 PM   #11
Clark Turner
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The ethenol fuel has a lighter specific gravity. The tune should be able to handle this kind of change though. If you are tuned on the edge you might need to add a bit more fuel to the map with the lighter fuel.

AZ and Cali Gas are different. My experience is that in the winter our AZ gas is a bit better then California. In the summer, we switch to "Arizona Summer blend" fuel. This fuel is the worst I have tuned.

Clark
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