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Old 06-08-2008, 01:14 PM   #20
motronic
Leaky Injector
 
Join Date: Jul 2004
Location: MI
Posts: 133
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motronic is making a name for him/her selfmotronic is making a name for him/her self
This thread has sooo many misconceptions and mythis so lets clarfify few things
E10 gas which is required in some areas means that the gas contains 10% ethanol by volume, consequently E85 means 85% ethanol. Ethanol additon in gasoline itself is not new since certain states mandated oxygenated fuel for awhile now for example with E5 gas.
So what changes when you add ethanol to gasoline?
1. Octane
Adding ethanol in general improve gasoline octane number since they have much higher octane rating. That being said E10 gasoline does NOT necessarily have higher octane than E5. Remember that fuel is rated by minimum octane rating (R+M/2), so they may start with lower octane base gasoline and add the ethanol to achieve the same minimum octane.
2. Stoichiometric Ratio
In general most gasoline has about 14.7 to 1 stoichiometric ratio. Adding E10 ethanol changes this ratio up to 14.1. Most car compensates this by the long term fuel trim where you "learn" the ratio and changes your fueling. This is the "enleanment" effect of E10 so if you run open loop you could see your fueling off by about 2-3% average.
3. Fuel volatility
Ethanol has lower vapor pressure than gasoline. This has effect on cold start especially around freezing temperature where pure ethanol is very difficult to vaporize. This does not matter if your car is already warm and running.
4. Water solubility
Ethanol has higher propensity to absorb water. This is not a problem since most tanks and delivery in gasoline distribution are not exposed to open air or water. Car fuel tank and fuel system also designed to be contained.

So judging the facts can this cause all your problems of stalling, no power, bad idle, low fuel economy? Very unlikely. Millions of car out there running E10 wothout any problems.
I think you may have other problem with the car, I would suggest get a wide band and check your AFR to make sure it is still running right AFR.
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