- Thu Jun 22, 2017 6:14 pm
#68512
Well, I try to avoid E10. BTW definitely don't put E85 in it by mistake. Only a few "green" cars can safely use it. The stoichmetric AFR (air: fuel ratio of petrol is about 14.7:1. That for ethanol is 9:1. That is to say the optimum AFR in terms of clean burning differs significantly between petrol and ethanol. Therefore if you add 10% ethanol to petrol the overall stoichmetric ratio will not be the same as that for petrol (or ethanol). I understand that 10% ethanol effectively weakens the fuel mixture by 7%. That is why on a carb engine you can't just stick in what you like and expect it to fuel the same. In theory the O2 sensor(s) should try to adjust the mixture so that it falls within the programmed CO emissions range. But that assumes that the O2 sensor is effective over all rev ranges, particularly at those at which the engine is mostly run when riding. It is a known fact that on the Triumph twins the O2 sensors only operate at up to 6% of throttle opening (I'm talking about the now superseded air cooled ones here). In this case if the map is set up to handle petrol, it will not compensate for 10% ethanol in the tank. That is why there are various ECU Triumph maps for up to 10% and 25% ethanol. A lot of us disable the O2 sensors anyway so that we can fit more free-flowing exhausts and air intakes, liberating a lot of the power in these engines. As for RE EFI bikes AFAIK they cannot be remapped by flashing. The fuelling can only be adjusted by fitting a Power Commander or similar, or, like I have done, a carb. I'd be surprised if the standard EFI compensates in the short term for changes in fuel composition. Half the time mine wouldn't fuel properly on 98 RON, which in the U.K. cannot yet contain more than 5% ethanol. It doesn't surprise me that some REs run very badly when filled with E10 if they are used to 98RON. Best avoid it; easily possible in France.