you’re right, though as some others have stated, because ethanol has less energy by volume you need to push up to 40% more fuel than with gasoline…my point is just that a random mix of e85 and gasoline seems like a bad call. While an ECU can compensate somewhat, extreme variables make it less likely that you can maintain a proper A:F mixture…I’m not certain how the FFV’s do it, though I’ve read that they have some kind of equipment that actually measures the amount of ethanol in your fuel
A good point, though my guess is that E10 gasoline probably doesn’t require a great deal of compensation. If it did, I think you would see earlier vehicles (like F.I. OBD0 cars) have trouble running, but even unmodified they are fine. From 1000cc of E10 gasoline (assuming it’s exact, and 900cc is pure gasoline), you would in theory need 1030cc of fuel. That is sort of an extreme example since you aren’t burning 1000cc (about 1/4 gallon) in a single cycle, so you can imagine just how little additional fuel is required in each ignition cycle. It seems so small that really the average ECU is going to have no problem making the compensation, if any is made at all, since most engines don’t have a 100% burn or a perfectly stoich mixture most of the time.
Brazil has been using higher ethanol blends (E20/E25) for quite a few years, though they also have a sizeable fleet of E100 vehicles, and a good deal of their success is owed to the use of sugarcane instead of cornstock. A lot of their cars still have a tiny “starting reservoir” with gasoline, since ethanol can make cold starts difficult if the ambient temperature is below I think about 50.
Your comment about being a little rich makes perfect sense, and if I was ever going to set up an E85 car, I would certainly plan on being rich. Awesome that it got your Volvo to pass emissions, 242’s are the Swedish hotness.