ORIGINAL: cjuetten

Here's an off the wall question. ( I'mgetting cabin fever, too much time indoors and no time on the scooter).Anyways I know at least a few of you have some extensive knowledge on the automotive side of EFI. so here goes a question. My knowledge on E85 vehicles is limited because I spent all of my professional tuning on high performance/race applications, some with methenol.

On an E85 vehicle itneeds toknow what type of fuel is in the tank. E85, regular gas or a mixture of the two.Say you were running 100% gas and just added a 3/4 tank of ethanol soyou now havea 75/25 mixture. The ECMmust add fuel across the entire range to offset the reduced BTU of the current mixture or you will run lean, (this is verified by reduce mileage). Stoich on pure methenol is 6.5:1 as apposed to 14.6:1 A/Fratio for pump fuelso when the O2 sensor reads .45 volts youare at this ratio if you are running pure methenol. Better hope your fuel delivery and injectors are up to the task. When you start blendingalcohol and fuel,youractual A/F ratio is different then what an pump fuel (not ethenol)applicationedO2 sensor indicates.Today, on most automotive ECM programming, there is alocation to program what thestoich A/F ratio is of the fuel being utilized which getsthem in the ballpark for such applications. How the E85 cars are handling this for various fuels, I'm not sure.

Doesitdetermining the mixture based off closed loop operation and applying it full scale?? Is it possible it's capable of calculating open loop based onRate of acceleration vs Throttle position vs Load, Engine temp rate increase, ect? I think we all agree that Open or Closed loop is determined byO2 sensorsusage, but I find it hard to believe that otheravailable datawould be ignored because the O2 sensors are out of range. I can see that, onan E85 vehicle, it would be easy to compute the fuel's stoich's actual A/F ratio by measureing the amount of air with the mass air flow sensor (MAF)then measure the fuel byinjector flow and compare thisas the O2 sensor reads 14.6 volts. But I'm not sure if this is the way they do it.

Here's a test: Next time you come to a down grade approach it in 5th gear.Shift to sixth but hold the Clutch in and see how long it take for the "6Th gear light to come on". Or pull the clutch in while coasting in sixth gear and see what happens. In most automotive applications, there is a programmable ECMtable for shift lightset up that monitors MAP sensor signalVs RPM to setshift light on or off, possibly done here this wayalso.