Yes, sneaking up on it for sure. I had hoped to get to E50 as that seems to be the sweet spot for really getting the advantage from ethanol and it diminished somewhat above that. See below for my results thus far.
I believe it was Livernois that posted up they were running E85 on ID1050x a while back and when I asked them how, they said the fuel system behind them was the key. Remember my car is a simple upper pulley 17-18psi setup. Most folks running flex are running smaller pulleys or upper/lower making 20psi, so I'm hoping my fuel system demands are less and we'll be good to go. Testing will see but if what I'm reading is right, E50 is almost 100 octane and that's far better than just 93. Anyone know the actual octane ratings of the mixes? I read E40 is like 98 octane.
My first test results are in and very promising. Mike@OSTDyno and I have been working on this in pieces, and he and I work well together since we tend to think similarly. Step one was to get alcohol % to read correctly and consistently. I started with Shell 93 in the tank and Mike had to do some adjusting based on our assumption the fuel had around 10% ethanol since pumps say "fuels can contain up to 10% ethanol". We got to where I was seeing 5 - 11.5% in the logs which felt right. I then tried a different brand fuel as a test, Racetrack 93 and it read 18-23%. Mike thought something wasn't right but when I ran that fuel out of the car and put Shell 93 from the same station back in, the readings dropped back to 0-5% after a bit of driving on the Shell brand. I did some reloading of the 93 octane tune, thanks
@hellno for that tip, resetting of adaptives, etc to confirm we would get consistent readings and we were. I put in more Shell 93 and one batch just read 0%.
Now that alcohol seemed good time to add some pump E85 and start testing the fueling. I tested the fuel and beaker showed E83. I had just under 3 gallons of Shell 93 in the tank which had been reading 0% alcohol. I put in 7.1 gallons of the pump E83 and started driving. After 2-3 minutes the log showed 10% alcohol, then 15%, then it started going up quickly to 26%, 38.5%, 47%, and finally after 5 minutes or so 57% and leveled off there. I was shooting for E50 and according to my math the 3 gallon 7 gallon mix would put me right around that mark and it did.
I wanted E50 so I could test my injectors and fuel system to see how much we could get to. On gasoline my inj DC was 50% in cold dense 50 degree air and nearly 18psi of boost so I had some overhead. Fuel pump DC was in the low 70s%. I made a quick WOT hit from 4,000 - 6200. It was mid 60s ambient air temp and the car made right at 17psi of boost. Inj DC was 64% and fuel pump was 75% with steady 83psi fuel pressure. Mike reduced the timing in the alcohol tables for this test to not only keep things extra safe but to also confirm the right tables are being used for the change in fuel type and they are. I sent him the logs and we'll see what's next.
One cool thing is he set my onboard AFR gauge in a way that I can tell when it's reading alcohol. When the reading is below 5% the AFR reads 14-14.3 idle and cruise. As alcohol starts to be read the AFR reading richens up. 20% is low 12s idle and cruise, 57% was mid 10s idle and cruise. I like that so I always have a reference point to know it's working as expected.
This is all new to me and it's been fun to start learning about it, but you quickly realize that just when you think you've gotten some tuning stuff figured out there's a whole other ball game to get in to. This is pretty complex and not just some simple tweaks to a tune to make it flex ready. One thing I'm curious about is how the fueling and timing adjust based on the percentage of alcohol detected. For a gasoline and separate E85 tune it's a simple binary tune change. For flex it's going to have to blend fueling and timing tables together in some way and use a percentage of each based on ethanol content. I haven't quite figured out how that works yet but I assume it's some kind of multiplier table and also why flex tunes can't be as aggressive as straight E85 tunes. You have to leave some cushion for an alcohol % calculation factor.
More to come....