E85 Conversion - 2016 Scatpack
I just want to sanity check my approach here if anyone is willing to lend some input.
I'm switching over to a straight E85 tune since this isn't a factory WB car like the Hellcats (so the flex fuel patch is NOT applied in this case). The car is a 2016 Charger Scatpack, so it's an A8 392. It has an intake and exhaust (with factory cats) along with an AEM wideband.
Here's my approach:
- Adjust FA Stoich values for E85
I'm assuming a pure E85 blend here and no winter blends to account for since it's not running the flex fuel patch with any kind of ethanol content inference. Stock value looked ever so slightly rich to me (maybe to split the difference with E10?).
- Adjust PE Aircharge and PRatio tables
I worked out a spreadsheet to compute the target FA and lambda values based on the new stoich values plus the PE adder values. I then compared to lambda for E85. They were a bit leaner after the stoich point change so I've added roughly 30-35% to the PE tables as a starting point, which puts commanded lambda somewhere between .80 and .87 after the E85 switch depending on the cell. I figure I can adjust if need be, but that should be a close starting point.
- Adjust WOT Spark
Plan to tune on the dyno. But generally, I expect about a max of 3-4 degrees additional based on what I've read about these cars.
I have a couple of questions now:
- Open Loop/Base - Do I need to add fuel to the cold/warmup table to account for more difficult starts on E? I've seen others mention the Startup Inj PW table for startup. Which would be correct, or is it both?
- Fuel Mass Multiplier - I've noticed the alcohol multiplier table here for flex fuel as well. Should this change to account for E85?
- Injector PW - I've heard people talk about changing this, but wouldn't the adjusted stoich values negate the need to adjust here? I'm aware of the approach many take with ANN on to adjust Inj PW instead of VE tuning. But isn't that to account for airflow characteristics rather than fuel characteristics?
- Have I missed anything else?
And pardon me if any of these are obvious. I'm fairly new to this. The little bit I did know was GM based and probably out of date by now.