We have decided to release our Volterado tune. We're currently tweaking the upper ethanol tables so this is not the final version, but it good enough for every day driving. Attached is the 2012 version (see attachment).
To install, you'll have to compare your stock tune with a US stock 2012 tune (see my upload in the repository) to determine what's safe to copy over to your tune and there will be limited support. For a 2012 US Volt, everything is safe to copy over.
This tune was adapted primarily from the 2014 Chevy Silverado FFV V8 (high compression) pickup by Laz. It has better valve timing and about 5 mpg better mileage than the stock tune.
Our tune works as-is on lower blends of ethanol (E0 to E50 and 91/93 octane premium) with/without an ethanol sensor. Using it with upper blends (E70/E85) would require the sensor or altering the first value of several multipliers. So without a sensor you're limited to lower OR upper ethanol blends and will get a CEL if you cross over. For best results or if you want a true FFV, consider adding the sensor. We're considering a lean burn (E30?) version later, which would require the sensor. See this thread for info on installing the sensor.
We tuned the LO spark table with E10, the HO table initially with 93 octane premium and continue to tweak HO with E50. Mr Comment optimized VE, injector flow rate and MAF. Laz's knock learn allows you to have optimal timing as it now properly moves incrementally from HO toward LO each time more than 1.5 deg of KR occurs. The stock Volt tune always uses timing from the HO table and just removes knock as it occurs, so never optimal timing. A lot of timing was removed from the IAT adder as it caused KR at low temps. Open loop fueling has been tweaked leaner we were seeing KR at hybrid engine restarts. One of our most recent changes was to change the alcohol multipliers from stock (0, 10, 50, 70, 80) to 0, 50, 65, 80, 100 to make tweaking higher ethanol blends more precise. If you live in a warm climate and have access to ethanol blends over 90%, we'd be interested in how that works out for you.
Octane in the US now ranges from 87 (E10) to 96-98 (E85). Premium fuel is 91 octane in the north and 93 is common at sea level. These were the fuels we used to tune.
What's not tested? Blends above E70 (for this version), and high altitudes, although that should change soon as one of our members lives near the mountains.
The fan settings (Laz) turn off the engine cooling fans when the vehicle is moving and have been tested in Florida summers.
Driver Demand settings (Laz) are a more sport-like throttle change to all driving modes.
This is a work in progress and there will be future updates.
This is one of the best Volt tunes you're going to see.
Credit goes to LazMan and MrComment for their hard work. Please do not bug them for support.