You guys that are adjusting your own tunes, what is your idle, full throttle and part throttle ignition timing? When I was driving around recording data on the laptop, I thought the timing was low across the board. I wrote to BB and asked them if they would add a couple degrees advance at idle and part throttle. They didn't refuse to, but said they didn't think it was necessary.
I have been building carbureted/distributor chevys since 1981. They idle best with 12-14 degrees initial timing. It takes half as much throttle opening for a good idle with 14 degrees initial compared to just 5 or 6 degrees for typical stock. But of course they need no more than 34-36 degrees at high rpm and wot, so you must limit mechanical distributor advance to about 20 deg total. That's what I do on my race engines, 14 initial and +20 mechanical.
Street engines also need vacuum advance for part throttle conditions. It's good for 3 mpg and much cooler running. I use vacuum adv msd dists, which give +10 degrees at 15 inches of vacuum. I use ported vacuum rather than direct manifold vacuum, because manifold idle vacuum would push total advance to 24 deg at idle and that's too much. Plus you will often get part throttle ping when running direct manifold vac. So part throttle cruising at say 2000 rpm would be 14 initial plus 5-6 mechanical plus 10 vacuum for 29-30 total. At 2,500 rpm cruise there would be about 10 mechanical for 34 total.
The highest advance I recorded when driving was only 37 deg, and that was when coasting down from a wot run. At that moment of max vac and high rpm, timing should have peaked at about 44 deg by my method (14 + 20 + 10). Of course the efi is more sophisticated and maybe it knows best but I'm not sure.
My question is, what do you see at idle, wot, and cruise? Do you mess with it? Do you bump it up until it pings? I have matched and polished my chambers and polished the valves to mirrors to reduce preignition. When I was recording, the ecm never saw anything from the knock sensors. So I think it can use a little more timing and get better mileage.
