So what do these boxes cost? The MegaSquirt 3 can run individual cylinder timing trims as well as individual cylinder fuel trims. You don't have to use the fuel side to use the timing side. A know a couple people that use MegaSquirt just for timing and still have a carb on the engine. I haven't delved into it enough to know if it'll do feed back from the knock sensor to a specific cylinder, but this is stated in the ignition manual: "Monitor per cylinder - when sequential fuel or spark are in operation the code can determine which cylinder the knock signal applies to. This enables the individual cylinder data to be recorded."
I've installed a knock sensor in my Buick 455 by enlarging a water drain plug hole, but I found valvetrain was too noisy to get any good readings. There is an updated MegaSquirt add-on chip now that supposedly makes it so it will only listen for knock during a very specific time of crank rotation so in theory won't hear the valvetrain but true piston knock, and sensitivity is scaleable by rpm. There are coolant temp trims too for engines that have valve trains that are noisier when cold, etc. "This internal module allows knock to be monitored over a specific crankshaft angle 'window', allows gain to be adjusted and knock level thresholds to be set depending on rpm. This allows far greater tunability and should help to distinguish between engine noise and knock."
I might go that way eventually. I've already sunk the costs of the Mega Squirt 3 with fuel and spark control so it's just a matter of purchasing the add-on chip and a knock sensor.
I plan on doing a full AFR and EGT balance on my L6 engine to get the most out of each cylinder. This may eventually include individual timing trims, but that is getting down to splitting hairs and I'd need knock sensor data to back that up that kind of change (caused by something like rear cylinders running hotter, etc). I've also shifted my engine to an electric water pump with reverse flow cooling to keep the head cooler.
