With a sensored brushless motor, the timing can be altered on the fly by the esc.
Boost - increases the timing over the entire rev range, amount adjustable.
Turbo - increases the timing only at when certain criteria are met - normally when full throttle is applied for a certain amount of time. Useful for long straights.
You can use a combination of both so say boost set to 5 degrees advance over the entire rev range, and 10 degrees advance turbo after full throttle has been applied for more than 0.3 of a second.
there's a few more tweaking options too but that is it in a nutshell.
I also ran one of those Quicruns for a year in a 4WD with an 8.5, 7.5 and 6.5 with zero issues either.
