You don't "need" a new tune. In fact, I didn't have the tune changed at all when the converter first went in, and my 60', 330' and 1/8 mile ET's all dropped by 3 tenths of a second while my 1/4 ET dropped by 2 tenths.
However, there are benefits to tuning for a converter. The factory only locks up the converter in 4th and 5th gears. I later had my 3rd gear programmed to lock up, as well. I also have the lock up happen much sooner at wide open throttle (1/2 second after each upshift) to pull even harder on the tall end of the dragstrip for higher trap speeds. For example, most supercharged Mustangs with the same horsepower as mine tend to trap in the 107-109 mph range, but mine traps in the 110-112 mph range.
You don't "need" a new tune. In fact, I didn't have the tune changed at all when the converter first went in, and my 60', 330' and 1/8 mile ET's all dropped by 3 tenths of a second while my 1/4 ET dropped by 2 tenths.
However, there are benefits to tuning for a converter. The factory only locks up the converter in 4th and 5th gears. I later had my 3rd gear programmed to lock up, as well. I also have the lock up happen much sooner at wide open throttle (1/2 second after each upshift) to pull even harder on the tall end of the dragstrip for higher trap speeds. For example, most supercharged Mustangs with the same horsepower as mine tend to trap in the 107-109 mph range, but mine traps in the 110-112 mph range.
I had the supercharger tuning, and subsequent transmission shifting and torque converter tuning all done at a dyno shop (HorsePower Ranch in Maple Valley, WA). It was all done on a Mustang Dyno with DiabloSport software, then downloaded into my handheld DiabloSport Predator tuner and into my car's PCM from the tuner.
I've since had small changes in shift points and torque converter lock up (that don't require being on the dyno) done remotely by having the HorsePower Ranch email me the revisions, which I download into my handheld tuner then into my car.