I originally set my MSD window switch at 3000 and 5800. With 3.07 gears and Mickey Thompson ET's (26.25" dia) I was nowhere near the 5800 cutoff at 135 in 4th gear, however, I recently changed gears from the oem to 3.33's. I verified the rpm/mph difference and I still had room within the window switch.
I was wrong, my mph was down and it felt like a high speed miss when the NOS would drop off. Initially I did not know why the power was down. To make a long story, short, the 5800 rpm setting was about 10% off, in other words, it was dropping the NOS at approximately 5200-5300. It is hard to verify the exact point because the device is a non-linear solid state switch. My test scheme was to put a 4000 rpm pill in the high side, then, increase the rpm's till the yellow wire output changed state (off). I was tracking the rpms thru the OBDII port.
MSD has been pretty nice to deal with, but, when I called to ask about the accuracy, they said less than 1% error. Almost in the same breath the tech support person added, unless the calibration is off. The way it was put it seemed as though inaccurate calibration was commonplace.
FYI - The Chuckware calculator (http://chuckware.net/viper/gears.asp) is a great tool for estimating top speed for different gear ratios and tires. Just insert the following tire diameters into the calculator:
OEM: 25.4 new
ET's: 26.25
Kumho's: 25.8
I was wrong, my mph was down and it felt like a high speed miss when the NOS would drop off. Initially I did not know why the power was down. To make a long story, short, the 5800 rpm setting was about 10% off, in other words, it was dropping the NOS at approximately 5200-5300. It is hard to verify the exact point because the device is a non-linear solid state switch. My test scheme was to put a 4000 rpm pill in the high side, then, increase the rpm's till the yellow wire output changed state (off). I was tracking the rpms thru the OBDII port.
MSD has been pretty nice to deal with, but, when I called to ask about the accuracy, they said less than 1% error. Almost in the same breath the tech support person added, unless the calibration is off. The way it was put it seemed as though inaccurate calibration was commonplace.
FYI - The Chuckware calculator (http://chuckware.net/viper/gears.asp) is a great tool for estimating top speed for different gear ratios and tires. Just insert the following tire diameters into the calculator:
OEM: 25.4 new
ET's: 26.25
Kumho's: 25.8
