I am having trouble explaining to a friend why you need a lower stall converter with nitrous. I told him it will flash to high and you can't use the nitrous as long. This is what I was thinking, the numbers are just an example. If I was not using nitrous and in 3rd gear at 6200rpms(not redline) with a 4000 stall I would cross the line at 122 mph(depending on tire size, gear, etc). But if I was using nitrous the 4000 stall will continue to slip to much from all the torque(now becoming a much higher stall than 4000) and when I reached 7000rpms(redline) in 3rd gear I would cross the line at maybe 128mph. Only 6 mph more when in fact I should have crossed the line at 138 mph when at 7000rpms, but since I was using the incorrect stall it kept slipping well before the intended mph could catch up to 7000rpms. Since the converter was slipping way to high I lost the ability to use nitrous for at least 10 more mph in 3rd gear. Does this sound correct?

 

I think you are overanalyzing the question. It helps to remember why an N/A motor needs a high stall. A lower stall works with nitrous because nitrous greatly increases low rpm torque. Since nitrous usually flows at a more-or-less constant rate, each cycle receives a larger charge at lower engine speeds. This is the reason it is so important to not spray below 2500 or 3000 rpm - too much torque. Conversely, an N/A motor needs to spin.