Sorry for preaching, but I want to be sure everybody is aware of how badly the NHRA's battery cut-off rule endangers their vehicles and their lives:
The reason for the switch is simple...if you crash, the rescue crew will be able to kill your electrical system (and your engine, if it's still running after the crash). The positive side kill is the easiest way to accomplish this, but let's look at a very real scenario: 1) You tag the wall. 2) Gasoline, or some other flammable(s), leak as a result of the crash. 3) Your NHRA mandated positive-side switch gets crunched against a metal body panel during the crash. 4) The resulting sparks from grounding the positive switch against metal ignite the flammable(s). 5) You become a "crispy critter".
Why does the NHRA still mandate a positive side switch, when so many other motorsports sanctioning organizations have long since converted to the safer negative side (which would simply ground your battery to the body in case the switch is damaged during the crash)? 1) They claim that the positive switch is necessary to kill the motor...but, that's not true. Simple & reliable wiring kits are available to isolate alternator feedback and insure that the motor shuts off when the negative is cut-off. 2) Any retreat from this long-standing regulatory position could open them up to extensive liability for prior damages/injuries/deaths that have resulted from positive switches.
Do whatever you want, but be aware of the dangers of this NHRA mandate. Many participants (including me) run "illegal" negative switches with alternator isolating kits...these will pass tech at least 99.9% of the time, because I've never seen a tech official trace the wiring...they just insure that the switch kills the motor. Some people get nervous about killing the ground to the ECM, but I've never hurt an ECM with a negative switch. And, even if that was an issue, I'd rather risk damaging the ECM vs. burning to death.
That's my 2 cents...
Rob
