MacGyver

I could be wrong on this one, but I'm not so sure this is a concern with our system. The coil packs are direct drive through FETs, so while the rest of the system is busy building up a spark, the packs aren't really in the circuit until the ECU switches on the individual FET.

jimknapp

Yeah but the FET still has to build a charge and then collapse the field to fire the spark. How much spark it provides is a function of among other things the spark gap. More important here though is get rid of heat as fast as possible with NOS.

MacGyver

No, the FET merely acts as a switch. The switching times are not so high as to worry about stray inductance/capacitance. The charge would be built up somewhere else (can anyone confirm that a charge actually DOES build up, or if it's merely a high-voltage pulse (my guess)?). Assuming the charge is built up elsewhere, the coil pack is not part of the circuit yet. When the FET's gate is pulsed, the stored charge is allowed through to the pack (once the back-EMF in the pack lets up enough to let it flow).

Road Rage

That's right, the FET is a switch - the coils fire directly - are they capaciive discharge, or step-up transformers?

MacGyver

My guess is merely a step-up transformer considering the number of loops in each pack (200, give or take, would be my guesstimate from the pic I have in memory). If that number is right, there's a spark of around 2,500V on those plugs.

S2KNOS

question?
I also went NOS in my S.
Ran it last night (75shot) with factory plugs.
Someone told me I am supposed to be running colder plugs.
Does anyone know which plugs exactly?
I dont know much about this so I need to know a part #.
My O2 sensor is not working. Is it important to fix this before running the car again? or can I replace it with something else? Or I just have to get a new one ?
Thanks!

MacGyver

I believe one notch colder is suggested for a 50-75, much more and I believe 2 steps colder is the way to go...but don't quote me as I'm not a NOS expert.

jimknapp

Again (see previous post) the reason you go to a colder plug is because of the extra heat generated (you're making more HP so you make more heat). Look for a SHORT, FAT side electrode so it will dump heat rapidly. Extended tips are probably the WORST thing you can run. You don't want it sitting there like a glowing ember in your chamber pre-igniting the next rev of NOS/Gas combo.

No reason to open the gap either. .026 to .032 is plenty