charlay86 wrote:Haha I like it Delco, maybe you could use a flex output instead of a tacho to trigger the coil earth relay (with a brake switch wired in series, so it only cuts spark on the brake) and for extra points use a double pole relay and get it to switch to map B with loads more fuel while there is no spark
Could you please explain what I would need to do to make this work in more detail? preferably utilising a button and the map b function to controll extra fueling at launch?
I am very interested to give this a go. Just installed a larger gt4294 and it needs some help off the line. getting nothing till 4,000 rpm but goes like a rocket after that.
Is this right? If the map b switch and 2 step switch held on at same time ? how do you get it to activate map b and dump more fuel only during
spark cut?
If you swapped things around a bit so that the flex out ground causes the relay to apply power the coil, then set up the flex out so it switches off at the rpm you want to cut spark then you will get what your thinking... but I dont think it will be very good. The resolution will be really low and you'll get heaps of fuel (too much?) in the exhaust at the same time. Im not sure what that'll do but It might cause damage. You really need a custom ignition module to do this properly.
I don't think you will need to add any extra fuel, the combustion will be the hottest around stoich.
extra fuel will just cool things down possibly doing the opposite of what you want.
The idea of bang bang / antilag is that you cut the spark and you have the correct amount of air and fuel for combustion and it will just occur in the exhaust manifold rather than the cylinder.
a big problem with switching the power to the coil is that the spark can occur at the wrong time (when the circuit is interrupted)
Yeah, I guess my diagram wont work. dunno what I was thinking there. The msd 6al-2 must cut the spark signal from somewhere. I wonder which circuit they have disconnect on the 2 step and make sure it fires again at the right time. The dizzy cap wouldn't let it fire at the wrong time would it?
its more about if the dizzy is halfway between two posts and it fires, its going to fire whichever cylinder its closest too, and that could either be the wrong one, or it could be the right one but way wrong time = knock or backfire!
No matter what the question is, the answer is always more horsepower!
If you happen to cut the coil power using the relay half way through a dwell it will just fire the spark plug early - ie instead of the 15deg advance under boost you just got 30+deg of advance.
The MSD will be monitoring RPM and spark events, it will be dropping the spark events before it even begins to charge the coil. Dizzy handles the spark distribution, so it might skip one cyl and fire the next three events, skip one, fire two, skip a couple more, fire a few etc etc
ok. I might give this backyard 2 step a miss I think. The map b function utilising same tune as A but with lower limiter setting and retarted spark and richer mixture does work to build boost to an extent.
I guess I'll need to let some moths out for the propper thing. Thanks for the info, probaly saved the motor.
I just bought a frequency to voltage converter from
Jaycar and wired it up to cut the coil when it hit a certain rpm
Was a heaps cheaper option!
But this was on a v6
maybe you could use a flex output instead of a tacho to trigger the coil earth relay (with a brake switch wired in series, so it only cuts spark on the brake) and for extra points use a double pole relay and get it to switch to map B with loads more fuel while there is no spark
Flex outputs are ground when active too.
