Factory, some ecu's (ka24 comes to mind) let the motor rev to 6500 rpm, then cut the fuel until the rpms decel to 5500 rpm then repeat. It basically bounces. A much more useable rev limiter would keep the rpm oscillating points close together like 6500 to 6100 rpm.
Launch control would see an extra input grounded (clutch switch usually) and would impose a lower rev limiter than normal. several other tuneable ECU's like mitsu, subie, hondata, even bikiroms modify the ecu code to do this.
Turbo guys use spark cut since it passes unburnt fuel straight out to ignite inside the turbo manifold and spool the turbo rather quickly. With spark cut its easy to build close to full boost just free revving the motor. Also it makes nice foot-long flames and loud pops and bangs
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I love your idea 4x4LE, and I'm going to try it soon! I wonder if a negative number would work in that field for more retard? For example our KA24DET running Megasquirt I have set up to pull 40 degrees.