What it does
End RPM sets the highest rpm the engine is allowed to reach while the launch control input is active. The ECU holds the engine at or below that number until the input switches off, then normal operation, and your normal rev limit, take over again.
A typical example: launch control is armed from a clutch switch or a trans-brake. You hold the clutch in or the trans-brake on, floor the throttle, and the engine sits at, say, 5000 rpm. Release the clutch or the trans-brake and the limit disappears, and the car drives away under full power.
Choosing the number
There's no universal answer, because the right launch rpm depends on the car's power, the tires, the surface and, on a turbo car, how much boost you need on the line. A few rules we follow:
- Start low and raise it in small steps. Too much rpm means wheelspin; too little means a bog.
- On a turbo car, pair it with the launch ignition table, which does the real work of building boost.
- Log rpm, boost and wheel speed on every launch and adjust from what the data shows, not what it felt like.
- On manual cars, remember a higher launch rpm puts more load through the clutch and driveline.
Make sure the input is set up correctly first; see Launch Control Wiring. The launch control overview covers the rest of the function.
