Driving performance calculations at the example
of the 1.2 liter engine |

Technical data VW 1200 25kW (34bhp) |

curb weight | 835 kg |

cd drag coeff. | 0,485 |

front area | 1,85 m² |

rolling resistance coeff. | 0,0124 |

tyre rolling radius | 30,9 cm |

const. drivetrain loss | 15 Nm |

drivetrain efficiency | 0,855 |

gear ratio 1st gear | 3,78 |

gear ratio 2nd gear | 2,06 |

gear ratio 3rd gear | 1,26 |

gear ratio 4th gear | 0,93 |

final ratio | 4,375 |

Max. engine power | 25 kW (34bhp) |

Max. engine torque | 76 Nm |

Max. engine revs | 4100 1/min |

With these input values the 1200cc bug achieves a top speed of 115 km/h and an acceleration from 0 to 100 km/h of 32 sec.

Engine power and torque diagrams |

Power and torque curves of the 1.2 liter 25 kW (34 bhp)
and 1.6 liter 37 kW (50 bhp) engines. Triebwerks eingezeichnet.
The maximum revs of the 1.6 liter engine increased from 4100 to 4600 1/min
(+12%), torque increased about 33% due to the greater displacement. Because
of the dual pipe intake manifold power increased about 47%. Further calculations
are made on the basis of the 1.2 liter flat4 engine.

Tractive force diagram (VW 1200 25kW/34bhp) |

In the third gear it is possible to climb a 10% slope between 30 and 60 km/h. The offered tractive force is higher than the demand (10% line). Below 30 km/h the 2nd gear has to be taken which enables the driver to climb an uphill gradient up to 20%.

All speeds from stillstand to the beginning of the red
curves must be driven with the help of the slipping clutch.

Acceleration diagram (VW 1200 25kW/34bhp) |

The VW 1200 acheives in the first gear at 15 km/h a maximum acceleration of 3 m/s² (about 30% of the earth gravity). In the 4th gear at 115 km/h (top speed) there is no further acceleration possible.

If the driver wants to accelerate from 45 km/h with max. acceleration, e.g. when leaving a city speed limit, he can do that in the 2nd, 3rd or 4th gear. In the 3rd gear a 50 higher acceleration is possible than in the 4th. In the second gear even twice of the acceleration of the 4th gear is possible. However the driver has to shift in the 3rd at 50 km/h and the acceleration will soon decrease

.

In real life changes in engine power, drag ceofficient and rolling tyre resistance must be taken into consideration. All the calculated forces and accelerations might change when the curb weight increases due to heavy options.

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