TARGA / MARC
912 · 1968 · 12871136
902/02 / KINEMATIC MODEL

Five gears. Every assumption visible.

A working notebook, not a top-speed prediction. The initial settings are historical references and an illustrative tyre circumference, not measurements of this car.

3,500

The slider range is mathematical, not an operating limit.

1.950 m is an example, not a measured tyre.

Calculated results only. Fitted gears, final drive and tyre input remain unverified.
107.9
km/h in fifth at the selected rpm
3,244
rpm in fifth at 100 km/h
GearRatiokm/hmphrpm at targetrpm after upshift

Upshift values assume unchanged road speed and no clutch slip. The fourth-to-fifth result changes with your fifth-gear selection.

Read the calculation.

v [km/h] = n [rpm] × C [m] × 60 / (i × i₀ × 1000)

n [rpm] = v [km/h] × i × i₀ × 1000 / (60 × C)

n_after = n_before × i_next / i_current

i = driven teeth ÷ driving teeth; i₀ = final-drive reduction. No drag, power curve or tyre-slip model is included. The source’s 7:31 tooth pair gives 4.428571, not the inconsistent 4.448 printed in the FIA table.

Read the transmission notebook ↗ · Porsche PET p.270 ↗ · FIA 580 p.11 ↗