+Vacuumpump / PowerBrakes

The Z3 Powerbrakes require (like almost all passenger vehicles) vacuum to operate. Without the vacuum the brake-action is heavier than with normal un-powered brakes. I have no means of measuring the brake stopping power (G-force as function of pedal action) so passing the individual conversion inspection might be troublesome. To prevent as many troubles I added an electric vacuum pump to restore the power brakes operation.

Brakes are a safety device and did not want to cut corners regarding any of the direct safety systems. In fact brakes are the most important feature of a car. Without it is most trips end up being a disaster.

Using components from vehicles that are already on the road makes passing these kinds of conversion inspections much easier. As for brakes, I took no chances and bought a new pump from a car brand and model that is already registered in the Netherlands.

vacuum pump

UPDATE Installation of the pump it self was quick and simple, but I ran into a little snag. 1 the pump did not hold vacuum after it was shut off. 2nd the BMW brake booster has the check-valve embedded into the booster. This prevents me from measuring the vacuum without an additional reservoir. An reservoir with check-valve & DIY 555 based relay-timer relais/mosfet is added:

vacuum pump reservoir

Vacuum is generated very quickly. ~ 15 seconds from normal air pressure. After the initial vacuum is generated the relay timer has been set to 5.5Seconds. This means that if the vacuum switch is triggered, the pump will run atleast 5.5 seconds even if the vacuum switch opens its contact. This adds hysteresis.

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