In my previous post on vacuum assisted power brakes I looked into vacuum pump. In some cases it might be a valid and low cost solution while accepting inferior braking performance and noise. I definitely wanted to prevent the sound of “prrrrr” when you switch on the car and looked into alternatives. Moving away from vacuum assisted power brakes can also be very relevant for muscle cars or hot-rods where vacuum pressure or space (or both) are limited.
I did a quickscan on three options:
- Stand alone hydraulic pump, matching master cylinder and accumulator. For example from ABS Powerbrakes you can buy their “Electric High Power Electric Brake System“. One of the downsides is the price of around € 1500 and in my case modifications required.
- Hydroboost, where oil pressure from the steering pump is being used for power braking. Since I already had electric power-assisted steering (EPAS) that was not really an option either.
- Electric power brakes, that seemed ideal, just power it with 12V and have assistance like the power steering.
The way forward was electric power brakes.
Available electric power brakes?
My next question was: what cars have electric assisted power brakes and looked into a couple of options.
Lexus: First I looked into the systems used in a Lexus since they have a ‘drive by wire’ philosophy, but it turned out it would require re-using multiple components.
Ford: The first type Ford Scorpio (1985-1994) had an electric brake booster. Advantage is that it is quite a stand alone system and I could even also easily implement the ABS.
In terms of weight of the car that could match quite nice. However I could not find any of the components new. And searching for and using 25 years old parts was not really an option.
iBooster: Finally the iBooster made by Bosch. It’s an impressive piece of engineering.
In the video the GEN 1 iBooster is shown and used in later Model S cars with Autopilot, in the model X, Chevrolet Bolt and Malibu and the Honda CR-V.
It can be used in “failsafe” mode just by implementing the pedal travel sensor on the unit and powering it up.
Conclusion: iBooster = go!
So my conclusion was: electric assisted power braking using the Tesla iBooster was the best way forward in my EV conversion project.