The conventional wisdom among car enthusiasts is that hydraulic power steering is good, and the electric-assist power-steering systems that have replaced it in most new cars are bad. Engineering Explained host Jason Fenske doesn't think it's quite that simple, and believes hydraulic power steering isn't dead yet, at least at McLaren
Both points are demonstrated by the car Fenske drove for his power-steering deep-dive video. It's a McLaren 620R, a hardcore track-focused version of the McLaren 570S, which uses an electro-hydraulic-assist power-steering system.
Electro-hydraulic power steering still uses hydraulic pressure to provide steering assist, just like a traditional all-hydraulic setup. But the hydraulic pump is powered by an electric motor, rather than the engine. This allows for more flexibility, since the ability to run the pump isn't dependent on engine speed.
McLaren 620R with MSO R Pack
The 620R is tuned to provide more steering assist at low speeds, making parking easier, and less assist at higher speeds, preserving road feel, responsiveness, and the linear effort that make for good steering, Fenske says.
This system is more complicated than it needs to be. McLaren could have used a straightforward electric-assist power-steering system, where an electric motor provides all of the assistance to driver, without any added hydraulic lines. However, Fenske says the motor would damp out some road feel, so McLaren opted for the electro-hydraulic system, which lets the driver feel all of the little forces from the road.
When it comes to transmitting every last bit of information to the driver, hydraulic power steering is still the best way to go. McLaren's electro-hydraulic system shows how hydraulic power steering can live on, especially in the most driver-focused cars.
Check out the full video to Fenske's excellent description of how hydraulic- and electric-assist power steering work and McLaren's philosophy on the subject.