Some notes on RAS (Rear Active Steering)
03-05-2017 | 10:26 PM
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From: Georgia
Some notes on RAS (Rear Active Steering)
I have some experience with RAS systems, so I figured I will share some of my comments for those who are considering it on their next 911.
RAS operates in three distinct modes based on vehicle's operating speed band:
0mph-37mph band:
Inside this operating speed range, RAS turns wheels in the opposite direction of the front wheels by up to 4 degrees. 4 degrees is a very small angle, so effects of RAS are rather subtle in this band. RAS reduces the turning radius by 1.5 feet, so you can make a U-turn on 3 feet narrower roads. It also allows you to pull out of tighter parking spots (approx 6 inches tighter).
37mph-50mph band:
RAS keeps tracking straight inside this speed band, so it does not make any difference at all.
>50mph band:
This is where RAS turns in same direction as the front steering by up to 4 degrees.
On the track, car's inertia pushes it wide (away from apex) but RAS counters this effect to a certain extent. To the driver it will feel like someone placed a giant rubber band at the apex and attached it to car, pulling the car in magically.
On the freeway, same-direction RAS mode allows car to "crab walk" between lanes. If an unexpected obstacle pops up in front of the driver, car can change lanes much faster than non-RAS cars.
Please keep in mind that the angle of RAS activation is not fixed at 4'; it varies along a curve programmed in ECU primarily based on front steering angle, speed, and traction data.
Hope this helps!
RAS operates in three distinct modes based on vehicle's operating speed band:
0mph-37mph band:
Inside this operating speed range, RAS turns wheels in the opposite direction of the front wheels by up to 4 degrees. 4 degrees is a very small angle, so effects of RAS are rather subtle in this band. RAS reduces the turning radius by 1.5 feet, so you can make a U-turn on 3 feet narrower roads. It also allows you to pull out of tighter parking spots (approx 6 inches tighter).
37mph-50mph band:
RAS keeps tracking straight inside this speed band, so it does not make any difference at all.
>50mph band:
This is where RAS turns in same direction as the front steering by up to 4 degrees.
On the track, car's inertia pushes it wide (away from apex) but RAS counters this effect to a certain extent. To the driver it will feel like someone placed a giant rubber band at the apex and attached it to car, pulling the car in magically.
On the freeway, same-direction RAS mode allows car to "crab walk" between lanes. If an unexpected obstacle pops up in front of the driver, car can change lanes much faster than non-RAS cars.
Please keep in mind that the angle of RAS activation is not fixed at 4'; it varies along a curve programmed in ECU primarily based on front steering angle, speed, and traction data.
Hope this helps!
03-08-2017 | 05:57 PM
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From: Georgia
Emergency lane change maneuvers >50 mph are far better with RAS; It feels like car teleports to another lane.
Over the years I had several close calls with logs flying out of a truck ahead, a drunk driver falling asleep at wheel and cutting across my lane, and multiple cars just stopped in middle of freeway at night with no lights. So RAS was the first option I put on my C2S before anything else.
Over the years I had several close calls with logs flying out of a truck ahead, a drunk driver falling asleep at wheel and cutting across my lane, and multiple cars just stopped in middle of freeway at night with no lights. So RAS was the first option I put on my C2S before anything else.
