Quick question for the experts pls: Does Servotronic Sport alters the ratio?

[cannga]

I've read that M3 steering is both
1. Active: variable ratio (ratio varies at higher speed vs. parking lot)
2. Servotronic: variable assist (assist decreases at higher speed)

I know Sport setting of Servotronic lessens level of assist versus the Normal setting, but I seem to feel that it varies the ratio as well and makes steering quicker (too aprupt for me). Does anyone feel the same?
TIA

[jphughan]

It doesn't. Easiest way to confirm is to observe that the lock-to-lock travel doesn't change between the two modes; the ratio is always 12.5:1. Both Normal and Sport have adaptive steering effort; Sport just adapts within a lower range of assist.

[Z K]

All of the modes feel pretty artificial. I wish they could have stuck with a traditional steering set up.

At least it isn't variable ratio, that would really suck.

[cannga]

Originally Posted by Z K

All of the modes feel pretty artificial. I wish they could have stuck with a traditional steering set up.

At least it isn't variable ratio, that would really suck.

To best of my knowledge, M3 does have "Active Steering" which means variable ratio. This is described on page 90 of manual, or web site below:

>>>>>>>>>>>>>>>>>>>>>>>>
http://www.bmw.com/com/en/insights/t..._steering.html

The new dimension in steering comfort: Active Steering offers precision, agility and comfort in every driving situation.
At the heart of the new Active Steering system is the planetary gear set integrated into the steering column. An electric motor in the joint adjusts the front wheels' steering angle in proportion to the Sedan's current speed.
When driving at lower speeds - such as in city traffic, when parking or on winding mountain roads, Active Steering increases the size of the steering angle. The front wheels respond immediately to small movements of the steering wheel, enabling the driver to manoeuvre through tight spaces without needing to make multiple turns of the steering wheel. Parking is easier and agility enhanced.
At medium speeds, steering is also easier. And to ensure smoothness at higher speeds, as of around 120 to 140 km/h (depending on the model) Active Steering becomes more indirect.
Active Steering therefore reduces the amount of change in the steering angle for every movement of the steering wheel. This gives the driver the advantage of more precise steering at higher speeds, and ensures great stability and more comfort.
If the vehicle is threatened with instability, such as by oversteering or braking on a changeable surface, DSC identifies the problem and can use Active Steering to help overcome it. For example, in order to reduce unsafe yaw, Active Steering can increase the angle of steering wheels faster than even the most expert driver.
Active Steering does not interrupt the direct connection between steering wheel and front wheels, so that even in the unlikely event of a complete failure of the electronic systems, the BMW remains completely controllable at all times. This is because at the first sign of any problems, an adaptation mechanism blocks the Active Steering immediately using a pivot so that the driver is permanenty in control of the situation.

[jphughan]

^ That manual applies to the base 3 Series. The M3 Supplement explains Servotronic, which doesn't exist on the base series models. The same manual you're referring to shows a DTC button between the center air vents, which doesn't exist on any M3, and doesn't even mention M3-specific features. Active Steering was an option on the E9x series models, but never on the M3, and it definitely wasn't standard.

Active Steering was designed to allow easier maneuverability at low speeds via a fast ratio (10:1) and more directional stability at high speeds via a slower ratio (18:1). But the M3 is designed with the track in mind, where you'd want maneuverability at high speeds, hence the fixed 12.5:1 ratio which is closer to the faster mode of Active Steering.

[cannga]

Originally Posted by jphughan

^ That manual applies to the base 3 Series. The M3 Supplement explains Servotronic, which doesn't exist on the base series models. The same manual you're referring to shows a DTC button between the center air vents, which doesn't exist on any M3, and doesn't even mention M3-specific features. Active Steering was an option on the E9x series models, but never on the M3, and it definitely wasn't standard.

Active Steering was designed to allow easier maneuverability at low speeds via a fast ratio (10:1) and more directional stability at high speeds via a slower ratio (18:1). But the M3 is designed with the track in mind, where you'd want maneuverability at high speeds, hence the fixed 12.5:1 ratio which is closer to the faster mode of Active Steering.

Thanks for the detailed and *very* helpful answer.

[pkimM3r]

M3 doesnt have active steering.

[Sinister Crayon]

Originally Posted by pkim1079

M3 doesnt have active steering.

+1. I had a 545i with Active Steering and the M3's steering feels NOTHING like that. The Active Steering was actually pretty decent but definitely felt artificial and fake. Helped with that big car though

[davesaddiction]

Related:

Mike Benvo's Servotronic Tuning

http://www.m3post.com/forums/showthread.php?t=859205

[///M Power-Belgium]

Originally Posted by davesaddiction

Related:

Mike Benvo's Servotronic Tuning

http://www.m3post.com/forums/showthread.php?t=859205

Spot on ! This is a must have....

[cannga]

Thanks everyone for the helpful replies and correction of my mistake. Next question for the experts, please be patient as I am learning and reading up on this topic as we speak LOL; from Wikipedia, I seem to see that there are different ways of implementing variable ratio:


1. Variable Ratio, "non BMW method" (??)
http://en.wikipedia.org/wiki/Steering_ratio
A variable-ratio steering, is a system that uses different ratios on the rack, in a rack and pinion steering system. At the center of the rack, the space between the teeth are smaller and the space becomes larger as the pinion moves down the rack. In the middle of the rack you'll have a higher ratio and the ratio becomes lower as you turn the steering wheel towards lock. This makes the steering less sensitive, when the steering wheel is close to its center position and makes it harder for the driver to oversteer at high speeds. As you turn the steering wheel towards lock, the wheels begins to react more to your steering input.

2. Variable Ratio, by BMW Active Steering method
http://en.wikipedia.org/wiki/Active_Steering
Active steering describes a steering system for a vehicle in which the relationship between the driver’s steer inputs and the angle of the steered road wheels may be continuously and intelligently altered. Whilst active steering systems may be found in agricultural equipment and heavy plant, this article concentrates on the application of active steering in BMW passenger cars.

Active steering describes a type of power electric variable gear ratio power steering technology introduced by BMW in 2003 first appearing on the redesigned 5-series which varies the degree that the wheels turn in response to the steering wheel. At lower speeds, this technology reduces the amount that the steering wheel must be turned – improving performance in situations such as parking and other urban area traffic maneuvers. At higher speeds, the performance is such that the normal increased responsiveness from speed is avoided and it provides improved directional stability.

Last question, I think :-), on this topic: Am I correct the above 2 systems are not the same, AND the M3 has neither?

[Z K]

Originally Posted by cannga

Last question, I think :-), on this topic: Am I correct the above 2 systems are not the same, AND the M3 has neither?

M3 has neither.

The steering assist is just boosting the power steering - either reducing or increasing the effort to turn the steering wheel.

[jphughan]

Originally Posted by cannga

Last question, I think :-), on this topic: Am I correct the above 2 systems are not the same, AND the M3 has neither?

The systems are not the same, and while both are variable ratio, only the latter is active. The M3 has neither system, and BMW to my knowledge only has the latter system. The difference is that the first one has a ratio that varies based on where the steering wheel is in its rotation range (but a given area of its rotation range will always have whatever ratio has been dictated by the rack design), and the second one has a ratio that can change the ratio of the entire rotation range, but at any given moment the entire range is using that single ratio. I don't see a reason you couldn't design a version of the second system that varies the ratio dynamically but where the changes are only applied to certain areas of the steering range, but I'm not sure that would be useful.