2014 Ford Focus ST Takes on Different Guises for 2013 SEMA Show

Comments

• engineer_mba Member Posts: 11

  October 2013

  Very colorful concepts. Speaking of the Focus ST, I noticed that Quaife makes a Helical Limited Slip Differential for the ST (http://quaifeamerica.com/qdf41z) which should eliminate torque steer and unnecessary wheel spin when the electronic aids are turned off (the car's only real flaws). If I owned an ST, it would be a mandatory purchase.

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• socal_eric Member Posts: 189

  November 2013

  The automatic torque biasing (ATB) diffs definitely help in putting power down and should complement the brake-based electronic aids of the Focus ST, especially when exiting a corner since the brakes won't be taxed as much, but the Quaife and Torsen-style helical gear ATB diffs do have a tendency to *increase* torque steer in many front drive applications. This is due to how they actively shift driveline torque across the front axle and how that driveline torque reacts with other factors that can cause torque steer including when and how much engine torque is applied, chassis and suspension geometry, alignment of both steering gear as well as the powertrain (to include axle half-shafts), the tires used and sidewall stiffness, electronics for torque management and traction control also moving power around on the drive wheels, etc. ---------------With the stability control on the Focus ST in full off mode it won't intervene if you push wide or the car starts to rotate too far but it's still using the electronics and ABS for torque biasing/vectoring across the front axle and the understeer mitigation also continues to uses the front and rear brakes to help rotate the car on corner entry and exit. Go in too hot and while the aids help with the chassis balance it won't interact to save you and put the car back on an intended line like conventional stability controlled is designed to do. When you fully disabled it the system does greatly reduce traction control aids too, allowing for extra wheel spin and it won't reduce engine power and use the brakes to selectively slow both front wheels if they spin up, but it will use the brakes and torque vectoring to shift power to the outside, slower spinning wheel if only one wheel is spinning.

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