What is torque vectoring
Where the magic happens
Disclaimer
Because I can't find the tribe for Engineering Explained (it wouldn't show up) I didn't have anywhere else to post it. Thanks
Torque vectoring is something common now. Just about every sports car, supercar, you name it has it. But what is it really? Well, that’s what I’m going to tell you today. I’m going to go over what it is and how it works as well as some advantages and disadvantages. As with previous blogposts, this will just be an overview, not an in-depth look. If you have any questions, feel free to ask. Without further delay, let’s get on with it!
What it is and what it isn't
Sport differential used on Audi's S and RS models
Torque vectoring is where in the differential can change the rotational speed of each wheel based on cornering. It’s like an open differential, except that power isn’t sent to the path of least resistance. Instead, a torque vectoring differential sends more power to the out side wheel to rotate it quicker, and can slow down the inside wheel to aid in cornering.
What it is: a method to help go around corners faster than normal while reducing understeer, steering input, center of gravity, etc.
What it isn’t: an open differential because it doesn’t send power to the path with the least grip*
Advantages and disadvantages
The Honda NSX's front electric motors can use torque vectoring to reduce understeer to aid in cornering
Advantages and Disadvantages
Advantages: Good for cornering harder and faster whilst reducing understeer at the same time, reduces steering input
Disadvantages: Heavier, costs more to make, can be expensive to maintain
Audi sport rear differential helps it's nose heavy cars corner easier with minimal understeer
To understand TVD (torque vectoring differentials), you first have to understand the difference between open, LSD, and locking differentials. On open differential, power is sent to the least resistant path, but that can backfire sometimes in situations where tractions is an issue because you’ll just sit there spinning one wheel while the other is sitting there hardly rotating. On a limited slip, power is distributed evenly amongst both wheels giving equal distribution of power regardless of situation. A locking differential is kind of the best of both worlds. In a locking differential, you can lock the wheels so that they are spinning at the same rate, like an LSD, however, because the wheels are locked together, it can ruin handling characteristics because one wheel is traveling at the same speed through a corner, rather than at different speeds normally.
Torque vectoring by differential
Now that differentials are out of the way, lets get on with it. As TVD goes, it’s a standard differential, (sometimes being a limited slip, sometimes an open) but on either side is a clutch pack that can engage or disengage based on cornering speeds, angle, etc. As you go around that corner, say a right hairpin, the left clutch engages so that more torque goes to the left wheel which will speed it up more, allowing for a better turn in. However, when you are going in a straight line, the clutches are disengaged so it acts like a normal differential.
Torque vectoring by braking
Now there is another kind of torque vectoring called torque vectoring by braking. It’s not too different, as the speed of each wheel changes in a corner, but rather than have a clutch pack on either side of the differential, the system is operated by the car’s brakes. For example: The McLaren 570S/GT has an open differential with McLaren’s “Brake-Steer.” What it does is when you go around a corner, the brake on the inside wheel is applied. Because one wheel is slowing down, more power is sent to the other wheel, speeding it up and allowing to corner faster. But, if the brakes get too hot, then the effect is very minimal or not available. Brake based torque vectoring is a cheaper way of getting the magic into a mass produced car (but that’s not always a bad thing, it keeps costs down)
All modern McLarens' have torque vectoring by braking, known to McLaren as "Brake-Steer"
TVD on a Lexus RCF, with the clutch packs in red
In the RCF’s case (shown above), there is actually an electric motor on each side of the differential casing right by the two sets of clutches that can automatically engage or disengage based on the scenario.
A good example of torque vectoring via Car and Driver
Torque vectoring is sort of like a sidekick. There when you need it, but doesn’t get in the way on a day-to-day basis. It’s there when you need it can fight along side you when deemed necessary. It’s proven to work, in a Car and Driver test of the standard Torsen differential and the TVD on the Lexus RCF, the latter lapped a 1.7 mile course 0.4 seconds faster than the standard Torsen limited slip. It isn’t just lap times it improves however, with the extra weight on the back, the center of balance is taken from 54.4/45.6, front/rear, to 53.5/46.5, front/rear. It also lowers the center of gravity by 0.5 inches (1.27 cm) from 20 inches to 19.5 inches (50.8 cm to 49.53 cm). It also grips on the C&D 300FT skidpad better as well, pulling 0.94g’s compared to the standard car’s 0.91g. Long story short, torque vectoring is an amazing thing. It turns 0s into heroes and as it gains popularity in more and more cars, from the $41,120 Focus RS to the $1.3 million dollar McLaren P1. It’s technology that’ slowly trickling down the car tree and will soon be available in just about every performance variant of every car on sale. That’s all for today, if you have any questions or suggestions, let me know in the comments below, bye!
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Comments (3)
I was wondering, who was the first to start developing some sort of yaw control?