LSD Lock percentage
The LSD lock percentage is a dynamic variable and depends on many factors:
As we know, factory-made differential lock is 25%. What does it mean? This means that the differential can transfer up to 25% of torque to the wheel with a grip, or a wheel that has more grip.
“Little pumpkin” and “big pumpkin” – you”ll say, whatever . All have a 25% lock. Well, but not really. These rates are relative. They are part of torque. 25% of torque to the average four-cylinder engine for ” Little pumpkin ” and 25% of torque to the average six-cylinder engine for the “big pumpkin “. So it appears that 25% of the little pumpkin is less than 25% of the largest medium case.
There is another point. Let’s say, that you have an original LSD and stock motor for example of 240Nm torque. However, you increase engine power, using a turbine and as a result you get a car with 360Nm of torque. In the end If LSD is has been transferred 60Nm (25% from 240Nm), now these 60Nm become 16.6% of 360Nm. So you need more percentage. The rule is: “the more the better.”
The most tuners and performance specialists prefer clutch type differentials on race and rally cars. So we offer various modifications that can be used for specific automotive applications.
The first method of increasing the lock percentage is inserting more friction discs.
The other method is to create the clamping force through etc. ramps. The bevel gears which rests in angled cutouts forming cammed ramps. The ramps work when an input torque of the driveshaft is applied. The internal clutch pack(friction disks) is forsed sideways by Bevel mate shafts, trying to climb the ramps.
The cammed ramps are not necessarily symmetrical. If the ramps are symmetrical, the LSD is 2-way. If they are saw toothed (i.e. one side of the ramp is vertical), the LSD is 1-way. If both sides are sloped, but are asymmetric, the LSD is 1.5-way.
There are three input torque states: acceleration, deceleration and no load. With no load, the coupling is reduced to the static pressure. During load conditions depends whether the LSD is 1 way, 1.5 way, or 2 way.
A 1-way differential will provide its torque transfer in only one direction. When torque is applied in the opposite direction it behaves like an open differential or reduced transfer. This is the best for FWD cars, as it allows the car to turn in on throttle release.
A 1.5-way differential refers to one where the acceleration torque transfer and deceleration torque transfer are different but neither is zero as in the case of the 1-way LSD. This type of differential is common in racing cars where a strong limiting torque can aid stability under engine braking.
A 2-way differential will have the same torque transfer in both the forward and reverse directions. This means the differential will provide same level of limiting under engine braking. This is the best for drift cars.
|mods||% lock relatively|
|2 friction discs 45ºramps(original)||25|
|3 friction discs 45ºramps||40|
|4 friction discs 45ºramps||60|
|2 friction discs 30°ramps||45|
|3 friction discs 30°ramps||70|
|4 friction discs 30°ramps||95|
According to the purpose of the car and driving style we recommend:
street – 25% – 40%
street/track – 40% to 70%
sport – 60%, 70%, 95%
For further questions, please ask here