- Apr 18, 2006
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Well, someone asked in a PM how can identify LSD by rotating tires.. well. I heard that too, but when I tried it out, the reality is different, and you can't really identify by rotating tires when the car is jacked up.
It's because of the wear and tear on the LSD, and also the thickness of the transmission fluid. thick enough, even a one way will behave like a two way.
Worn LSDs also sometimes appear like non-LSD gearboxes, and even a stock non-LSD can act like a one way (when driving, it will be apparent, because you can't apply torque by hand like the engine can with the gears on the wheels, and it's also by nature of the LSD to detect torque input via the spider gears and identify where the torque is coming from.)
So i queried about it to my mech friend, and he borrowed me a book on LSD. I've finished it a while back, but didn't really feel like posting about it because 'LSDs are damn expensive!' and most people don't have them, or are running the stock R ones. Even I consider it expensive. starting at 2.8K to the 3-4K OS Giken/Cusco LSD.
There are many types of LSD, clutch, gear and viscous.
Clutch type
Clutch type uses plates to lock the left and right driveshaft together, the plates have different types of compound (metal, carbon, etc) based on what kind of 'locking' the driver is looking for. Clutch has one advantage that gear doesn't, and that is progressive locking (low torque, slight slip, high torque, near zero slip). the higher the torque exposed to the LSD, the tighter it locks the left and right driveshaft, but too much, the clutch will slip.. it's just the way it is, and that's why clutch LSD are 'maintainance' items. You're supposed to service them at intervals.
Gear/Helicals
There's gear type, which is called helicals, honda stock LSDs are of this type, and so are Quaife™. These are almost maintainance free LSDs, but they can break once the teeth wears on the gears. Quaife is supposedly stronger than the R because they have more spider gears than the stock R, but since never opened/seen Quaife LSD before, dunno.., sorry! Gear types are usually one way only, there are exceptions, (see hybrid LSDs)
Viscous
Viscous, uses oil. When the gears spin, and the heat from differential is great enough, the viscous turns hard into something like thick gel. this locks the driveshafts. Other than that, I don't really care, because
a) I don't know, lol.
b) viscous is considered a lousy LSD, it exists because it's easier for beginners, slow speed, the car acts like it has no LSD (sharp cornering at slow speeds, even sharper than clutch/helical LSD.)
Hybrid LSDs
There's also hybrid LSD, using clutch and gear. This one, you won't find info on the net (except maybe from OS giken themselves), because most of the articles on the net are very very old, taken from one forum, cut and paste into another forum/article. It's not exactly new technology, but probably came into existence in the late 90's early 2000.
And example of this is the OS Giken Superlock LSD. It has both gears and clutch in the LSD. Supposedly it offers progressive lock but can withstand higher torque levels because of the gear type inside the LSD. The progressive lock is achieved by the clutch plates. Cusco LSD Type RS is also the hybrid type.
Full lock
There's also ratchet types, these are one way gear type LSD. like all gear types, it's full on or full off (full lock la), these are the ones that usually make the sound like your driveshaft is broken.
Why do we need/don't need LSD?
Why do we need to lock the driveshafts is a good question. Most of the time, we don't use LSD, the car also goes straight right? turns pretty well too... so why LSD?
The LSD locks the driveshafts for even distribution of power on the two driveshafts, and this is one of the things a drag racer is looking for. With LSD, torque steer is lessened somewhat (it still happens because the LCA flexes under acceleration, thank you rubber bushings!
)
The word 'lock' is a bit generic, due to the type of LSD, there's partial lock before torque overcomes the clutches, or full lock, where there is no slip. But even when I say no slip, there's always a little slip to preserve the LSD and driveshafts. A true no slip full lock 2 way is the solid axle type cars. But 2 ways are not full lock LSDs.
Situations where LSD is needed
For track racers, some of their cars are running short stroke suspension setups, which means a lot of time when railing/attacking the corners at high speed, one tire is up in the air. If you try that without an LSD, you will hit the car on the outside lane. What happens on cars without LSD is, when one wheel is up in the air, the other wheel has ZERO power. This is why you get stuck in the sand with one wheel spinning, if you're a beach goer.
When driving and one wheel is up, your car will understeer, and for most people that get the 'terbabas' accident, this is most probably what happened when they couldn't make the corner after entering the corner at high speed. (another would be because they slammed the brakes, but even if they didn't brake, the lack of LSD will make the car corner wide, and you'd go out of the track/road and into the parit or guardrail, roti canai shop, etc. etc.
This is something that needs to be experienced to know why LSD is a good thing to have, esp. on a front wheel drive car that's driven faster than average. :camo: ...................................................On the track.
Then one of the reasons LSDs finally for even braking performance. Since it's rainy season, I'm sure some of you have driven on the wet, and when you brake, you notice that sometimes one of the wheel locks earlier than the other. (if it doesn't, you're not driving fast enough) This is why there's the 1.5 / 2 way LSD.
What it does it lock the driveshafts when braking/coasting. The 2 way has full lock the moment you release throttle (whether you coast or you brake, it locks., while the 1.5way only provide partial lock for braking/coasting.) 2 way.
The LSD is an interesting part because it's non electronic, yet by design, it can detect whether you are on throttle, off throttle, or braking, all without using electronic sensors. (it uses inertia and torque input)
For a street car, you won't drive fast enough to actually need an LSD. For high hp cars, it starts to be a requirement because it doesn't take much to get wheelspin.
In the end, LSD needs to be experienced to feel the difference. I've driven an EK with OS Giken Superlock LSD, and the most apparent is probably the heavier steering feel when the LSD fully locks, and even at higher speeds, you can pull the car past any corner by simply whacking the throttle. It's like the car is on rails.
An EK with the type R LSD, at slow speeds, corners wider than a stock EK without LSD. at higher speeds, that's where the difference of having LSD will show. The EK with type R can turn sharper than one without as the speeds are higher.
My own car, the EG, without LSD, turns like crap at high speeds, understeer is obvious, and although I want an LSD, I'll only get it once I sort out a custom ratio gearbox. I'll need at least 7K to do it right (sans labour) Obviously I'm not talking about used LSD units with that kind of money. Slow slow jimat ler.
That's why I bought the EG rather than EK, and if the CRX parts were easily sourceable, I'd gone with that instead. If you want to mod a car, it only makes sense to go with the cheapest chassis you can get, because the performance parts will not be cheap.
Oh, and about LSD noise. It depends on the oil you use, and also the type of LSD. Gear LSDs can be quiet. Rathet type LSDs are the loudest, and also the most stressfull on the bushes, if you've seen a full lock ratchet type LSD in action you can actually see the wheel shaking with the ugly ('ktang! ktang!) sound as it does a turn under throttle. Some clutch types also can make noise, depending on the type of clutch pack they use. (I forget if it was the metal or the carbon type clutch pack that makes noise.)
Actually the OS giken full lock also makes noise, but it depends on how much torque, because at low torque, it's like a clutch type limited slip. The one I drove, at low rev and low torque (higher gear), it feels like a normal LSD, but at high torque (lower gear, high rev.) you do get the ratcheting sound, but not as loud as true one way full locks.
The OS sells the spring so you can custom tune the point where the LSD locks fully, but the price is $$$$$$$$$$$$$$$$
It's because of the wear and tear on the LSD, and also the thickness of the transmission fluid. thick enough, even a one way will behave like a two way.
Worn LSDs also sometimes appear like non-LSD gearboxes, and even a stock non-LSD can act like a one way (when driving, it will be apparent, because you can't apply torque by hand like the engine can with the gears on the wheels, and it's also by nature of the LSD to detect torque input via the spider gears and identify where the torque is coming from.)
So i queried about it to my mech friend, and he borrowed me a book on LSD. I've finished it a while back, but didn't really feel like posting about it because 'LSDs are damn expensive!' and most people don't have them, or are running the stock R ones. Even I consider it expensive. starting at 2.8K to the 3-4K OS Giken/Cusco LSD.
There are many types of LSD, clutch, gear and viscous.
Clutch type
Clutch type uses plates to lock the left and right driveshaft together, the plates have different types of compound (metal, carbon, etc) based on what kind of 'locking' the driver is looking for. Clutch has one advantage that gear doesn't, and that is progressive locking (low torque, slight slip, high torque, near zero slip). the higher the torque exposed to the LSD, the tighter it locks the left and right driveshaft, but too much, the clutch will slip.. it's just the way it is, and that's why clutch LSD are 'maintainance' items. You're supposed to service them at intervals.
Gear/Helicals
There's gear type, which is called helicals, honda stock LSDs are of this type, and so are Quaife™. These are almost maintainance free LSDs, but they can break once the teeth wears on the gears. Quaife is supposedly stronger than the R because they have more spider gears than the stock R, but since never opened/seen Quaife LSD before, dunno.., sorry! Gear types are usually one way only, there are exceptions, (see hybrid LSDs)
Viscous
Viscous, uses oil. When the gears spin, and the heat from differential is great enough, the viscous turns hard into something like thick gel. this locks the driveshafts. Other than that, I don't really care, because
a) I don't know, lol.
b) viscous is considered a lousy LSD, it exists because it's easier for beginners, slow speed, the car acts like it has no LSD (sharp cornering at slow speeds, even sharper than clutch/helical LSD.)
Hybrid LSDs
There's also hybrid LSD, using clutch and gear. This one, you won't find info on the net (except maybe from OS giken themselves), because most of the articles on the net are very very old, taken from one forum, cut and paste into another forum/article. It's not exactly new technology, but probably came into existence in the late 90's early 2000.
And example of this is the OS Giken Superlock LSD. It has both gears and clutch in the LSD. Supposedly it offers progressive lock but can withstand higher torque levels because of the gear type inside the LSD. The progressive lock is achieved by the clutch plates. Cusco LSD Type RS is also the hybrid type.
Full lock
There's also ratchet types, these are one way gear type LSD. like all gear types, it's full on or full off (full lock la), these are the ones that usually make the sound like your driveshaft is broken.
Why do we need/don't need LSD?
Why do we need to lock the driveshafts is a good question. Most of the time, we don't use LSD, the car also goes straight right? turns pretty well too... so why LSD?
The LSD locks the driveshafts for even distribution of power on the two driveshafts, and this is one of the things a drag racer is looking for. With LSD, torque steer is lessened somewhat (it still happens because the LCA flexes under acceleration, thank you rubber bushings!
)The word 'lock' is a bit generic, due to the type of LSD, there's partial lock before torque overcomes the clutches, or full lock, where there is no slip. But even when I say no slip, there's always a little slip to preserve the LSD and driveshafts. A true no slip full lock 2 way is the solid axle type cars. But 2 ways are not full lock LSDs.
Situations where LSD is needed
For track racers, some of their cars are running short stroke suspension setups, which means a lot of time when railing/attacking the corners at high speed, one tire is up in the air. If you try that without an LSD, you will hit the car on the outside lane. What happens on cars without LSD is, when one wheel is up in the air, the other wheel has ZERO power. This is why you get stuck in the sand with one wheel spinning, if you're a beach goer.
When driving and one wheel is up, your car will understeer, and for most people that get the 'terbabas' accident, this is most probably what happened when they couldn't make the corner after entering the corner at high speed. (another would be because they slammed the brakes, but even if they didn't brake, the lack of LSD will make the car corner wide, and you'd go out of the track/road and into the parit or guardrail, roti canai shop, etc. etc.
As for cornering performance, driving without LSD would be like driving, high speed entry, corner, and suddenly the car goes wide, even though you're already flooring the throttle, and you can see the RPM climbing faster than the speed (this is the time when you let off the throttle or else you miss the turn). That's because all the power goes to the wheel that's slipping, not the wheels that are gripping. Understeer! (and at high speeds, it's pretty scary)
For those that kena before,
This is also why when you blow a front tire on a front wheel drive car, you can't really accelerate anymore, esp. when one of your front wheel is off the ground. Forget engine braking too, it won't happen. Any engine braking will just spin the blown tire wheel that's not touching the ground. Brake and handbrake is the best you can manage. I experienced this on a friend's car that was using 2nd hand tires that he bought for 40bucks each. Lesson learnt, I never use used tires on my ride, even if buying new tires means reducing my modding budget..The tires that came with my EK9 wheels, I tossed the moment I got new RT215s in. New tires that aren't run to the metal radials usually won't blow, but it's not a 100% sure thing, isn't it? Anyway, my tires are never 2+ years old. oldest is so far a year an a half, and I already reached the wear limit.
This is something that needs to be experienced to know why LSD is a good thing to have, esp. on a front wheel drive car that's driven faster than average. :camo: ...................................................On the track.
Then one of the reasons LSDs finally for even braking performance. Since it's rainy season, I'm sure some of you have driven on the wet, and when you brake, you notice that sometimes one of the wheel locks earlier than the other. (if it doesn't, you're not driving fast enough) This is why there's the 1.5 / 2 way LSD.
What it does it lock the driveshafts when braking/coasting. The 2 way has full lock the moment you release throttle (whether you coast or you brake, it locks., while the 1.5way only provide partial lock for braking/coasting.) 2 way.
The LSD is an interesting part because it's non electronic, yet by design, it can detect whether you are on throttle, off throttle, or braking, all without using electronic sensors. (it uses inertia and torque input)
For a street car, you won't drive fast enough to actually need an LSD. For high hp cars, it starts to be a requirement because it doesn't take much to get wheelspin.
In the end, LSD needs to be experienced to feel the difference. I've driven an EK with OS Giken Superlock LSD, and the most apparent is probably the heavier steering feel when the LSD fully locks, and even at higher speeds, you can pull the car past any corner by simply whacking the throttle. It's like the car is on rails.
An EK with the type R LSD, at slow speeds, corners wider than a stock EK without LSD. at higher speeds, that's where the difference of having LSD will show. The EK with type R can turn sharper than one without as the speeds are higher.
My own car, the EG, without LSD, turns like crap at high speeds, understeer is obvious, and although I want an LSD, I'll only get it once I sort out a custom ratio gearbox. I'll need at least 7K to do it right (sans labour) Obviously I'm not talking about used LSD units with that kind of money. Slow slow jimat ler.
That's why I bought the EG rather than EK, and if the CRX parts were easily sourceable, I'd gone with that instead. If you want to mod a car, it only makes sense to go with the cheapest chassis you can get, because the performance parts will not be cheap.
Oh, and about LSD noise. It depends on the oil you use, and also the type of LSD. Gear LSDs can be quiet. Rathet type LSDs are the loudest, and also the most stressfull on the bushes, if you've seen a full lock ratchet type LSD in action you can actually see the wheel shaking with the ugly ('ktang! ktang!) sound as it does a turn under throttle. Some clutch types also can make noise, depending on the type of clutch pack they use. (I forget if it was the metal or the carbon type clutch pack that makes noise.)
Actually the OS giken full lock also makes noise, but it depends on how much torque, because at low torque, it's like a clutch type limited slip. The one I drove, at low rev and low torque (higher gear), it feels like a normal LSD, but at high torque (lower gear, high rev.) you do get the ratcheting sound, but not as loud as true one way full locks.
The OS sells the spring so you can custom tune the point where the LSD locks fully, but the price is $$$$$$$$$$$$$$$$
