LSD option - Wavetrac Differentials?
09-28-2011, 03:01 PM
#16
This didn't cost
me any drachmas
Rennlist Member
me any drachmas
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Thread Starter
Regardless of the direction of the "debate", I'm still getting a Wavetrac for my 951 and Bronco. I've read enough reviews about how it works for daily driving, modest track duty, and off-roading that it'll fit my needs perfectly.
Now, if only they'd lower the price!
Now, if only they'd lower the price!
09-28-2011, 03:28 PM
#18
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Ah! You're basing all this on wikipedia. Yes, the entry is incorrect in a lot of substantial ways. What's interesting about wikipedia is that as misinformation or incorrect terms get propagated there, they become "truth." The world would be simpler if we all stuck to proper definitions rather than convoluted ones.
Here's a simple version of the original definition:
http://www.guardtransmission.com/tech_faq.html
It seems like you're getting very upset by all this, but you really don't know how these things work. Here's the thing, that's ok. If the differences don't matter to you, then they don't and you can use whatever term you like!
Here's a simple version of the original definition:
http://www.guardtransmission.com/tech_faq.html
It seems like you're getting very upset by all this, but you really don't know how these things work. Here's the thing, that's ok. If the differences don't matter to you, then they don't and you can use whatever term you like!
you are also mistaken about how wikipedia works. Strike Two!
09-28-2011, 03:53 PM
#19
Rennlist Member
09-28-2011, 04:32 PM
#20
So would a Torque Biasing diff help in situations where one wheel is spinning and the other has traction. If you were in snow or slipping in rain it would spin both tires instead of the one with the least amount of traction.
09-28-2011, 04:47 PM
#21
Rennlist Member
Clutch pack style mechanical diffs are the way to go if you dont mind thumps and clunks as it locks/unlocks. Torsens are more daily driver friendly.
09-28-2011, 05:58 PM
#22
This didn't cost
me any drachmas
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me any drachmas
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Thread Starter
The advantage of the Wavetrac is that is doesn't leave you with an "open diff" like traditional limited slip's behave when one tire is off the ground and spinning. That's how we got to discussing it for my Bronco when off-roading vs. the stock Ford LSD which leaves you stuck like a pig in the mud when one wheel is off of the ground. I really loved the factory quaife style out of Type R that I put in EM1 and the factory LSD that came in my Starion but, alas, neither went off-road in deep mud/ice/snow (well, I did take my EM1 off-road quite a bit in PA for work up to cell towers).
So, I then found it for the 951 and decided it was a good option and still do. Heck, if LR has it for sale, then it must be a worthwhile option.
So, I then found it for the 951 and decided it was a good option and still do. Heck, if LR has it for sale, then it must be a worthwhile option.
09-28-2011, 08:08 PM
#23
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09-28-2011, 10:27 PM
#24
The advantage of the Wavetrac is that is doesn't leave you with an "open diff" like traditional limited slip's behave when one tire is off the ground and spinning. That's how we got to discussing it for my Bronco when off-roading vs. the stock Ford LSD which leaves you stuck like a pig in the mud when one wheel is off of the ground. I really loved the factory quaife style out of Type R that I put in EM1 and the factory LSD that came in my Starion but, alas, neither went off-road in deep mud/ice/snow (well, I did take my EM1 off-road quite a bit in PA for work up to cell towers).
So, I then found it for the 951 and decided it was a good option and still do. Heck, if LR has it for sale, then it must be a worthwhile option.
So, I then found it for the 951 and decided it was a good option and still do. Heck, if LR has it for sale, then it must be a worthwhile option.
09-29-2011, 09:34 PM
#25
Three Wheelin'
-----------------------
You seem to have a good understanding of the Wavetrac diff. Have you ever driven a Wavetrac equipped car on a road course?
Here is what Wavetrac says about their torsen type diff in deceleration mode.
"In the case where both wheels are on the ground during zero axle load, such as during a transition to deceleration, the Wavetrac® device is able to prepare the drivetrain for when the zero torque condition stops, eliminating the delay seen with ordinary gear diffs.
What this means for you as a driver is that power is delivered to the gripping wheels for more time and in a more constant manner – making you faster and improving stability."
You seem to have a good understanding of the Wavetrac diff. Have you ever driven a Wavetrac equipped car on a road course?
Here is what Wavetrac says about their torsen type diff in deceleration mode.
"In the case where both wheels are on the ground during zero axle load, such as during a transition to deceleration, the Wavetrac® device is able to prepare the drivetrain for when the zero torque condition stops, eliminating the delay seen with ordinary gear diffs.
What this means for you as a driver is that power is delivered to the gripping wheels for more time and in a more constant manner – making you faster and improving stability."
However, said wheels will only lock up during acceleration; they will not lock the drive wheels together during deceleration like a clutch-type limited slip diff will.
If you only do auto-X and street and maybe light track/DE events, a TBD like the Wavetrac will be perfect. No unwanted understeer mid-corner in tight turns from the rear wheels locking together like an aggressive LSD will. Heavy track use, you DEFINITELY want those wheels to lock on decel, makes the car much more stable under heavy braking and allows you to trail-brake aggressively. I notice the difference even with the wimpy 40% stock LSD in my 951. This is even more important in a mid or rear engined car.
Which leads us to the nomenclature: LSD=limited slip differential, which implies the clutch-type differential. It is called "limited" slip because although the wheels will partially lock together during acceleration/deceleration, they do not FULLY lock together in most cases. The friction discs are still slipping somewhat, which is why they eventually wear out, and why a transmission cooler is a good idea in an LSD car as the fluid gets very hot from the slippage (and why you should change it at least once a year if you track your car often).The optional LSD from the factory on the 951, which my car has, locks up only 40% on either acceleration or deceleration. This lockup ratio depends on the curvature of that ramps that the spider/pinion gear shafts ride in, and on the preload of the friction discs. Guard offers 40/60 (meaning 40% lockup on acceleration and 60% lockup on deceleration) and 50/80 for serious track use.
TBD=torque biasing differential, which the Torsen gear/helical type diff is one type, and the Wavetrac is another. They progressively lock up with increased torque, but only under acceleration.
Here is a link from Guard's site further explaining the difference:
http://www.guardtransmission.com/tech_faq.html
Oh yeah, one more thing, DO NOT weld your spider gears together! The inside wheel will hop around tight turns and the car will understeer like a pig.
09-30-2011, 12:30 AM
#26
Drifting
Oh yeah, one more thing, DO NOT weld your spider gears together! The inside wheel will hop around tight turns and the car will understeer like a pig.[/QUOTE]
This was supposed to make us laugh. My current offroad beast is a Toyota (Lexus) LX470 with most of www.sleeoffroad.com stuff. My differentials are open, when the computer senses wheelspin, it immediately locks the spinning wheel to the other many times a second. It's almost like having "welded" or locked axles. The beauty of this electronic locking device is that any wheel off the ground electronically puts the power to the other side of the axle MANY times a second. Trust me, it sounds weird till you get used to it.
You can still turn your wheel with ease. When my center diff is locked, and have one wheel on the ground, that's the one that gets the power. This system won't work well with a car moving over 100mph in a corner, as it uses the abs braking system to lock the wheel without traction. In slow, offroad steep climbs, or muddy ****, it works better than anything I've used to date. This includes ARB air locks, unless you are doing serious rock climbing.
Porsche delivered their cars with both torsen and the clutch type LSD units. All competitive motorsports transmissions have the clutch type LSD as delivered from Porsche. Some of the 968 cars had the torsion unit as delivered and it was better than an open differential. As long as you only care about straight line traction, you are fine. If you want both drive wheels to also act like a brake on deceleration, you have other options. My LSD is a factory type clutch LSD that has been rebuilt and is now in my 968 G44 (G50) box. I am also using a 997 Porsche PP, and sport clutch disc. What I've copied is courtesy of Ebodymotion. I quote from their website:
In the past, we used torsen or torque-sensing differentials, made by various manufacturers, Gleason and Quaiffe being most familiar to correct the loss of traction. These differentials seemed to be the end-all. After all what could possibly be better than a unit that actually sensed the torque, and applied it opposite to the wheel that slipped? The key with torque-biasing differentials is that the wheels must remain in contact with the pavement; even a minuscule amount of traction is needed to engage the diff. Early 911's flexed enough and kept the rear wheels on the ground maintaining the miniscule amount of traction needed (just look at the inside front tires off the ground in older 911s when racing). When the 944 turbo came around, with its stiffer chassis, cars would lift a rear tire in tight or bumpy corners and the torque sensing diffs were no good. We learned this first hand when we built the first Mini Cooper S's for Grand Am. Same problem with front wheel drive, when one drive wheel looses contact with the track, say over a curb or bump, all the torque went to that wheel.
Moving onto the GT3's and their limited slip differentials. A limited slip is a clutch type differential that, with stiff chassis 996/997 based cars, over curbs and in corners, is designed to apply the same force to both rear wheels. Porsche uses a four clutch disc pack in all GT3's. If you jack up one side of a GT3, put a torque wrench on one rear wheel axle nut, you may find it takes less than 20 pounds feet of torque to turn one rear wheel. That's called the breakaway torque. And, that's on a brand new 997. We have checked the differential breakaway torque on two dozen 996/997 GT3 street cars and after one or more track weekends the preload torque is at or near zero. Keep in mind, there are ramps inside the differential that, when drive, or accelerating force is applied, it forces the differential clutches to bind up and act to lock up the rear. However, little or no lock up occurs on deceleration. So, on hard braking, as the weight goes to the front wheels the rears get light, and the inside rear wheel will temporarily lose traction. This causes a slower entry into the corner and generally you will feel the anti-lock brakes engage when this occurs. But what if we could get the differential, to partially engage on deceleration and engage more aggressively the harder we accelerate off a corner, this would be having your cake and eating it too, wouldn't it? You bet it would!
The expensive solution was discovered by all of the long distance enduro GT3 Cup cars years ago. Install a billet, fully adjustable Guard limited slip differential. This nearly indestructible unit is also available for the street cars. Keep in mind, this solution requires removal and disassembly of the entire transaxle. However, the cost of the unit and labor can exceed $7500. This is a bit of over kill for street, track days and even club racing. The expense of the billet housing is way beyond most club race GT3 budgets.
However, using the same technology and top quality parts we can improve your differential beyond its original ability, and make it last for many track days. We can remove your differential (without removing the entire transaxle) and build the same adjustable ramp diff as the pro's have. The adjustable ramps in this unit allow for 40% lock on acceleration and 60% on deceleration. For more aggressive situations the same diff can be set to 50% acceleration and 80% deceleration. The friction plates in the new diff are far stronger than the Porsche factory parts and won't show near the fade. The break away torque is set to 80 pounds feet new, and after a few track miles they settle in at around 60-80 pounds.
Regards,
George
This was supposed to make us laugh. My current offroad beast is a Toyota (Lexus) LX470 with most of www.sleeoffroad.com stuff. My differentials are open, when the computer senses wheelspin, it immediately locks the spinning wheel to the other many times a second. It's almost like having "welded" or locked axles. The beauty of this electronic locking device is that any wheel off the ground electronically puts the power to the other side of the axle MANY times a second. Trust me, it sounds weird till you get used to it.
You can still turn your wheel with ease. When my center diff is locked, and have one wheel on the ground, that's the one that gets the power. This system won't work well with a car moving over 100mph in a corner, as it uses the abs braking system to lock the wheel without traction. In slow, offroad steep climbs, or muddy ****, it works better than anything I've used to date. This includes ARB air locks, unless you are doing serious rock climbing.
Porsche delivered their cars with both torsen and the clutch type LSD units. All competitive motorsports transmissions have the clutch type LSD as delivered from Porsche. Some of the 968 cars had the torsion unit as delivered and it was better than an open differential. As long as you only care about straight line traction, you are fine. If you want both drive wheels to also act like a brake on deceleration, you have other options. My LSD is a factory type clutch LSD that has been rebuilt and is now in my 968 G44 (G50) box. I am also using a 997 Porsche PP, and sport clutch disc. What I've copied is courtesy of Ebodymotion. I quote from their website:
In the past, we used torsen or torque-sensing differentials, made by various manufacturers, Gleason and Quaiffe being most familiar to correct the loss of traction. These differentials seemed to be the end-all. After all what could possibly be better than a unit that actually sensed the torque, and applied it opposite to the wheel that slipped? The key with torque-biasing differentials is that the wheels must remain in contact with the pavement; even a minuscule amount of traction is needed to engage the diff. Early 911's flexed enough and kept the rear wheels on the ground maintaining the miniscule amount of traction needed (just look at the inside front tires off the ground in older 911s when racing). When the 944 turbo came around, with its stiffer chassis, cars would lift a rear tire in tight or bumpy corners and the torque sensing diffs were no good. We learned this first hand when we built the first Mini Cooper S's for Grand Am. Same problem with front wheel drive, when one drive wheel looses contact with the track, say over a curb or bump, all the torque went to that wheel.
Moving onto the GT3's and their limited slip differentials. A limited slip is a clutch type differential that, with stiff chassis 996/997 based cars, over curbs and in corners, is designed to apply the same force to both rear wheels. Porsche uses a four clutch disc pack in all GT3's. If you jack up one side of a GT3, put a torque wrench on one rear wheel axle nut, you may find it takes less than 20 pounds feet of torque to turn one rear wheel. That's called the breakaway torque. And, that's on a brand new 997. We have checked the differential breakaway torque on two dozen 996/997 GT3 street cars and after one or more track weekends the preload torque is at or near zero. Keep in mind, there are ramps inside the differential that, when drive, or accelerating force is applied, it forces the differential clutches to bind up and act to lock up the rear. However, little or no lock up occurs on deceleration. So, on hard braking, as the weight goes to the front wheels the rears get light, and the inside rear wheel will temporarily lose traction. This causes a slower entry into the corner and generally you will feel the anti-lock brakes engage when this occurs. But what if we could get the differential, to partially engage on deceleration and engage more aggressively the harder we accelerate off a corner, this would be having your cake and eating it too, wouldn't it? You bet it would!
The expensive solution was discovered by all of the long distance enduro GT3 Cup cars years ago. Install a billet, fully adjustable Guard limited slip differential. This nearly indestructible unit is also available for the street cars. Keep in mind, this solution requires removal and disassembly of the entire transaxle. However, the cost of the unit and labor can exceed $7500. This is a bit of over kill for street, track days and even club racing. The expense of the billet housing is way beyond most club race GT3 budgets.
However, using the same technology and top quality parts we can improve your differential beyond its original ability, and make it last for many track days. We can remove your differential (without removing the entire transaxle) and build the same adjustable ramp diff as the pro's have. The adjustable ramps in this unit allow for 40% lock on acceleration and 60% on deceleration. For more aggressive situations the same diff can be set to 50% acceleration and 80% deceleration. The friction plates in the new diff are far stronger than the Porsche factory parts and won't show near the fade. The break away torque is set to 80 pounds feet new, and after a few track miles they settle in at around 60-80 pounds.
Regards,
George
09-30-2011, 01:34 AM
#27
Drifting
Quote from George D: Porsche delivered their cars with both torsen and the clutch type LSD units. All competitive motorsports transmissions have the clutch type LSD as delivered from Porsche. Some of the 968 cars had the torsion unit as delivered and it was better than an open differential. As long as you only care about straight line or corner traction under power, you are fine. If you want both drive wheels to also act like a supplemental brake on deceleration, you have other options. My LSD is a factory type clutch LSD that has been rebuilt and is now in my 968 G44 (G50) box.
I think Wavetrac is making a great product, as long as you are providing power to the wheels, no matter which ones, if not all. Trust me, I wished they had these when I was running GTI cars.
When downshifting while using engine braking with brake pedal, it's nice to feel both or all contact patches "tires" helping with braking. Only a clutch type LSD will do this.
I run a Kawasaki KQ modded 750, and trust me, without a true clutch plate engine braking LSD on all wheels, I'd never do well in the descent part of our events. Full bore power, fine, braking without a consistent braking LSD, I'd just be working my handle brakes with too much locking on the front, because the rear brakes will kill you on a fast downgrade. A good LSD gives you traction on power, and suppemential braking on deceleration. I can go full throttle on a descent, and allow my diff to brake without using much braking effort. Makes me much faster.
A tq biased diff is open without power to the wheels.
Still, the new Wavetrec is better than what Porsche delivered within some of their cars with a factory LSD.
If it was my decision, I'd spend the few extra bucks and get a clutch type true LSD.
George
I think Wavetrac is making a great product, as long as you are providing power to the wheels, no matter which ones, if not all. Trust me, I wished they had these when I was running GTI cars.
When downshifting while using engine braking with brake pedal, it's nice to feel both or all contact patches "tires" helping with braking. Only a clutch type LSD will do this.
I run a Kawasaki KQ modded 750, and trust me, without a true clutch plate engine braking LSD on all wheels, I'd never do well in the descent part of our events. Full bore power, fine, braking without a consistent braking LSD, I'd just be working my handle brakes with too much locking on the front, because the rear brakes will kill you on a fast downgrade. A good LSD gives you traction on power, and suppemential braking on deceleration. I can go full throttle on a descent, and allow my diff to brake without using much braking effort. Makes me much faster.
A tq biased diff is open without power to the wheels.
Still, the new Wavetrec is better than what Porsche delivered within some of their cars with a factory LSD.
If it was my decision, I'd spend the few extra bucks and get a clutch type true LSD.
George
09-30-2011, 12:55 PM
#29
Rennlist Junkie Forever
George is correct about the effectiveness of the Guard LSD differential.
ALL the fast cars on the track run it for the very reason that it's assemetrical in its locking characteristics, which is exactly what you want on the race track. That is... a little lock on acceleration, and a lot of lock on deceleration. It's the decerlation lock that allows you to trail brake deep into a corner without the back end of the car coming around on you.
Historically, you would have to shim up a conventional LSD very tight to get the deceleration lock you needed to effectively trail brake. But when you did that, the car would want to push due to the tight differential. So you were fast in some places, but slow in a lot of places because the car didn't want to turn.
With the Guard LSD, you get the gest of both worlds... lock where you need it under deceleration, and not too much lock under acceleration.
I run a 50/80 in my 951 and as long as your on the gas, the car turns real well. Get off the gas, and the car straightens out. This allows me to literally pitch the car going into a turn wtihout the back end coming around. Pretty amazing really.
As far as cost goes... they are about $2500-$2800 and you can slip them into an existing 951 transaxle pretty easily as long as you don't change the transaxle side plate or change the differential carrier bearings (changing those will cause the R&P lash to change, which gets expensive to shim correctly). I pay about $750 to have the Guard LSD installed into a transaxle that I bring to the shop.
So if you're considering a differential in a car that will ever see track time... it's a mistake to use anything else but a Guard LSD. And even on a street car... that's the only LSD I would use.
TonyG
ALL the fast cars on the track run it for the very reason that it's assemetrical in its locking characteristics, which is exactly what you want on the race track. That is... a little lock on acceleration, and a lot of lock on deceleration. It's the decerlation lock that allows you to trail brake deep into a corner without the back end of the car coming around on you.
Historically, you would have to shim up a conventional LSD very tight to get the deceleration lock you needed to effectively trail brake. But when you did that, the car would want to push due to the tight differential. So you were fast in some places, but slow in a lot of places because the car didn't want to turn.
With the Guard LSD, you get the gest of both worlds... lock where you need it under deceleration, and not too much lock under acceleration.
I run a 50/80 in my 951 and as long as your on the gas, the car turns real well. Get off the gas, and the car straightens out. This allows me to literally pitch the car going into a turn wtihout the back end coming around. Pretty amazing really.
As far as cost goes... they are about $2500-$2800 and you can slip them into an existing 951 transaxle pretty easily as long as you don't change the transaxle side plate or change the differential carrier bearings (changing those will cause the R&P lash to change, which gets expensive to shim correctly). I pay about $750 to have the Guard LSD installed into a transaxle that I bring to the shop.
So if you're considering a differential in a car that will ever see track time... it's a mistake to use anything else but a Guard LSD. And even on a street car... that's the only LSD I would use.
TonyG
09-30-2011, 08:11 PM
#30
Drifting