Factory LSD
12-01-2007, 02:12 AM
#1
Burning Brakes
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Factory LSD
How good is the factory LSD in the 964? For those that have it - how desireable would it be in your used car search if you were buying again? Does it make a significant difference in the daily driving?
12-01-2007, 05:07 AM
#2
Racer
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For general day to day use you'll never really get to use the diff unless you tend to drive it like you've stolen it. Standard ZF diff from memory has 20% lock under acceleration. For track time you need to alter the ramping to 40% or it will still tend to spin the inside wheel out of a tight corner.
12-01-2007, 09:34 AM
#3
Nordschleife Master
The G50/03 and 05 have a 40/40 locking differential, the G50/10 has a 20/100. My opinion is that the 40/40 is the better one. The diffs have friction plates that wear out, but can be replaced easily. Personally, I would not buy a sports car without an LSD. Look for option code 220.
12-01-2007, 12:20 PM
#4
If you find a nice car w/o lsd, it can be added later.
even if the car you buy has one it may(probably will) be in need of a rebuild. GT can rebuild a stock 40% 2 plate to 40% 4 plate. It makes for a much more effective lsd.
If adding one to an open diff, the later 40/60, 40/65, 50/80 4 plates would be very desireable.
even if the car you buy has one it may(probably will) be in need of a rebuild. GT can rebuild a stock 40% 2 plate to 40% 4 plate. It makes for a much more effective lsd.
If adding one to an open diff, the later 40/60, 40/65, 50/80 4 plates would be very desireable.
12-01-2007, 03:54 PM
#6
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12-01-2007, 05:15 PM
#9
RL Community Team
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The C4 has 0-100% variable locking based on the PDAS function; it's a regular open differential when the PDAS is not working...
(rear and middle differentials apply - the front is an open differential)
(rear and middle differentials apply - the front is an open differential)
12-01-2007, 05:52 PM
#10
Rennlist Member
I have a book from the SAE by Peter Wright on the Ferrari F1 cars of the early 2000's and Ferrari used exactly the same type of differential as the C4 in that car. I think Ferrari also use this type of differential in the latest 430 street cars. They call it "E diff" and it integrates steering angle as well as other inputs to calculate the lock percentage and I understand it works very cool.
It is sad that Porsche has walked away from this clever stuff. I understand that one of the reasons that a real LSD is not available on most of the latest Porsche cars is because of the interaction of the LSD with PSM since the PSM can apply braking to one rear wheel which would drive a tightly set up LSD nuts.
The solution would be a differential that could be integrated into the PSM package which the C4 type differential could be.
Alas, Porsche once the master engineering company now the master marketing company...
12-01-2007, 06:28 PM
#12
Rennlist Member
Quaifes work great, particularly for autocross, but one doesn't get the lockup under braking that helps stabilize the car that a variable lock diff gives.
How does one test a variable lock differential for wear?
It seems without the appropriate loading of the plates by engine drag/drive torque the diff would be open and the diff would allow the opposite wheel to turn in the opposite direction when unloaded on a lift indicating the diff was worn when it was OK, wouldn't it?
.
How does one test a variable lock differential for wear?
It seems without the appropriate loading of the plates by engine drag/drive torque the diff would be open and the diff would allow the opposite wheel to turn in the opposite direction when unloaded on a lift indicating the diff was worn when it was OK, wouldn't it?
.
Last edited by Cupcar; 12-01-2007 at 09:03 PM.
12-01-2007, 08:31 PM
#13
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This C4 type LSD is really the coolest differential of all. It works by using the high pressure hydraulic system of the C4 (also used in the braking system and the middle differential) to vary the pressure on the friction plates. This is all controlled by a microprocessor and the lock can be 0 to 100% depending on need.
I have a book from the SAE by Peter Wright on the Ferrari F1 cars of the early 2000's and Ferrari used exactly the same type of differential as the C4 in that car. I think Ferrari also use this type of differential in the latest 430 street cars. They call it "E diff" and it integrates steering angle as well as other inputs to calculate the lock percentage and I understand it works very cool.
It is sad that Porsche has walked away from this clever stuff. I understand that one of the reasons that a real LSD is not available on most of the latest Porsche cars is because of the interaction of the LSD with PSM since the PSM can apply braking to one rear wheel which would drive a tightly set up LSD nuts.
The solution would be a differential that could be integrated into the PSM package which the C4 type differential could be.
Alas, Porsche once the master engineering company now the master marketing company...
I have a book from the SAE by Peter Wright on the Ferrari F1 cars of the early 2000's and Ferrari used exactly the same type of differential as the C4 in that car. I think Ferrari also use this type of differential in the latest 430 street cars. They call it "E diff" and it integrates steering angle as well as other inputs to calculate the lock percentage and I understand it works very cool.
It is sad that Porsche has walked away from this clever stuff. I understand that one of the reasons that a real LSD is not available on most of the latest Porsche cars is because of the interaction of the LSD with PSM since the PSM can apply braking to one rear wheel which would drive a tightly set up LSD nuts.
The solution would be a differential that could be integrated into the PSM package which the C4 type differential could be.
Alas, Porsche once the master engineering company now the master marketing company...
12-01-2007, 10:29 PM
#14
Three Wheelin'
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You don't ? I've driven several cars....and am sure that it is there. Drive at 50-70 kmh (for example) and take your foot off the gas without touching the brakes and you can feel the thing do it. Unless you are talking about something completely different.
12-01-2007, 11:23 PM
#15
I don't know what you are feeling, but it is not the result of a gear type lsd in action. They only work to limit side to side axle speed difference on acceleration. They revert to open on deceleration. The gears only transmit torque in 1 direction.