LSD and Autocross
12-10-2003, 05:16 PM
#16
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Dear Jeff,
Part number would solve the issue for you.
Dear Jim,
I am afraid those statements are not entirely accurate. The 40% was available for the C2 for model year 1990 only. It was also available as an optional option for the Carrera RS and the Carrera Cup. How many RSAs are fitted with 40% lock from the factory?
Ciao,
Adrian
964C4
PS: I should also point out that the 40% and the 20-100% are fully interchangeable. The data I provide is what rolled out the factory and what was offered via the spares department. There was nothing stopping somebody asking for an exchange or fitting a 40% later or whatever. However as options offered my statement above is correct. In my book I actually use the breakdown of the 40% lock for the racers really. The key is what was offered with the transmission not with the model.
Part number would solve the issue for you.
Dear Jim,
I am afraid those statements are not entirely accurate. The 40% was available for the C2 for model year 1990 only. It was also available as an optional option for the Carrera RS and the Carrera Cup. How many RSAs are fitted with 40% lock from the factory?
Ciao,
Adrian
964C4
PS: I should also point out that the 40% and the 20-100% are fully interchangeable. The data I provide is what rolled out the factory and what was offered via the spares department. There was nothing stopping somebody asking for an exchange or fitting a 40% later or whatever. However as options offered my statement above is correct. In my book I actually use the breakdown of the 40% lock for the racers really. The key is what was offered with the transmission not with the model.
Last edited by Adrian; 12-10-2003 at 05:35 PM.
12-12-2003, 12:48 PM
#17
Rennlist Member
To answer the question LSD or no LSD for autocross, ask yourself the question: "Am I spinning the unloaded inside rear wheel on corner exit?"
If the answer is: "YES", then you 'may' turn FASTER times with a LSD. I use the conditional 'may' because you also have to ask yourself: "Do I autocross a lot of very tight corners that I understeer in, and have a hard time getting the car to rotate?". If the answer to this is "Yes", then you may be SLOWER with a LSD.
This is because the increased corner exit speed advantage is lost turning the car into the corner.
My car came with the 20/100 LSD, which for autocross was exactly what you don't want since you drive into the corner with the differential choosing a 100% locking factor trying to keep the rear wheels turning at the same speed just when you want them to turn at different speeds as the car rotates. Then when you put your foot down the car still spins the inside rear wheel since then the locking factor is only 20%. I changed to a 40/65 Porsche Motorsport LSD and things work much better.
Having said all that, my bet would be for most courses in autocross your times would improve with a 40% LSD, if the answer to the question on wheel spin is: "Yes".
If the answer is: "YES", then you 'may' turn FASTER times with a LSD. I use the conditional 'may' because you also have to ask yourself: "Do I autocross a lot of very tight corners that I understeer in, and have a hard time getting the car to rotate?". If the answer to this is "Yes", then you may be SLOWER with a LSD.
This is because the increased corner exit speed advantage is lost turning the car into the corner.
My car came with the 20/100 LSD, which for autocross was exactly what you don't want since you drive into the corner with the differential choosing a 100% locking factor trying to keep the rear wheels turning at the same speed just when you want them to turn at different speeds as the car rotates. Then when you put your foot down the car still spins the inside rear wheel since then the locking factor is only 20%. I changed to a 40/65 Porsche Motorsport LSD and things work much better.
Having said all that, my bet would be for most courses in autocross your times would improve with a 40% LSD, if the answer to the question on wheel spin is: "Yes".
Last edited by Cupcar; 12-12-2003 at 01:06 PM.
12-12-2003, 01:29 PM
#18
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Join Date: Oct 2003
Location: Renotn, WA
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Thanks everyone. As usual I learn a ton every time I log on; there is a lot of great knowledge here. I am still looking for my first Porsche, I see a lot of nice one’s but not as many that have LSD. I thought I really wanted the LSD, but maybe I shouldn’t worry about it. I wouldn’t use the car for racing but I might use it for DE or Autocross. Ahhh, more to ponder. Thanks again.
