traveller09

Hello All,

I would think that for all around use (DE, Race, Autocross, daily driver) that a car with LSD would be the preferred option to one that doesn't. But, I have been told that some of the people that are into Autocross prefer Porsches without LSD. Is this true? What would be the reason for not wanting LSD?

Thanks,

David

PS Still looking for a 964, since the one I decided on didn't pass the PPI.

Jeff Curtis

I agree, LSD is the ticket...can't see why anyone would argue that one.

BIG difference when gettin' on the gas amid apex and out of the turn!

Anyone who says otherwise is possibly referring to a higher slip percentage, which would not be advantageous during an autocross. Most factory units are set at 40% I believe...some racers bump up the grip to 60 and 80% - my factory unit is just fine.

Drew_K

I have a 92 C2 w/o LSD and haven't ever had problem with wheel spin at an autocross. I think the real question is whether a 964 will turn a faster autocross time with an LSD. I don't know the answer, but it seems like the times would be the same so long as you aren't getting wheel spin.

The question becomes even more complicated when you consider that there are different types of LSD's, and the type most suitable for autocross isn't the best for track use.

JoeW

Jeff, am I right to understand you that the factory unit is adjustable? If so, I didn't know LSDs could be "adjusted" & hadn't heard that before.

But I'm probably misunderstanding. Nothing new there!! J

chris walrod

the different lock-up percentages are from different ramp angles inside the differential. The more shallow the angle, the more lockup % you get.

An LSD, typically, reduces corner exit steering. It could reduce entry steering, depending on the coast angles of the ramps. I will try to post a sketched cross section of this type of diff. Kinda hard to explain...

Adrian

I am afraid there is a little misunderstanding here.
Firstly the factory optional LSDs are not adjustable.
Secondly, only in model year 1990 was option M220 using a 40% lock LSD.
In model year 1991 this was changed to a 20-100% lock LSD. This was developed for the Turbos and offered for the NAs as well.
The 40% lock LSD could only then be obtained by very special request. It was an option on the Carrera Cups (as against the standard 20-100%) but this was all handled by Porsche Motorsports at Weissach.
The 40% lock was preferred for the track. The 20-100% was designed for road use.
Ciao,
Adrian
964C4

Roygarth

LSD and Autocross???

Don't do it!

Jeff Curtis

...kidding me!??

Piers, you say autocross + LSD is a "no go"??

I've won a few autocrosses in my time...and it's ALWAYS been with a LSD. If I'm not FTD, I'm crawling right up the A** of the person that is.

I remember when I first had my 964, no LSD, would to to track events and spin the inside wheel quite frequently while approaching apex and out of a turn.

Worse at an autocross.

Autocrosses are so short with abrupt turns, in my book a LSD is MANDATORY. Sure, you can control wheelspin by not mashing the pedal on the right as much - but you will be SLOWER.

As for factory LSD units, Adrian, you may be onto something with the G-50 and beyond LSD units - because I really don't know. What I do know is that the factory LSD units available for the 915 are COMPLETELY adjustable with shims.

The G-50 unit I installed looked quite similar to a 915 unit - but then again, I didn't mess with it at all...just lined it up, sealed up the trans. and never looked back.

Chris W. is right on with the description of the basics regarding the inner workings of a LSD unit, but a factory unit for the G-50 isn't going to affect turn-in or exit steering a considerable amount - IMHO.

Christer

Jeff, I would presume that Piers is referring to the pharmaceutical version.

Jeff Curtis

DUH...good one Piers, I'm not awake just yet.

Thanks for "adjusting" my sense of humor this AM.

I feel sooooo stupid!! ...okay, revenge is sweet...I'll get you my pretty!

Adrian

Dear Jeff,
You are quite correct. I have the adjustment process. However this is the 964 forum and not the 911SC forum
Did you know that the Sportomatic 911SC even had a 40% LSD option? and I found one with it.
Ciao,
Adrian
964C4

RSAErick

I was under the impression that in 1993, option 220 was, in fact, a 40% lock LSD.... at least on those very special RS Americas. Probably because Porsche Motorsports at Weissach intended for them to be race cars.



Erick

Adrian

Dear Eric,
I actually thought they supplied the 40-80% adjustable ones for the RSA

Ciao,
Adrian
964C4

Jim Michaels

According to Bob Gagnon's article comparing the C2, RSA, RS, and Carrera Cup USA (Pano, May 1993), the optional LSD for the C2 and RSA was 40% disc, while the standard LSD on the RSs and Cup USAs was 20/100% variable.

A question also came up earlier about suspension bushings; those on the RSA were the same rubber as on the C2, whereas the RS and Cup car had harder rubber bushings.

Jeff Curtis

I'm quite certain my unit is a 40% unit - I did the homework back then (2yrs ago) and seem to remember that's all I found.

...and yes Erick, the RSA is "special"...now WHERE is that icon with the short bus?