Larry Herman

Sorry to see them take you out of C. I really would like to have seen how we compared at Watkins Glen where the difference between C and B (the GT3s) was only .4 seconds. Well, I'm starting to get an itch for a 964 Euro cup, so maybe I'm not long for C either.

Geoffrey

I think the aftermarke LSD was a poor choice. I don't see how to determine if you are running the same locking ratio as the factory, in fact, I'm not sure if Quaife or Guard offers the same ratios. This will be too hard to police. How is a scrut going to know if the diff is a 20/100 factory or a 50/80 Guard unit? The performance will be noticable to the driver, but not readily apparent to anyone else. Stock means stock, leave the cars alone.

Greg Fishman

That sucks. I guess you could always put the 3.6 (stock) motor back in.

Would your car have been competitive with the GT3's at Daytona?

Greg Fishman

Isn't a quaiffe open during braking and locked during acceleration?

Geoffrey

Yes, a quaife is completely different in design from the original Porsche unit and by my interpretation of the rules would be illegal.

Larry Herman

No, even with the X51. The GT3s were running 2:04s and Jim's best was a 2:06 & change. Daytona is just a huge HP track. The GT3s were 4 seconds faster than me, and at the Glen they are only .4 faster. Too many high speed corners there that help the lower HP cars keep their momentum up.

Greg Fishman

How would you detect what LSD was in a car without taking something apart?
Speaking for the 993's the stock LSD plates were garbage and wore out very quickly if driven on track. It needs a more robust LSD, and if it is difficult or impossible to detect what LSD someone has in their car then why not just make it an open modification.

Larry Herman

So what you are saying is that if you have a 993 that you race, and the LSD is working, it's illegal?

TheOtherEric

I think the change means that if you weigh 200 lbs, you'll be able to lighten your car next year by 50 lbs. If you weigh 150 lbs, it has no effect on you. Sucks for women and lighter men.

The rule change says: "Add 150 lbs to the minimum weights in all classes that have minimum weights and weigh cars with drivers."

Oddjob

I think there has been some reading between the lines even on the original rule regarding factory LSDs - it didnt say that the factory LSD had to maintain the stock lock %. And it still does not say that an aftermarket LSD has to have factory lock %.

Now Im not saying that I agree or disagree with that interpretation - I just know that it has been interpreted that way....

I agree that the rule still does not allow torque biasing differentials (Quaife, Torsen) in place of the factory clutch type ZF LSDs. I think the only supplier of clutch type LSDs is Guard (which are significantly more expensive than the Torque biasing type).

It is practically impossible to check loaded and unloaded locking %. I guess the only thing you could check is if the car has a torque biasing type diff (in which case the rear wheels have 0% unloaded lock and will spin in opposite directions - but that would also indicate a regular open diff.....)

JimB

I'm going to the bar...

Geoffrey

I am taking issue with a rule that is not possible to police. The wording says "equivalent" which means the same. 50/80 locking ratio is not "equivalent" to a 20/40 stock or 40/40 stock, or 20/100 stock which are the most common locking ratios. The 50/80, 80/80 from Guard and the 40/64 from Porsche Motorsport are NOT equivalent. The real issue here is that the factory plates wear too quickly as Greg pointed out. The rule needs to read something like "the LSD friction material is free" meaning that you can replace the disks with the more robust Porsche Motorsport of Guard parts, leaving the locking ratio alone.

The effect of this rule is nothing, you cannot use an aftermarket LSD and comply with the rule since they don't make one of a) the same material (cast housng), b) in some cases the same size (Guard and PM are larger than the early diff housing), c) plate material (Guard and PM are different material), and d) different locking ratios. Therefore, you cannot use an aftermarket LSD and be 100% compliant with the wording of the rule. My interpretation.

}{arlequin

guess 911's w/ sc motors are still not allowed to run w/ sc's... (i'm running out of "morose" icons )

analogmike

Not true of the earlier diffs like in the 915.

In a stock 915 you can just stack the disks in different orders to get different locking ratios with factory parts. All stock parts, and shown in the factory manual.

The Guard diffs for the 915 are exactly the same and all discs are interchangeable with the stock housing so you can make a guard 915 dif exactly the same as a stock one, or stack the discs for more or less slip just like the stock one.

There is no way to tell from the outside if you have a stock or a guard dif in your 915 if you set them up the same. I was always of the opinion the Guard was legal in a 915 due to this.

A torsen/Quaife was never legal and is still illegal. And not as good anyway on the track.

Dave Parker

I agree with you on this one. I wrote in against this. Older cars (like my SC) don't have the screw in tow bolts ... this will mean that I now have to cut holes in my bumper for a tow hook. The rear and front have both been successfully used, so I totally don't understand the need for this rule.