Martin S.

It seems that our cars are a bit screwed for PCA Club Racing. In G stock they must compete against 964 RSAmerica cars, which with headers, legal in Stock, allowing the RS America to put out nearly equivalent HP to the heavier 993 car. The factory provides "free" headers for the 993. The 964 is also lighter by over 100 Lbs....so it is a tough row to hoe in G Stock from the get go, at least on paper. With the value of the RS America cars climbing, and with so few built back in the day, it would seem that fewer and fewer folks are willing to take their RS America to the track. So maybe PCA G Stock is a solid place to be...if all you want to do is race with PCA.

KalB mentions that a gear change puts the 993 into GT class...not a good place to be with something other than a full tilt race car. This means that a lot of weight needs to be stripped out of the car...there go those power windows, etc. Change the ring and pinion and you go to PCA Prepared, where you move you move up an alphabet class to H class where there is some stiff competition from late model cars such as the early 996, the 05 - 08 997 cars, Boxster S and and Cayman S cars....this I clearly understand.

Another West Coast Racing Club (Porsche Owners Club) that puts on 9 to 10 track events per year, allows a gear change with a very light penalty. Make the change to gears, you take your alphabet class, in the case of the 993 KI (K Class Improved), and move to KP (Stock, Improved, Prepared, GT). There you'll compete against lightly modified 996 cars with no gear change/ring and pinion change allowed.

So west coast racers wanting to drop $10,000 into their transmissions for a gear change must make up their minds...its either POC where gears are allowed, or PCA, and do battle in GT class. I am on the fence here as the reality of the consequences of a gear change become apparent. The other factor, PCA only holds about 3 races a years in California...I am in the middle of the state. There would be more PCA race opportunities if I were willing to tow to Portland or Utah...that is a haul.

POCs rolling race starts are at 55 mph, + or -. It would almost seem that a ring and pinion change would get you a lot of bang for your buck because instead of being toward the top end of second gear....you'd be toward the sweet spot of of 3rd...drop the hammer and away you go. A ring and pinion would also allow the car to be semi-competitive in PCA H stock...bumping up from G stock as a result of the ring and pinion. But I feel that a set of close ratio gears would be the best mod if you don't mind the consequences of having to race on PCA GT class.

Regardless of what way I finally decide to go, I have learned so much from this thread, and especially the detailed posts of Bill Verberg.

Nader Fotouhi

If one decides to change the R&P on a stock class 993 to get into prepared H in PCA club racing, what would be an ideal R&P ratio when running 245/40/18 F and 285/35/18 R?

race911

I see this has popped up while I was "in the dark" over the weekend.

Funny that I'm at the track today with an oh-so-properly geared car (see other thread I just posted) today.

But let's take a step back and understand what I really said re: the yellow car v. 964:

1. Yellow car is fantastic at Thunderhill and Sears. Horrible a Laguna.

2. 964 5-speed as-delivered works well enough at all three tracks.

All for now, car's back in the pits...........

Bill Verburg

That's correct 7000rpm instead of 6800 for the 2 charts I did Sun night

Bill Verburg

A CWP change is not a good solution
a /20 wants small changes, I know a guy, very good driver that has this setup in hid track only 993, it sort of works there


here is a nother way to look at them


and another

Martin S.

Great transmission gearing graphics!!!!

Thanks Bill

ToSi

I uploaded a gearing calculator to google docs for you guys to tinker with. Doesn't make plots yet but provides a quick way to compare different combinations. Enjoy!

click me -> Porsche Gearing Calculations

Bill Verburg

Just a FYI
If you do your own calculations of speeds and try to compare too mine, there may be differences.

I do not use the unmounted tire diameter which is most often published is tire O.D.

Where ever possible I use the tires dynamic loaded radius, to derive the effective diameter of the tire at speed, I've noticed a few of the tire manufacturer's actually posting the static loaded radius which is a close approximation of the dynamic loaded radius

callipygian 911

Wow.

So, Jordan and I went for a joyride in his 993 last night and I've got to say, he's got one hell of an impressive machine.

I am now absolutely convinced that I need to work a re-gear into my budget in the coming year. This is a wholly "different animal" compared to a stock 993. Of course, he has lightened the car up considerably (along with many other performance mods) so it is challenging to discern how much acceleration the re-gear alone responsible for. Of course, the engine roaring though those Fister IIIs overwhelmed my senses even more. <Adds these to the to-do list>

I believe I'll defer to Jordan's gear ratios when the time comes.

Remarkable. Just remarkable.

Thank you Jordan! This place is great!

doc_porsche

man i need to take a ride as well.....

matt777

Absolutely. That rpm drop chart really illustrates the issue with the stock G50/20. There is nothing like upshifting at 6500rpm a few times and still being in the power zone each time.

il pirata

I am looking at a regear on my 1996 C4S with OEM 18 wheels and tires (285/30-18). Car is essentially 100% street use. I am looking at either going with G64-21 gearing or RS gearing. Any feedback would be appreciated.


G64/21 (ROW AWD) G50/31 ratios (RS).


1st gear 3.818:1 3.154:1

2nd gear 2.150:1 2.000:1

3rd gear 1.560:1 1.522:1

4th gear 1.242:1 1.242:1

5th gear 1.024:1 1.024:1

6th gear 0.820:1 0.821:1

Reverse 2.857:1 2.857:1

Rear final drive 3.444:1 3.444:1

Bill Verburg

Unless you go the expense of changing out the mainshaft you are stuck w/ you stock 1 & 2. Many move 5 to 6 then fill in the remaining 3 slots

if you use /21 or /31 for 6 that's ~ 172mph top end, moving 5 to gives ~157mph top. JMO but ~160 is a nice place to be but it depends on the individuals taste

il pirata

I was aware of the issue with a C4S and the first two gears...for me I would change out the mainshaft and depending on whether I go G64/21 or RS, change just 2nd gear or both 1st/2nd. So 5 or 6 gears, steel syncros, etc etc.

I have seen a lot of your charts including for the above two setups but with a different tire size. I am running stock 18" turbo twist with stock tire size (285/30-18 in the rear) Can I assume the tire size will have little effect on the RPM drops?

Bill Verburg

When I post i try to use a standardized setup, 285/30 will be a very small amount shorter, how much depends on the specific tire, so the net gearing will be a small amount shorter.

The big difference between /21 and /31 is in 1 & 2, the /31 is more of a track oriented setup, but I like it for street use too. The taller 1 & 2 gives you shorter drops for 1 - 3