The oil pan brace would technically be illegal in any class but SM, becasue if I understand correctly its original purpose is a performance modification (even though a stock one wont need it). My suggestion would either be to keep it stock and run in stock class, or not worry about it and run in whatever class the modfications you do put you in and just have fun.
If the OP has a base FC, those came with an open diff. The GXL came with a clutch type limited slip stock. This is not the same unit that came in the Turbo II cars.
In the usual run of things in SCCA Solo classification, if the base FC and the GXL were 'on the same line' in the rule book, then swapping complete assemblies (engines, diffs, etc) would be legal. For that matter if the TII were on the same line, swapping assemblies from one of those would be legal as well.
Now, if the OP were to have, say, a 4:10-1 open diff which was the only one available in the FC and a 3:90-1 limited slip diff which was only available in the GXL, then it would not be legal to remove the limited slip from the GXL 3:90 diff and install it in the open diff's case with the 4:10 gears since that would not have been a factory available combination.
I am not up on STS2 so I am not qualified to comment on the limited slip's legality.
The 86 Sport, 86-88 GXL, and 88 GTU all came with the 7" clutch type limited slip differential. The 89-91 GTUs was the ONLY n/a model sold with the viscous diff. The viscous differentials are extremely rare compared to the clutch type, since only a couple thousand GTUs' were sold in the US. Best case, the newest viscous diff's are 17 years old, the fluid breaks down over time and they can not be rebuilt. It really is an unfair advantage to new cars/ anything that isn't a FC RX-7.
I thought the GTUs used the same diff as the TII, i.e. it was actually a TII without the hairdryer? Didn't know they were viscous.
Tell you what, if the viscous Mazda diffs are as much a pain in the butt as the Nissan versions I think I'll stick with the clutchers. I have a buddy who runs SM2 with a 300ZX and he is ALWAYS going into that thing.
Jensenman wrote: I thought the GTUs used the same diff as the TII, i.e. it was actually a TII without the hairdryer? Didn't know they were viscous. Tell you what, if the viscous Mazda diffs are as much a pain in the butt as the Nissan versions I think I'll stick with the clutchers. I have a buddy who runs SM2 with a 300ZX and he is ALWAYS going into that thing.
The S5 GTUs was a base model with turbo suspension, n/a drivetrain, and aluminum hood. The GTUs has a viscous limited slip w/ 7" ring gear (vs 8" turbo ring gear) with a 4.30 (4.11 standard) final drive.
I've decided not to get the oil pan brace. After rereading the rx7club thread, I've decided that longer oil pan bolts and careful application of RTV and the gasket should keep it from leaking again for a while. SInce the stock LSD (it's an '87 GXL, BTW) is verboten in STS2, I'll keep my FC in E Stock. Should I decide to go to STS2, I'll probably swap in an open diff.
ReverendDexter wrote: +1 Reading back through this, I'm confused. If I'm understanding correctly, this FC came with an LSD from the factory that makes it illegal to run in a stock class? That's asinine.
agreed. the only mod that puts me in csp vs sts2 is the stock torsen in my miata. i still run a street tire because it's my daily and i can't afford two sets for it and a set for the challenge car. still, I run in csp and loose. i can still read the board to see how i compare against the sts2 guys so what's it matter? i know my car is just a little more prepped than the sts2 guys so i know if my time is significantly better, then i was a better driver that day. same vs. the csp prepped miata that beats me every time. when i get to within less than a couple seconds of him, i'll know it's mostly his tires and other mods.
bottom line, prep the car the way you want to drive it. whatever class that is isn't really as important as measuring how much you're improving.
SCCA autocross "rules"? Sure; that's how e36 M3s stay in STU with e46 M3s as well as Evos and Stis which can smoke all 4 tires in a straight line in 2nd gear. Altering boost isn't permited, so no one would ~ever~ do that!
To the O.P:
Since this is degenerating into the usual rules discussion, I'll give you some great advice and maybe a little perspective.
Come out and have fun, that's all. Just have some bloody good fun and don't worry to much about classing your car.
When and if you want to step up, pick a class that's right for you and build your car accordingly.
To everyone else:
Let's not scare new people away with too much back-and-forth about discussing car classing and what one should and should not do.
After all, we're trying to get more people interested in this sport, not scare them off, right?
To all of us, myself included:
Add up all the money you won in this sport last year.
Now subtract all the money you've spent on this sport.
If the number you have is negative, congratulations, it's a hobby and we shouldn't get too wound up about it.
Shawn
I have never before looked at the STS/STS2 rules. The '79-'92 non turbo RX7 are classed in STS but if the car has a clutch type limited slip stock (a factory available combination) it ain't legal. I get the funniest feeling this needs to be addressed.
Straight from my '08 GCR/Solo rules.
14.11 STS2 STS2 follows the STS rule set, but the eligible cars will be restricted to two-seaters with engine displacements of 1.9 liters or less. This class includes a number of popular vehicles, including the Honda CRX and del Sol, Mazda Rx-7 (non-turbo, ‘79-’92) and Miata (‘90- 81 ’97), Toyota MR2 (‘85-’89), as well as other similar vehicles. STS category rules 14.1 to 14.10 apply. Further, as in STS, only original equipment viscous limited-slip differentials are legal in STS2. Excluded vehicles include Lotus (all), Mazda Miata (‘99+), and Toyota MR2 (‘91-’95 and ‘00+).
Ain't THAT a kick in the nuts. 
IMO, and likely that of pretty much every existing STS competitor, this most certainly does not need to be addressed. It could very will kill the class nationally to allow one car to have the HUGE advantage of a functional LSD. Especially a car that can probably be made competitive in the existing class without any such help. I know this is not the discussion to get into right now, and I won't go any further, but think about all of the people who have invested in building a car for the class as it exists today, and then tell them they may have to throw their cars away if they want to stay competitive. The class is an open-diff/viscous-diff only class, and the competitive balance would be drastically altered if any of that were changed. Diffs are huge game-changers in autocross competition for most cars.
confirm that the FC can be entered in the class with SCCA.
Then just run for time only (no trophy) in STS2 while developing the car.
Be upfront with competitors as to why you are doing this.
If any competitor has a problem move up to SM2. I would just run there anyway. Infact that is where I am running my 944 Turbo and getting my arse kicked at every event mostly because I am on old 225 tires not new 315s.
I have run cars in classes that I have no hope of winning because of some mod many times. Sometimes I just run for time only to not screw up others points for year end if I am only running that class once.
Short answer...Do what you feel is right.
Hi,
I was searching for info on a slightly different topic and this popped up.
The reg you are quoting was specifically created to make all the performance mods I did/do for the Miata 1.6 and 1.8 illegal. This is not a huge mystery and it's a compliment, really.
I get asked about pan sealing all the time. As you are now planning, there are RTV products out there that will seal. Some of them are guaranteed to seal.
Some Suggestions for RTV Silicone Gasket Maker use:
~~~~~~~~~
Lastly, if you are allowed to modify the baffles -- wow, that is wide open. I assure you that no consistent definition of baffle exists in the industry and I make more windage control items for more different engines from more different marques than any other company in the world. I am constantly surprised by the number of people and OEMs referring to windage trays as baffles.
Kind regards,
Kevin
ArtOfRuin wrote: I'm planning on running my FC RX-7 in SCCA STS2 in 2009, since most of the mods I plan on doing to it fall in line with what's legal in STS2 anyways. I already know the stock clutch-type LSD on the car isn't legal, but I doubt I'm going to the podium anytime soon or that I'll be challenged for it, since the FC isn't the hot ticket for this class. The oil pan is leaking a little and needs to be fixed. There's a thread on this at the rx7club forums. One of the vendors suggested their oil pan brace and also says discounts are available for rx7club members: http://www.banzai-racing.com/products_fc_oil_pan_brace.htm This is a little more obvious than the LSD. I'd rather not be bumped into Street Mod for it. Rule 14.10A in the SCCA Solo handbook says this: Internal baffling of oil pans may be added or modified. Addition or modification of windage trays, crankshaft scrapers, and oil pump pickups is not allowed. Am I to assume the external oil pan brace is illegal for STS2?
One more thing about the regs that makes me chuckle. I don't see any regs about what oil can be used. 
You can easily pick up some hp by running a lightweight oil. I mean, after all, the regs do not say you can use a different motor oil than what it was delivered with. By the exclusionary logic employed this means you must run the oil that came with the engine as delivered.
Right?
Hey, money talks. Big Time.
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