Project Update for August 14th, 2013: I am still playing catch up on the event coverage in an "STU prepped" 2012 Mustang GT I co-drove in July, some changes in SCCA classing that affect the S197 (both good and bad), and some major aero work on our 2011 Mustang GT that we are attempting before NASA Nationals in a few weeks. Let's get to it.
Since the bulk of this post has to do with a test we did in an STU prepared Mustang, I will give some background on the many SCCA autocross classes that an S197 Mustang can be raced in, with my personal views on each. I've raced in every single one of these classes at some point in the past 25 years, and many of those times were in an SN95, Fox body, or S197 Mustang. Or a Camaro, Subaru, BMW or EVO.
SCCA Solo Classing - Many Choices, None of Them Great
I have been fairly vocal about my disdain for some of the rules and rules makers in SCCA Solo (autocrossing), but it is still the biggest club doing these lower speed events in the country and it cannot be ignored. Many other clubs just adopt the SCCA rules, letter and verse, so this big book of rules is the one most people go by (346 pages in the
2013 Solo Rule Book, plus
another 28 pages for supplemental event regulations and tire clarifications). Honestly I try to get S197 racers to
NOT build around SCCA rules, as it will likely only cause you frustration and pain, but if your goal is to become a competitive autocrosser and nothing else, then this is the series to build around. If you are a casual autocrosser, just know the basics below, build what you want, and "run what ya brung" at local events in the class that is the closest to your car.
Let's examine the basics of each of the optional SCCA Solo classes for the S197 Mustang:
F Stock - Aftermarket shocks are allowed (up to custom double adjustables with remote reservoirs), aftermarket front
OR rear sway bar, R compound tires (which goes away in 2014 with Street class), but stock sized wheels, stock springs, and very few cars can have any additional camber adjustment (and virtually all stock cars need it). If you don't have a 2007-08 Shelby GT (which is essentially an "ESP-Lite" car from Shelby/Ford), then you're wallowing around on stock spring rates, super tall ride heights, and hating life.
I really dislike the Stock category due to the excruciating restrictions in some areas, yet wide open rules for tires and shocks (which can really drive up costs), and calling it the "entry level" autocross class is a bit of a misnomer. The super sticky tires needed at the top levels to compete puts the costs of this "entry level" class far out of the reach of the average autocrosser, and the restrictions on modifications keep just about every car's suspension tuned so poorly that they handle for crap AND eat tires too rapidly. There were a lot of good, proposed changes to fix this category for 2014 (camber addition, banning crazy custom shocks, sway bars open, 200 TW street tires, +/-1" of wheel diameter), but the rules makers backed down and in the end only really got one change through - the switch to 140 treadwear street tires for next year. It is still going to be a painful class for the typical (non-Shelby GT) Mustang S197. It will still have too much pitch, roll and brake dive and it will handle like the images shown above.
Street Touring (STX -> STU) - For most of the ST category's existence, the S197 5.0L cars were able to run in
either STX (on a max 265mm street tire and 9" wheel)
or STU (on a max 285mm tire, unlimited wheel width). In 2012, they locked this car into STX which I felt was a slight mistake. We raced our 2011 GT in STX for two painful years, where it sucked badly, then stepped up to a 275mm tire on a wider wheel and ran in STU twice. The handling and fun was a lot better for such a modest increase in tire size. Suspension options are
mostly unlimited shock, spring, camber, and (non-metal) bushing choices, with some out of date rear suspension restrictions. Motor has to stay stock from throttle body to exhaust port, with headers, full exhaust (with catalytic converters) and a cold air intake being open.
You can tune the engine (EFI) to your heart's content, which essentially allows for unlimited boost on factory turbo cars (there is no policing of boost controls - nor any scheme to ever do this). We pushed hard to start a letter writing campaign in early 2013 to get the V8 S197 Mustang moved to STU, and it seems to have worked. Supposedly this is going to happen starting 1/1/2014 (or 2015 depending on how you read the confusing rules update). Will this car do any better in STU relative to STX? Probably not a WHOLE lot better, but the added tire is badly needed on these heavy, powerful cars - we tested this theory in the event described below. Even as uncompetitive as it seems on paper, I feel STU is the class that 90% of the casual Mustang autocrossers would end up in.
E Street Prepared - If you've been reading this build thread for a while you know that we left STX/STU and went to ESP in our 2011 GT in late 2012. We had limited success there (4th at Nationals), due to a lack of testing time, excessive weight of our car relative to the top ESP car (a hybrid Firebird build of a drivetrain/chassis combination only allowed in this class), and some other mods we had not explored yet. This class allows the same weirdly restrictive yet expensive suspension mods as Street Touring, plus unlimited wheel and tire width, and super sticky R compound tires (with treadwear ratings approaching 0 and slick tread, yet still "DOT" certified). Again, some weird aero mods are allowed (circa 1960), plus unlimited intake manifold, no emissions regulations, some obscure amounts of port matching, unlimited EFI, and unlimited boost (which is explicitly allowed in this category).
This is still a "good" class to build for, if you can stomach the tire bills, and with enough time/money/testing a fully built S197 could win this class. An expensive tire budget is a key issue. The Hoosier A6s start to fall off after about 20 runs (usually 60 sec in length), and are probably corded after 40-60 runs. If you want anything more than local competitiveness, you will be building a purpose built race car, sans A/C, radio, emissions, and more. But it will still have the stock camshaft, heads, internal engine parts, and the funky rear suspension issues are likely to be in-curable without extraordinary measures.
Street Mod - This class takes Street Prepared rules, then adds a good bit more. Cars in this class must have four seats (from the factory) so that puts your Mustang up against a lot of AWD turbo cars, lighter BMWs and several other four seat RWD cars.
Winning SM in an S197 can happen locally (we've done that a few times), but at the National level you will be hard pressed to get the car down to minimum weight and still be fast enough to beat the other cars here. Still, the relatively unrestricted nature of the rules - unlimited engine mods, metal bushings allowed everywhere, big wings and splitters - will attract a limited few S197 folks to this category.
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