I’m running my first autocross* in 15 years this weekend, and have been in discussion with the local club (spokes.org) on classing my Mustang. They’re not an SCCA** club, but they follow SCCA rules. Vehicle classification is based on what the vehicle is, and what changes has been made to it. Classes are used to make sure that everyone is playing on a level field and that cars with obvious performance potential (Corvette, Camaro, Mustang, etc..) aren’t competing with economy hatchbacks and sedans, or all out race cars. Anyone can show up for an autocross event, pay the entry fee and drive whatever they showed up in, provided it passes a basic safety inspection.
Our discussion so far has centered on what mods have been done vs. what I’m planning vs. what the rules say. Honestly I’m not modifying the car for autocross. I’m modifying the car for me, and just happen to be doing autocross, so if I’m competitive in class that’s great, but I don’t really care. I just want to have fun and improve my driving. My only real competition is me.
The car is a performance pack Ecoboost Mustang with upgraded brakes, suspension, and tires from the factory, and so far I have installed a COBB stage 1 tune with a high flow drop in air filter. Future plans include an upgraded intercooler***, full turbo back exhaust with a high flow catalytic converter and upgraded BOV**** and wastegate***** for the turbo. I’m planning on upgrading the intercooler sometime between now and June, because Texas gets hot and the ecoboost intercooler isn’t quite large enough. That upgrade is actually a problem for the autocross folks...
D Street - This is out since I don’t want to uninstall the COBB software every time I run, and it precludes doing any other changes. The point was made that only tire and suspension changes make much difference. I’m already running 19x9.5 wheels with 255/40-19 Pirelli P Zero tires. I do want to do a more aggressive lowering spring at some point, and that’s still legal here.
E Street Prepared - This is where I would currently fall with the COBB modifications. This class allows me to change the intercooler, but not the BOV or wastegate.
Street Touring U - No changes are allowed to boost levels, intercoolers, or boost controls. It doesn’t make a lot of sense to me, since a lot of modified Subaru WRXs (Turbo All wheel Drive) seem to end up in this class.
Street Modified - Engine components are generally unrestricted. No rules restrict turbo boost, intercoolers, or computer tuning. All of my proposed modifications are allowed, but then so are a lot of suspension and tire modifications that I won’t be doing. I wouldn’t really be competitive here.
Classic American Muscle Contemporary - This is a recent class, specifically designed to get muscle car guys who may have been doing autocross with Good Guys Car Shows into regular autocross. Mostly because their regular modifications are incompatible with every other available class. This sounds familiar.
I’m going to have to re-classify on Sunday, as currently I’m in STU. I am running as a Novice, but it would be nice in a few months if I can lose that designation and be in a regular class that I’m going to stay in for a while. At the End of the day I’m a “law and order” kind of guy, so I’ll likely end up in either Street Modified, or CAM Contemporary, just to avoid future argument and discussion.
*autocross is an amateur motorsport where normal people with a speed problem get together and see who can go faster around a race course outlined on a parking lot with orange traffic cones. Hitting the cones is considered bad.
**SCCA - Sports Car Club of America is an amateur motorsports sanctioning body. A lot of professional racers get their start in SCCA events.
***an intercooler is basically a second radiator, this one to cool down the air that has been compressed by the turbo. Cooler air is better for an engine, and an intercooler that’s too small can cause heat soak and loss of power in hot conditions. As noted, Texas gets HOT in the summer.
****BOV is shorthand for Blow Off Valve. This is a device that releases excess air pressure that is generated by the turbo to avoid engine damage when downshifting. By replacing the stock one with a BOV that can be adjusted it allows better control over when this occurs.
*****a wastegate is a device in a turbocharger that allows exhaust gas to bypass the turbine to keep it from spinning too quickly. By replacing the stock one with a stronger one it allows the turbo to spin up faster and give more power to the engine.