Well, its official. We need to do something about that torque curve of the BRZ between 3000 & 4000rpm. The direct injection is the majority of the problem, and unfortunately in the engine configuration there isn’t much we can do about it for STX as a class. [In case you didn't know, STX is the class in Solo in which the BRZ competes in, after suspension upgrades.]
We have to live within the SCCA Solo ruleset if this is going to be a champion autox car. Lucky for us, we are also in a very competitive region for STX drivers, with several national drivers within the NER region.
Take a look at some of the torque curve issues as visualized on the dyno. Great overview of this at the tune86.com blog. We need to ‘open up’ the exhaust. This means, we need a nice high-flow cat in the mid-pipe section of the BRZ, along with some equal-length headers (eliminating another restrictive area and another cat). HKS makes a nice-looking equal-length header for the BRZ. Gains of up to 20% in WHP can be had by opening it up.
Another change that needs to be made is that the Cusco lateral links which had planned to be used, will have to have back-dating done to the pillowball mounts that connect to the subframe. Thanks to SCCA STX Rules, we can’t have the upgraded pillowball bushings there, but they are allowed on the tophats/camberplates. Seems silly, but alas, it is in the rules. Challenges to this will be made as it is more about protecting the car, than about speed. Various bushing and engine mount changes have been made recently for STU with the solid-engine mounts now being allowed after the Group-N mount issues with the STI’s running rampant, especially within the ProSolo circut. [I've blown through two of them in regular SOLO competition even.]
The Racecomp Engineering Tarmac II’s will be going on, and initially we will be trying a 7/5k spring setup along with the Racecomp valving. Modifications to this valving will likely take place given that the springs will be along the stiff end, and we want maximum adjustment to these. Can’t wait to get these guys in! [Currently they are stuck in customs as they utilize KW3 components.]
We are also going to upgrade the shifter in the BRZ. Is this for powergains, no.. but rather to eliminate the ‘row row row your boat’ feel of the shifter. A good connection between the driver and the transmission is always welcome in competitive driving. Kartboy makes the best.