No it's performance, hp and weight. BTW two different Focus ST's placed 2nd and 5th in G-Stock at the SCCA National Championships last week. And if anyone has ever been there, that's no easy feat! CONGRATS TO GORDON MACIULEWI!
The competition and intensity there is like qualifying in F1. Over 1200 competitors competing on 2 courses and over 7200 runs in 4 days.
The 2nd place GS Focus ST was out by only 0.004 of a second after 2min 17 secs on course. Like doing quali........You get three hot laps and then your done.
It would have been a massive victory over perennial GS winners, the '03 Celica GTs but alas, the Celica won. The GS winning time was 136.893.
The DS winning time (now dominated by late 2000's Audi TT Quattros; 6 of the top 10) was 133.021. So there is 3.8 seconds difference over 2 courses.
Audi TTQ DS P1 times vs. Focus ST GS P2 times: 56.439/58.384; 76.582/78.513 (+1.945; +1.931). So there you have the best performance comparison of a Focus ST vs. a V6 Audi Quattro.
Is the Fiesta ST 2 seconds faster than a Focus ST? Could be, but the Focus had to have been running 245/40x18s if not 255s. I know the Audi's run 265s. Can the FiST compete with 215s? That's the big question. My buddy running a turbo Mini (DS) runs 245/35x17s and placed 3rd in Road Tire FWD (59.573/81.086) (+1.189; +2.573).
Right now, based on what I can find at Tire Rack, the optimum tire-wheel combination is 225/45x16 Toyo Proxes R1Rs on 16x7 wheels. Based on what I've seen the dia is the limiting factor and has to be under 24".
BTW, I'm all about the competition performance of these cars; I'm not the parking lot tuner type. I usually run about 20 autocross weekends across the midwest adding up to around 130 runs plus testing. (The GTI spun a bearing on about the 300th run...)
Next year there will be plenty to keep you updated with a FiST if all goes as planned!
SCCA was trying to update the rules earlier this year to allow the newer, heavier, FWD, no front camber cars to be competitive but then slogged around in their own crap and did little but to ban R-Comps for next year. Typical of committee work. But the good news is Ford gave the FiST some negative camber on cornering and a boosted engine with light weight. From the autocross photos by BRGT350 there is still too much front roll but that can be corrected. Ford lowering it an inch is still a limiting factor in wheel and tire but who knows where we will end?
If anyone has an inside with Ford ST division engineers and competition, send me an IM.....