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View Full Version : Learned a few things at first autox



jguerdat
08-12-2012, 08:57 AM
Had my first chance to autocross my Abarth yesterday. I had no idea where to start so I just started completely stock. Tire pressures were a little low (36 psi) due to cool morning but warmed up to 38 and stayed there. We ran two heats - 3 runs in the first heat and 4 in the second. For the first heat, I turned off ESC to leave the simulated limited slip enabled for all runs. Tried launching at about 2500 RPM but too much wheelspin so I dialed it back. I was slowly whittling down my times but not in large increments like I was hoping for. Tires were an obvious limitation - the P Zero Neros are fine for the street but not so much for competition (locally - FLR SCCA region - stock classes run non-R comps so it's not like I was out-gunned by slicks) so an upgrade to the 215/40-17 Dunlop SS or Yoko AD08 will be needed. I kept waiting for grip in the turn-arounds, rather annoying. Transition-wise, the car/tires seemed fine. Much less body roll than I was anticipating. On the street, it seemed like my torso wasn't really being held by the seat but I didn't have a problem in anger, although my left knee was getting rubbed raw by that abrasive surface of the door panel. Might have to find some sort of pad to keep from bleeding all over the car - that finish really sucks. Anyways, after the first heat, I was falling short of my goal of ~48 seconds.

The second heat started with me dropping the rear tire pressures by 2.5 lbs to try to get the rear to rotate better (easier to drop than add air). Didn't help much. I also totally turned off ESC and immediately dropped .6-.7 second. I was concerned about inside wheelspin but had very little to contend with. The surface wasn't that grippy so I feel it was a function of wheel droop and lack of body roll that played the biggest role here. Props to the suspension! Tried dropping rear pressures again to 33 psi (fronts had raised to about 39) and felt that the car was behaving better. The rear tires were definitely being worked more as evidenced by increased rollover. On my third pass of the heat, I tried re-enabling the limited slip function and went slower (that run kinda sucked but it wasn't all my driving unless it was caused by my trying to drive like ESC was fully off). Won't do that again - ESC fully off is the ticket unless some condition calls for a change.

I did get down into the 48s although not as quickly and fully as I hoped. Since all stock classes were lumped together and indexed, I was 5th out of 7, not bad for a first outing with less than desirable tires. Wish there was more competition to see where I really placed but the first 3 were good drivers and were may 1.5 seconds faster on index (HS PAX can be hard to beat). The car performed admirably - it just is under-tired. Tire choices are going to be a real issue since anything wider is also taller. Only choices are the Star Specs and AD08s to keep the stock diameter. I'm not going with R comps at any point since street tire classes are rapidly becoming more popular.

One variable I don't know about yet is alignment. I haven't had the car on a rack so I can't even say that it has the stock -1.5 deg. camber for sure. If it can truly be adjusted out to -2.5, I may have to do that to see what happens. Along with better tires, it might be the ticket. I need more data here to see if -1.5 is more of a street spec for even wear than for track. Anyone done any alignment work yet?

GileraWarren
08-12-2012, 09:50 PM
Do you autoX your s2000 also? How does it compare to the Abarth? Just curious because one of my old racing buddies (operative word for us is old) has one and I know he'll want me to show up with him at an autoX. with our cars

jguerdat
08-13-2012, 07:53 AM
I autocrossed the S for years before slowing down a few years ago. My daughter and son-in-law used to trash the beast regularly. Not a fair comparison, what with 80 hp more, only a modest increase in weight, fwd vs rwd, center of gravity, etc. The S is certainly more capable but the Abarth is hardly a slug. We just need to get a bunch of us actually using the cars the way they were intended and start swapping tips for go-fast operation. Get you friend to run on street tires - he should be faster but maybe not by as much as he thinks.

And I'm an old (62) fart, too... ;)

Abarthman
09-27-2012, 06:48 AM
Do you autoX your s2000 also? How does it compare to the Abarth? Just curious because one of my old racing buddies (operative word for us is old) has one and I know he'll want me to show up with him at an autoX. with our cars

Actually I just beat an S2000 (quite easily) at my last autocross.
Maybe the guy couldn't drive, or maybe the course favored the Abarth.....

jguerdat
09-27-2012, 07:50 AM
Yeah, "It depends." (TM) ;)

I had an event last weekend where a former S2000 AS/BS (depends on what year we're talking) that I would run pretty much evenly with had his lightly modded STR S2000 on crappy tires slightly beat me in my stock on the crappy Pirelli P-Zero Neros on PAX. His raw time was a bit under two seconds faster than me but PAX was only about .5 second faster. The S is definitely a faster car and always will be but the loose nut behind the wheel will always make a huge difference...

pro4art
12-11-2012, 10:10 PM
Don't forget camber gain happens. I'd certainly start off at 2 degrees neg, which should also be streetable. Haven't autocrossed in years, but am of the opinion that tire pressures should be adjust UP, not down. Stock is for smooth ride, which gives tire roll over in hard turns, which in a FWD car makes for more understeer. I always started at 4 pounds over stock front pressure. In rears, I'd go higher, as those wheels have to follow the fronts, and more pressure will decrease rear traction, for more rotation. When you almost spin it the first time, drop the rear pressure a couple pounds.
With a piece of chalk, mark on the side walls, from outer edge of thread, to an inch up the sidewall. That will tell you when you get the pressure TOO HIGH, of if it's TOO LOW, in the fronts. As you approach proper front pressure, you will see less chalk mark missing. I'm guessing you know about handbrake turns, for 180's and the like.

jguerdat
12-12-2012, 09:10 AM
Haven't seen/heard anything about camber gain as yet - most folks seem to be out only for looks rather than performance with these cars. I'm thinking about some coilovers down the road but need to research them first.

Tire pressures seem right on this car from the factory, at least for the Pirelli P-Zeros. I think they did their homework - sidewall rollover is very controlled. I do think some minor tweaking is in order - I don't have enough time on-course to make strong statements. I'll be changing tires to something stiffer/stickier (AD08s or Star Specs) which will probably require pressure changes. I do need to either start playing with rear pressures or learn trail braking to help rotate the rear. Some folks have said the rear is loose while my experience is the opposite. Of course, I may simply be over-driving, forcing terminal understeer. Fix the driving style first and then head for tweaks.

As for parking brake turns (I call 'em Rockford turns from the James Garner show which almost always had at least one such turn per show), haven't used them in years because our courses tend to be wide enough to not require them. My wife even learned about them from my descriptions and used it to good effect one time. She was driving home in the snow with our two young (at the time) kids in out '70 Fiat 850 Sport Coupe and tried to make a 90 degree turn onto another road in the country. The car was headed straight for a ditch so she popped the e-brake, rotated the car, and drove on home safely. Then she changed her drawers...