This Sunday I had my first chance to autocross my 2011 BMW M3 at El Toro airfield. While I had done an autocross in Oakland many months ago, it was a poor chance to feel out the car as the course was very short (maybe 40 seconds long) and pretty slow. Today’s El Toro event was fast and long, composed mostly of 40 mph to 50 mph corners, a few widely spaced slaloms, and several broad hairpins including one at the end of a 75 mph straightaway. The event was hosted by the Porsche club, and the course suited 911’s and other powerful cars like my e90 M3.
My instructor Clint drove a stock e92 M3 (DCT) with slightly upsized Advan AD08-R tires (255 mm front/275 mm rear). I rode with him first, and was quite impressed with his speed and aggression. His car seemed to have huge front-end stick, and he would aggressively pivot the car into corners. Clint would also accelerate through the first cones of the slaloms, brake through the middle of the slalom and then gas his way out of the final sections in a way that had not occurred to me. He was hard, yet judicious, on the throttle in every available straight and would often be slightly oversteering the car through the exit of the corner. Entering corners hot his BMW would sometimes understeer and then Clint would try to shake the car into oversteer with throttle or brake adjustments. When I rode with him Clint’s times were in the 84 seconds range, but I think he got into the 82 seconds in his solo timed runs.
I had twelve runs today (well, actually thirteen since I had one rerun) and my quickest times were a 85.6s and a 85.9s. My e90 M3 is stock too but has somewhat tired Bridgestone RE-11 245 front/265 rear rubber. I’m no pro autocrosser and it took me a little while to build up to the levels of aggression and speed with which Clint drives, but I never matched his pace.
Launching from the standing start was a bit tricky with the DCT. I could either start rolling with moderate throttle and then tip into full throttle for a full-grip getaway, or I could get hard on the throttle immediately which causes the DCT to slip the clutch and spin the rear tires. My fastest time was with a hard, tire-spinning launch, but I don’t like abusing the car that way so most of my other departures were done in the former manner.
The first turn of today’s course was a moderately tight left-hand sweeper, which I would prepare for by short shifting into 2nd gear. I could balance the car on the edge of oversteer through this turn and keep the tight to the inside cones. When entering corners with power the M3 has a tendency for oversteer, which is useful at keeping you tight to the corner’s line (instead of pushing wide).
Next came a right-left-right complex onto a taxiway. Braking was required to set up for the final right turn onto the taxiway, because otherwise the M3 will understeer through the corner. When decelerating (but not braking) the M3 will plow a little entering a corner. A moderate amount of trail braking can help with the understeer, but if I dialed in too much brake and steering I would encounter understeer again.
This understeering behavior would again become an issue at the NW corner of the track (see the picture above), where a nearly-straight left-right-left led into a very tight right-hand hairpin. This corner was basically a stop-and-go for me. I would slow way down (maybe to 20 mph?), turn the car hard to the right and then accelerate hard as the corner opened onto a straightaway that crossed the width of the runway. Getting out of this corner was one of the trickier maneuvers as the car would oversteer massively under the combination of cornering and hard second gear acceleration. A few times I had to make exciting hand-over-hand corrections on the steering to keep the car in-line (I never spun). Also, the straight was long enough that I could get to the top of the rev-range in second gear, where the V8 produces another burst of power that can knock the rear tires loose again!
After the NW hairpin were three, ever-tightening sweepers which were the highest-speed transitions on the course. I would often be leaving the NW hairpin with some amount of oversteer. I’d have to try to stabilize that oversteer as I set up and braked the first, more open, left hand sweeper. Since the rear was already sliding as I was setting up for the left, the M3 would often pendulum into oversteer under braking. The following right-hand sweeper had a decreasing radius which would provoke understeer that I would try to convert into oversteer (to pivot the car) by tapping the brakes or throttle. This would cause a major pendulum effect for the final left-hand turn of the complex, which combined with the hard throttle I’d be using leaving the corner sometimes put me very sideways; so much so that I actually missed the entrance to the slalom once!
These fast transitions and wrangling with weight transfer were a standout of the day; I found it to be a really rewarding challenge to tame (or enjoy!) all the skidding. Getting the car to go from power-on oversteer in one direction to grip turning in another direction is not something I could immediately do; I would often transition into even more oversteer in the opposite direction! I never spun the car but I certainly had to add more than the typical 90-degrees of steering correction and do hand-over-hand corrections to keep the car heading in the desired direction. Adding these inputs felt instinctual to me, and the M3 was relatively easy to manage in these situations. It was also immense fun!
I learned how to approach the slalom such that I accelerated past the first and used steady speed through the central cones. The end of the slalom was at the NE corner of the track (see picture above). We started heading south towards the east-most hairpin. What would have been one long sweeping left into the hairpin was made a bit more challenging with a pinch/chicane in the middle which forced cars to do a little left-right zig. This could cause some understeer in the M3. I’d still be entering the east hairpin with very hard braking. The car would naturally understeer through the first half of the hairpin and oversteer under acceleration, but I could provoke a tail slide through most of the corner if I just wanted to have fun. I could carry some of that slide through the 90-degree left onto the southbound straightaway.
Beyond entering the straightaway through a tight gate, all that was required was full throttle and a shift into 3rd gear (at maybe 75mph) before the hairpin. I got to use lots of brakes into the first half of the hairpin and then stayed tight to the hairpin inside past the apex and through the exit. This would set me up so that I could hit the next optional-entry slalom with a right-sided entry. A right-sided entry worked best as the slaloms exited into a pinched left prior to the finish line. I would have to brake a little into that final left in order to avoid the pinch cones, and then accelerate for a short burst (often with understeer) to the line.
In the aggressive and safe environment of an autocross, the M3 shines in a way that it does nowhere else. Entering corners the M3 tends towards understeer, but this can be shaken away by substituting aggressive inputs for the smooth and measured inputs which are more typical of my track driving style. Exiting corners the car is very oversteer prone under hard throttle. It is not hard though to either be more careful with the throttle or to just ride the oversteer with some opposite lock.
The way you can move the BMW around on the pavement is similar to the amount of adjustability I when drifting the Evo in the snow. There are so many options adjusting the car’s angle in a corner and all of the options I have encountered so far have been benign. It is really thrilling!
I have recently been shopping for an Evo IX or e46 M3 because I’ve been a bit bored with the e90 when driven in town and in the mountains. Today’s autocross in the e90 M3 has me second guessing my Craigslist searches. Clint had an e46 M3 last and he says it is much more understeer-y in autocross. I had autocrossed the Evo and did not find it much fun. The Evo’s softer suspension means that through slaloms it never has a chance to settle. Trying to get the Evo to rotate into oversteer into a tight corner is very difficult to do, so you have to drive grip lines which emphasize corner exit. The e90 M3 just has such adjustability and dances through the course! I want to go again.
Mike's Steering Column 