F82 at Willow Springs

[brian99997]

I was reviewing some data from this last weekend at the Streets of Willow Springs, most of this is with extremely hot tires (Michelin Pilot Super Sport) and some pretty thick deposits from the stock pads melting on the second day due to nearly 20% of the lap time being spent braking.

Overall this is a small 1.6 mile, 14 turn course that benefits traction and light cars. The car was great for about 7 minutes and then the brakes fell off sharply, very nimble for a stock car and responds to throttle steering well especially in that 13 area. There was a bit of side to side action under heavy braking at around 0.8g but nothing too unstable. If anything I had a hard time putting power down in second gear (3 turns) without straight line wheel spin. Overall cornering saw 1.2g consistently in turns with a slight camber advantage.

Suspension: sport plus (sport yielded the same lap times but didn't feel as stuck)
Steering: sport
Engine: comfort
Transmission: S2
DSC off

My only real complaint is the brakes that you can see in the middle of the second image with 6 fairly distinct heavy braking areas on a short track. The pads are toast, the rotors need some attention but the fluid held up.

CW

CCW, drizzle but not wet.

[FTS]

I am not familiar with this track; are the traces between 5000 to 7500 ft marks correspond to the section between T11 through 13?

You must have been using the stock brake pads I assume, since the maximum deceleration G does not exceed 0.8, but your cornering can generate 1.2 and combined Gs exceed 1.5, so you have enough grip in the tires to generate enough Gs, but I guess the pads weren't up to the job as you mention.

[brian99997]

Going by the map (that I took roughly the data points from the Randy Pobst article) 5000' is just coming on to that top straight and then 7500 is just entering the U turn before the main straight on the bottom.

Btw, those numbers are here. Lets use that same last U before the straight where the article says 1.09g, my peak was only 0.84g. Clearly I have been away from the track too long as I appear to be missing over 6 seconds from his time and a lot of g's.

btw, edited the first post to include a youtube video of the lap CCW, and then CW.

[VMRWheels]

Great write up. Thanks for sharing! Definitely going to consider all this next time I go up

[FTS]

Originally Posted by brian99997

Going by the map (that I took roughly the data points from the Randy Pobst article) 5000' is just coming on to that top straight and then 7500 is just entering the U turn before the main straight on the bottom.

Btw, those numbers are here. Lets use that same last U before the straight where the article says 1.09g, my peak was only 0.84g. Clearly I have been away from the track too long as I appear to be missing over 6 seconds from his time and a lot of g's.

I suspect you are not familiar with the car and how it feels when pushed harder in the corners yet. I know I will have tough time, as I always do, initially figuring out how to be comfortable with a new car, I at least give myself a year or so before I can say I know what the car will do, then start hopefully pushing the car

Regardless, it is great to have some data, especially a baseline, well done!

[brian99997]

The overlay in that track map with the red line is me driving a spec miata at the same track two years ago, faster than these laps..... I didn't post the rest because the miata kills the m4 everywhere except the straights.

[brian99997]

Here is the same data vs a F30 328i 3 years apart. The main difference being that the lap was about 400 feet shorter in the F30 so this specific view doesn't match up quite right all the time but you can see where the black line (F82 M4) clearly outshines the F30 in basically every way.

also included different track segments from the first, but its roughly the same.

The F30 was about 8 seconds slower (on the stock runflats)

[CanAutM3]

Engine in Comfort (I assume you mean efficient)

You are missing out big time on the sweetness of the S55. At the track, Sport+ is fantastic (on a dry track). Sport is the minimum setting IMO.

In comfort, the anti-lag features are not activated and I find the power delivery less easy to control when running constantly at high power such as on a race track.

[brian99997]

Originally Posted by CanAutM3

Engine in Comfort (I assume you mean efficient)

You are missing out big time on the sweetness of the S55. At the track, Sport+ is fantastic (on a dry track). Sport is the minimum setting IMO.

In comfort, the anti-lag features are not activated and I find the power delivery less easy to control when running constantly at high power such as on a race track.

Interesting tip. I tried each very briefly and decided that I would rather be able to modulate the throttle more accurately

I'm not sure if anti-lag is required if thats a between shift type of thing. I could maybe see it in a few places but the only time the turbos lagged, I was thankful that the tires were not spinning. I will test this out though, I thought it was purely a throttle pedal curve setting.

I have some Hoosier R6's and some Pagid RS29's on order so we will see either on the 21st or March 1st how the car holds up at a different track with higher MPH. I am expecting some body roll and to cord the front right tire going around the oval banking.

[m4 java green]

Great info!!! Are you keeping the OEM wheels with R6's?

[brian99997]

Originally Posted by m4 java green

Great info!!! Are you keeping the OEM wheels with R6's?

stock 19's, 265x35zr19 and 295x35zr19. More info to come later in the week on how that worked out.

[m4 java green]

Great! Looking forward to the update. I'm trying figure out a good track setup on my OEM 19's. I was considering getting 18's for more tire options but would rather save the money.