2023-02-18 Data Comparison, Buttonwillow #13, Aprilia Tuono V4 Factory, Two Riders

Data is big for me, and as mentioned before, having trusted source reference data is huge. A couple of weeks ago I was at Buttonwillow (config #13) with a trusted source instructor and he took my bike out for a few laps and got to a respectable pace pretty quickly. I've just spent over an hour dissecting a clean lap of his compared to mine. There's about a 9-second differential so it's significant but not unmanageable for me to find a few seconds. This event was also the first time that I was able to run a fairly comprehensive data acquisition setup courtesy of AiM--their Italian and US teams worked to decode the ECU data on the Tuono since the channels changed significantly when Aprilia updated the electronics for the 2021 V4 models.

Because I don't ride Buttonwillow very often, the track isn't burned into my mind quite the same way my more local tracks are (Sonoma, Thunderhill East, Laguna), I don't have the same confidence with some corners and am apprehensive about using as much of the track as I can in blind areas. This will come with more experience at this track, just as it did last year with The Ridge.

With a Solo 2 DL and a SmartyCam 3 Sport, I can review control timing, degree of application, etc., side-by-side.

Part of my reservation about this is that I want to get closer to theoretical limits than I do presently while minimizing risk (I'm looking for a good value proposition). If I see that my trusted source is still accelerating in an area while initiating turn-in, then I *can* do it. That itself was actually a big question mark for me in a couple of areas (exiting Riverside, Club Corner, etc.). Having the reference data and accompanying video lets me see these things. In this instance, I'm also able to better re-trace my reference rider's exit from Sunset, which has a very significant big bump followed by some smaller bumps. I took the line you would expect exiting, however, I hit the bumps hard enough that the TC kept cutting power so I'd lose my drive out of it. There is one other area where we deviate and that's the entrance to The Sweeper. I've been taught to turn in from the middle of the track whereas my control rider swings quite a ways to the left before turning right. A couple of items I did notice where it will take more time. My control rider demonstrated up to 1.5G in braking force on the way into Sunset with the front end wiggling. My typical maximum braking force, on a hot lap, is closer to 1.15 (this is from a high enough speed where aero plays a role). 1.5G from a high speed braking area means the rear wheel is off the ground for a good bit.

Now I'm never going to be able to execute on all of these items in a single day or weekend, but keeping them in mind and actively picking one or two items a day to work on until the improvement is there gives me a plan. It may take me a good 10 track days there to figure these out but because I have solid reference data, I can build that plan.

After my detailed analysis, I noted the following specifics for my riding development with this bike at Buttonwillow 13 (at the bottom of this post are screen captures of data + still photos to highlight specifics in further detail):

1. Front straight to Sunrise - Aron should be WOT & longer more braking, should see about 140mph GPS speed; finished with lighter/longer to get used to the huge horsepower difference on this bike versus the little bikes

2. Sunrise exit - Aron needs to use more of the track, run to the outside curb, this can be done with more throttle longer

3. Sunrise to Off Ramp (T2), Reference rider (RR) never stands the bike all the way up because he's used all of the track (above)

4. Off Ramp (T2), brake release is good but RR carries more speed & lean

5. Braking into Cotton Corners, Aron too aggressive with initial braking, brake point and release fine

6. Cotton Corners left, Aron should adjust apex closer to the end of the right-hand curbing

7. Grapevine, Aron chops throttle to 0% whereas RR reduces throttle to turn the bike

8. Exiting Grapevine, RR uses more track sooner while reducing lean angle

9. Club Corner - RR turns in earlier, never fully cuts throttle, just reduction and is on throttle past the apex; exiting RR only goes 1/2 of the track toward the right, Aron goes further, no need; Aron’s exit is good on the left before the Bus Stop

10. Bus Stop - Aron’s brake release is late and turns in too early; Aron needs to turn in later and be alongside the right hand curb

11. Riverside - RR carries light acceleration all the way until turn-in for apex, Aron is scrubbing speed; exit - RR never chops throttle, turns in on throttle

12. Phil Hill - Aron uses too much brake for the speed, sheds too much speed; brake timing, shape, and release are okay; Aron needs to be careful to not turn in too early

13. Entrance to The Sweeper - Aron needs to hold throttle just a little longer; RR takes a wider entrance, this is the biggest divergence in lines

14. Sweeper - Aron carries quite a bit less roll speed and lean angle; try to carry more speed and lean into it, be sure to drift wide whether on throttle or just carrying more speed into it; on the exit, get direction before adding throttle, saw some impatience from Aron

15. Esses - basically okay but don’t chop the throttle for the last left entirely, minimize reduced throttle time; exit is good

16. Sunset - entrance, brake initiation point is fine, Aron goes to too much brake, reduces, and returns to big brake pressure

17. Sunset Exit - the bump is an issue for Aron, he had trouble navigating the least bumpy path; RR gets the bike outside very early after the apex, well before the end of the right-hand curbing, Aron follows the expected line; before apexing, be thinking about getting to the outside as soon as possible

Since I'm going with revised gearing (old gearing was stock 15/42t or 2.80 overall, new gearing will be 15/44t 2.93 overall), I've mapped out my tentative gear selection in advance, just so I have one less thing to think about and can hopefully hit the ground running.

• T1 (Sunrise) - G2

• T2 (Off Ramp)- G2, short shift to G3 on exit

• T3 (Cotton Corners) - G2/G3?  Definitely G3 short shift for...

• T4 (Grapevine) - G3

• T5 (Club Corner) - G3/G4 - might short shift to G4?

• T6 (Bus Stop) - G3, short shift to G4 before Truck Stop

• T7 (Truck Stop) - G4

• T8 (Riverside) - G4, maybe G5?

• T9  (Phil Hill) - G3, G4 on exit

• T10 (Sweeper) - G3

• T11 (Esses) - G4 short shift

• T12 (Sunset) - G3, exit to G4

Details on the bike and data setup:

• 2022 Aprilia Tuono V4 Factory (TV4F)

• AiM Solo 2 DL (S2DL) + AiM SmartyCam 3 Sport with custom AiM ECU profile, mounted to the handlebar with RAM ball mounts

• OE Aprilia RSV4 Factory forged aluminum wheels, stock 15/42 gearing with 520 chain conversion, OEM Pirelli Supercorsa SP v3 in 120/70 Front, 200/55 Rear, no warmers, cold pressure of 31 psi front, 23 psi rear

• Akrapovic carbon fiber slip-on with mid-pipe and Gabro tune

• Brembo RCS 17 Corsa Corta master cylinder (I really like this master cylinder and the lever, the stock one was fine)

A complete lap, reference rider fastest lap (red) versus my baseline consistent for the day (blue). The 1st graph represents the speed at a given part of the track, the 2nd is the effective braking force (measured in G), and the third is the time spread. While I certainly see some gaps in the speed trace, overall in the third graph I don't see any glaring rapid spreads, which generally indicates degree of application is what's needed.

In the following graphics, when discussing speed, I'm referring to GPS speed, not what's on the bike's dash. Motorcycle speedometers are notoriously inaccurate due to manufacturing and tire circumference when leaned over. If you look at some of the dash speeds versus GPS speeds you will see up to around 15mph variances. Slip is the speed differential the bike's ECU measures between front and rear wheels, higher positive slip numbers will trigger TC/WC, higher negative numbers may trigger ABS. Hand throttle position is indicated, as well as GPS speed, gear selection, and RPM. Roll angle is lean angle with positive and negative numbers and reported by the bike's internal IMU. Unfortunately the lap time infographics weren't configured correctly that day and I had fixed it for day 2 but that ended up being littered with red flags so I never got a clean session. In the still shots of the video, reference rider is top right, I am bottom right.

I don't have a ton of experience at Buttonwillow but I did review several laps of my own and this was the fairly consistent execution I saw on my faster laps (even if it wasn't the fastest) so I feel it is representative of what I did that day.

Point 1 - Front straight, WOT until here

Point 1 - About 1/3 the distance past the 2nd to last access road on the right, assuming I'm able to get to WOT

Points 2 & 3 - Sunset - The reference rider uses more of the track (above image); also note that the reference rider doesn't get as vertical as I do because it's one continuous left for him

Point 4 - Off-ramp - While the slow point speed is nearly identical (fractionally after this point), the reference rider has more condensed braking (3rd graph, 2nd braking segment) with increasing brake pressure toward the end

Point 5 - Cotton Corners entrance - there's a lot to unpack here. There isn't an easily identifiable beginning of braking marker and being a vital point (it's a decent straight for WOT) so for me, it's more of a sense of appropriate brake initiation. The dip creates a wheelie bump so WOT is challenging, even for the reference rider. I turn in a bit too early (as seen in the video) and I over-slow the slow point.

Point 5 - First right in Cotton Corners - notice how the control rider's apex is not only appreciably faster but closer to the end of the right-hand curb. My throttle was earlier and faster which will run me wide sooner (though it's 3rd gear vs his 2nd gear so it's not hugely dramatic). This tells me that I need to remind myself that it's an entry corner with a slightly later turn-in point and that my apex needs to be later in that right-hand curb.

Point 9 - Club Corner - Reference rider has initiated turn-in significantly sooner (immediately after the wheelie bump) while using more throttle at virtually the same speed. At the same point on the track, the reference rider is at 24° of lean and I'm at 1°.

Point 9 - In the 1st graph you can see that the reference rider has given up almost no speed whereas I have rolled off considerably, this results in a 13+ mph speed discrepancy with similar lean angles, the lean angle because I had turned in later. The slower speed with more weight on the front makes the bike easier to turn (for me) but I give up too much speed.

Point 10 - The Bus Stop - While I had more speed coming out of the left before the Bus Stop corner, I didn't use as much of the track as the reference rider. In order to navigate the corner at a higher speed (without adding greater risk), I need to be closer (or on) the right-hand curb. As a result, my slow point was 5mph slower with nearly the same lean as the reference rider. This turn's exit also is one that will take time for me to burn into my memory because you can't see the exit fully until you're well into it and overshooting the exit will put you in the dirt.

Point 11 - Riverside - Data zoomed into this area; the reference rider is mildly accelerating at this point whereas I am between scrubbing speed (frictional forces of the corner). You can see what it requires: a bit more throttle and a little more lean. Our relative position and speed at the apex are nearly identical though the reference rider dives in from a further left position on the track. I'm not comfortable running high up on the outside of Riverside yet.

Point 12 - Phil Hill - I'm generally happy with my technical execution of this corner though I can condense my braking a bit and carry more roll speed through it. It is a bit tricky because it's a blind rise and a later turn-in works better for it. As it drops a few feet on the exit it's bumpy but you know you got your position right if your rear tire hits right about where the curb and the asphalt meet.

Point 13 - en route to the Sweeper - We both short-shift to 4th gear and I briefly get to WOT but I roll out of it. Granted, this is a fast section and on a liter bike, it's pretty bumpy. The reference rider stays in more throttle longer than I do and goes to the brakes later. My average brake pressure in this section is higher than his even though he carries an average speed of 5mph more (which means I'm using too much brake overall).

Point 15 - The Esses - While my initial exit of the sweeper and entrance to the Esses was very similar to the reference rider's, I completely chopped the throttle to turn for the last left-hand turn. I couldn't get the video to line up quite the same but in going through frame by frame our direction was very similar. The reference rider does shed some speed for the last left but by reducing throttle, not cutting throttle as I do. The result is a pretty significant difference in the slow point roll speed. I also short-shift into the Esses, otherwise, I would have shed even more speed had I also been in 3rd gear.

Point 16 - Sunset entrance - The reference rider and I end up with identical terminal speeds (125 mph) however he begins his braking about 10' later than I do and goes to quite a bit more initial brake pressure whereas I start earlier, never build as much pressure and my release is about 5 feet sooner than his. I still manage a higher overall average in this section (3.5 bar vs 2.6) which results in me over-slowing for the slow point. Part of this is my anxiousness about the bumps just past the apex (recall, 'go to the brakes when you're scared?). My reference rider also hits as high as 1.5 G in deceleration, which coming down from ~120 mph, means the rear is probably starting to lift. In the video, you can also see the front wiggling which would indicate he's collapsed the front end. That's more deceleration than I'm comfortable with so that's not my immediate goal but condensing braking a bit and tapering off more is my goal. I'm using 3rd gear vs him using 2nd, my hopes being to have less aggressive power so I can get through the bumps with less TC intervention.

Point 17 - Sunset exit - more than the speed, notice how quickly the reference rider gets to the outside of the corner, navigating a cleaner path. Also telling is that even though our throttle usage is nearly the same, my gear selection is 3rd vs his 2nd, I'm going slower and my slip numbers are higher than his, demonstrating that his path was cleaner. The reference rider also gets to WOT whereas I'm kind of playing with the throttle instead of committing to it.

Buttonwillow Raceway, Config #13 Track Map