Beating the Heat
I managed to squeeze in two more events before the full heat of summer arrived.
At the end of May, my friend Shane Reetz (@trackdailycrx) was in town to hang out for a few days and co-drive my Fiero at Buttonwillow Raceway during a Speed District track day. Shane's track car is a tastefully modified and upgraded 2nd gen Honda CR-X that he tracks & autocrosses nearly every weekend in the PNW. He's also a performance driving coach and has a good handle on using data to improve driver and vehicle performance.
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Buttonwillow Raceway Park from the sky, with the fresh black asphalt of Track 2 still curing in the foreground
Shane showed up with small bag of clothes and a giant bag of race gear and data logging equipment.
The event was Saturday morning, and we had Friday to prepare with a reasonably short checklist of items to complete:
- Mount AIM SOLO 2 DL and configure CAN protocol for ALDL->CAN bridge and BMW MK60E5 ABS
- Mount tablet for CircuitStorm app
- Mount GoPro
- Mount Android phone with RaceChrono Pro
- Mount Qstarz Bluetooth GPS on the windshield (for RaceChrono)
- Shakedown run up Angeles Crest Highway with all dataloggers on
- Fill the fuel tank
- Load the truck and put the car on the trailer
By around 9pm, we had tested all the loggers and were seeing reasonable data. The AIM Solo was recording everything from individual corner brake pressures, wheel speeds and accelerometer data, to engine coolant temp, oil temp, throttle position, and fuel level. The only really useful things missing are ride height sensors and steering angle, but I will be adding those soon.
After we got back from the Crest we filled the fuel tank, jacked up the front of the car to do one last check of the front brakes, and took a break for dinner. An hour later we returned to the garage and were assaulted with gasoline vapors. There was a giant puddle of fuel on the floor and a steady drip from the back of the fuel tank. 10pm...
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We got the ass end of the car up in the air and quickly assessed the situation. The vent pipe on the back of the fuel tank was loose where it had been swaged/crimped by the factory. The only option to resolve it was to replace the tank. As luck would have it, I had purchased a new tank from Rodney last year to use for a future swap. By 1 am the new tank was in and filled and the car was on the trailer.
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After 4 hours of sleep, we were on our way to Buttonwillow.
Track Day
If you are lucky enough to have Speed District events within driving distance of your home, you probably know how exceptional these events are. Unlike the racing + HPDE orgs that cram track day activities in with lots of club racing, Speed District hosts HPDE-only events with limited car counts and give drivers so many sessions per day you will pack up and go home due to exhaustion before you're out of track time. It's a great environment for testing, tuning, and driver development. Attendees also tend to be very fast and very courteous, so you're likely to have a few unimpeded laps per session as getting stuck in traffic isn't a problem.
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It was going to be a long day and we had a lot to get done, so we loaded up on coffee and got to work.
The goal of the first session was a more thorough shakedown run for the chassis (the Crest drive was just to make sure the loggers and dash were working) and to get the tires up to temp, set hot pressures, and check brake temps. No problems there -- we bled 3 psi out to achieve a hot pressure of 29 psi, checked the rotor temps (they reached bedding temp), and confirmed the brake fluid was staying cool. No engine error codes, no ABS codes, all looked good on the car.
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As for the data systems, the AIM Solo 2 DL had recorded a full trace, RaceChrono was looking good, my dash was logging but CircuitStorm never even started recorded and didn't trigger the GoPro either.
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For the second session, Shane hopped into the passenger seat for his first ride around Buttonwillow in real life. He has set some great lap times in the simulator but some of the surface irregularities (especially the bumps/dips around Riverside and Sunset) are different. Still, a simulated Buttonwillow is accurate enough to serve as a refresher if you've been to the track before. Time in the sim also gives you a huge head start if you've never been to the track before, as there are multiple blind corners.
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We found the issue with CircuitStorm -- sort of. If the GoPro goes to sleep, CircuitStorm won't be able to start it on its own and complains about the camera being off. Since I couldn't see or reach the tablet from the driver seat in my first session, I didn't know what was going on. With Shane sitting shotgun we he turned it on for this run.
For the next few sessions, air temp stayed under 90*F and we had no problems with oil or coolant temperatures. Shane adapted fairly quickly to the car and we were both setting reasonable lap times, but no personal bests and we were getting slower as the day went on. This is typical for sunny days as the track temperatures skyrocket by the afternoon and soft tires get greasy. However, neither of us could consistently brake for some of the corners on the track, and the steering alignment seemed to be getting progressively worse as the day went on.
So we dug into the data to try to figure out what was going on. The drawbacks of some of the systems became immediately clear, and I'll summarize here as there is really a clear winner.
CircuitStorm was too brittle and clunky to manage, and we couldn't get it to connect to the online Podium service which would have been a nice benefit. RaceChrono Pro is a nice tool if you're just looking to improve lap times and don't have a coach or need to develop the car. It's very easy to quickly compare laps and see what corners you need to work on. It also has a very useful lap timer display while you're in the car.
AIM Solo 2 DL and Race Studio 3
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The AIM Solo 2 DL was the real star of the show. It started automatically when the car started moving, and recorded basically every CAN channel on the car at 10hz, plus it has built in GPS and accelerometers. When I pulled into the pit garage and turned off the car, the Solo 2 DL would stay on with its internal battery to allow downloading data to a laptop. Shane didn't even have to get up from his chair. The Solo 2 DL has a WiFi access point that you connect to from a laptop, and a few clicks later you have data loaded and visualized in a very professional tool.
The most immediately obvious issue was both of us were over-braking before most high speed corners, leaving a lot of cornering force and exit speed on the table. There were easily seconds to work off with improved technique. We were also inconsistent in braking into some turns -- particularly Off Ramp and Sunset -- and even overshooting the ideal turn-in point at times. It was something we noticed while driving but couldn't pin down what was going on.
It took some digging but I eventually found that in a few particular corners the brake pressure generated by the pedal (about 100 bar out of the master cylinder at peak force) didn't result in the same amount of longitudinal acceleration, and it wasn't due to ABS intervention. This meant the effective brake friction coefficient was going down. Sure enough, the thermal indicating paint on the brake rotors had turned a color that was literally off the charts of the operating temperature range for the racing brake pad compound I'm using.
The next event was two weeks away and with a guaranteed hotter air temperature, so brake ducting and improved braking technique would both be necessary. The first to get cool air to the center of the rotors so the cooling vanes can do their job, and the second to reduce the over-braking and the additional heat generation it causes.
There were more fixes to make too but I wouldn't discover those until the post-event teardown...
