Lemons Telemetry Analysis

After a race I like to look at telemetry. It shows what each driver is doing. It’s important to also run video so you can point at a corner that is 10 mph off and say “there was a yellow flag”. As usual, my telemetry is recorded with an AiM Solo DL and I view it with Race Studio Analysis. I’ve taken a screen shot of the fast laps of each driver (actually a pair of fast laps) with my fast lap as the reference lap (black line). The screen shows three graphs (1) GPS speed (2) engine RPM (3) time delta. Ideally, I’d love to have brake pressure and steering angle, but these are generally enough to infer what’s going on inside the cockpit.

One of the first things to note is that the blue driver’s RPMs are so much lower. The blue driver shifts well before he needs to. However, this doesn’t impact his speed or lap times very much. The red driver shifts much more often and is in 2nd gear several times, also not affecting lap times very much. When in doubt, drive the higher gear.

None of these laps were completely free of traffic. The red driver lost ~4 seconds in T3W to a yellow flag, for example. You can also find GPS errors where the speed is clearly recorded incorrectly for a brief time. That’s why it’s a good idea to examine multiple laps and have the corresponding video.

The biggest issue I find in the driving is that the green and red drivers slow down too early and too much in the faster corners. They do okay in the slow corners, and their final speeds may be as good as the reference lap. In slow, out fast, does actually lead to high speeds on straights! But in slow also leads to throwing away speed, and in a momentum car with very little engine, that’s a no-no. The better mantra is: in on the limit, out on the limit. That’s easy to say, but not easy to do.

Exiting a corner on the limit is like tightrope-walking; entering a corner on the limit like jumping onto a tightrope while blindfolded. — Mark Donohue

So how does one get better at jumping on a tightrope blindfolded? Do I really need to say it? Practice. And where does one practice such a dangerous activity? Do I really need to say it? Simulation.

Race Report: Lemons Thunderhill

I’ll be updating this post each day.

Thursday – arrival

In the picture below you can see how simple my race operation is. I flat tow my Yaris behind a 3.0L Ranger. It’s a very flat route so the 145 hp Ranger has no problems towing the car and gear. I arrived at the track at 4:30 the day before the test and tech day to try to get a good pit spot. I wanted something under the awning so I could shelter the pit from sun/rain. Mission accomplished.

Friday – test and tech

Tech was a breeze. The car has raced in several other series and all the safety issues are well sorted. We got into the B class with zero penalty laps. That was what we expected.

We had decided that the full test day was too expensive. $349 for 1 driver and $149 for each additional. We considered doing the half day at $249 + $100 but then decided to play a joke instead. People walked by and  puzzled: “why is the wing on the front”. We dead-panned “it’s front-wheel drive”. The look of disbelief on Daniel and Mario’s faces was worth the effort.

The weather forecast changes hourly. The latest news is that Saturday should be dry all day with a high of 78. Sunday may be wet in the morning. I told the team I get to drive the wettest stint. That may screw up driver order, but as team owner, I’m putting my foot down on that. There’s no way I can keep up with the fastest cars on a dry track, but give me puddles and let’s see who comes out on top.

Saturday – race day

The race day didn’t start the way we wanted. Our first driver got 2 black flags. One of them was for going off track to avoid a collision. I’ll take a black flag over dents any day. But 2 black flags pretty much put us out of contention. Also, there was some blisteringly fast B cars we could never catch. Our second driver didn’t like the way the car was driving. Actually, neither did the first driver. When I asked if the rear had no traction, he said neither end had traction. Puzzling. So we decided to turn the rest of the race day into a tuning day.

Mario went out and came back in after a few laps complaining that the car was oversteering badly. We were running Federal 595 RS-RR 225/45/15 15×9 on the front and Falken RT615K+ 205/50/15 15×7 rear. So we decided to switch the rears out for a stickier compound: Brigestone RE-71R 205/50/15 15×7. This time he stayed out a while and had a great race with a pickup. When he came back in, he said the car was much more neutral now and that I should get in to see what I thought.

The first thing I thought was the brakes are still mushy. The pedal starts hard but just mushes out and goes to the floor. That’s really disconcerting because it gives you very little brake feel. And without a firm pedal, it’s pretty hard to heel-toe shift. Oh well, I just did more straight-line braking and eased in the clutch. Not ideal, but I’m okay working around problems. It’s likely an aging master cylinder.

The next thing I thought was that the 225 RS-RRs 15×9 aren’t that much different from the 205 15×7 I had run in earlier races. The tires don’t actually feel very fast. Part of that is because they are miserable under braking. They slide way too easily. They aren’t a particularly loud tire, like say the NT-05, and in 225 they are definitely on the quiet side. I started to understand why driver 2 thought the car had no grip on either end. The RS-RR doesn’t feel like it stops very well, so it appears to have no front grip. But once you get into a corner, it’s side grip is really good and overwhelms the thinner and harder rear tire, leading to oversteer. Mario said it was a lot of work just keeping it on track. I didn’t get to try the 615K+ rear setup, but the RE-71R rears felt pretty well planted.

While the car felt like it had better acceleration at low speeds, surely due to the weight loss, the drag was noticeably higher. This may be because the cut down doors don’t have mirrors or the wind deflectors I added. So the inside of the car turned into a parachute. It meant that top speed on the main straight was just 90-91 mph, or about 5 mph lower than usual. That didn’t stop me from having fun though. I managed a 3:43 in my few laps on track. You can see the entire stint in the video below (quality is not good because Windows 10 Movie Maker sucks. I may re-encode this on my Mac later in the week).

Sunday – race day

The forecast was wrong. We arrived at the track to find it drying. I was expecting a lot of rain early so I could one-up some fast cars but it just wasn’t very wet. Discouraged, I decided not to drive first. Danny drove first and while he was out we got our pit crew member, Tiernan, a driving wristband. He got in the car next and despite all the warnings about the blind turn 9C that connects the East and West tracks, he did what a lot of people do, and drove straight though. When he got to the penalty box, they decided to throw the book at him. My book. I had dropped off about 15 copies of the book to be sold for the Alex’s Lemonade Stand charity. Tiernan’s penalty was to read a passage from the book while being filmed. If it doesn’t make the Lemons wrap-up video, I’ll post it here.

The rain started picking up and it seemed there was enough rain to have a bit of fun. And fun was had. I got my wish and was able to dice with the fastest cars on track… and beat them.

Mario drove next and also had a blast splashing around (in the muck and the mire). But then the track started drying and he decided it just wasn’t as much fun. We wanted to get Daniel and Tiernan back in the car one more time, so they split the time on a mostly dry track. In the end, we were 56th out of 110 entries, or something like that. After we realized we weren’t in contention, we relaxed and had a lot of fun. This weekend reminds me how much fun Lemons is. That said, Lemons is changing, and not necessarily for the better. I’ll comment on that later.

Winning B Class: part 1, fuel consumption

When I built my 2007 Toyota Yaris for racing, I aimed it at the SCCA B-Spec rules. Only after competing in an SCCA sprint race did I realize that sprint racing is not for me. It’s much more expensive per hour, the “win every corner” mindset makes it more dangerous, and it’s lonely not hanging out with a team. With that in mind, the decision was clear: re-build it for endurance racing. Sadly, it’s a little too slow for most applications. In Lucky Dog, it’s slower than most class C cars (when it doesn’t get protested for being too new). In ChampCar, the build is 120 out of 500 points so there are plenty of points to work with. But in order to compete it would take an engine swap or forced induction. Given that I want to keep it emissions legal in California, these options are mostly out of the question. Neither World Racing League nor American Endurance Racing league run events out West, so the target is Lemons. In 24 Hours of Lemons, it would probably be placed in class B. Could we win the B class with a little luck and a lot of planning? Well, this post is the first in a series where we document our efforts.

So what are our advantages? Reliability and economy. Unlike half of the cars in B class, we have a very good chance of running the whole 14.5 hours of a typical race (8 hours on Saturday and 6.5 hours on Sunday). However, we will be competing against much faster cars. We need to be on track as much as possible. This means zero black flags, of course, but it also means as little time as possible in the pits. In fact, we’re hoping to cut out one pit stop.

Most endurance driving stints are 2 hours or less. Lucky Dog and ChampCar actually limit drivers to 2 hours. Lemons has no such rule. However, most cars burn fuel fast enough that they pit between 1.5 and 2 hours. That means that a typical team will run 4-5 stints on Saturday and 3-4 stints on Sunday. I believe our best chance to win means driving only 3 stints on each day. The question is, can a single tank of fuel last 2 hours and 40 minutes on Saturday?

Our previous racing at Thunderhill, Laguna Seca, and Buttonwillow shows that the Yaris burns about 4 gallons per hour. With its 11.1 gallon fuel tank, it should be able to run 2:45. That’s no problem for Sunday but Saturday could be. If our calculation is off by 10%, we might find ourselves running out of fuel, and there would be no chance of winning if that happened. So we need to figure out how to extend our range.

The simplest answer is to install a fuel cell. That would instantaneously solve the range problem but would bring up new problems. They’re expensive. It would require removing the stock fuel tank and fabricating a new structure. The car would also no longer be street legal. The center of gravity would be higher. Too many negatives, so I’m not getting a fuel cell. Lemons does not allow one to modify OEM fuel fillers, so I can’t increase capacity with a fat intake tube either. So if we can’t increase fuel capacity, we’re going to have to increase efficiency.

Economic driving

Who knows how to get the most miles from a tank of gas? Hyper-milers. I’m sort of a closet hyper-miler myself. On the street, I often drive under the speed limit, conserve as much momentum as possible, pump my tires up pretty high, and draft trucks on the highway. I don’t go as far as making aerodynamic improvements though. But we will on the racecar. However, that’s a topic for another day. Today we are going to consider the act of racing more conservatively. The driving can’t change so much that we do more harm than good, though. We have these two connected questions to consider.

  1. How much fuel do we save by changing our driving style?
  2. What style of driving optimizes our chance of winning?

To answer these questions, I’ll be using Assetto Corsa, Brands Hatch, and the NA Miata. While I do have a Yaris model for Assetto Corsa, I don’t think it’s very accurate. The NA Miata is one of the highest quality models and besides, Miata Is Always The Answer. The car is loaded up with 5 liters of fuel, “Street” tires at 30 psi, max camber, and zero toe.

So let’s define a few different driving styles.

  • Hard – Hit the brakes hard. Hit the throttle hard. Steer like a mad man. In slow, out fast. Brake in a straight line. Shift at red line (7k). Lots of amateur racers drive like this, especially those in powerful cars. Clearly we’re not considering this, but I wanted to investigate the efficiency of a typical sucky racer. Intensity 9/10ths. Intelligence 3/10ths.
  • Soft – Conserve momentum as much as possible with early apex lines. Coast slightly before braking zones. Shift at 6K and choose a higher gear if there’s any question. Steering corrections are unnecessary driving like this. Intensity 5/10ths.
  • Enduro – Drive fast but with a lot of margin for error (not much yaw). Shift at 6.5k. Use lots of trail-braking but only a little brake-turning. Intensity 7/10ths.
  • Sprint – Drive faster with plenty of yaw. Still keep some safety in reserve. Shift at 7k RPM. Intensity 8/10ths.

The most interesting finding for me was that Soft driving increased fuel economy by an amazing 40% over Hard driving while having nearly identical lap times. My typical Enduro style results in decent fuel economy and speed. I’m only about 1% off my Sprint pace but my economy is up 13%. Compared to driving Soft, Enduro is 3.3% faster at the cost of 22% less economy. So which style is best for endurance racing? Is it better to drive slowly to get a tank of gas to last 148 minutes, drive as fast as possible while only getting 103 minutes, or something in between?

Style Laps Fast Median Laps Minutes
Hard 10.3 63.96 64.18 98.88 105.8
Soft 14.5 63.84 63.97 139.2 148.4
Enduro 11.9 61.31 61.91 114.2 117.9
Sprint 10.5 60.84 61.29 100.8 103.0

The track is live for 480 minutes on Saturday. But not all of those 480 minutes are hot. Lemons does live towing and when there are several tow trucks on track at once they will fly full course yellows. Sometimes that goes on for 5 minutes and sometimes for 30. I recall one race where they threw a red flag and I waited nearly 20 minutes with the engine off. It’s hard to predict how much of the 480 minutes are green and how much are yellow. So we need to investigate what happens with 10 to 120 minutes of yellow flag time, which results in 470 to 360 minutes of race time.

The next thing to consider is how many driving minutes there are. The car isn’t lapping when it’s in the pits. My calculations use a pit stop time of 10 minutes. It doesn’t take that long to fuel a car and change drivers, but Lemons pit stops occur in the paddock, outside the timing loop on the track. So every time you pit, you lose 1 lap in addition to transit time.

Taking into account lap times, fuel burn, yellow flag time, and number of pit stops, we arrive at the table below. I have highlighted the driving style that produces the most laps in red.

Yellow Hard Soft Enduro Sprint
10 401 412 426 420
20 392 403 416 411
30 383 393 407 401
40 373 393 397 391
50 364 384 387 381
60 364 375 377 372
70 355 364 368 372
80 345 356 358 362
90 336 347 348 352
100 327 337 339 342
110 317 328 329 332
120 308 318 319 323

When Enduro beats Sprint, it does so by 5.67 laps on average. Conversely, Sprint beats Enduro by 3.67 laps on average. The difference comes down to how many stints there are. Enduro sometimes runs one less stint, and when it does, it has a huge advantage. It doesn’t impede lap times that much and has the added benefit of reducing fatigue and the chance of a black flag (which pretty much guarantees we won’t win B class). Driving Soft never wins. It can be as much as 10 laps better than driving Hard, and there are a few situations (highlighted in blue) where it is better than Sprint. But it never beats Enduro. There isn’t much point in driving super Soft. The hyper-miler in me wanted that to be useful, but it isn’t.

Telemetry or it didn’t happen!

The line colors are:

  • Red Hard
  • Blue Soft
  • Green Enduro
  • Black Sprint

The panels from top to bottom are:

  • Brake pressure
  • RPM
  • Speed
  • Steering angle
  • Throttle
  • Time delta

Click on the image to open it in a new window and then follow along with the text below.

There are 4 braking zones (top panel). In Soft style I only applied brakes in 2 of these. Note how low the RPMs are in general. You can also see long periods of coasting in the 5th panel (throttle). But the speed graph (3rd panel) isn’t that terrible. Driving economically is a kind of intellectual challenge, which is why I hyper-mile in real life. I have to do something to make street driving entertaining.

Hard style sees me sawing the fuck out of the steering wheel (4th panel) and mashing the brake and throttle pedals mercilessly. The brake trace (top) shows early and hard application of the brakes followed by no trailing pressure. Just on/off. It’s not a fast or economical way to drive.

There isn’t a huge difference in driving style between Enduro and Sprint. I use more brake pressure in Sprint mode to turn the car and I also choose a lower gear in a couple of places. I consciously take an earlier apex line in Enduro to favor momentum over engine.

Race Report: Thunderhill West

One way to get a trophy is to be the fastest car on track. Another way is to be the slowest car. Haha no, ChampCar Endurance Series doesn’t actually give out trophies to the slowest car on track. We got the Sportsmanship trophy! I’m really proud of that because the team was full of first-time racers, and I didn’t want our inexperience to cause problems with the other racers. During the pre-race meeting I made a quick announcement along the lines of “We’ve got a bunch of first time racers here. Please don’t try to race us, we aren’t in your race. And please don’t try to scare us, we’re already scared”. We received nothing but encouragement all race long.

ChampCar uses a point system where each car has a base value and modifications with additional points. The Yaris was valued at 100 points plus 10 points per corner for lowering springs, so 140 total. Most of the field is near the target 500 points. The Yaris is really under powered for ChampCar. It was kind of depressing being the slowest car on track. But it’s a good car for a first race as it doesn’t have bad manners and is cheap as dirt to race.

Saving the brakes

If you’ve been following along, you know that last week we placed 3rd in a 24 hour endurance race and that we had to make a set of pads last as long as possible. With 2 drivers left, there was about 2 mm of pad remaining. So the plan was to save the brakes. The next driver in decided to completely ignore those team orders and drive as fast as possible. How do I know? By looking at the telemetry. I can also see that he needs some coaching on how to drive. So let’s take a look at the traces. You’ll probably want to open this in another window to see the details.

The blue and red lines are driver #1 (going as fast as possible). The green and black lines are driver #2 saving the brakes (green) and driving faster on the very last lap of the race because there were no brakes to save (black). The panels are speed, RPM, throttle, and time differential going top to bottom.

  • At 1100 and 1400 feet, the red line speed graph hits the bottom of the graph. Driving so fast that one runs off track (1100 ft) and spins the car (1400 ft) in the same lap were not part of the plan and could get you pulled from the car.
  • The plan was the green line. Notice how the slope of the line goes gradually down at 8500, 10000, and 13500. Driver #2 is coasting into braking zones. As you can see from the RPM trace, he’s using the gearbox to help slow the car. Normally, that’s a no-no, but in this case, we wanted him to do that. My favorite part is that he hits the same minimum speed at 9000 ft on his fast and slow laps. He has planned out how to arrive at the same speed at the most critical corner without using any brakes. Well done.
  • The blue and red traces generally follow the black trace on the speed graph. The speeds of the black line are higher everywhere, which is why the lap time was 2:29 rather than 2:32. The deceleration slopes are similar. This indicates that driver #1 was hitting the brakes hard. Nooooo.
  • Do you see the weird throttle blip at 1300 feet on the red/blue lines? That’s not a downshift, but an upshift. Is that some kind of slam shift technique I’m not aware of?
  • Look how the black line gets to 100% throttle and stays there. That’s how to go fast in a momentum car. There should be very little time at partial throttle in the Yaris. The red and blue lines are often at partial throttle. This is because the driver lacks confidence when the tires are slipping in a corner. Tires are supposed to slip.
  • Driver #1 has some misconceptions about how to drive fast. It’s not about braking as late and hard as possible. The fastest drivers did 2:26 on this track. You can’t make up 6 seconds by braking late. You have to enter faster, back up the corners, get to 100% throttle before the apex, and leave it there until the next corner.

So driver #1 has some learning to do. We all do. The car finished higher than it had any right to so I still wouldn’t change anything about the weekend. Except maybe eat another bowl of tortilla soup. I should have done that.

Race Report: Buttonwillow 24HR

I wouldn’t change a thing…

That doesn’t mean everything went to plan. It didn’t. And that’s probably why it was such a special event.

  • 340 treadwear tires. I was feeling cheap and didn’t want to spend a lot on tires. Having such a slow car, I figured we had no chance at doing well, so why bother with fast rubber? We’re here to do our first 24hr race. It doesn’t matter if we’re competitive. All that matters is we’re there.
  • Unknown brake pads. There aren’t many brake pad options for the Yaris. I’ve had EBC Greenstuff before, and they melted. I had G-loc R10s, but they only lasted 14 hours. So I decided to bring Hawk HPS and EBC Redstuff. There isn’t really anything else unless I get them custom made. The HPS were down to the metal after 8 hours. We thought they would last least 12 hours, but no. So we were a little unprepared to do the brake swap when the car came in. We had no idea how long the Redstuff would last and needed them to go 16 more hours. So we coasted into braking zones, used the gearbox to help decelerate, and scrubbed speed with decreasing radius entries. At the end, we were scraping metal to metal.
  • Inexperience. 4 of our drivers had never driven Buttonwillow before the race. 4 of our drivers had never driven the Yaris. 5 of our drivers had never raced at night. 2 of our drivers were on their 2nd wheel-to-wheel race.
  • Street legal. The car is street legal and smog legal. It has the unleaded restrictor in the filler neck. It takes forever to refuel. I think the fastest pit stop was about 10 min.
  • Radios. I don’t know why but the radios hardly ever worked.
  • Live streaming. The live stream from the car was surprisingly robust and was up most of the race. It was fantastic watching the car from the pit or clubhouse. The video below shows my favorite moment of the race. I had just spent the first 90 minutes saving the brake pads and then decided to chase down some faster cars for fun. A back-n-forth battle with the race-winning Miata, the 949 Racing Honda, and the Death Race pickup ensued. It ended when I hit the 2 hour limit.

Controversy or Compliment?

Lucky Dog rules state that your car has to be at least 15 years old. Otherwise it goes in the Super Dawg class where the really fast cars can play outside the standard classing. The last time we raced with them, they classed us in the C (slow) class. And that’s the class we ran this race… until we got protested multiple times and sent to Super Dawg. Apparently some other C class cars didn’t like that we were doing so well. Wait a second. We have 100 hp, 2500 lbs with driver, 340 TW tires, fragile brake pads, and insufficient lighting. Apparently that doesn’t mitigate our 2007 model year. The design is basically the Echo, which is from 2001 or something, but heavier. FOR FUCKS SAKE, learn to drive your car. It’s not like we’re racing gods on this team. OK, that’s not quite true. We had Pablo Marx driving with us, and he is a racing god. But that was 1/6 of the team, and the rest of us are mortals. Protesting us was probably the highest form of compliment anyone could have given us, so whoever you are THANK YOU. You have no idea how happy this made us.

Oh yeah, we finished 3rd place overall. Congrats to Risky Whiskey on the overall win from the C class. Well deserved.

How expensive is racing?

Back to back racing weekends? An endurance race at Laguna Seca with Lucky Dog followed by a sprint race at Thunderhill with the SCCA… Being able to race on world-class racetracks is not something I take for granted. I’m living a dream and I fully recognize it. It saddens me that not everyone has the chance to do these things. Auto racing is an expensive hobby. But exactly how expensive is it? Let’s investigate with my B-Spec Yaris as an example of a really cheap car to build and run.

Initial Build

The initial build cost me about $7000. I saved a lot of money getting the cage built by students at an Evil Genius Racing fabrication workshop. Sometimes I think $7k for a hobby is too much. But it’s also a completely legal street car that gets 45 mpg on the highway. So it does have some utility. Note that none of the costs below figure in my time. I spent and continue to spend many weekends working on the car.

  • 2007 Toyota Yaris $3040 (used)
  • Cage fabrication $1080
  • Fire system $370
  • Kill switch $40
  • Interior net $90
  • Window net & mount $90
  • Driver seat $100 (used) & bracket $100
  • Harness $140
  • Seat brace $200
  • Roll bar padding $60
  • Steering wheel quick release $130 + adapter $70 + wheel $30
  • Convex mirror $20
  • Front tow hook $12
  • Crash bolts $20 (for alignment)
  • Hood pins $10
  • Cold box $50 (cold therapy unit used from ebay)
  • Exhaust pipe fabrication $20
  • Wheels $400
  • Cold air intake $300
  • TRD suspension $520
  • Fuel testing port $80
  • Numbers $50

Operating Costs

In addition to the initial build, there’s the stuff that costs money on a regular basis. This includes alignment, motor oil, filter, diff oil, brake pads, brake rotors, brake fluid, and gasoline. Less regular, but still expected, are things like the engine, transmission, clutch, and body work. All of this amounts to about $65/hr. But we haven’t gotten to the big ticket items: event fees and tires. Endurance race fees are roughly $100/hr and 200 treadwear tires are about $25/hr ($500 per set and they last 20 hours). Sprint race event fees are about $300/hr and tire costs are $200/hr ($800 per set and they last 4 hours).

Endurance racing: $190 / hour

Sprint racing: $565 / hour

Other expenses

The build and operating costs do not include my personal safety equipment, cameras, radios, or telemetry. That stuff adds another $2500 or so. Those items are good for 10 years and can be carried from car to car. In addition, there are expenses for transportation, room, and board. I camp at the track and subsist on sandwiches, so those expenses are pretty low.