Starting Off the Season With Some Twists and Turns
- Sam Dignan
- Mar 23, 2023
- 9 min read
Dealing with the strain of IndyCars at Suzuka
iRacing's second season of 2023 started out with a very entertaining combination Dallara IR18s* at Suzuka. This race, while being closer than any I have run in a while, was also one of the most mentally demanding races I have maybe ever done. The race was 35 laps, would require two pit stops, and at least one change of tire compound. This introduced a surprising number of strategy options that I am still trying to fully wrap my head around.
Check out the whole race on YouTube
The Circuit
Suzuka is know best for hosting the Japanese Grand Prix. It was originally built by Honda as a testing facility and prioritizes handling and control. The circuit is 5.8km (3.6 miles), has 18 turns and only sweeps through 40m (131ft) of elevation, Figure 1. With only two main
straights, both of which are level or down hill, lateral grip and downforce are the priority. Figure 2 shows the maximum end of straight speed, minimum cornering speed, and cornering acceleration around Suzuka. The lap shown is my fastest lap of the race.
The average lateral acceleration through most of the corners is over 2.5G. With so many fast, high commitment corners and such short straights Suzuka can be an extremely fun but there is no where to relax and refocus. Because of this I find races here to be abnormally mentally taxing.
Pre Race Prep
Since the end of the LMP1 era in iRacing I have been looking a new car to drive. The new BMW LMDh seems like an obvious solution and I was hoping that it would be. Unfortunately, I have had a really challenging time getting my head and driving style around it. I've also had a strange desire to give the IR18 a try. It is a car that I have never actually tried to race outside of a handful of fixed oval races. But I figured it was worth a try.
Over Week 13, iRacing's week off to roll out new content and features, I did a few AI races with the IR18 and really enjoyed the feel. I looked up some YouTube videos on how the IR18 wants to be driven. This one was particularly helpful and suggested the iRacing supplied setup was pretty good. Once week 1 rolled around I gave it a try, and to my surprise the setup was pretty good and very competitive. Figures 3 - 5 show rising lap time results for the three practice sessions I joined last week.
Figures 3 and 4 show that while I am not leading the pack I am in the ballpark of the fast people. It is also challenging to look at many of the stints and not suspect there is a lot of hot lapping / qualifying practie because most of the stints are only three or four laps long. When looking at longer stints I am certainly not that far off the pace. This was really exciting to see. Some of my frustration with the LMDh is that I feel meaningfully off the pace.
The next major thing to look at is tire life. There are two tire compounds in the IR18 series and both need to be used in the race. The "Primary" tire is the harder compound and the "Alternate" is the softer compound. The obvious solution is to run the softer, faster, tire for as much of the race as possible. This assumes that the soft tire is always faster than the hard tire. Figures 6 and 7 are the same sessions as Figures 3 and 4 but the lap times are shown in
order and not sorted fastest to slowest. This helps define the break over point between the soft and hard tire lap times. Stints 1 and Stint 4 in Figure 6 are on the hards, stint 5 in Figure 6 is on the soft tire. The only stint in Figure 7 is also on the hard tire.
I seem to be relatively consistent on the hard tire putting in lap times in the 103s (1:43) range. Looking at Figure 6, the soft tire is faster than 103s for the first five or six laps. Between laps five through eight they seems to be about the same as the hard tire. Then after about six to eight laps they become slower than the hard tire. Stint 5 started with a full fuel load, 70l (18.5gal), in the future I need to compare the soft tire life on lower fuel loads.
The final check is fuel consumption. In practice I was using about 4.67l/lap (1.2gal/lap) and the IR18 has a 70l tank. This results in a 14 lap stint, Figure 8, and needing 163.45l (43.2gal) in
the race. I will need to stop twice and add at least 23.5l (6.2gal) on the last stop. Because I will likely want to change tires at both stops it is important to consider the time it takes to change the tires. The IR18 can change tires while it is being refueled and it takes 5s to change all four tires. The fuel flow is 2.96l/s (0.78gal/s). If I were to only add 23.5l at the last stop I would be waiting on the fuel to finish and not adding time to my stop waiting on tires. It is worth noting for the future that if I need to change tires the minimum amount of fuel I should ever take is 15l.
Going into the race I am planning on starting on the hard tires. Running a full fuel stint, changing to the soft tires and add 50l (13.2gal) of fuel. Doing seven or eight laps on the soft tires. I should have less than 20l (5.3gal) of fuel in the tank and should be able to add the remaining 45l to 50l needed to finish the race on the hard tires.
Race Results
Surprisingly I joined the highest SoF race of the week at 2.6k. Knowing this in hindsight I am really happy with my qualifying and race pace. I qualified 6th, 0.5s behind 5th, 1s behind 4th, and 0.5s ahead of 7th. Starting the race I was expecting more chaos leading into turn 1 but everyone around me got through safely and I started to settle into a comfortable race pace. Table 1 shows the tire usage by each driver and the laps they starting using each compound.
As I expected, and my qualifying showed, the leading five cars started walking away from me but I also starting walking away from the car behind me. I also got a free pass on lap 3 when one of the cars ahead of me crashed in turn 2. Figure 9 shows the gap from me to the rest of the drivers. Ivan was the only driver ahead of me to start on the softs and he quickly moved into the lead before pitting on lap 7 and using a soft, hard, hard strategy. Daniel and Pascal, behind me, started on hard and soft tires respectively. This helped Pascal pass Daniel in the opening laps but he used up too much of his tires and was not able to challenge me in the opening phase of the race. I was able pull almost 10 seconds on
Pascal before he pitted on lap 10. He then can out on the hard tires before pitting again for softs on lap 26.
Daniel and I both pitted on lap 15, I chose to use the softs and he chose to use a second set of hards. Looking at the slope of my gap to Pascal I do not think I used the softs as well as I could have. First, I think I took on too much fuel. I only needed to take on 23.5l but I elected to take on 55l. The added weight very likely hurt my tire life and it forced me to do at least 8 laps to guarantee I would be able to take on enough fuel to go to the end. Second, I forgot to change the brake balance and rear anti-roll bar to the soft tire configuration. This forced me to divide my focus between warming up the tires and getting my tools in the correct position. Forgetting to change my tools in the pit lane is just one example of how mentally maxed out I was. The softs had a significantly more understeer facing balance than the hards and this contributed to the slow out lap and underutilizing the softs.
These mistakes and issues led to me not gaining enough time on Pascal and coming out of the pits just behind Jak Kent. Jak was in the middle of a tire stint and slower than me throughout the first ~20 laps. I was immediately being held up and lost even more time to Pascal. I did pass Jak after 2 laps and thankfully I did not lose too much time to Pascal.
The last few laps ended up being quite a bit more exciting than I had expected. After not using the soft tires as well as I should have and getting slightly held up by Jak, Pascal was able the drive me down and pass me through 130R (turn 11 in Figure 1) on lap 30. But he
had run his tires off and was not able to continue driving away. Figure 10 shows the gap between me and the other drivers from laps 25 - 35. Notice how Pascal takes 7.5s out of me from lap 26 to lap 30, but then cannot get more than 1s away from me after that. Realizing that he was not going to drive away I noticed I was a bit faster out of Spoon (turn 10 in Figure 1). On the second to last lap I got a very good run out of Spoon got on the push to pass and was able to pass Pascal back through 130R. I think both of us were racing hard and I think we both considered it fair enough for the phase of the race but I don't like that I had to go off the track on the outside to fully make the pass stick. That being said I don't think either of us were going to give an inch at the end of the race. Pascal unfortunately spun coming out of Spoon on the final lap, certainly trying to set up a run, and finished behind Daniel.
Conclusions and Future Work
Despite a somewhat boring start and middle phase of the race my first IR18 road race was extremely exciting at the end. The strategy options for fuel and tires really introduced a level of complexity that I was not expecting. Of the top three cars, who finished within 10s of each other, there were two different strategies. Among Pascal, Daniel, and me there were three different strategies and we finished within 5s of each other. The focus required to drive the IR18 was a lot for me and adding the strategy options on to that, I was feeling a bit mentally overwelled and really exhausted by the end of the race.
In the future I need to do more work before the race on different tire strategies. I also need to have a better understanding of how to use the soft tires straight out of the pits. Some of this is just more practice and experience in the car but I also think I might be able to come up with a tool to help with tire options. For example, going into the race I would not have expected Pascal's strategy to work, but obviously it was a viable option for our level.
Hopefully I will have more time to race this season than last season and I definitely want to try the IR18 a few more times. But before that happens George and I are going to take on the 12h of Sebring on Saturday 25th. We will be driving the BMW LMDh and I will be streaming it from my YouTube channel. Check it out and a bunch of our other races there.
Additional Charts for Nerds
Figures 11 and 12 show my lap times relative to some statistical metrics, average, median, and standard deviation. The standard deviation values are pretty wide and I think this is mostly do to small field sizes and a lot of people doing different things. My main take away from these is that I am as fast or faster than the average and median lap times, so I am in the ballpark for being on the pace.
Figure 15 shows that there really where two races within this race. The leading four cars and the midfield. Being 50s off the lead at the end it is not surprising that I was 1s - 1.5s off the leader's pace for the entirety of the race. But Figure 14 also shows that this race was quite bottom heavy. I am faster than the average and the median, and the median is faster than the average. This suggests there are some really slow cars in the race and that it might be better to consider this to be a field of 8 - 10 cars instead of the official 15.
Figure 16 continues to show that I just really did not get enough out of the softs. The slope of my soft tire stint relative to many of the other soft tire stints is quite a bit less, slower. I would like to work on a metric similar to Figures 11, 12, and 14 to compare soft and hard tire performance.
*iRacing has lost the license to use IndyCar to Motorsports Games. There is some ambiguity around using IndyCar and iRacing together so I am going to refer to the car as the Dallara IR18 or the IR18 for the remainder of this piece. -Return to the top
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