This post is about a test day at Thunderhill with the Yaris. I’ll update it a few times as data comes in.
The day before
Tiernan came over today to help get the car ready. There were lots of minor things to do like make sure the radios, cold box, and telemetry were all working. Also the usual packing of jacks, tools, tires, etc. The Lemons Race is about 2 weeks away, and making sure everything works now will save us time and worry in the future.
So what exactly are we testing? Mostly tires and wings.
In the past, I’ve set the car up the way I like it and it turned out that nobody else liked it. So this time, I want to get several different drivers in the car to determine what setup everyone else likes. What we’re talking about here is the tendency to oversteer or understeer. I like a car that oversteers. That can be tuned with tire pressures, but even more drastically with tire compounds. There are 3 configurations I want to test.
- Hankook RS-4 front and back (225/45/15). This is the “baseline fast setup”. To be sure, there are faster 200TW tires. But the RS-4 strikes a great balance between speed and longevity. It’s also the spec tire for Lucky Dog Racing League. I don’t plan on using tires stickier than the RS-4 because I don’t want the cost of switching out stickier rubber. I have rims in 15×9 and 15×8. I may test out both configurations to see if there’s a difference.
- Hankook RS-4 front (225/45/15), Federal RS-Pro (215/40/17) rear. When I tracked my Elantra, I used Federal RS-Pro tires, which melted horribly. I still have 3 that are hardly used, and I want to try using them on the rear, where they might survive. I’m not sure what the grip balance is between these and the RS-4. Let’s see what my teammates think.
- IRIS SEFAR front (215/40/17), Federal RS-Pro (215/40/17) rear. This is the Lemons Class C setup. It will probably understeer a lot as the IRIS tires are 300TW and the Federals are 200TW. I don’t want to go the other way around because too much oversteer in a race might not be very safe.
I wanted to test 2 different wings: eBay vs. 9 Lives Racing. I wasn’t able to get the 9LR wing mounted in time, so it looks like the test will be wing vs. no wing. In my previous testing, I thought the wing improved handling in fast corners. I’m curious what the other drivers think.
I’ll be running an AiM Solo DL and video camera all day. Check back for to see that data.
I may have as many as 4 drivers, but I’m not 100% sure who is showing up. I’m not planning on taking many laps myself, as I know the car pretty well. But I am curious to see how the RS-Pros feel on the rear and experience how bad the Lemons setup will be.
As they say, no plan survives contact with the enemy. In this case, the plan to test rear tires somewhat failed. The rear wheels were rubbing on the wheel wells, so we weren’t able to try the larger rear tires. I’ll have to cut the metal to make enough clearance. However, we were able to test a variety of tire pressures with the RS-4s and also test the IRIS SEFAR tires up front.
Weather or power?
There was a head wind on the main straight all day. This caused our top speed to be about 88 mph. I’ve seen 95 before. I don’t know if this was entirely due to the head wind or it was also a loss of power. I’ve experienced a loss of power before and found that changing the IAT solved it. I’ll have to get in there and clean it just to be sure.
Ideal tire pressures
Running RS-4s on all corners produced too much grip in the rear. Everyone complained that the car was pushing. We ended up overinflating the rears and that made a car that was pretty neutral. The final hot pressures were 34-35 front, 40-42 rear.
The $53 Lemons tires were nicely loud and produced okay grip. I took a few laps and posted a 2:26.01. This was about 5 seconds off my fast lap on the RS-4s (2:20.90). I don’t know if they will survive a whole race. Or even a whole day. But we’re going to try running these as a way of getting into C Class.
Here’s a picture of the abuse the SEFAR took after about 1 hour of hard driving.
My very expensive Li-ion battery died. It had been acting weird lately and it stopped working entirely right before the last stint. This is why we have test days. I’ll be replacing that pronto.
Hasn’t happened yet