Last weekend (July 28 & 29) was the first time on track with the FR-S. We went to buttonwillow raceway to run clockwise config 13 – the yardstick for lap times on the west coast. We had a pretty ambitious schedule as we were not only putting the car on the track for the first time, but we also were testing incremental improvements. Which meant crawling around under the car in the summer desert heat to make changes to the car. I;m not referring to myself in the plural 3rd person, I actually had help. Big thanks to the folks at 949 racing for being track side to help make the changes and assist in set up. I’m pretty sure I wouldn’t have been able to accomplish all of the rounds of testing that we did if I was by myself. They have a lot of interest in these cars, and have started carrying parts for them. Check out their racing blog: http://949racing.blogspot.com/
The timed results below were with Emilio of 949 driving. He got more out of the car on this weekend than I did. Hats off to him. He’s fast and never put a wheel wrong with little seat time. We recorded tire pressures, pyrometer readings, damper travel, gps data and timing. We combined this with alignment and driver feedback to start building our own setup manual.
Test 1: Baseline – 2:12.1
We needed to know what the car did straight off the showroom floor. The only change we made was brake pads before our first run. We decided a stock pad test was pointless considering the ambient heat of the weekend. I just wasn’t willing to trash parts we knew wouldn’t be up to the task. We installed Carbotech XP10 (front) and XP8 (rear) before we got the the track. I bedded them late at night on the drive out of LA on the way to the track. Nothing like 80 to 20mph braking runs over and over until you can smell the melting pad material transferring material to the rotors.
Stock alignment includes an average of -.3 degrees camber in the front and it showed. The pyrometer data shows that we’re destroying the outer shoulder of the stock wooden wagon wheels and the insides aren’t sharing the burden. This is to be expected with this little amount of camber. The car is fun to drive this way, and pretty well balanced, but mushes its way around the track. Not sure why these tires were picked for the chassis from the factory.
Tread squirm overheated the tires really quickly. There isn’t very much braking feel coming through the pedal in this config. I attribute this again to the non-track oriented tires and having way more brake pad than rubber on the ground.
The car has a pretty big tendency to oversteer stock when you get close to the limits. Driving at 8/10ths the car does what you want it to. But if you are trying for the penultimate lap it is not very forgiving. It never puts you in danger, but the car starts to rotate slowing you down. Messing with tire pressures helped this some, but in our experience when you tune out the high speed oversteer, a low speed understeer starts to show up when the car is pushed. This criticisms are minor in light of how good the car is stock. Out of the box, this is one of the most well balanced and fun cars to drive on the track I have ever driven.
Test 2: wheels, tires, and crash bolts – 2:07.1
In a previous post, I went through wheel selection for this car. We are using 17×9 hub centric Mach V wheels. They weight 17.8s, and there simply isn’t anything else on the market that meets all these specs. I’ve painted them blue instead of powder coating them, and may outline in another post how I did this. We’ve mounted 255/40/17 Hankook RS3’s on them. Sometimes hellafunctional and hellaflush cross over. This is one of those instances. I noticed after we returned home that the rears just barely touched the rolled fenders. Nothing dangerous – just enough to discolor the tire.
We also installed factory crashbolts for the impreza (part # 20540AA090 at a subaru dealer). All these are is a bolt with a thinner shaft diameter so there is some slop between the suspension upright and the damper. This slop allows you to tilt the top of the hub and wheel inboard creating more static camber. These bolts gave us an average of .7 degrees of camber gain in the front (total of 1 degree). 1 degree clearly isn’t enough for the soft sidewall of the RS3s that really like to roll over, but it was a start, and helped us get the front tires to clear the fenders.
The addition of the larger tires calmed the oversteer at the limit. 5 years ago, the fastest street tires were only good for a lap before they overheated. the RS3s soak up as much heat as you can create on an almost 100 degree day lap after lap.
The only weakness is that braking feel isn’t as good as traditional r compounds when they heat up, but way better than the stock tires. In this configuration, the car has way more grip than it does suspension control. Its fast, but sways through corners in a manner that isn’t confidence inspiring when trying to go fast. But to pick up 6 seconds in tires and a little front camber is pretty staggering.
Test 3: AST prototype dampers- 2:03.75
AST has just released their newest damper technology – the 4150 series. (http://www.ast-usa.com/) Our test day included not only the first prototype of AST’s designed for the FR-S, but also one of the first examples of the 4150 damper internals in use in the US. We sourced tophats from other vendors to get these dampers on the car in time for this weekend. (Vorshlag adjustable ones in the front, and OEM WRX rear ones) Our goal was to ensure fitment and figure out what “works” on the track and street.
We installed them in the garage at Buttonwillow while the thermostat said it was 99 degrees in the shade. Stock damper removal on this chassis is a breeze. The front struts fall right out with the removal of 5 bolts (plus the sway bar endlink and disconnecting the abs sensor and brake line), and the rears don’t even require disconnecting the sway bar to come out. Very refreshing compared to other small cars on the market today.
The whole swap took less than an hour plus time to realign and corner balance. We lowered the car about 3/4″ and got decent cross weights on the car. For those that care about these things, the cross weight changed only about .1% when you add a 175lb driver. We didn’t play with the alignment after the first install, and there is probably a little more time in the setup from getting this just right.
Out of the box, dampers and front alignment made about 3.5 seconds. My earlier complaints of unpredictability and lack of balance at the limit are gone. Other dampers may have more adjustment knobs and other bells and whistles, but there is something really nice about simplicity that works. You can actually tell a difference with each of the 12 clicks the AST monotubes make to the ride. We were able to balance the chassis with these. While it wasn’t the fastest way around the track, more than once we had a very controllable oversteer slide at 90 mi/hr through the riverside turn (high speed right hand sweeper). It soaks up pavement transitions and imperfections in a manner the stock ride couldn’t. You can hammer over most of the track bumpers without upsetting the chassis a huge amount. And while this was a track focused test, the spring rates we chose rode almost like stock when the damper valving was set to its softest settings.
The feedback document we provided to AST will be incorporated into the final design. I think this will prove to be a competitive advantage for AST. There were some things discovered through our testing that I don’t think manufactures could account for without real track testing and and data. After this test, I’m a little skeptical of other dampers that are on the market that never saw the track before being released. You can only fine tune a design so much from behind a computer. After the AST design is finalized and on the market, I’ll point out some of those differences and talk about spring rates, etc. Sorry for being cloak and dagger about it. I look forward to seeing these on the market so that others can provide feedback as well.
Going to the track in this sort of heat really beats on cars and drivers. The FR-S only has a water temp sensor that never moved from the safe zone throughout the whole weekend. But I suspect there is a dead spot in the middle of the dial from which it won’t move until things get really hot. I hope to get an oil temp sensor in the car in the near future to see what is really going on. The car now turns hard enough that the stock seat isn’t really sufficient. I left with a sore left knee from holding myself up against the door, which means a more supportive seat is needed. I’m not quite sure how to handle this with the desire to keep the car street comfortable yet.
I posted a quick video in the previous blog entry, and will put another one up in a bit when I have a moment to edit. Admittedly, the focus for the weekend was collecting data and consequently, the cameras weren’t always in the car, or always on, etc. Photo credit here goes to Vanhap Photography. With little time to do more than take a shot with a point and shoot, its always good to have a local pro hanging around for beauty shots.
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