S2000 vs BRZ at the track: track oriented discussion
 

I'll start with this video, which has my commentary:

[ame="http://www.youtube.com/watch?v=gaArJZOMCpI"]BRZ vs S2000 - YouTube[/ame]

Seems like a pretty good match up if the drivers are both of the same ability. The obvious power advantage is obvious. Do you guys think that changing the suspension setup on the BRZ to have less understeer would result in better lap times? It seems that quite a few mags have decided to use the BRZ as their test car rather than the FRS because the understeer is more predictable and allows for later breaking into corners.

Is it that the FRS has too great a tendency to oversteer and maybe dialing out the understeer of the BRZ to so something more neutral, but still less oversteer than the FRS is the ideal setup?

Edit: Also, thanks for the vid!

I'm impressed with both the BRZ and the S2000. I think the S2000 is truly a remarkable car even though it's getting a tad aged.

I had my FRS out on a track on Sunday and I don't think it has a "tendency to oversteer" at all. In fact I came to the conclusion that it doesn't happen by accident, you have to want it to happen, to forcibly induce it. It might be better for oversteering than the BRZ but the FRS by no means is overly tail happy.

I would even enter a corner and lift the throttle on entry and I still got understeer (neutral to understeer). I attribute that to the lack of dynamic camber in the Mac struts and the front tires getting over burdened abruptly. I surmise with 1-2 degree of negative camber up front that same lift-on-entry would then result in oversteer.

Would someone who has increased their negative camber up front chime in on this please?

In my AP1 that would have lead to full opposite lock and a "pucker". I feel the FRS is less tail happy, even on corner exit than the AP1. I attribute this not to one thing but a combination. Spring/shock setup, alignment, sway bars and power differences, along with the FRS/BRZ's complete lack of camber up front even under compression.

I agree in the video that the brakes on the 86 are very good (but the OEM pads do fade pretty quick). Also, that video is very good and I'd be interested to see what 86 can do vs the S2000 if the 86 had another 30-40bhp and -1 degree of camber up front.

Our alignment in this video is:

Front
-1.1 camber
0 toe

Rear
-1.4 camber
0 toe

Surprisingly, we experienced MORE understeer turning into turn 2 (the sharp right hander), but overall the car was more stable than with the stock alignment; you don't see the large corrections when upsetting the car by hitting curbs from our hot lap two weekends ago. Under steady state cornering, the car still refuses to rotate; lifting mid turn did nothing, as did stabbing the throttle. However, large weight transfers could get the rear to come out during the higher speed (90+) turns. You can do things with this car that you would NEVER be able to get away with in a S2k.

Our stock alignment was:

Front
0 camber
1/16" toe-in

Rear
-1.25 camber
3/64" toe-in


We're going to add some toe-out to the front this week :D

Try disconnecting one side of the front sway bar and see how it feels for a session, could be fun.

With the understeer were you able to be a lot more aggressive on your trail-braking, almost to the point of entering a corners as if you were driving a FWD setup? If not, give that a try too. You might be able to take the brake pedal right to the apex and then immediately return to WOT.

uh God... Now I want to get back out on track! :burnrubber:

I'm interested in hearing your thoughts on your tire size choice. I was planning to go with 245/40-17 Star Specs or RS3, on a 17x9 wheel. After watching your video, I'm questioning whether or not I really need something that wide. It'd be nice to save a few bucks on tires every year for track purposes, plus I could go with a lighter 7.5-8" wheel.

So, what made you settle on 215/45-17? If you could purchase new tires today, would you still go with 215 or get something a little wider? Are you running the stock wheels?

Great video by the way - loved it.

I wondering about the tires too. It looked like the S2000 had a lot of tire.

Oddly enough, the car doesn't allow me to trail brake the way I want to. It "freaks out" and flashes an orange "traction" light in the tachometer, and just plows. This happens when you get to about 85% of the grip of the front tires. The same light was on solid when we were doing dyno pulls.

Left foot braking seems to work though :)

TemeCal: I know your post was directed at the OP but I wanted to chime in as I've been facing this conundrum on my race car. Do I run the 205 tire at 180 degrees or the 225 tire at 150 degrees?

Hankook for example, on their C51's say that it's most important to run the tire in the optimal temperature zone that it best performs. Some also say that using a tire that's too wide increases rotational drag which decreases the ROI of going wider.

Next year I'm going to buy 205 and 225 Kooks and do back to back testing at a test and tune and measure the temps and compare my data logger to see what lateral G's each of them max out at and what my top speed is at the end of the longest straight. I hope this testing puts my questions to rest.

So, getting back to the BRZ... The car is quite light and with only a 200hp engine the power isn't over taxing the rear tire at corner exit very much. Running a 245 may be so much tire that you end up facing what I face with my race car... You won't get the tires hot enough to where they reach and operate at their peak, but maybe not. I think, considering the weight, balance and power of this car that a 225 RS3 or Star Spec would be a great fit. However, I'd love to see (2) Toyobaru at the race track with 225 Star Specs and 245 Star Specs and collect back to back tire data and lateral G loads.

Our original decision to go with 215/45/17 was to keep the tire size consistent with the stock Michelins. At this point, I've theorized that a larger tire may actually be TOO MUCH tire for the car. I plan on slowly increasing the front tire size until the rear is running out of grip before the fronts do, while keeping an eye on lap times, to see where the balance point is for tire size/lap times. As it is, the car cannot break the rear tires loose, even at WOT in 2nd gear, so I see no reason to increase rear grip when it's not the limiting factor.

HOWEVER, this time around at Buttonwillow, I was brushing the limiter going into Buttonhook in 3rd, 4th before Lost Hill, and 4th before Sunset. Going to a 225/45/17 may increase gearing JUST enough to stop me from needing to make additional shifts. Once we get some coilovers on the car, lengthening the gears with tires will not be enough, and we will need to make the extra shifts, but for now, it may be a band-aid fix.

We had actually taken a pair of 225/45/17 RS3 with us in case the front tires started chunking, but having -1.1 camber was enough to prevent that (although I'd still like to get more).

We're also waiting on a set of conversion spacers, so that we can share wheels with our S2ks; s2ks run REALLY high offset, so a 15mm conversion spacer with my +55 wheels will fit perfect; we also have a set of 17x9 +63, which will also fit great with the spacers.

Also, for reference, here's a lap in my personal S2k from the same weekend.

[ame="http://www.youtube.com/watch?v=s1syrlAw1ek"]S2000 CR Buttonwillow CW13 (2:03) - YouTube[/ame]

Interesting. I turned off my TC while I was on track and when I experienced corner entry understeer I didn't see any flashing lights on the dash.

S2000s have enough power that they can break the rear loose, even with 255 RS3. They get looser with speed due to the variable rear toe (toe-out with lift, toe-in with compression; car has rear lift at speed) which only makes them want MORE rear grip. A lot of track s2ks run square setups to eliminate understeer on corner turn-in, as well as having the ability to rotate tires.

It's remarkable how different the rear grip is, given the relative similarities between the BRZ and S2k on paper.

If you watch in HD, you can see it. It's an orange light further to the right of the "shift" light, and much dimmer. First instance is at about 0:34. You can see it on other corners where I'm trail braking as well.

The video is washed out on purpose, so that everything inside the car including the gauges/dash can be seen better.

[ame="http://www.youtube.com/watch?v=qqfvDEOuuZY"]Buttonwillow 13CW Subaru BRZ 2:07 - YouTube[/ame]