GSpeed's 2015 BRZ- SCCA Super Touring Build

[TCR]

Ah right.

I'm not familiar with the Tarmac coilovers and just assumed they came with an adjustable pillow ball top.

[GSpeed]

Today was a lovely day to get on track and see how fast we could go. We tweaked our damper settings in compression and the car calmed down a bit over disturbances. I'm in love with the stance of this car now. We're 1" lower, with 3/8" of rake, and it looks so purposeful with those 245s filling up the fenders.



Track temps were well over 100F for our second session, so we decided to drop the tire pressures way down and see what happened. We went with hot pressures of 31 psi front, 30 psi rear, and the car was awesome! IR data shows temps decreased about 15 degrees mid-corner:



Blue traces are beginning of the session, green traces are end of the session. Top set is fronts, lower set is rears. The rears are actually slightly warmer, the scale is just shifted down for clarity. Those two laps shown there were within half a second of each other, so they were both at full speed. The first lap with the lower hot pressures was about 3 tenths faster than the previous lap.

Our best time this morning was a 1:26.3. We were hoping to get into the 25s, but traffic was heavy and we just couldn't make it happen. We'll post up some videos tomorrow, hopefully. With the horrible internet service we get being out in the middle of nowhere, uploading a full session to YouTube takes hours. We're still going to try and start putting all of our sessions online in their entirety, though.

We did get our fuel pressure sensors put together for sale, though, so that's a plus. We've got a big break coming up in August when the track slows down (less available track days), so we'll use that opportunity to catch up on part development work and other more Viper-shaped projects.

Summary
Configuration: RCE Tarmac 2 Coilovers, PFC Z-rated Front Pads
Best Lap: 1:26.3

[Lee]

sensational thread

[GSpeed]

Swaybars!

Today, we installed some Whiteline 22mm and 18mm sway bars. They were provided by the guys at AftermarketSuspensionParts.com in exchange for our thoughts and test data. We'll be putting them on track this coming Friday, and posting up our results here.





We're really looking forward to seeing how these guys affect the mid-corner balance of the car. We've got some push that we'd love to dial out, and these bars should help us keep more load on the inside tires. I'd love to see the IR data show a little bit lower temps on the right tires through left handers, and maybe a temperature increase through right-hand corners.

[Icanfaptothis86]

Curious what went into the idea to run a 17 x 9 wheel.

Was wondering if you think the weight advantage of a 17 x 8 setup might outweigh (stupid pun) the added traction advantage of 17 x 9. Also what is the real traction requirements of a stock 200hp 86.

[GSpeed]

There may be some gains to be had from a narrower tire and wheel, like reduced unsprung weight and reduced rolling resistance. It might be possible to guess/calculate, if we had some accurate figures on the rolling resistance difference between the 225s and 245s. I'm hesitant to say it would be faster overall on our specific setup, though, since we're working the 245s VERY hard according to IR data. I'm not a tire engineer, but I feel like the amount of energy going into the tire would have to be lower with a 225 in the same conditions, so we'd probably slow down in the corners. If someone running this track has an Aim system in a similar car, I'd love to compare sector times and see.

Are we traction limited? No, definitely not in a straight line. Peak acceleration is somewhere around the 0.2-0.3 G mark. We are braking at north of 1G, though, so we could argue the wider tire is helping pick up some time there as well.

All that being said, though, we're not going to be staying at the 200hp point. That's the main reason. We didn't want to buy a second set of wheels and tires just for one test, however interesting it may be. We've also been testing out various parts as we go, and changing tire size would further confuse the results by adding yet another variable. The car will be living it's life at around 300 whp, so we will definitely be getting our money's worth out of the 9" wheels.

Does that answer your question adequately?

BTW, just got off track after 3 sessions this morning. Analysis to follow this afternoon or tomorrow morning. Short summary- Tires and Brakes are destroyed. We really need to go talk to Subaru and see how a car goes through 4 sets of brake pads with only 450 miles on the odometer, must be something wrong with the damn thing.

[Icanfaptothis86]

Originally Posted by PST

There may be some gains to be had from a narrower tire and wheel, like reduced unsprung weight and reduced rolling resistance. It might be possible to guess/calculate, if we had some accurate figures on the rolling resistance difference between the 225s and 245s. I'm hesitant to say it would be faster overall on our specific setup, though, since we're working the 245s VERY hard according to IR data. I'm not a tire engineer, but I feel like the amount of energy going into the tire would have to be lower with a 225 in the same conditions, so we'd probably slow down in the corners. If someone running this track has an Aim system in a similar car, I'd love to compare sector times and see.

Are we traction limited? No, definitely not in a straight line. Peak acceleration is somewhere around the 0.2-0.3 G mark. We are braking at north of 1G, though, so we could argue the wider tire is helping pick up some time there as well.

All that being said, though, we're not going to be staying at the 200hp point. That's the main reason. We didn't want to buy a second set of wheels and tires just for one test, however interesting it may be. We've also been testing out various parts as we go, and changing tire size would further confuse the results by adding yet another variable. The car will be living it's life at around 300 whp, so we will definitely be getting our money's worth out of the 9" wheels.

Does that answer your question adequately?

BTW, just got off track after 3 sessions this morning. Analysis to follow this afternoon or tomorrow morning. Short summary- Tires and Brakes are destroyed. We really need to go talk to Subaru and see how a car goes through 4 sets of brake pads with only 450 miles on the odometer, must be something wrong with the damn thing.

Yeah I figured you went straight to 17 x 9 because 300+hp is the end goal.

I am just in the research phase as I already have a track dedicated toy and am really trying to gather lots of info so I get it right.

I am thinking that if I go the NA route and keep it pretty sack-less than rolling resistance might and unsprung weight might be the most important consideration

I mainly track at GSS and MSRH in Houston which I am sure you guys are familiar with so with the small straights there with an underpowered car it might actually make more sense to run the wider tire. Not sure.

Thank you for the color.

[GSpeed]

Yeah, it's definitely a toss-up. I'd love to see how much of a difference it really makes, because I have a feeling it's a marginal difference. In my personal opinion, it's blown out of proportion when you're talking about 2cm worth of tire, we're not discussing putting some 335s on here, you know? We see almost a second's worth of difference between 80° mornings and 95° afternoons, so I think it might get lost in the noise. I know those are the types of questions we seek to answer, but that one seems like a lot of money for a small improvement. It would take many sessions and lots of statistical analysis to prove one was faster than the other.

Next time you're up this way, stop by the shop and say hi.

[bertio]

I was so sad when I got to the end.

Amazing work guys keep it up!

[Jonsey]

Can't believe you killed the tires already! Is it a camber issue and just wearing the outsides or are you just wearing through the RE71Rs that fast? I certainly hope not as I am considering those as my next set if I don't decide to wear big boy pants.


Also, your post was missing some really important information. Each week I wait to see if it will be the week when you surpass my time.

[GSpeed]

Alright, so today was interesting.

We installed the Whiteline swaybars (22mm & 18mm) this past week, and put them on track to see what they did for us. The roll stiffness was dropped substantially, but times did not improve. Given the fact that we've put nine sessions on these tires in the brutal Texas summer heat, I can't say I'm surprised. For street tires, they've held up well at a race pace.

We've got an IR sensor watching the track temps, and we've seen temps over 140°F averaged over the course of a lap. The front right tire has been seeing temps mid corner of almost 250°F. It's not beyond reason to assume that ten test sessions at those temperatures is just more than these tires can handle. They're designed for low-temp grip, not this stuff.

So let's talk swaybars. Here's a plot of body roll over a lap.

Red- Stock shocks and springs, stock sway bars.
Orange- Tarmac 2s, stock sway bars.
Green- Tarmac 2s, Whiteline bars (Front Hard, Rear Soft)
Blue- Tarmac 2s, Whiteline bars (Front Hard, Rear Medium)



If you take the above data, and blend it in with some lateral acceleration data, you can see the roll stiffness:



Straights are a little messy, but the corners are very clear.

We ran the first session with the bars at hard/medium this morning. The car was extremely stiff, but body roll was noticeably reduced. There was quite a bit of steady-state oversteer, so we ended the session after 8 laps.

The second session was with the bars at hard/soft. The steady state balance was much, much better. Not perfect, but almost. We were hoping to at least match the times from last weekend (since we knew it was a bit hotter this time), but we weren't close. The best we got today was 1:27.2.

If you just look at the lap times, it would appear the swaybars slowed us down. That's so contrary to conventional wisdom, that we figured that something else had to be going on. We switched back to the OEM swaybars for a third session and see what happened. Sure enough, the OEM bars were slower. So what made us slower? Tires. They're toasted.



Here's a plot showing tire temps (averaged across the tire) for the front and rear, across two different sessions. The blue lines are from July 30th, and the time was 1:26.4, damn near our fastest so far. The green lines are from today's second morning session, where we ran a 1:27.2 (with swaybars, so in theory we should be faster). Fronts are on top, rears are on the bottom. The Y-axis is shifted down 100° for the rears so you can see both on the same plot coherently.

You can see in that graph that the tires are more or less operating at the same temperature. Aside from the big slide through Big Bend on the blue trace, they're within a few degrees of each other, yet one is significantly slower than the other. Not saying it's a conclusive proof, but it shows that the car is being driven just as hard for both sessions.

So where do we go from here? Well, for one, new tires. We've got some sexy prototype camber plates on the way from a vendor that will remain nameless at this point, but we're pretty excited. So we'll be able to get a more appropriate amount of camber up front. We'll also be switching out our rear bar from 18mm to 16mm to see if we can't get an even better balance.

We'll run a session or two in that configuration (new tires, camber plates, and sways), then we'll be installing some super sexy underbody aero parts courtesy of Velox Motorsports. We'll be running the race splitter and rear diffuser, and we're very excited to see how it improves the handling of the car. Nothing like real-world track testing to back up your CFD!

On the non-dynamic front, we've got a Perrin oil cooler in the mail, and a Kartboy shifter to install. Since we've got a few weeks until our next available track day on the 1.7 CCW, this may be the last track session update for a while. There will be more updates forthcoming, but they'll be increasingly technical in nature. We'll probably be working on our monster 96 GTS Viper project car, so some pictures of that car may find their way into this build thread.

As always, we hope everyone enjoys this content as much as we love creating it. Our doors are always open (at least, 8-5 Wed-Sun), so please feel free to stop by for a tour.

Why aren't we posting videos from the SmartyCam? Our ISP is awful out here and we can't hardly upload anything significant. We've got lots of footage, and eventually it WILL be posted on our Youtube channel. No dubstep overlays. Promise.

[philooo]

another awesome / convincing update... nothing beats a nice set to graphs !

I am VERY impatient to see the result with the VELOX aero parts. they look really cool, but I wonder how much faster they can make you.

[Icanfaptothis86]

Please dont flame me but please try not to change too many things at once to make sure youre getting good data. If you are running the swaybars on shit tires than the data is called into question. If you upgrade tires and aero than it will be difficult to account for the overall gains. Just my worry here.

I am going to the track next weekend down here in houston. We are looking at highs of 103. I dont expect my Michelins to hold up.

[GSpeed]

Originally Posted by Icanfaptothis86

Please dont flame me but please try not to change too many things at once to make sure youre getting good data. If you are running the swaybars on shit tires than the data is called into question. If you upgrade tires and aero than it will be difficult to account for the overall gains. Just my worry here.

You're absolutely right, and that's something we strive to do. It's a tough balance, because each session does cost a fair amount of money, so we have to make them count. But we also need to be as scientific as possible, which means making as few changes as possible.

Next session, we will be installing camber plates and sway bars, then running a session or two and getting times. THEN we will be installing aero parts. We're going to accept installing sway bars and camber plates at the same time because camber plates should be on the car regardless, and tuning the bar stiffnesses to match a known bad condition is a waste of time. We got a feel for the bars today (even though the lap times didn't respond appropriately). Over the past six weeks, we've learned that while lap times are a very useful metric, they're not perfect. They're strongly influenced by weather, traffic, and as we've seen today, tire and brake degradation. It would be nice to run every session in 80 degree weather on fresh tires and brakes, but that's just not realistic.

More than that, though, we haven't actually truly tested anything new. We haven't set out with a prescribed objective. Whiteline knows their bars work, they don't need us to tell them that. Same with camber plates. They're well understood parts. When we do the underbody aero parts for Velox, we absolutely will eliminate every other variable besides their parts. Our goals are to learn as much as we can about wheel position varying with speed. Once we start testing our own custom parts, we will be testing the hell out of them and abusing them as much as possible. That's where we're going with this. We're still in "street car" mode, but we won't be for much longer. We're going to be going racing with this car, and making any parts we find along the way that don't exist.

Not trying to flame you, just trying to elaborate a little more.

Originally Posted by Icanfaptothis86

I am going to the track next weekend down here in houston. We are looking at highs of 103. I dont expect my Michelins to hold up.

Are you running an oil cooler? If not, you really should be. Make sure you're running 5W30, too. (Sorry if you already knew this.)