GSpeed's 2015 BRZ- SCCA Super Touring Build
 

We bought this car from Hiley Subaru in Ft. Worth, TX with the express purpose of learning as much about the car as we can, in order to make parts to help people get (and stay) on track.

This little guy showed up on the 4th of June with all of 52 miles on the odometer.

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The very first thing we did was get it on the scales. We've got to know what we're working with here. The following numbers were taken with 7/8ths of a tank of gas, and 175lbs of lead shot in the driver's seat.

Total Weight- 2917 lbs
Front Weight- 54.5%
LF/RR Cross- 50.1%

LF: 820 RF: 769
LR: 688 LR: 640

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Clearly a very well balanced car. It'd be nice to get a little more weight over the rear, but looking at that crossweight, I can see why they put the battery where they did.

The second thing we did was swap out all the fluids with Motul stuff. We have no intentions of being nice to this car, so we want to make sure the fluids in the car are up to task. Why Motul? We believe in it so we sell it, not much more to it than that. It's not cheap, but compared to both the problems failing fluids can cause and the overall costs of racing, it's a drop in the bucket. Cheap insurance, if you will.

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The next thing on the list was a Cool Shirt tank in the trunk. Conveniently, it's within 2 pounds of the spare tire we removed, so the balance of the car won't be adversely affected. Texas track days can get really hot in the summer, and we don't want to be running the AC.

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Our goal for this project is to be as scientific as our budget allows, so the first significant modification to the car was an Aim MXL2 dash and datalogger. I've got a detailed thread here, but here's a picture of the finished product:

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Now we're moving on to the engine sensors we want on the car at the moment. We bought a TRD sandwich adapter from FT86 Speed Factory (Thanks guys!), and installed an AEM temperature sensor in one of the ports. It's even got a DTM connector built in. Isn't that cool? All NPT connections were sealed with Loctite 567.

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Since one of the problems we hope to address is fuel starvation, we need a good way to quantify the problem. We designed a little sensor block to hold a pressure transducer and mount to the shock tower brace. This pre-production one isn't anodized, but future ones will be hard anodized black.

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Next on the list are shock pots, tire temp sensors, and lap times! Hopefully next weekend we'll be able to get it on track and start getting some baseline lap times to use for comparison as we add modifications.

Jake

Subbed

Looks super cool, interested to see where this goes.

Thanks guys.

I decided to start off the morning by installing our little oil pressure sensor. We bought an adapter from FastWRX.com to install in the little galley plug on top of the block.

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It's a little close to the throttle body connector, but not so close that the wires are binding. I'd prefer a little more clearance, but it'll do. If you go this route, be sure and clock the tab on the connector in a direction you can reach it, it'll make detaching the harness MUCH easier.

We need to capture video of all our shenanigans (tests), so we bought and installed a SmartyCam HD. It'll talk to the dash, so it'll start and stop recording automatically, and it's got a nice data overlay.

I didn't have a mount to install it, but I had some bar stock and a Bridgeport, and that's basically the next best thing.

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Looking forward to seeing the development on this car.

In for results. Loving all of the AIM products.

First track weekend!

We put the car on track for the first time last weekend. Our goal for this weekend was to get ideal cold tire pressures, and establish some baseline lap times for a bone stock car.

The car is completely unmodified, save for the data system, camera, and cool shirt. As of the first session, the car had 62 miles on it. All laps were done on the 1.7 CCW.

Thursday's first session was with VSC and traction control off with the buttons on the console (no pedal dance). We ran 13 laps, and the best lap time for this session was 1:34.9.

Thursday's second session was an hour later. Tire pressures were adjusted slightly, and we did the pedal dance to completely remove the electronic nannies. Immediately, the car was "WAY MORE FUN!!! :)" based on driver notes, and the best lap time from that session was 1:32.9. So we've confirmed what we already knew, the pedal dance is well worth the hassle until a more permanent solution is worked out. It got us two entire seconds.

Thursday's third session had a best lap of 1:32.7. We adjusted the tire pressures a little bit more, and settled on hot pressures of 34 psi front, 33 psi rear. Driver notes indicate the car could get into the 1:31 range with a little more seat time.

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(Please excuse the cell phone pics, we'll get some better ones next test day.)

On Friday, we got some more time on track. By 9:30A, the track temp was already 97F. At the end of the 5th session for the weekend, the OEM pads were done. They hit metal on metal, so we called it a day. Best lap time up to that point was a 1:33.3. Damage to the rotors was superficial, so we turned off 0.012" off of each rotor and got some NAPA "Pro-Former" replacement pads from across the street.

Saturday morning was a little bit cooler, with track temps around 84F. It was fairly humid, and the track felt noticeably slicker than days prior. The best lap from the day was a 1:33.0, though. We learned exactly how worthless the NAPA pads are from a track standpoint. Within about 5 laps, they had faded horribly. The diff was smelling a little toasty, too, so we called it a day after 12 laps and changed the fluid just to be safe. It didn't seem to hurt anything, but the fluid did smell pretty cooked.

I decided to see if I could recognize the brake fade with the data system.

Here's a GPS trace showing longitudinal acceleration. Blue is negative, so the blue spots on the track are the braking zones.

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I took the data from the Aim system and exported it to Excel. I wrote a formula to sequentially number each braking event, and then average the pedal pressure and deceleration during each event. Messed with the units and signs a little bit, then I was able to get a brake gain, in units of Gs per ksi of line pressure.

Here's a graph of the brake gain per braking event. Each lap is a different color. You can see after the 5th lap, the braking force generated by the pads is falling off rapidly. It's always nice to see data matching driver notes.

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It would be really nice to be able to factor in pad temperature as well. I'll have to add some brake temp sensors down the road when we get heavier into brake development. The pads were probably falling off even earlier, but without temperature data, it's hard to say that for sure.

I also need to brush up on my Python, too, since processing the data in Excel took waaaaaay too long to use as a regular analysis tool.

Here's a quick shot of the owner next to the car:

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So, lessons learned:

-Stock car can run 1:32 flat.
-OEM brakes are good, but last about 5 sessions (2 hours).
-NAPA brakes are no good.
-Fastest cold tire pressures are 29 psi front, 31 psi rear for these tires on this track in this weather.

Agenda for next test:

-Wider, stickier tires
-Tire temperature monitoring
-Fuel pressure monitoring
-Oil temp & pressure monitoring
-Better pads

We've got some good video from the Smartycam, but I'll have to go over that later.

Jake

subbed...

I can't wait to read your tire temperature monitoring ? do you plan on installing some IR sensor ;) ?

Yep! We've got some little guys going on this week.

OMG I am so looking forward to this .

this is one of the install that would push me to get an AIM MXG...if I ever see someone documenting it.

Great seeing the car on Friday and all the work you guys are doing with it. Looking forward to watching this progress and hopefully getting out on the track with Dave sometime to play.

Nice build!

I think you guys would become quite popular if you could sort out a solid solution for E85 fuel starve.

I like the oil pressure sensor, definitely going to look into that.

Keep up the good work.