GSpeed's 2015 BRZ- SCCA Super Touring Build

[BigFatFlip]

Originally Posted by PST

Pretty graphs to come.

Is it weird that I'm excited?

[GSpeed]

We spent yesterday dynoing all 4 of the Tarmac 2s through their adjustment range. 10 in/s CVP with 7 tests per shock. Since there's an uneven amount of bump and rebound clicks, there was a little interpolation involved, but basically we ran full soft on both, 2/3rds soft on both, 1/3 soft on both, neutral, etc. Why? Purely a time-saving measure. Even distilling it down to seven tests per shock, it still took 9 hours to get them off the car, make fixtures/spacers/shims to mount them to the dyno, run the tests, and reinstall them on the car.

Since we didn't design these shocks and we can't revalve them, this is really just a "Let's see what we're working with here." Here's a graph showing the fronts overlaid.

[philooo]

This is invaluable information for all of RaceCompEngineering Tarmac 2 out there.

You guys are really putting the amount of work hours to make this the most scientific build ever made

I wish I could read the graph with some more perspective. Can you tell us what these lines tell you ? happy ? unhappy ? expected ? unexpected ?

[civicdrivr]

Originally Posted by philooo

I wish I could read the graph with some more perspective. Can you tell us what these lines tell you ? happy ? unhappy ? expected ? unexpected ?

x2, can you tell those of us with little experience what that graph means?

Sent from my XT1095

[GSpeed]

The purpose of overlaying those graphs is to verify that the left and right shocks behave in a similar manner. These do.

At the higher stiffness levels there's a bit of hysteresis ("up" and "down" lines don't match up exactly) and non-linearity, but again, it's not bad given the price point. To get perfectly matched shocks, you'd have to get some custom tuned shocks that someone spent lots of time working with on the dyno.

For a car like this (soft chassis, rubber bushings, etc), you would see no difference between out-of-the-box shocks and custom massaged shocks with perfectly overlapping graphs. So in short, we're happy with what we found.

We bought the Tarmacs because we knew we could count on them to be a good value, and this testing confirms that. Maybe after we log a season or so worth of time on these, we'll see how they compare. That'd be interesting to see.

[GSpeed]

Here's another interesting graph. This is all seven tests we ran on one shock showing the adjustment range. Test 1 is full soft on rebound and compression, Test 7 is full hard on rebound and compression, and Test 4 is neutral. The other tests are evenly spaced in between.

Again, this shows us exactly what we expected to see. Adjustments are less sensitive towards full soft, and non-linear towards full hard.

Hopefully this illustrates how you want to set up your car as "soft" as you can for a given setup. Soft setup equals grip.

Also, keep in mind that putting shocks on a dyno is roughly equivalent to looking at them through a microscope. Any differences will be magnified, which means something that looks like a noticeable difference is likely somewhat minor. Once we have the free time (ha, ha) we'll put the stock shocks on the dyno for comparison's sake. I think someone's already done that, though...

[Top-Secret]

awesome stuff so far, keep it up!

[GSpeed]

Update time!

Last week, we installed an Innovate LC2 in the OEM overpipe. What a great location! Perfect vertical orientation, and great access from the top.





We mentioned last time we installed the Tarmac 2s, and we put them on track for the first time today! After a full cornerweight and alignment yesterday, we went out about 10AM this morning for a few laps. We didn't get any pictures of the cornerweight and alignment, but it's pretty standard stuff. Here's what we settled on for our alignment settings:

RF/LR Cross- 50.2%
L/R Balance- 51.6% Left
F/R Balance- 54.6% Front
Total Weight- 2924 lbs

Front Toe- 1/16" (total)
Front Camber- -1.03°, -1.08°
Rear Toe- 0"
Rear Camber- -1.82°, -2.07°

We cooked yet another set of Z-rated pads, so we turned the rotors again and installed another set of Z-rated pads while we wait on the race compounds to show up.

Initial reaction from the driver is VERY positive. We were able to drop a full second almost immediately, and there's a lot more time there. The handling of the car has been improved so significantly that the driver has to adjust his shift points and braking points, so there's quite a bit more time to find on top of that. The best lap we ran this morning was a 1:26.4, and we will be attempting to break into the 1:25s tomorrow morning.

But we know why you're really here. Graphs!

Here's great illustration of the accelerated weight transfer provided by the lower CG and stiffer springs. This heavily zoomed graph shows the roll angle of the car at the right-left transition at the very beginning of Rattlesnake. Google Maps



The blue line is our last session on the stock shocks on July 18th, and the green line is today. You can see not only are we rolling less, we're also getting there faster. The blue triangles show the maximum roll to the left, and the red angles show the maximum roll to the right. If we assume those points indicate when the transition begins and ends, we can quantify the time it takes for weight to transfer from the left side of the car to the right side. For the blue line, the transition took 1.491s, and the green line took 1.198s. That's an improvement of almost 20%!

That leads us to our next question. What about the roll stiffness? Here's a graph that shows a math channel that calculates that. We're taking our roll data, and dividing it by lateral acceleration to get a raw deg/G figure. You can see it's not filtered or processed, and fluctuates wildly through the straightaways as lateral acceleration hovers around zero. But through the corners, we get smoother lines that show we moved from a ballpark stiffness of 2.75°/G to below 2°/G.



Has pitch been affected the same way? Yep! Here's the pitch angle of the car plotted over distance. You can see the sharp dives under braking, and the gentle pitch-up under acceleration.



The tendency to raise or lower the nose has been greatly reduced as well, leading to the faster weight transfer like we saw in the first plot. Weight transfer will always happen, but our goal is to help it happen as fast as possible while still maintaining a chassis compliant enough to handle the bumps and divots of a racetrack.

We'll tear into the tire data a little more at a later date after we've had a chance to analyze it. We're finally at the point where all the data we collected over the past month is useful for comparison's sake.

Summary
Configuration: RCE Tarmac 2 Coilovers, PFC Z-rated Front Pads
Best Lap: 1:26.4

[philooo]

That's what I call being ANALytical
For once before and after curves that really make sense. As usual awesome stuff.

2 questions:
- what setting on the tarmac 2 you had: rebound compression ?
- what's the point of the Innovate LC2 in the OEM overpipe ? newbie here

[GSpeed]

Originally Posted by philooo

That's what I call being ANALytical
For once before and after curves that really make sense. As usual awesome stuff.

2 questions:
- what setting on the tarmac 2 you had: rebound compression ?
- what's the point of the Innovate LC2 in the OEM overpipe ? newbie here

Tarmac settings are neutral right now. We've got a little oversteer on corner entry that we're going to try and dial out for tomorrow by removing some of the compression damping in the rear.

The LC2 is doing nothing right now besides gathering data. It will be VERY important down the road once we're making more power than stock, but we're going to stick to the original power level until we feel we've got the chassis sorted. Handling issues show up more readily when you can't correct with the throttle.

[Jonsey]

Great content as always. I look forward to hearing Dave's impressions once you are able to add in some negative camber, that made a huge difference for me. Bryan has my settings on file for a starting point once you get there.

[Bramick]

Originally Posted by Jonsey

Great content as always. I look forward to hearing Dave's impressions once you are able to add in some negative camber, that made a huge difference for me. Bryan has my settings on file for a starting point once you get there.

I'm interested in this too as I've added power via the JRSC and no suspension mods. IE. Power correction is real.

[TCR]

Front Toe- 1/16" (total)
Front Camber- -1.03°, -1.08°
Rear Toe- 0"
Rear Camber- -1.82°, -2.07°

Can't recall what tyres you're running, but this doesn't dseem like a lot of front camber?

[GSpeed]

Correct, it's not. We definitely need more front camber, which will be coming in the form of camber plates.