SS Roadster AutoX Setup

[dhrivnak]

Race weekend update: I added one camber shim to the rear to get rid of the understeer from running zero rear shims. We ran at a different (smaller) venue so it's hard to tell how much it helped with rotation, but the car felt pretty good (I ended day one 2nd in PAX, and day two 1st in PAX and 1st in raw time ). Rear dampers were set to 8 (I think) with the single "thin" shim in the rear. The weather was pretty cool, high 60s to low 70s, so we decided to try some runs in Sport Mode. The power and throttle response benefits are pretty obvious while on course, but as expected the car can't keep cool for long. Thermal management is a whole nether aspect of trying to race a Roadster competitively. If you live in a cooler climate and only have a single driver, you could probably do a whole autox day in Sport Mode and be quicker.

The previous race weekend was in hot weather and we ran into overheating issues. Debug warning ID:1463 HVAC: Compressor OverTemp. I'll have to take apart some stuff in the front to find the compressor and figure out a way to cool it with a battery powered leaf blower, since we can't make any modifications for the "stock" class. If anyone has an HVAC schematic or advise on cooling, im all ears.

Congratulations on placing so well. If it recall performance mode widens the thermal limits on the battery so you will likely run hotter. If you can charge in range mode but run in performance mode I think you will do best as a range charge cools the battery a bit more.

 

[Oricle]

Congratulations on placing so well. If it recall performance mode widens the thermal limits on the battery so you will likely run hotter. If you can charge in range mode but run in performance mode I think you will do best as a range charge cools the battery a bit more.

Thanks!

The venue is about an hours drive away, so we charge and drive over in range mode to preserve as much battery as possible. The event this last weekend was a lot cooler (50-60f), so I was able to run the whole day in performance mode. The car really chews through battery in performance mode though, we may have to limit how many runs we make in performance mode just to insure we can make it back home.

 

[Oricle]

Event Update:

I upped the front dampers to 9 (from 7) over the weekend and feel like it makes the car more responsive on turn in with minimal change to steady state cornering. After driving a friends national championship winning STU class 350Z the previous weekend I feel like having the front more pointy and being more aggressive with steering inputs can yield quicker times. Stiffening up the front and being quicker on turn in helps the car rotate early on entry which can be beneficial in sweepers where the car would typically understeer. Finding that balance of a few degrees of oversteer (quick) and a full on slide (slow) will take some practice, but overall will return quicker times by getting the car pointed to the exit earlier and allowing the application of the accelerator earlier.

I finished the weekend 5th overall in PAX time, which is pretty good for the Roadster on a technical course with a lot of transitions. After the event I did a few spectator ride alongs trying to show people that electric cars aren't lame but ended up cooking the brakes in the process, so if you're going to race the Roadster on a track with a lot of braking zones you'll need a better pad than the EBC Reds (they work great for a regular AutoX format though with several minutes cooldown between runs however). This was the last event for the Roadster this season, so it's back to my STS class Miata for a few more events before the weather moves in.

 

[Oricle]

We had the first failure this past weekend. The BWR super stiff sway bar managed to break the sway bar mounting tab on the lower control arm. Good news is Tesla has several in stock, they go for $355. We will probably weld in a reinforcement on both control arms over the winter to reduce the likelihood of this happening again.

 

[hanknum]

For autox and street performance, I really wanted to reduce the understeer. I decided to start with a different wheel/tire setup first before I started in on the suspension geometry. This is what i did...

The rears are 17x8 with 245/40 on them. The offset is 30, so the extra width and offset bring the outer edge right to the limit. The bolt pattern and center bore were spot on. I was able to use the OEM lug bolts.

The fronts are the OEM rear wheels that I plasti coated...I will end up painting these gloss black to match the rears. These are 17x7.5 with 205/40 on them. I added a 8mm spacer on both fronts to account for the offset difference and thus had to use longer bolts.

Both the overall diameters of the fronts and rears are within a tenth or two of the originals so no problems with traction control or regen braking. This also opens up for other tire options.

I will next look into adding more negative camber to the fronts as well as maybe reducing the negative camber in the rear to get a more balanced setup. Unfortunately, to reduce the camber in the rears, would bring the tops of the tires out further and with the offset of the new wheels, it already skims the fender liners. I'll just drive a bit and see how it goes first...any suggestions?

Thanks,

Henry