Track Day 41 - PIR W/ SCCA Track Night in America - Trackspec Hood Vent Wickers, Data Acquisition & More Wing Angle

Coming into this track day I had a bit of a gap driving, and had actually been driving our Lemons Accord more. Fortunately, I was able to wrap up a few last minute modifications to get the car ready to go for the event.

Weight Reduction with a Carbon Fiber Targa Top

So you can read all about it over in my weight reduction article, but the short version is I switched to a carbon fiber roof panel from the stock acrylic and I ditched 8.5lbs of high up weight. Minor by itself, but all part of the picture of trying to get the Corvette's weight down to 3000lbs, or less if I can manage!

Trackspec Hood Vent Wickers

So I didn't order the wickers with the hood vents when I first set the Corvette up, but finally got around to ordering them. To be honest... they suck. Trackspec, I'm really unimpressed with what you sent me. They are rubbery garbage. They don't come drilled, and the hardware you sent with them is borderline unusablly tiny and just pulls right through the wickers. That said, with the correct hardware and some adhesive, these worked out not half bad. Still, I'm really underwhelmed and think a 3d printed product would be vastly superior.

Suspension adjustment

Having been surprised by how well my friends C5 Corvette with no sway bar handled, I decided to try and soften the rear sway bars on the Corvette. Nothing award winning or picture worthy here, I just had to make some adjustments to the swaybar end link length to clear the rear tie rods, allowing me to go outward on the sway bar to soften it up.

How the Track Day Went

The event itself is a fairly short one, with just 3 sessions starting mid afternoon onwards. The temperatures however were a very nice and mild 72 or so degrees, and while these events are always crowded with a significantly mixed bag of drivers, I still enjoy them!

The first session out though I just wasn't feeling the car. The last event I was here was 10 or so degrees hotter, and yet I was turning a .75 second slower lap time. The brakes felt a lot greasier than usual and had a lot less bite than normal. I also was struggling with the rear end feeling loose at entry, and the front end understeering at exit. So yep, I had a bit of every problem you could have.

For my second session I decided to try less wing angle (6 degrees). A fellow had talked about how under hard braking his wing angle would increase and stall resulting in a loss of downforce, which seemed like what could perhaps be happening to me, although my wing angle of 9 degrees didn't seem terribly extreme.. Turns out, nope that was not the case! I ran slightly slower lap times (1 second under PB) and the car felt nearly identical.

Lastly, I decided to try increasing the wing angle to 12 degrees. This in turn really tamed the rear end of the car down and had it feeling pretty good under heavy braking. I was also able to turn a new fastest lap by .25 seconds, so there were definitely measurable differences in my ability to put speed down with different amounts of wing angle.

New Personal Best at PIR - 1:27.269

So I was able to turn a new personal best, which makes sense since I have added a bunch more power to the car since I was here last. Not too shabby, but I think as long as I'm struggling with braking and understeer at exit I am losing a lot of time both on how long I can carry my top speed, and just how much I can accelerate out of turns.

Side by side Comparison to my old best lap:

So it goes without saying that with a horespower increase, I should see increased top speeds. Here you can see it for sure with a top speed of 131.7 on the back straight and 129.4 on the front straight, a gain of 5mph for both straights. You can also see the speed difference nearly everywhere involving power. Unfortunately, you can also see my corner speeds are down. nearly everywhere, with some by as much as 5mph like the hairpin! 

What changed? Well, I made some suspension adjustments, my brake rotors and pads are a bit older now despite having a lot of material left it would appear, and I've been trying to make some suspension adjustments to tame the rear end which I think has instead made the front end push. I also added some big old bump stops up front that are way too big and would definitely massively increase my front spring rate when they make contact and in turn cause understeer. Infact, I'm fairly positive it's that, haha. So I'll be cutting those down for sure!

Next projects are hard to say at the moment. Winter is about to start here in the PNW, which means no more track days for quite some time. I'll definitely be doing some analysis on the front bump stops to see about getting them to provide help just before the splitter makes contact with the ground. The brakes are also likely overdue to be changed out, especially the rears, so I'll have fresh pads coming into the next few events.

Data Analysis

So I'm new to capturing data with track addicts, but one thing I thought was interesting was that I could capture intake air temperatures and coolant temperatures. I thought it would be interesting to see just how those were doing temperature wise, and sure enough there was a bit of interesting data to see there. Specifically my takeaways were that coolant temperature holds pretty steady around 205 degrees or so. No surprise there despite having a 160 degree thermostat. What was interesting though was to see intake air temperatue mostly stayed around 90 degrees once I got moving, and didn't pick temperature back up until my speeds dropped coming off of the track.

Unfortunately, I didn't run the GoPro for my 3rd sessions, which happened to be the session I ran all my data logging for. I am going to look into adding additional data logging channels, but here's an example of what I can overlay with just IAT and coolant temperatures:

The video you are seeing above is from session 2, and the data from session 3, so it's not terribly useful, but you can see just what adding the overlay information is like.

I'll be delving more into data analysis at future events, but I specifically want to try and capture oil pressure and oil temperature, as logging all of that will prove useful to me. Unfortunately, I'm told that sampling is pretty poor on the C5, at or around 1-3hz (3 updates a second) which will also gloss over any sudden/short drops in oil pressure... but capturing something is better than nothing!

Video Of Session 2