[eimarshall]

Thanks Tim! Ive seen the group but not joined. Ill give it another look.

[eimarshall]

One of the last little things I had on my list was to make a set of smaller canards. The ZLE canards are pretty aggressive and probably suffer from lots of drag, but given that that car(ZLE) makes 200 more hp, it can put up with a little drag. Lat year, when I swapped the ZLE wing for the GTC300 I added the ZLE canards to try to keep some semblance of balance. But in doing so, I lost ~5mph on the straight at the ridge. obviously the wing has something to do with that as well, but I think the canards are also a culprit

With the new splitter, end plates, and tire blockers, I figure I've reduced the drag a bit on the front end and made back some of the downforce. So bolting on the big canards may not actually gain me much. Maybe a little more DF but probably a lot more drag. In one of AJ Hartman's wind tunnel videos, he showed that adding a tire blocker and a large canard greatly increased the drag, but running only one or the other got you nearly the same downforce.

I figured my tire blockers are little different than the "spat" or "air dam" style blockers, so having both may not suffer from the efficiency loss AJ described.

Thus I threw together a simple model, 3D printed a mold and layed a couple layers of 12K carbon fiber onto the mold. The finished product is about 7" long with a taper from 3" to 2" front to back and total curve of about 30 degrees. I also mounted it at a slightly less steep angle as the ZLE canards. I think I might try to re-make them 4" wide at the front, but these will do for now.



I got her all shined up(before the canards) and ready for the first event.



Loading was a little tight with the splitter on. I also had to take off both trailer fenders to get it to fit width wise.



I did a quick Track Night in America at the Ridge for a little shake down. beautiful weather and chasing a couple of other fast cars(GT350 and a C6 ZR1) helped me knock nearly a full second off my best on 200TW RS4s. Last year I couldn't get those tires under a 1:50.5 to save my life. Second session out I clicked off a flier at 1:49.5. My optimal sector times had me closer to 1:49 flat even. So something is working!




3 days later I drove over to Pacific Raceways in Kent for a Time Trial. PR was hosting the SCCA Pacific Grand Prix on Saturday and Sunday but decided to add a time trial on Saturday. They only had 10 participants signed up but to make it more competitive they lumped many of the classes together. I qualify as Max 2, but ran in a group with Tuner 1 and Unlimited 2.

I had never been on track there before but used the practice and first session to get comfortable and learn the track. I ran the RS4s to start because they talk a lot and would let me know when I was hitting their limits. I was sitting in first overall by only 2 tenths of a second with a C8 Z51 and a tuned Audi TT RS hot on my heels.

I will say, Pacific Raceways is NOT a smooth track. I am spoiled at the ridge. It is butter compared to the variations at PR. PR has some crazy bumps, yumps, and undulations that look like they can get real hairy real quick given that the track has little to no run off. I forgot to grab my PDR recording, but there are a couple points where I know I could make time, ....... but the consequence could be a dirt berm or a tree..... only 10 feet off the asphalt....

That said, I wanted to push it a little more, so I swapped to my SC3Rs for the afternoon and knocked another 2 seconds off. That locked down first place and I took the top time overall with a 1:29.8! WOOHOO!!



I really want to dive into some of the data (a la KHCoaching) but I'll have to save that for another post. Plus I have another full track day booked in 2 weeks where I plan on doing a bunch of back to back comparison runs with various bits on or off the car. Hopefully that will shed some light on the efficacy and efficiency of various components.

[khcoaching]

Nice!

Send me the data.....

[That1guy_tim]

Congrats on the first place man!!

And again you are killing it with the aero components for our cars!

[VaporPressure]

Great thread! Really impressive craftsmanship and attention to detail. I'm just starting to go down the aero pathway and despite really wanting splitter tunnels, I abandoned the plan because of those aux coolers and some heavy metal framing further inboard that sits pretty low. I'll be interested to see if you're able to make something work there.

[eimarshall]

End of summer update and data dive!

I ran a couple of casual track days in June and July, with no real changes to the car. At the 2nd event in June I was feeling confident, so I requested a test ride to move up to the advanced group with Turn2 lapping. Unfortunately, by the time the primary instructor had time to do the ride along, it had started pouring. Doing a check ride in the rain with all the nannies off was a bit nerve wracking. I haven’t driven much in the wet and I think it showed. I slid and waggled my way around some pretty slow laps, but did my best to be consistent and aware. Thankfully, the instructor took mercy on me and gave the green light to move up!! Sweet!!



At the first track day in July, I enjoyed the pace of running with the A group, but never seemed to piece together a good lap. Right after to the lunch break, I was checking my tires before heading out on track and discovered that one tire appeared to have some cording. I swapped to my backup set of tires (RS4s) and discovered that 3 of the 4 SC3R tires had cording on the inside edge. I had been a little concerned about the wear and think this is due to a little too much toe in both the front and rear, but the car had been driving fairly well. I had been noticing a little mid corner understeer, but the car had been very stable under braking and on throttle. I have a couple sets of 3R tires ready to go since that crazy ebay deal...



A month later I decided to do some aero testing during an oddly cool august day. I spent the day swapping canards(small canard(SC) and Large ZLE canard(LC)), and tire blockers(TB), adjusting the wing angle(W#) and managed to beat my previous PB twice. I ran the same setup first and last runs of the day to try to bracket the data for environmental changes (intake temps went from 65 to 81 degrees F). It was a little difficult to pull consistent numbers from the data, but what I got seems helpful.



For drag considerations, I used top speed on the main straight and high speed acceleration rate (110-130 time delta to avoid the 3-4 and 4-5 gear changes) to find the effects of each component. Pulling the values from each sessions fastest lap, showed some decent numbers. My baseline top speed went from 136.8mph at the start of the day to 137.7mph at the end, which was the opposite of what should have happened given that it was nearly 20 degrees warmer. Maybe it was the ~hundred pounds of fuel? Idk. The data was consistent for wing AOA changes. Adjusting the AOA from 0 to 5 to 10 degrees lost me 1.7 and 2.5 mph respectively. Accel rates were a little less consistent but at least correlated with more drag slowing me down. Removing all front end aero bits(canards and tire blockers) and setting the wing to 0 AOA, did net me another 1mph on the straight and slightly lower accel times. I’m not sure why the tire blocker run went so poorly. But keeping the TB on and adding the small canards got me within a tenth on the 110-130 times and about 0.5mph at the end of the day. Maybe there is some sort of combined effect of the two. The ZLE canard lost a little top speed and accel compared to my SC/TB combo. Not surprising given the aggressive size and angle of the canard.



For lateral acceleration, the data was pretty noisy and harder to pull meaningful info from. I tried averaging the lat accel over a 2 second period to find a sustained peak G to help eliminate noisy peaks from bumps and drops. The Average lateral G and Average Combined G per lap might provide some insight but it really is hard to tell if anything truly stands out. I’m not sure why the ZLE canards showed so poorly, nor why the Average G per lap showed such little deviation. If you take the Average G per lap as real, then its clear the wing changes added DF, but it also shows that the changes at the front of the car had minor effects and the first and last runs establish a good bit of noise in the data.



I’m satisfied with the drag data but the DF data left me wanting more. So I found another possible solution and I……..leave you with a cliffhanger!!