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Track day report: 5/4/2019 Auto Club Speedway

 
Old 05-07-2019, 12:19 AM
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Michael Jarvis
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Default Track day report: 5/4/2019 Auto Club Speedway

I wanted to share a track day report with my 2016 C7 Base Stingray A8 from this past weekend, to see if others have thoughts on the track or the line I'm using. Here's a video I made earlier tonight:


I cut 6 seconds off my previous best! I have installed the Z51 rear anti-sway bar to my base car, and have started to take some different lines. My new best time was 1:58, finally sub 2-minutes!

A8 Transmission issues
After doing some research on the A8, I saw that 2nd gear requires an additional brake to be applied inside the transmission. I was thinking that this additional brake could be causing the transmission to overheat when it's triggered. My A8 typically gets to 275-280F after 20-25 minutes, and I have to come in from my session early. I decided to not use 2nd gear outside of the out-lap on this day. I had NO problems overheating while avoiding 2nd gear! A few corners require ~40mph min speeds, and 2nd gear would provide a bit more torque coming out of the corner, but I really didn't miss it. I did accidentally go into 2nd gear on one corner, and I instantly got the 'shift denied' message afterwards. The temperature traces did not show any real spikes, engine oil temp and pressure look fine, so there's only 1 remaining idea: Maybe 2nd gear requires a lot of oil pressure, and after using 2nd gear the transmission gets upset because the transmission pressure is low? I don't have a transmission pressure sensor reading, so I really have no idea. I think I've found a way to avoid the 'shift denied' message, but the root cause investigation continues.

http://www.speedventures.com/images/SV_ACS_Roval.jpg
Turn 2 aka Bank turn
There's a bank turn, and some guys will run 160mph around it. Previously, I would let my min speed hit about 105, the car felt more planted this time, and I set the min speed to be closer to 112, which is where I think I've made up most of the 6 seconds. There's some serious banking, so if I had nothing to loose, I could probably go around the turn at 125+.

Turn 5-6 aka 1st hairpin
I didn't realize that you shouldn't be on the inside of turn 5, that you should turn in around the seam in the pavement. Staying to the outside of this turn sets you up great for the next straight before the chicane.

Traction Control/Active Handling
I have the base car, so no PTM modes for me. It's traction control off, or traction control+active handling off for me. I've tested turning off traction control during an autocross event, and I felt much more connected to the car. Still to worried to turn off the traction control at ACS, but looking at where the traction control+active handling are triggering, I'm not sure it's helping me much. I see it triggering when I'm coasting on the track, or under braking. I think these aids really help me during corner exit, but I don't really see them turning on during corner exit. My next test is to turn off the traction control while leaving active handling on at Chuckwalla - lots of run-off room.
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FASTZ (05-10-2019)
Old 05-07-2019, 04:43 PM
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Steve17GS
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I was there too, fun day!
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Old 05-07-2019, 07:23 PM
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I'll take a look later. I have a couple thousand plus laps on this track at this point.

Right off the bat, never listen to anyone or believe them when you hear things like, "I never lift in the esses" or "I do xxx MPH in Turn ??." They are almost always wrong. I look at the data or video of drivers, some who are quite accomplished and for whom I have great respect, who say "I never lift there", but then video or data shows they are clearly wrong. Or people say "I do 120 MPH in Turn X." What does that really mean? Corner entry? Minimum speed at apex? Turn exit? Do they really know? What is the definition of their speed they are quoting?

For the record, I can name on one hand road racing drivers I personally know who exceed 160 on Turns 1 and 2 at ACS and they are in GT1 cars with vastly more tire, less weight and bigger wings than just about any other cars with a fender and roof that can turn both right and left.
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Old 05-07-2019, 08:38 PM
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I enjoyed your video. I loved seeing the data from the C7s. I have never seen that before.

BTW - Great driving for your first track day and first time at this track.

My comments on your driving and the video, mainly focused on your lines at this time:
  1. I am not sure why your traction control should be activating going into Turn One. You should be well within the limits of the car there at that speed. Which setting did you use? A very conservative setting may be reacting to a slight amount of oversteer coming from you lifting off the throttle, but that is normal behavior for most Corvettes. In fact, most of them are sluggish to turn-in on throttle.
  2. Your car is capable of much more speed through turns one and two.
  3. I would be a little tighter to the big black apex block at Turn Three at mid corner, but I like how far left you get before turning right for Turn Four.
  4. Turn Four looks great.
  5. Turns Five and Six look good. You track a bit wider than I like going into Turn Five and you can carry a bit more speed running out past the white line a car width on Turn Six. You did good nailing the Turn Six apex. Sometimes I even hang my driver side tires over the dirt/grass at the apex.
  6. Your Esses look good, but you can tighten up a little closer to both curbs as that will slightly straighten the line.
  7. Entering the brake zone going into Turn Nine, the toughest turn to get right on that track, I don't like your lazy curved braking and entry into the turn, although a lot of people do that. It is much better to quickly straighten the car after the esses, give the throttle a squirt and then brake hard in a straight line into the Turn Nine turn-in point.
  8. You are late turning into Nine and run quite wide of the apex curbing. Turn-in sooner, apex tighter, and you will widen your arc, carry more speed and shorten the track distance slightly.
  9. In the esses after the footbridge, I think they call those turns 12 and 13, I almost always tell people to turn in slightly earlier, get up more on the curbs, and overall just straighten it out a bit. You will carry much more speed through there doing so. You are driving a conventional late apex line. Imagine using a segment of string to mark your late apex line through there, and then imagine pulling the ends slightly and how the string will now lay through the two corners. That is the fastest line.
  10. For Turns 15 - 17 or whatever the last turns are depending upon who you are talking to, tighten up the line on the first cone and carry speed in letting the car rotate and then get on the throttle while in tighter against the last cones on the left. Your toughest corner on the track is also arguably the most important Turn on the track next to Turn Nine since you head out onto the long straight.

Your mileage may vary and other drivers may disagree, but that is my input.

Oli

Last edited by Olitho; 05-07-2019 at 09:18 PM.
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Michael Jarvis (05-08-2019)
Old 05-07-2019, 08:41 PM
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Just as a point of interest, I was racing at Circuit of the Americas for my second time this weekend in Spec Corvette. Friday was a day called Test and Tune. I took my fast lap from that morning and sent to Dion at Racer360.com for some coaching feedback from him as I had a race on Saturday and two more on Sunday. Here is his feedback cool tool he uses to coach. Actually let me post a the full unedited lap and then his coaching feedback integrated.


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Old 05-07-2019, 09:15 PM
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Olitho
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For a perspective from my other Corvette race car running in NASA ST2 trim at Auto Club Speedway for a perspective on my driving lines vs. yours.

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Michael Jarvis (05-08-2019)
Old 05-07-2019, 10:31 PM
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Can't add any more than what Oli did regarding the line and to say that what he outlined is what I also attempt to do.

Regarding Traction Control, you should be able to put it into "Competition Mode" like on the C5 and C6 cars. Not sure how to do that (I have a GS with PTM), but I do recall seeing it in the Owner's Manual. That'll give you a level of comfort with a reasonable amount of freedom from the nannies.

I wanted to be out there but alas had to travel for work. Gotta pay the bills!
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Old 05-08-2019, 11:52 AM
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Michael Jarvis
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@Olitho Thank you so much for providing feedback on my lines! This is extremely helpful! I also like your 1:43 lap. It looks like your spec corvette can do ~145mph in the banking - you've got a lot more downforce than me tho. I do believe I can still carry much more speed through that banking.

I was trying to find a video showing the line through turn 6 that goes past the white line on the outside, and I finally saw it in your flying lap. I didn't find any drivers to follow in the intermediate group to follow who took a line like that. Your lines are roughly drawn on the SpeedVentures track map: http://www.speedventures.com/images/SV_ACS_Roval.jpg but I couldn't really follow every line without an explanation or demo on how to do it.

I think the information on what lines to take for a given track in "today's" sports cars with is pretty universal. The lines you're talking through are probably applicable for modern Porshe's, Camaro's, and GT-R's. I also find this information extremely hard to find, there's probably space in the market to provide this info for all tracks in the USA.

Cheers,
Mike
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Old 05-09-2019, 12:21 AM
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wtb-z
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I think this is a good reference lap for no aero and low grip tires:

Plenty of folks do worse than 1:58, but:
1) push the car more
2) don't miss so many apexes
3) turn off ah/tc

And you should be able to do improve your times. Chuckwalla will demand execution on all of the above much more than ACS.
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Old 05-09-2019, 12:42 PM
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Olitho
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Originally Posted by wtb-z View Post
I think this is a good reference lap for no aero and low grip tires:.
I agree. William Chen is an outstanding driver who has a few thousand laps at ACS. And his car he is driving in this video is much like the OPs car config even if a C5. William has several other track and race cars. He is very experienced.
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