teamking

I upgraded from Bridgestone RE-11's to Hoosier R6's this winter and made no other performance modifications to the car. I dropped six seconds at VIR this past weekend, from 2:22.xx to 2:16.xx! I'm actually sort of amazed at how much like the RE-11's the R6's are, just with more grip. Breakaway seemed equally progressive. The only real difference was the the Hoosier's seemed more prone to want to rotate the car if there is any steering input under braking, but this may just be because there is more load transfer to the front.

Here's video from a slower lap earlier in the day... I ran out of batteries and didn't get video from my best couple of laps. As always, I'd be much obliged to hear constructive criticism of my driving. TIA!

http://youtu.be/KoHg6tacA9A?hd=1

Steve113

.I watched only the first lap line not bad at all. Biggest thing is do less coasting and/or holding of throttle in one position, go back to power sooner. It may take more braking at the end . Take baby steps, don’t bite off more than you can chew. Hoosiers are amazing tires take advantage of their grip. The key is to check exit RPM's and find that sweet spot for carrying as much speed through the corner as the tires will allow. Also remember when you coast you are losing some weight transfer and the car reacts completely different then may be ideal for the turn. Just my 2 cents but over all good job

ProCoach

Thank you to the original poster debunking the "danger" of R-comps. You have seen not only performance improvement but a confidence improvement!

teamking

@Steve: Thanks for the critique. I definitely feel like I'm coasting a bit through 2 and into 3 (it's the one spot on the track where I'm not sure what I should be trying to do). Are there other specific spots where you felt like I was coasting/not getting back on the power?

@Peter: Yeah, I wish I'd done it earlier! Question: in the 'Ask the Coach' thread, you had commented on a previous video/data that I was not braking evenly, especially during heel/toe downshifting. As I watch the g-meter in the video posted above, it seems pretty good to me, but when I look at the data in the AIM RaceStudio, the longitudinal acceleration is pretty squiggly during braking. Can you comment on what you see in the video, and is there an optimal filtering setting that you use to discriminate noise from signal?

Veloce Raptor

Definitely between 2 and 3. You need to remain on the power here until the true brake zone for 3, in order to keep the back end squatted.

Also, a bunch of coasting prior to 14a. It seemed as if you were also content to hold 4th gear down th eback straight, and your speed never really got above 128. I'd like to see you keep accelerating and get to 5th...

Steve113

agree with Veloce ...... go back to power smoothly dont jump on it but smooth throttle application

teamking

Thanks for the advice on 2/3, I will work on that!

For the back straight and 14a, I need a little more explanation of what you are telling me.

Watching the video again of the back straight, I can tell from the boost gauge that I am WOT all the way until my braking point. Now, my braking point is at the three. Am I braking too early, and thus not carrying enough speed through 14, and thus creating the need to coast between 14 and 14a? And so your advice is to brake later (let's say the two), carry more speed through 14, and finish my braking prior to 14a?

Thanks!

Veloce Raptor

Well...remember what the topography is there. After all the brake marker numbers, it goes sharply uphill. So that means topography aids braking. In many cars--incluuding for example 993's that see a bunch more than 128 MPH there--I won't initiate braking until the track begins to go uphill....which significantly shortens my brake zone. In addition, even though you may be WOT, winding it out in 4th may not be the best option there, considering the torque curve of your turbo motor. Especially since it appears you stop accelerating around 128 MPH. Were it me, I'd upshift to 5th, use the torque, keep accelerating, and brake as I go uphill.

teamking

Got it. Can I assume that your advice would be to begin moving the braking zone forward one bit at a time. From the 3, try at 2 1/2 and see if I can make it work. Then, the 2... etc?

Ah hah! Now I see what you're saying! I'll investigate that.

Veloce Raptor

Yes, absolutely. Take it in small doses, get used to it, and you'll realize it is no big deal. Remember, the car compresses as it goes uphill, so braking is more efficient due to gravity, widened contact patches, etc.

And then you'll amaze yourself at how early others brake there every time you drive VIR!!

dbryant61

Just another data point regarding 14 & 14a:
I am normally at about 125 mph entering the braking zone and have worked on compressing that breaking zone for a long time. On a good day with sticky Hoosiers (less than 10 heat cycles) I am braking just before the arrow. I learned this following Chris Cobetto in his SpecE30 begin braking about halfway between the arrow and the apex of 14. His brake zone begins there and ends at turn-in for 14-a. It is a lighter car, but he is racing on RA-1s. Like you wrote and VR confirmed, go a little deeper each time WITHOUT CHANGING ANY OTHER VARIABLES. That hill really hlps your braking.

With tired tires, I brake at the 1.

teamking

OK, well it took a little while for the investigation.

I used the time, GPS velocity, and GPS elevation to build a model from which I could estimate the drag coefficient by looking at the back straight and the power delivery in gears 2, 3, and 4. From this I was able to get a power curve for my car.

From this, I was able to determine that the optimal shift point from 4th to 5th is 127 mph. So VR was right - I should shift to 5th!

But, if you account for the fact that that shifting loses power for a fraction of a second, the model indicates that you never gain that lost time back in the 2 seconds that I would be in 5th gear. So VR was wrong, I should stay in 4th!

Inconceivable!

However, at the end of that 2 seconds, I would be, in fact going faster in 5th than 4th, so if the straight were any longer, I should shift to 5th. And since I need to work on braking later into 14 anyway, VR is right-- I should shift to 5th!

So I've made my decision? Not remotely!

Factor in consistency, the very marginal gains in the straight could easily be thrown away by poor braking performance during the extra shift from 5th back to 4th.

So I don't know. It's really close.

Guess I gotta drink from both goblets and see what happens.

KaiB

I hate to do this, but....

Perhaps a long Kibortian discussion regarding torque v. hp and optimal shift points would be in order here.

teamking

I don't know what you mean by that. But it should go without saying that the calculations done as torques and forces would yield the same ambiguous result. F=ma vs P=dE/dt. Gets you to the same place.

Veloce Raptor

Q.E.D.