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View Poll Results: Which Turn Is Harder To Take?
VIR T3 (NASCAR) 1 20.00%
VIR T10 (South Bend) 4 80.00%
Summit T3 0 0%
All Are The Same 0 0%
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  #16  
Old 06-12-2011, 06:33 PM
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Default Re: I Am Agonizing T3 at VIR...

To end the aggony, I had to visit VIR once again, so I went for a day during the Marque Madness event Mercedes, BMW and Audi clubs organize last Friday. I had plans to test various theories we discussed here and the "How To Brake?" thread that has been very helpful to me in conceptualizing varying approaches.

I haven't had the chance to look at my data in every details, but few things emerged that were pleasant surprises. To set the stage, I am looking at three sets of data, March Zone 2 event, May FSR event and the last Fridays. Weather and tire conditions play a big role in the difference between data set, but the biggest factor was my driving attitude and approach where last Friday I was significantly cooperative with the car rather than forcing it to do things. My biggest offensive driving was during the May FSR event, when nothing felt smooth, cooperative or productive.

March: low 80s, low humidity, hot tire pressures: 32F, 34R, best lap: 2:10.0, TBL: 2:09.5, 5 heat cycles on R888s
May: low 90s, low humidity, hot tire pressures: 32F, 32R, best lap: 2:13.0, TBL: 2:11.4, ~20 HCs on R888
June: high 90s, very high humidity (heat index ~102-105), hot tire press.: 31.5F, 33.5R, best lap 2:11.7, TBL: 2:10.7, ~24 HCs on R888s

First, the best lap vs. TBL difference during May is a critical indicator on how inconsistent and pushy I was. Whereas during March and June, I was more consistent and cooperative (I am avoiding using the word "smooth" )

T3 data:
March time slip: 6.143 secs
May time slip: 6.310 secs
June time slip: 6.109 secs

Goal was to better position the car for the turn by not clipping the apex at T2, but coming in a little wider, braking more gently and carrying the braking a little closer to the apex. The following chart from RacePak shows how that looks from the accel Gs.

Click the image to open in full size.

June lap shows a deficit of 8 mph compared to March lap; however, because of late braking with less force (-1.1 G vs. -0.8 G), the deficit turns into a 3 mph advantage by the apex. Additionally, because of releasing the brakes later but more gently (see slope of G traces), an earlier turn-in was possible while having a wider arc through the turn, which results in almost identical exit speeds for both runs. Although the avg. speed for March lap through the turn is 0.9 mph higher, the tighter arc results in a very slight improvement in segment time, 14/100s. The significance of this is that I could achieve the same performance between the laps despite negative environmental and tire conditions, because I was more gentle with the inputs and did not upset the car through this very transitional section between T1, 2 and 3.

In contrast, it is obvious, even just through this turn, that during May I was pushing the car and not cooperating with it, which resulted in slower times and much less fun ride. The May braking force similar to June, but for much less duration to "make up time," which is not possible, we just try to "loose less time."
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Last edited by FTS; 06-13-2011 at 08:53 AM.
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  #17  
Old 06-13-2011, 08:43 AM
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Default Re: I Am Agonizing T3 at VIR...

So whats the take away? Brake less, turn in earlier?
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Old 06-13-2011, 09:11 AM
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Default Re: I Am Agonizing T3 at VIR...

Quote:
Originally Posted by FTS View Post
The following chart from RacePak shows how that looks from the accel Gs.
Chart? Not visible. Now I can see it

Glad to hear you had positive results with only 1 day to try it. I imagine there's more to be gained with some practice.

How about T10? Did you try anything new?

Got video?

Last edited by bman; 06-13-2011 at 09:12 AM. Reason: couldn't see linked chart
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  #19  
Old 06-13-2011, 09:15 AM
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Default Re: I Am Agonizing T3 at VIR...

Good question. My take away thus far, although seems obvious in some ways, is both braking techniques are valid and dependent on the corner.

For T3 @ VIR (IMHO):
  • it is more important to use the brakes to gracefully change the attitude of the car going into the turn until such time that you can see the exit point as early as possible. So, for this turn, the purpose of the brakes is not to slow down to a certain speed, but to settle the the car on its suspension in such a way that the fluidity of the transitions results in maximum acceleration as early as possible.
  • Once the exit is in sight, powering out will not only increase the exit speed, but also tighten the turning radius ensuring proper arc; remember, T3 is a decreasing radius turn, which is the main difference of it compared to T10 and T3 at Summit.
  • The faster the entry speed (less brake pressure), the earlier the turn-in, the more agressiveness needed with the throttle, and the faster slip times. Of course there is a limit to this

A way to clarify the differences in braking techniques required think about the entry to T4 as it relates to bullet #1 above. For that turn, the priority is actually to get down to a certain speed, hence braking abruptly initially then easing off the brakes on a straight line is the proper approach IMO, at least for approach to the turn. As you are down to a reasonable speed to have enough lateral speed, then we use the brakes/throttle to adjust the attitude of the car, sometime trailing the brakes and sometime throttle oversteer to go through the turn.

Same also applies to T10 from what I can see in the data, but it is less conclusive, I will keep looking at it though. However, Scott, you should see the T16-17a data, which was a surprise to me as it was not a section I was particularly working on. I had better slip times there as well, although my entry speeds were actually lower by 3-4 mph.
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Last edited by FTS; 06-13-2011 at 09:26 AM.
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  #20  
Old 06-13-2011, 09:25 AM
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Default Re: I Am Agonizing T3 at VIR...

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Scott, you should see the T16-17a data, which was a surprise to me as it was not a section I was particularly working on. I had better slip times there as well, although my entry speeds were actually lower by 3-4 mph.
It sounds like everything was working better for you at this last event.

Better slip times? Do you mean 'sector' times? Can you clarify?
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  #21  
Old 06-13-2011, 09:35 AM
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Default Re: I Am Agonizing T3 at VIR...

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Originally Posted by bman View Post
How about T10? Did you try anything new?

Got video?
Yes I got videos, but I have been looking at data and haven't had the chance to edit and overlay data to post, darn process takes 4-5 hours

I had some late revelations at T10. I kept running as usual trying to figure out what I am "feeling" through that turn, what is making me uncomfortable. I think during my last session or one before I figured out that because of the way that turn is, I actually do not see the apex until late in the approach, hence my turn-in has always been quite late, which results in having more steering angle at turn-in, which either upsets the backend at those speeds, or forces me to over slow. When I started turning in earlier, before even seeing the apex or the curbs on the inside, I felt more comfortable and had either similar speed as in March or close to it. The part that I haven't looked hard yet is the turn or the tires felt more slippery (due to heat or worn tires or both), so I don't yet have a conclusion. I just need to keep looking at data.

This one day nearly open track session was very useful to me. I identified exactly 0.9 secs/lap of savings in total that I can now repeat at any time by changing my line and/or braking technique.
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  #22  
Old 06-13-2011, 09:40 AM
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Default Re: I Am Agonizing T3 at VIR...

FWIW, I aim for the beginning of the inside curbing for my turn in at 10, which you can see easily.
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  #23  
Old 06-13-2011, 09:42 AM
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Default Re: I Am Agonizing T3 at VIR...

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Originally Posted by SH || NC View Post
It sounds like everything was working better for you at this last event.

Better slip times? Do you mean 'sector' times? Can you clarify?
I certainly needed these sessions to "feel" the car rather than just drive or over-drive it as I did during the FSR event.

I use the term "slip time" to identify a corner or a series of corners, whereas to me "sector times" is much larger sections of the track. For example T3 is just one corner, or up-hill essess is a small section, so I use "slip time." I generally brake the track into 3 or 4 sectors, areas which have a continuous characteristic to itself than the rest, For example, T1 through T6a is sector 1, the rest until the exit out of Oak Tree is sector 2, then the rest until braking zone to T1 is the 3rd sector at VIR for me.
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  #24  
Old 06-13-2011, 09:44 AM
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Default Re: I Am Agonizing T3 at VIR...

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Originally Posted by SH || NC View Post
FWIW, I aim for the beginning of the inside curbing for my turn in at 10, which you can see easily.
Yes that is exactly what I was doing and I found out that is too late Now I turn in before seeing the curb at all, which results in less steering angle and I actually started getting on the curb, which seems to help tremendously.
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Last edited by FTS; 06-13-2011 at 09:49 AM.
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Old 06-13-2011, 09:44 AM
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Default Re: I Am Agonizing T3 at VIR...

I see. I haven't done it yet, but I like to break it almost down to each corner, unless its a close series of corners like snake, that way I can more easily identify deltas per corner.
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Old 06-13-2011, 09:46 AM
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Default Re: I Am Agonizing T3 at VIR...

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Yes that is exactly what I was doing and I found out that is too late
Really? If you turn in any earlier you'll be in the flag worker hut?? OK though, if it works for you.
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  #27  
Old 06-13-2011, 09:56 AM
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Default Re: I Am Agonizing T3 at VIR...

Look at the positioning of that picture, for you to be at that point in which you see the start of the curbing you MUST have turned in before actually seeing it, no? I am, now, at a similar position to you, whereas before, I would actually turn the steering wheel the first time when seeing those curbs; you have it right I think, and I am just figuring it out
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  #28  
Old 06-13-2011, 10:02 AM
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Default Re: I Am Agonizing T3 at VIR...

This is how I broke down the track:
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  #29  
Old 06-13-2011, 10:03 AM
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Default Re: I Am Agonizing T3 at VIR...

I think I see your point (I think) . You are correct; I am turning in based on muscle memory, because I know (at least I think so) that if I don't, I will run out of track, or be in a bad place.

My first turn in is @ ~1.04.5 vs. that picture above which is ~1.05.4

We need to go back for like a week and review video and data after every session!
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Old 06-13-2011, 10:04 AM
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Default Re: I Am Agonizing T3 at VIR...

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Originally Posted by FTS View Post
what is making me uncomfortable.
I agree the later turn in can get uncomfortable. I found, in my car, getting the chassis flatter or more balanced allows you to carry more speed without the drama.

Ironically, because this turn can feel uncomfortable, my tendency is to scrub too much speed, which means holding the brake too long, which means addind some steering with a light rear end.....which is why the corner feels "uncomfortable".

Quote:
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FWIW, I aim for the beginning of the inside curbing for my turn in at 10, which you can see easily.
Agreed, if not a fraction sooner. ^^ opps...too slow.
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