I Am Agonizing T3 at VIR...
 

The analytical part of me gets me crazy sometimes, can't help it. It's been two weeks since we came back from VIR, and T3 just bothers the heck out of me. Here is the question I have for anyone that care to comment:

Which turn is harder to take: VIR T3, VIR T10 or Summit Point T3? Each is slightly different in some ways, but I think they are have more similarities than differences.

Re: I Am Agonizing T3 at VIR...
 

Sorry Fatih, but I do not agree with you at all. Each of the three turns have nothing in common save that they are all left handers. Nascar, the easiest IMHO, is a straightforward, fairly flat left hander with a straight runup and a predictable exit followed by a very short straight. It is probably the visual aspects of it that make it seem harder than it is.

Wagonbend (Summit T3) is a tricky corner that requires you to brake over a bump, bending gently to the left, and get on the power before you commit to the turn, because the hill will catch your car, and you do not want any rotation going into it. Otherwise the front will bite, and the back will slide. It is your consummate DE, brake straight corner. You cannot be timid here because there is a lot of time ot be lost if you are slow over the hill.

South Bend (VIR T10) is by far the trickiest as it not only is the fastest, but you come in hot, with the car light, farther over to the left than is optimal. You have to get it slowed under control, but if you overbrake, it kills your momentum and your grip, and you have nothing going down the hill. If you over cook it, the runoff is not pretty. Just ask Rick DeMan.

Re: I Am Agonizing T3 at VIR...
 

As a matter of fact, I agree with your comments. T10 at VIR has an arc of 315 degrees and radius of 185, T3 at VIR has an arc of 280 deg. and radius of 140. I could not find the planimetric drawings of Summit Point, just ball parking T3 has similar radius to T10 at VIR.

My issue is I have not yet figured out why my avg. speed through T3 of VIR is between 55-59 mph vs T10 with avg. speed of about 82-88 mph, and similarly T3 at Summit my avg. speed is 74-79 mph. Given that T3 at VIR is the easiest out of the three and radius differences being relatively small, I am trying to figure out how I can best go through T3 at VIR with closer to 70 mph avg. speed.

There is no question that I am over slowing into that corner, but why? It may have something to do with the curve at the approaching line to the turn that prevents me from looking into the corner sooner, or something. I certainly don't want to hit the tire wall on either side by trying drastic speed increases, but I gotta try something different for sure :)

Re: I Am Agonizing T3 at VIR...
 

Is there more track out at 10 vs. 3? It seems like it to me. I take 10 early, then track out far right, vs, if you take 3 super early, you run out of track early. 10 is smaller than 3, to me

Re: I Am Agonizing T3 at VIR...
 

I don't think the track is wider at T10, at least not that I can tell from the drawings, but it has slightly larger radius which may be giving us the illusion that it is wider.

Re: I Am Agonizing T3 at VIR...
 

Not so much wider, but you can make it through T10 without a lot of steering angle, which allows for more speed, at least for me comfortably. Watch your inputs for 3 vs. 10; I bet you have more at 3

Re: I Am Agonizing T3 at VIR...
 

Here is a quick and dirty of what I am trying to communicate. I could be totally wrong, but 10 just flows better to me. :)

Re: I Am Agonizing T3 at VIR...
 

Those are great comparative pics and you are right. However, I am not yet convinced that the steering input difference is the sole source of being 20-25 mph slower through a turn that is actually easier to see; would you not agree?

Re: I Am Agonizing T3 at VIR...
 

Of course! Rarely is there just one source of variability.

I haven't sat down and tried to dissect it, but perhaps its because you're already carrying more speed at 10, in a short, flat straight and needing to brush the brakes or lift slightly vs 3, where you are accelerating hard out of 2 and trying to maintain balance in a sweeper and then brake right before turn in. IDK There are a lot more competent drivers than me who I'm sure will chime in.

Re: I Am Agonizing T3 at VIR...
 

Do you mean your average "lowest" speed?

Assuming you mean your low speed, than 59mph is not too shabby in Nascar bend.

I've "studied" a 1:59 lap where the low speed in T3 was 59mph. And another with a stock '10 GT3RS doing a 2:04 with a low speed of 55mph.

So you're in good company :-8

That's a cool picture!

Re: I Am Agonizing T3 at VIR...
 

I should have been clearer, avg. speed at the apex, not lowest or avg. through the whole turn. That is good that I guess we are at normal speeds, but I haven't figured out the 20-25 mph difference yet. If I can figure it out, then I'll be able to, hopefully, have a different strategy for it.

For example, I need to remind myself to try trailing a good bit into T3 to see if I can make up some of the time I am losing there, but don't have the guts to do that at T10 :D as some drivers are able to do.

A 135 driver claims to even take T10 at 105 mph on run-flat tires, so I am way off on some of the turns still :(

Re: I Am Agonizing T3 at VIR...
 

That's good info re: speeds in T3. I am mid 50s there as well IIRC. It feels like it could be faster; I think Alex (ukrbmw) was faster (link) but that wasn't min speed I don't think, and he had no on screen data.

Thanks Brian. A couple of screen captures, cropped in Paint, pasted into Word, and then captured and cropped again; best I can do on my work machine. :D

Re: I Am Agonizing T3 at VIR...
 

Here is my only video from the last FSR event. The data is also quite revealing, but also generates new questions for me, just quite interesting for me. The short of it, I think it is much more mental approach to T3 and all others and I am just not able to use most of what the tires could offer. Keep learning...

Re: I Am Agonizing T3 at VIR...
 

- Agree 100%; T3 is mental for me as well
- our turn in speeds I think are nearly identical
- tilt your camera down a little! :)
- ugh; the trains
- man I want to get back out there so badly

My only comment that is on topic is, yes, I think it is mental, however, like you said, much faster laps than ours, their speeds are similar through these turns, at least T3.

Re: I Am Agonizing T3 at VIR...
 

I'd like to see that! Again on the 1:59 lap the driver is 95mph through T10. 105mph on run flats ???? Best I've done is 89mph :o

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.


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."

Re: I Am Agonizing T3 at VIR...
 

So whats the take away? Brake less, turn in earlier?

Re: I Am Agonizing T3 at VIR...
 

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?

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.

Re: I Am Agonizing T3 at VIR...
 

It sounds like everything was working better for you at this last event. :-8

Better slip times? Do you mean 'sector' times? Can you clarify?

Re: I Am Agonizing T3 at VIR...
 

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. :)

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.

Re: I Am Agonizing T3 at VIR...
 

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.

Re: I Am Agonizing T3 at VIR...
 

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.

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. :)

Re: I Am Agonizing T3 at VIR...
 

Really? If you turn in any earlier you'll be in the flag worker hut?? OK though, if it works for you. :)

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 :D

Re: I Am Agonizing T3 at VIR...
 

This is how I broke down the track:

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!

Re: I Am Agonizing T3 at VIR...
 

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". :beatinghead:

Agreed, if not a fraction sooner. ^^ opps...too slow.

Re: I Am Agonizing T3 at VIR...
 

That's a big difference, nearly 1 sec, and that's what I am just figuring out or being conscious about it. :)

Yep, that how I felt and just had to find a way to get to the track, thankfully I have some friends who were very accommodating in the BMW club :pals:

My next VIR is not until the FSR one in September though :(, will you and/or Dell be there?

Re: I Am Agonizing T3 at VIR...
 

Very true; hence if you employ your T3 technique to T10, "brushing" the brakes as you put it previously, the car then feels significantly more settled and you just "trust the grip" as Patrick Long put it. Easier said than done of course :D

Re: I Am Agonizing T3 at VIR...
 

I likely won’t be back at VIR until the Carolinas PCA 3-day event in November; 3 days of Full Course = heaven.

Honestly, I might be able to swing an earlier additional event, but my repair (bumper and coolant fittings) is taking quite a bite out of my track budget this year.

I’m slated for August at Charlotte MS, September at CMP, and November at VIR. I might be swayed to swap my CMP for another VIR; I’ll have to give it some thought.


+1

Re: I Am Agonizing T3 at VIR...
 

November would be great too, but I am worried about the weather in that month.

Re: I Am Agonizing T3 at VIR...
 

Its been perfect the last 3 years. It can be a little chilly in the morning, but no big deal at all.

Re: I Am Agonizing T3 at VIR...
 

South Course? Why not the Potomac event? Too busy rubbing elbows at the IRL event?

Re: I Am Agonizing T3 at VIR...
 

Ahh, I wasn't aware it is just the south course :( Yes, I have to meet with PMNA and PCNA crew during the labor day weekend.

Re: I Am Agonizing T3 at VIR...
 

So, here is the Turn 10 data, comparing May vs. June:


Stats (typical on majority of laps):

June lap turns in 85.8 ft earlier, or 0.57 secs
Braking G at turn-in are -0.38 for June lap @ 101.3 mph vs. -1.04 G for May lap @ 104.3 mph

Max Accel G: -086 for June vs. -1.10 for May,
Time to max braking force: 0.81 secs in June vs. 1.08 secs for May

Brake application duration: 1.83 secs for June vs. 0.97 secs for May

Speed at brake release: 81.86 mph for June vs. 80.7 mph for May

Slip time: 5.542 sec for June vs. 5.516 secs for May

Avg Speed thru turn: 87.65 for June vs. 85.17 for May

Duration of final release of brakes: 1.0 secs for June vs 0.23 secs for May

Re: I Am Agonizing T3 at VIR...
 

Nice

turned in earlier
used the brakes longer, but less (long brush, or short drag)
less G
faster through turn

Essentially, you were smoother!

Re: I Am Agonizing T3 at VIR...
 

Yep, that's the take away I guess. Also, not overslowing for the turn ;) this is in a way quantifies what may be called "smooth"

I don't know what the heck I was doing in May; if someone told me that they braking at over 1G and turning in at the same time, I would have called them crazy. But that is why I was feeling uncomfortable going into the turn, pushing the car to do this that's not so nice, basically overdriving.