Optimizing the 911 and the Driver: Finding 1.05 Seconds at WSIR

[Jack Olsen]

I recently posted a thread where I was trying to get a context for my cornering speeds relative to faster cars that run at my home track, Willow Springs. When I was looking at the lowest speed in a given corner, I was surprised to discover that my 911 with its 1972 suspension and streetable R compound tires was actually not dropping down to as low a speed in some corners than much faster cars with slicks and pro drivers at the wheel.

There are two illustrations from that other thread. The first is a 997 GT3 Cup Car with a pro driver running a 1:25.53 lap.



He's faster than me. There's no surprise there. But he slows down more than me in several of the corners. I'm just about 10 mph faster than him through the turn 1 left-hander --- he drops down to 80 mph there and I go down to 90. Then I'm 4 or 5 mph faster than him through the long turn 2 sweeper (again, measuring by the speed at the slowest point in the arc). I drop down to 67 mph for turn 3, but he goes down to below 60 mph. He slows to about 52 mph for turn 4, while I'm never slower than 61 mph. For turn 5, he brakes down to 60 mph, while I only have to slow down to 70 mph. He's much faster through turn 8 and I'm about 4 mph faster at the apex of turn 9.

The second example is from James Sofronas punishing a whole pack of Porsches with the GMG Racing World Challenge Spec Audi R8 in a POC race. In the clip, jump to 2:54 to see his fast lap:



On the front straight, he gets up to 151 -- I only get to 132.
In turn 1, he drops to 91 -- I drop to 90.
In turn 2, he drops to 95 -- I drop to 96.
In turn 3, he drops to 62 -- I drop to 67.
In turn 4, he drops to 61 -- I drop to 61 too.
In turn 5, he drops to 67 -- I drop to 71.
On the back straight, he gets up to 152 -- I only get to 132.
In turn 9, he drops to 109 (which is amazing) -- I drop to 105.

Now, what is the point of all this? Well, it's not to say I'm faster than either of these cars. I'm not -- not by a long shot. And I never will be. But I'm trying to see if there's a way for me to get down to a 1:25.99 lap at Willow Springs -- that's 1.05 seconds faster than my best lap so far.

The problem is that I can't really do much about top speed -- my engine is what it is, and I'm just about out of gearing with the 132 top speed I'm currently hitting. My rev limiter in 5th gear will kick in at 134 or 135 mph. So I need to improve my cornering speeds -- and as the comparisons I've drawn show, my cornering speeds are already pretty good.

Here is my best lap to date (a 1:27.04), with the start/stop set at the cone at turn 9 of Willow:



A set of slicks would probably do it -- but I'd rather earn it the old fashioned (and less expensive) way. My primary new weapon is the change from Bilstein Sports in back to adjustable Öhlins shocks, customized for me by Wevo. So far, they haven't gotten me back into the :27's, but ambient temperature is very important for my car at Willow -- I need all the power I can get -- and it was something like 34° when I ran the 1:27.04.

So, I'd love to hear input from people who might be able to offer useful advice. It could be that I should be slowing down a little bit more at the slow part of some of these corners (like the faster guys), although it might also be that I'd need their horsepower to make that worthwhile.

I continue to play aorund with ride height, ARB settings and shock settings. I've gotten the car so it doesn't push as much as it used to. I've gotten better parity between front and rear tire temps. I've added some front and side skirts to improve my aero.

But I think for that last second, I'm going to need all of that and more. So I'm throwing the question out to anyone who's interested.

Where's my 1.05 seconds?

[Fubawu]

Jack
I would look at his exit speed at turn 9. My guess is he is getting onto the power a little sooner. I know your apex speed is faster but it could hinder when you can get back on the throttle.

I did not look at the data but this looks like the obvious section to gain time. 9 to 1 and 5 to 6 look key. How much throttle do you use through 5 to 6 exit ?

[Jack Olsen]

I'm full on the throttle from pretty early in 5. But I agree with you about turn 9. The reason the clipped lap is timed from 9 to 9 is because I accidentally went through 9 much quicker than usual (about 4 mph more) and it got me a full half second on that lap, even though I didn't carry the same speed at the very end of the lap as I came back to 9.

Also, I've compared my laps to other similarly-timed laps and I have to conclude that I'm a little slow through 9. I think I could go even faster than I did in that fast lap. The only problem is that the price of blowing 9 is high. It's a bad place to go off:



But it's one of the big areas I'm going to be working on. Thanks.

[Peter Zimmermann]

Jack, I respectfully suggest that you make two changes to the driving line in your above diagram.

1. Exit of Turn 2. Don't try to pull your car inside, as pictured, stay outside a little, and let it float out toward the left side of the track. Yes, it's blind there (small crest), and there might be some marbles, but trust that the track is there. Make sure the surface is clean before you do this at speed, and be sure to know where your car will straighten out. I used to reel in cars at that point of track, and pass under braking going into 3.

2. Experiment with the area between 4 and 5, an earlier apex, than the diagram shows, for 5 will get you more speed into 8 (I know, you'll touch the rev limiter sooner!). This, 4, is a very tricky turn, almost to the point that you don't want to over-hurry the car coming out of 4. No need to slide the car, just get it set for 5, and you'll carry more speed all the way to 9.

Let me know what you think!

[Zuluracerx]

Less weight and less wing and see if you can still hit the same corner speeds, even a couple mph's faster through less drag will pay dividends on a track like Willow.

[Jack Olsen]

Thanks, Peter. Do you mean wider as in missing a little more of the late apex in 2, or tracking out more after that apex? I think the line in the graphic goes wider than I do if you're talking about the 'track out' after 2. I am flat on the throttle at that point, and I usually only drift out as far as I have to.

But if you mean missing the apex by a little more, then that's interesting. I know I've had some fast laps where I'm noticeably off the apex, and I've never known if that was a plus or a minus.

I've played around a lot with 4. I know my 'all the way to the top' line is unconventional. But in going for the usual compromise line, my car has always been slower. I reel people in pretty effectively on the downhill from 4 to 5. And I consciously turn in early for 5 -- but gauging the best speed there is a trick. That stretch of pavement seems to change more than any other segment of WSIR, in terms of grip.

Thanks, Zulu. The last time I was there, I was aiming in that direction. I belive the front and side skirts will help slightly with drag, as they keep turbulent air from getting down underneath me. I also made some larger endcaps -- which will make the wing more effective at a lower angle of attack. One of them started to come loose, though, so I went back to the small ones and the maximum AOA on the wing. But I'll have that fixed by next time and it might get me something.

I'm also thinking about ditching the canards. They made a noticeable improvement in terms of planting the front end when I put them in, but I know they come with a high price when it comes to drag.

[Peter Zimmermann]

Yes, staying wide through the exit of 2 seems to help. There is a "groove" in the track at that point, almost like the pavement has a slight bank, that really holds our cars - this might be completely different in a small open-wheeled car. I, at one point, followed the recommended line, but always had the nagging sensation that I was forcing the car to get there, or that I was going too slow. Once I started leaving the car about two car-widths wide outside of that recommended line (at the point in the diagram where the white line appears to go to the inside edge of the track), and letting the car go over the slight rise further to the outside, I was much happier at how the car felt under me. For a while I didn't realize there was as much track available on the outside, at the exit, as there is, but quickly discovered that not all of it can be used - you don't want to get outside too soon!

[Jack Olsen]

I'll try it.

I have gone off the left side there, before 3, and it wasn't fun. But even in my 1:27 lap, I've still got a couple of feet there. It'll be very easy to see if it works, based on the speed data from the point where I brake for 3.

[Mahler9th]

Respectfully....

First you have to know that your car, in its current configuration, can achieve that lap time. And of course this must be possible for a range of ambient conditions as these relate to grip and engine output. You would NOT want to have a computer analysis that said it could achieve that target but only at y degrees ambient with z wind in q direction and w relative humidity and so on. You'd need to know it can achieve that time with a reasonable range across those variables. I don't think you know that, and if not, it is a waste of time to try to ask the question.

Instead of a computer analysis, we benchmark. You seem to be doing some of that, but I think the references are way too far off. That is the vehicles are way too different. The best benchmark is an extremely similar vehicle, or your exact vehicle driven by a a computer that 100% optimizes the inputs (accelerating, turning, braking) to get the fastest possible time with the prevailing range of ambient condition variables.

The closest thing most of us have to a computer is a driver familiar with our platform and the track.

Have you had such a driver create such a benchmark for you? If not, then the question cannot be answered in this type of forum. We can suggest things to try, but we cannot guarantee that you won't go off or otherwise fail to succeed.

You are an experienced and accomplished driver so it is highly unlikely that anyone here will come up with an idea that you have not previously considered.

If you really want to succeed, create and appropriate benchmarking exercise. Know that the car can do it, then work on the driver to achieve it.

[Mahler9th]

And by the way, I don't think an accomplished driver or racing engineer can help either unless a real benchmark is set.

Now if you were in a standard 2010 RSR, then yes, CW could probably do this on paper. Or a 200x Fabcar DP car, then sure HB could do this on paper. But your platform is not a standardized vehicle, as far as I can tell.

[Mahler9th]

And as an instructor you should know how important it is to have an appropriate benchmark for comparison. It is wholly inappropriate for an instructor to tell a student that he or she can go faster without knowing the vehicle/platform is capable. Ask me about the idiot "instructor" I encountered once that said "any car in the paddock" can go through 1 at Thunderhill flat. Not qualified to be an instructor. He had seen my car. He had no clue.

I know that you have a clue. I do not know if you have an appropriate benchmark.

[johnman001]

Sorry, but none of my suggestions may be a benefit, but here they are.

I would suggest taller gears as you seem to spend a disproportionate amount of time at or near redline. Do you know what the torque curve of your specific engine is? I think you could probably benefit from slightly taller 3-4-5. You could try taller rear tires to attempt similar results, but 18" wheels may not look right on your car, and they may not fit.

Another route you may not want to take is to get the car lighter. It's like free horsepower, but potentially at the expense of aesthetics, and I assume that you probably don't want to go there.

Tires could probably be worth a second or two, depending on what you are currently running vs what you choose, but the tradeoff is shorter life on the street (and the fact that they tend not to offer full traction until they get good and hot).

As a last ditch effort, try to brake less.

[Fubawu]

Jack
A little off topic but can you post some of your suspension set up? What changes did you make that you felt were most beneficial?

Scratch the first part of the question, I found the details on your site. Cheers John

[dede911]

Jack,

I too got the advise from a local suspension guru to install öhlings adjustable at the rear and Bilstein on the front (but custom valved).
His other option is a group B shock on the front (expensive).

What is your experience with the öhlins?

Thanks,

André

[cabgrapes@aol.c]

PM sent...

[Jack Olsen]

Thanks, guys.

Mike, I'm really not hoping for a specific solution here. I agree with you; it's hard to be systematic or precise in my case. My car is a hodge-podge -- so there isn't going to be a way to set a meaningful benchmark, outside of maybe letting a pro get comfortable in it and having him generate some data from a hot lap. I guess what I'm hoping for is for someone who's more familiar with the track than me offering something like JR Gordon did on the Rennlist thread -- he talked about my line and throttle point in turn 9, and also my shifting point over 6. Like paddock talk, it's not scientific, but sometimes there are useful pieces.

I agree with you absolutely that an instructor should never throw out a number for a run group -- even for a particular car. Too many factors to consider.

Fubawu, (as you've learned) my suspension is all laid out in this post: pelicanparts.com/bb2

The rear end owes its effectiveness to the revise mounting points and 935 atyle spring plates. The Öhlins shocks don't hurt, either. In front, the geometry of the A arms hasd been changed, and the JRZ struts are a little unusual -- they have positive camber built into them (although the end effect is negative).

dede911, I'm still tuning things to the Öhlins. But so far, I like them a lot.

Here's another side by side clip I've put together. This is me next to a guy who is impossibly faster than me. It's James Sofronas in the WC Spec Audi R8 that ran a 1:19 at Willow. But the gap vetween us is not so great in turns 3 and 4. The interesting thing in the clip is the freeze-frames with speed comparisons. I wish I understood more about suspension and cornering, but there are small sections of the corners where I carry more speed than him -- and many sections where he is MUCH faster than me. (Disclaimer: grabbing video isn't very precise.)

Here's the clip:

[Jack Olsen]

Baby steps toward the 1:25. I got a 1:26.88 at Willow yesterday.

[tdw28210]

nice work...congrats. Change any of the aero bits? Canards, etc.?

[crashmy911]

Great lap. I've only driven that track on xbox360 so I can give no constructive criticism.

[Brant]

I have recently found the old saying "slow in - fast out" to be pretty useful at improving my lap times

try running a session where you brake more... slow down more... and get on the gas in each corner 1 length earlier

you just might find that your cumulative lap time drops.

brant