JCP911S

Hot discussion treads... might as well stir the pot with some provocative statements so we don't have to wade through 6 pages....

First, the "fastest driver model" is simple... who has the lowest lap time... maximizing G-forces is just a means to an end... unless you are in a drifting competition.

Second, there is no single "right" way to take a turn. It depends on the position on the track and the physical layout of the turn. Generally on turns leading to a straight, smooth earlier braking for "slow in fast out" is best to maximize exit speed, and at the end of a straight late, deep braking and "fast in slow out" is best to "lengthen" the straight. Also, maintaining car balance or setting up for a more important turn later will require modifying the entrance to a turn in a way that would look stupid if seen in isolation... it is all about making good tradeoffs for lap time.

So the good news is all of you are right...part of the time.....

ColorChange

Actually JCP, lat g's are maximized at the optimal slip angle, long g's are optimized at the optimum slip ratio. Both of these are way higher (g's) than the levels shown in drifting competitions.

I agree, lowest lap time is the answer. The question is how do you do it? The answer, pretty sure, is to drive the optimal line while maximizing g sum (while eliminating unnecessary g creation maybe). It may be correct to maximize the are under the g sum curve; I’m still working on this.

JCP911S

CC... correct on the slip angle... I was just trying to be a wise guy.

If I had to pick one "G" to maximize it would be forward accelleration... all other Gs just slow you down... my dream lap is 1G forward accelleration with 0 Gs braking and 0 Gs cornering... oh and get to the pits with my car in one piece... always a catch... just being a wise guy again

Seriously, I think trying to measure track driving by optimizing the mathmatical sum of G forces just won't work...its sort of like measiring lovemaking by total stroke inches... there are alot of non-quantitative factors. that just cannot be captured, or feasibly captured, maybe.....can't prove that... just my sense... of course I'm old and in the way.

JC in NY

Again, "g-sum" is too simple. We know at least one constraint is laptime. Maybe another contraint should be tire saturation?

JCP911S

Yes... if you think about it maximizing cornering or braking Gs is actually bad... assuming speed is equal.... a driver who can get through a turn with fewer braking or cornering Gs is actually driving better... I think one problem here is that Gs do not measure speed.

If I am driving at top speed e.g. terminal velocity, I should experience no Gs (other than gravity)... yet being at top speed is the best possible situation for minimum lap time.... so the G maximizing model gives me no "credit" for doing the best thing I could do....

So this argues that the fastest driver is the one that MINIMIZES total Gs... but that doesn;t make sense either, because the doofus doing 50 in the fast lane in his Towncar is also minimizing total Gs.... so the model is incomplete.

That said, intuitively, we know that higher Gs are probably better... but if I pull high Gs in a turn by going off the line... that is not good...there is no way to actually measure a "good" G from a "bad" G.... and ranking G's by determing whether they are "on line" or "off line" injects a subjective opinion into the model... essentially the model says "drive the line"... which doesn't really help... because now we have a thread about the "right line"

Robert Henriksen

I've been trying to maximize my G-sum on the track, but the wind keeps ripping my protractor, pencil & paper out of my hands.

I tried to explain to the officials why I should be allowed to run with my windows up -- I'd share my model with them -- but they just laugh at me.

Bob Rouleau

While attempting to maximum my G-Sum, I have occasionally muttered "Gee I won't try *that* again.

JCP911S

Is that like maximizing your G spot? Not sure this is the right forum for that.... do they have chat rooms on this thing?

M758

JCP brings up excellent points.

The classic example is a track the Indy. 4 turn 2.5 miles and no brakes. The key with modern cars is to srubb as little speed as possible in the corners and thus minimize g-loads.

Of course the simple answer to this is the proper line.

Bottomline is that there is no "line" There are actually many variations on the "Line" These variations depend on car type, set-up weight driver style and at alot of other things. If you happen to find the "ideal line" for your car then you max'ing the G-sum makes sense in some corners. The problem really comes in when you say all coners need to have the G-sum Max'ed. This is really a gross over simplification and neglects all the other factors and the huge effort on developing the line. Yes driving with the idea of max'ing gsums in the corners is good one. It becomes counter productive however when you focus on that and begin to overlook line, balance etc.

The baisc problem with a DAS system is that it can't get you the "line". It cannot determine the comfort level of the driver. As they get more complicated and expensive they can yeild more and more data, but they can't determine the true feeling and balance of a car. Properly set-up instruments can support or contradict the feeling of the driver, but we do not yet have the technolgy to get all that feedback without a driver.

The entire discussion is was intersting, but at the end of the day we as drivers still need to go out there and make it happen. In the end the best way to determine who is doing what is with the stop watch. Lap times and segment times will tell you who is getting it done. Problem is it takes alot of study and talk to attempt to figure out how and once you have figured it out the wind could blow or the sun comes out and changes all of it.

mitch236

The real world answer is practice, practice, practice. Of course coaching helps a great deal and that is where DAS etc. becomes relevant. All this talk about g-sum and area under the curve, is great but it won't make you a better driver. Only seat time will. I read an interesting exercise in Speed Secrets vol. 2 last night. He states that we should practice speed sensing. I like this idea since I can do it all the time on the street. If you cannot get your entry speeds consistent to within 1 mph (his recommendation) then how will DAS help at all? We need to be able to execute the basics flawlessly before we try to reel in that last 10th of a second.

Brian P

I'm still trying to reel in that last 10 seconds... I must make the HWFMR team proud.

bob_dallas

This whole "G Sum" discussion reminds me of some advice from one of Bentley's Speed Secrets books. I'll paraphrase but he basically says that G forces are not good in and of themselves. G-force junkies can get caught up on feeling Gs and thinking they are faster because of the G forces. your goal through a turn is to generally minimize G forces and find the fastest line through the turn. If you are driving for the G force feel then you are typically doing things that are not good like turning too tight or braking too much, etc.

I'm sure that's not a verbatim quote but it's correct in principle.

Damn - I blew it now - I kept telling myself to let this one die but I just couldn't get over it... G-Sum? G forces are meaningless enough when taken in isolation but then to dilute them even more by just munging them together?

IMHO, YMMV, ABCDEFG, EIEIO

Mike in Chi

"Damn - I blew it now - I kept telling myself to let this one die but I just couldn't get over it... G-Sum?"

Bob

the first day is very difficult. After that it gets easier.

"IMHO, YMMV, ABCDEFG, EIEIO "

bob_dallas

LOL, thanks - I feel like I just started my 12 step process...

Brian P

You were close. Bentley says that we are all G force junkies and we want to maximize G forces. There's only two ways to do it:

1) Drive faster on the best line
2) Drive on a non-optimal (tighter) line

He said that we have to make sure that we are doing #1 and not #2 and that it's really easy to think you are doing it right, when in fact, you are doing #2.

The issue with very late braking is that it's easy to continue your braking too deep and you go into the turn at a later apex than a faster driver would. This means that you would be driving a tighter line. As such, you can take the turn slower and still experience maximum possible G force. Remember, just because you are experiencing maximum possible G force DOES NOT MEAN that you are taking the turn as fast as possible. It's very easy to drive a bad line at the full speed that it's capable of, while still being MUCH slower than someone driving the correct line.