[Purist]

Alright, here goes.

A Crucial Misconception
I want to go after a key argument that is often used to justify how few high-speed corners we may see on more "modern" road courses. What I mean is, car aerodynamics is frequently blamed for issues of not being able to follow closely or having a harder time making an overtaking maneuver. While I do not dismiss, out of hand, that this factor can play a part, the extent to which this is used is utterly overblown.

In super speedway racing, especially with NASCAR, where they're trying to make the cars edgier, while also messing about with the conventional draft, as well as the side draft, those big, heavy, draggy machines are quite vulnerable to the aero forces, but then, they're big, heavy, draggy objects putting off a HUGE wake, especially when they're doing 170-205-mph at the start of a run, and still doing 155-190-mph with worn tires.

I'm not going to get into that kettle of fish in this post. As I said, I want to look at this in road racing.

Too much of the time, we misinterpret a very basic phenomenon as something totally different than what it is. The occurrence in question is the accordion/concertina/rubber-band effect. Very simply, if the time gap between the vehicles in question remains roughly constant, the physical gap varies with the speed at which they are traveling. On the other hand, if you maintained a more or less constant physical gap throughout the speed range, it would mean that you have lost time in the slow areas, and narrowed the gap in the high-speed sections.

Now, here is where this can become a useful illustration in practice in a circuit's design/layout. Take Mexico City, and you're going to compare the impact of using the "stadium section" and the unmitigated Peralta(da) corner. What's going to happen?

So, for an Indy Car, it reaches 150-mph on the Recta del Ovalo. Making liberal use of track limits, it drops to 75-mph entering the stadium. The car pushes back up to about 100-mph, drops to 30-mph for Foro Sol, picks back up to 90-mph, and finally falls to 45-mph to make the hard right out onto the middle of the Peraltada. And for this exercise, maximum speed on the Recta Principale reaches 180-mph. So, we go from a spread of several car lengths to the trailing car having its nose just a fraction of a length off the tail of the leader in Foro Sol, and for the turn out onto Peraltada (45-mph) there is right on one length between the leader's backside and the pursuer's nose. Now, I should note here, with the transponders in the nose of each car, the time gap at that 45-mph is, in fact, representing a lead of TWO car lengths, not one; in this situation, we cannot treat the cars simply as point particles. This is where the distinction becomes quite critical, because with a set time gap, that physical gap grows from two lengths to EIGHT lengths at 180-mph heading for Turn 1 (seven lengths from tail to nose). That's what has to be made up.

Going back, using the full Peraltada, the IndyCar reaches 160-mph on the Recta del Ovalo, and drops to 120-mph at the apex, before it accelerates to that hp/drag-limited 180-mph at the end of the straight. The trailing car has a gap of three lengths from its nose to the leader's rear wing, and this is reduced to two lengths, but in time terms, a gap of three lengths, around corner apex. At terminal velocity at the far end of the Recta Principale, that gap is back out to 4.5 lengths (3.5 lengths of the visible, physical gap).

It should be clear, then, that making up twice the gap to just nudge the leader's rear end, and almost twice the time gap, is going to be MUCH more difficult. Also, entering the straight at a higher speed and in closer proximity allows the slipstream to take affect sooner, and therefore magnifies its impact several times over the case in which you've just come out of the stadium.

Getting back to the slow stuff again, there is another issue to examine. If you go from 180-mph down to 45-mph for a corner, and at terminal velocity, you had one length between you and the guy in front (two-length time gap), but were unable to make a pass, in order to NOT run over the guy, you are FORCED to give up time to maintain a physical gap between your cars. Thus, if you have repeated starts and stops, and then a long straight after yet another slow corner, it's no wonder you end up with a MASSIVE physical and time gap between cars out on that straight.

It's no surprise to me then that you NEED these 0.65-0.8-mile-long straights at F1 circuits when the setups for the straights are like that. You've set yourself up for it from the start. I might add, it REALLY does NOT help your land efficiency when you HAVE TO stretch out your circuits like that.

I had another look back at some old F1 turbo-era races at places like Zandvoort, Osterreichring, Kyalami, Silverstone, Brands Hatch, etc., and competitive cars certainly could stay close enough through the high-speed corners to keep things interesting. Keep in mind, too, those F1 cars were wider than the present ones, had some pretty honkin' substantial rear wings (i.e. wake turbulence). and were running on narrower tracks than what we have today.

If you want a more precise comparison, watch the Mexico City races for the A1GP series from the 2006/07 series, and compare that with the 2007/08 races when the series used the ChampCar chicane before entering the Peraltada. The difference it makes in how the field spreads out, and the passing that can be done, is quite apparent.

Hope you guys find this informative and useful. Also, I won't blame you if you're tired after reading this; I'm tired after having written it.