[brucepick]

Here's something I struggled with in the 2015 event, and also in 2014.

I recently did a major math exercise to work out the solution to this problem. Hopefully someone here will find it helpful.

I was coasting the last two turns (#10 and 11 on the map), and typically emerged from the final turn #11 at about 38 mph. This was after achieving a nearly perfect average speed of 45 as I entered the two turns.

Well, that caused all kinds of trouble. Obviously I didn't want to burn fuel if not needed, over that distance. But emerging at well under 45 mph, I needed to accelerate to cross the finish line with a 45 mph average. Math indicates that I'd need to achieve something like 59 mph at the time I crossed the line, in order to average 45 between the start of Turn 10 and the finish line, thus restoring the lap's average speed to 45 mph. That assumes consistent ("straight line") deceleration through the turns and acceleration between the end of the turn and the finish line.

Well that solution is no good, because now I'm cruising a slight downhill at 59 mph, approaching a turn (#1) that I wanted to enter at about 40 - without ever touching the brakes! Not good. If you haven't driven this track before, just consider that with brake use forbidden, you'd probably enter that turn at about 25 with your mom in the car. Maybe 35 if you're not trying to prove anything. 50+ will risk serious trouble without brakes. Even 45 was hairy in my two cars.

So a few weeks ago, I did a whole bunch of calculations to determine WHAT AVERAGE SPEED - from the finish line to the start of Turn 10 - would let me emerge from Turn 1 at say, about 38 mph?

Of course the easy answer is, "just go a bit faster from the finish line to turn 10". And you'd be right. But, how much is a little?

Well, multiple calculations in Excel, through three versions of the spreadsheet, gave me this result:

Calculated average speeds for Finish Line through Turn Start of Turn 10
Exit Turn 11 at 36 mph: avg 47 mph
Exit Turn 11 at 38 mph: avg 46.5 mph
Exit Turn 11 at 40 mph: avg 46 mph
Exit Turn 11 at 42 mph: avg 46.6 mph
Exit Turn 11 at 45 mph: avg 45 mph

I strongly suggest you write or print this out. Add it to your navigator's clipboard.

One important component of this, not yet stated:

The calcs above assume you will maintain your Turn 11 exit speed until you enter Turn 1. That is, all the way down the straightaway, through the finish line and on to Turn 1. I am guessing that this is doable, and also gives you an opportunity to coast that stretch, thus saving fuel. If it plays out slightly differently on the track, so be it. Anyone using this logic will have to see how it plays out, and make minor adjustments during the event.

So, to repeat:
The table shows AVERAGE SPEED from the finish line through the start of Turn 10. So you zero the RallyTracks app (or GPS) as you cross the finish line. However, you exit Turn 11 at whatever speed works for you and your car - and MAINTAIN that speed until you enter Turn 1. That's what the calculations are based on. It's based on you NOT trying to achieve any particular average speed at any time between the finish line and the top of the hill after Turn 1. Just drive that stretch the way your car needs to drive it. Then use the stretch after the hill climb, up to the start of Turn 10, to achieve the average speed in the table above.

I expect this information to give me the best combination of lap times plus MPG that I've been able to achieve. I hope it does the same for any other EcoModder who uses it.