Lotus (79) Stew

by Ray Bryden on August 28th, 2009

I had an embarrassing start in the Lotus 79 and was far off the pace in my first online practice at the Glen. It was due to a couple of reasons – I’d never tried Watkins Glen in iRacing, and I was using the baseline setup. I was doing okay in the fast sections but through the medium and tight turns it understeered noticeably.

I figure that making a good setup is not unlike making a good stew, and only people with a lot of knowhow, experience and some special combination of ingredients can make it palatable. So I envision the setup gurus to be some talented chefs cooking up tweaks to make their car’s handling a perfect balance of flavors/traits.

With the help of the new skidpad, I have worked on trying to figure out the differences in the iRacing setups (baseline, high/med/low downforce) for the Lotus, and maybe learn a bit more about setting up a car in the process. The skidpad is a great tool, but beware of relying too much on the results, as it only provides steady-state performance feedback, and not how the car behaves during weight transfer such as on corner entry or exit. Still, it will provide some guidance on how changes to the setup will affect mid-corner grip (lateral acceleration) and handling behavior.

First question: How did I measure lateral acceleration? Easy. Do enough laps to ensure the tire temperatures have stabilized and record the best laptime at the radius in question. Then apply the formula:

Lateral Acceleration [G] = 4.026*(Radius in meters) / (laptime in seconds)2

Next question: How did I measure understeer/oversteer on the skidpad. Well frankly I just created a formula out of thin air which used the right-side tire temperatures, wear, and pressures. Sure it is not an exact science, but it appears to roughly coincide with my notes on some runs.

The first interesting thing I found was that the baseline and medium downforce setups are not all that different in skidpad performance although the baseline appears to suffer from much more understeer in tighter radius corners (Ah-ha!). Second, the high downforce setup is best for grip (duh) until you get to the really big radius turns where it cannot overcome the excessive drag from the higher wing angles.

Then I decided to download a Lotus setup to see how a guru can change the grip and handling, and I came across a Lotus setup from Volker Hackmann which was intended for Silverstone – note I added fuel to equate to the iRacing setups. I figured this would be a good fit for a skidpad comparison since Silverstone is pretty flat. It turns out this one is a hearty concoction that will stick to your ribs – I mean track. It is a high downforce derivative and the great thing about this setup is that it not only provides better grip than all the default setups, but also is absolutely neutral in terms of handling behavior.

Note, however, that the top-speeds of the setup varieties need to be considered, and as always, the best setups are a compromise. The secrets behind the gains will have to wait for another day, but suffice it to say many of the tweaks which resulted in the skidpad improvement were only a click or two away from the iRacing high downforce setup. In any event, Volker’s recipe is one Carl Weathers would rave about.