Rumors & Gossip
Note: I disclaim all responsibility for accuracy of the info contained herein.

Substantive Stuff
We are still running our first set of BFG’s.  They are as fast or faster than new tires.  The undertread on the tires is clearly sufficient to last a long time.  I’d estimate 5 to 6 race weekends on a set with no drop off with number of heat cycles.

Substantive Stuff
From the “For What It’s Worth” department:  The Oval setup seemed to us to be -- positive camber on the inside tires, slightly more negative on the outside, about 2 degrees of caster lead (more positive front caster on the right side) and full soft on the rear bar.  We tried lots of tire pressure combinations, but came back to our standard setup.
We developed a terrible miss in the car during the race...and twice during the weekend we had vapor lock problems.  Vapor lock at the fuel pump.  We had to put cold water on the fuel pumps to get the cars running again after a vapor lock problem during an extended practice.  I think this has something to do with the local fuel.  I didn’t have a Reid Vapor Pressure tester so I can’t tell you much about the fuel.

Substantive Stuff:  During post-qualifying inspections, a high-buck Snap-On exhaust emissions analyzer was used to “sniff” the exhausts of most of the field.  Naturally, our car was one of the few that didn’t fall into a common emission range (high idle CO).  We started hunting down the reason.  Here’s what we found:
The car passed the normal KOER (key on, engine running) Star test (it gave us the “111” code).  But on the subsequent cylinder balance test, the diagnostic reading produced a “90”.  “90” means “Cylinder #4 Low”.   We changed the fuel rail with injectors (thanks to John Versey for the loan of the fuel rail, by the way) and the car now passed the cylinder balance test.  Our belief is that the injector in cylinder #4 was leaking fuel, and that when the Star tester turned off the #4 injector, fuel continued to flow (This was substantiated by listening to the engine sounds during the test.  Number four cylinder didn’t miss as badly as the others when the injector was turned off.).  The high idle CO reading was caused by excess fuel in #4 cylinder due to this leaking injector.  Bottom line, it probably would be good to run a cylinder balance test now-and-then to ID flaky injectors.

Substantive Stuff:  Thing #1:  Check the routing of your oil lines and battery cables.  We had a DNF at Mid-Ohio after the crankshaft pulley wore through one of the oil lines.  DUMB on our part...and expensive...no prize $ and a $100 “Start-Lite” hose shot.
Thing #2:  Starting to dial in the BFG’s.  Most guys are now running more camber.  We’ve been raising tire pressure and it seems to help.  It’s also clear to me that we’ll be able to get at least 3 race weekends on the tires before they’re worn out....and maybe more.  Tire performance appears to improve (or at least stay the same) over time.
Thing #3: John Bowden had another one of those weird intermittent high speed miss deals on Stevie Ray’s car.  The miss went away after he changed the battery, alternator and master switch (he’d already changed the EDIS, relays, fuel rail and injectors,plugs, and plug wires).  I’m becoming increasingly suspicious of flaky alternators.

Substantive Stuff:  The differences in setups on the BFG’s between the front runners was amazing.  Some guys had big camber, some small.  Both seemed fast.  Over time we’ll figure out what is optimum.  A couple of things seem clear, however.  First, proper break-in seems pretty important.  There is a big difference between scrubbed-in tires and new tires.  Second, based on the total number of spins and “sideways events” by all the cars, the coefficient of friction vs. slip angle curve of the BFG is clearly steeper than the Yokohama.

Referring to the graph on the right, if you imagine the curve of the Yokohama being the one labeled “Street Tire” and the BFG the one labeled “Radial Race Tire” you’ll get the picture.  The only difference from the graph is that it appears that the Yokohama has slightly more overall total grip...that is that the “Street Tire” curve would be higher on the graph than the “Radial Race Tire”/BFG curve.  The bottom line: when you go past the “limit”, it’s more likely you could “save” a Yokohama tired car...the value of precise driving has just gone up.