[s-cars] VIR Driving School-Carrera GT-Misfire (longish)

[manuelsanchez at starpower.net]

S-heads,

Glad the list is back up. (Sorry if this is duplicated, but it
didn't seem to go thru the first time)

I attended the Potomac Chesepeake Chapters' VIR Driving School
last weekend. Lots of fun of course. The big pig did rather
well I thought. My run group consisted contained some of the
following;

lots of VW GTi's, VR6's and 1.8t's (another group had some
R32's that were very nice)
Bi-turbo S4's
V8 S-4's (an Avant in the mix as well)
Some turbo an NA TT's
One 4000
A couple of C4 Corvettes
Lots of E36 M3's from the mid to late 90's
One Mercedes SL 55 AMG
Acura Integra
Mazda Miata

No UrS4/6's in my group, I while I did see one there I don't
think it ran.

Some other exotics, Porsche Carrera GT, Nissan Skyline, Elise,
Late Model Maserati Coupe, 
various race prepped 911's, late model RX7's, Ford spec
racers, Ford Cobra R 

Ms Piggy did pretty well in her group. Removing the drivers as
variables she was able to pass more cars than not, even the SL
55 (although the SL would open about 6-10 car lengths on the
straights I would catch up in the corners and actually be held
up through the twisties). The hopped up Gti's are fast and
quick thru the corners. 

There was a bit of what I'll call Station Wagon Prejudice
practiced by the flaggers, as they'd give me the ol' "faster
car behind" flag even though I just passed the various cars
just moments before.  I was glad to be quicker than some of
the smaller cars thru the turns, especially the uphill esses,
my favourite part of that course.

Some general thoughts on this mostly RS2 95.5 S6 Avant,
M3's are a tick faster rolling out of corners
The pig is suprisingly quick through the twisties (90 mph thru
the uphill essess,  and maybe faster with a better driver)
Reasonable grunt on the straights, although no match for the
brute force of the AMG SL55
The Big Reds were worth every penny
It's fun (mostly)having the tail end slide about in the big
pig, especially at turn 4, the left hook. A little
disconcerting at turn 17a the Hogpen, I need to work on that
one some more.
Must -- have -- more -- power

Here's a link to the track map 
http://www.virclub.com/cms/index.php?option=com_content&task=section&id=23&Itemid=106

My instructor for this event was Jim Bauer, proud owner of a
silver Porsche Carrera GT. I got a ride in that car for a 20
minute session and that car was amazing. It was accelerating
thru 115 mph a third of the way thru the back straight, Ms
Piggy took all of the back straight to reach that speed. The
brakes are just awesome, good thing too as the corners come up
quick afer reaching 160 mph on the straights.  All in all the
ride was quite memorable.  

Some guy won 5 laps as passenger in that car with Randy Pobst
as the driver the night before at the banquet. The Carrera GT
was on the track by itself and while I don't remember hearing
any tire squeal when my instructor drove me around, I could
hear those giant treads squealing when Randy Pobst was driving
the lucky winner around. 

One strange thing that did occur however, was that I developed
what I think was a misfire on my fourth track session. This
misfire seemed to always occur at the same spots on the track,
which is why I started to wonder if it was a fuel (lack there
of) question, as one spot which is located between turn 10 and
11 and the hairpin turn before the back straight at the Oak
Tree, has a very severe dip, and one theory is that someohow
these (negative?) forces some how messed with fuel delivery. I
have no data or gauges that would support this, but it seemed
that the misfire was most pronounced going thru this section
of track.  I had plenty of spots where I had my foot buried
against the firewall where I didn't feel a miss, but in this 
particular spot   I would feel it and feel it badly.  The 2
variables that occured prior to the manifestation of the
problem where:

1. Pulled coilpack to gain access to plugs to check for
tightness (they were tight). I did this very carefully, and
laid the coilpack atop the fuel rail/intake manifold.

2. Added 10 gallons of 110 Octane leaded gas (no kitties for
the track) as I was low on fuel.  After I burned thru that
tank, I only refilled with 93 pump gas and I still had the
misfire/stumble.

On the street I haven't felt the misfire/stumble at all under
full throttle, but that's only for a few seconds. Nothing like
doing that for a full 20 miinute track session.

All 5 coils were replaced less than 6 months ago (pre-Dave
Forgie experiiment) and the coils were spliced into the
existing wiring under the coil pack cover using solder joints
with heat shrink tubing to cover the joint.

If anyone has any ideas on this misfire/stumble problem I'd be
glad to hear them.

Sorry for the long post.

-manny
95.5 UrS6 Avant (mostly RS2)

Mihnea Custom Chipset, Bosch 3Bar, RS2 Turbo, RS2 EM, Lucas
Delphi Injectors, Tom and Marc FMIC, ECS Stage 2 Big Reds,
Happersized Rear Sway Bar,John Tilden bracket, H&R 29971 S6+
springs w/ Bilsteins, 2B Camber Plates, Forge 007 BPV, 
Samco's,  

All of the above needed to stay in front of E36 M3's, TT's,
Biturbo S4's, V8 S4's, Miatas, Integras, 944's (one was race
prepped) and yes an AMG SL55 (although I can't speak for the
quality or agressiveness of all drivers, but on that weekend
the pig was faster)