Re: Playing in Pueblo

[susan griffin <griffin.susan@epa.gov>]

What a coincidence, as I just returned from a day of testing the 4000 TQ
at Pueblo. It was a dreary day in the Denver area, with snow imminent, but
in the Pueblo oasis it was sunny and in the 70's.

I loaded up the spare wheels/tires , tools, etc and picked up a friend who
is an ex-Formula Mazda racer. When we got to Pueblo Motorsports Park, it
turned out the vintage racers, FF's, and some others were practicing for
this weekend's events. Our objective was to test the new Kumho's -
205/50-15's - and diagnose the f#@%$ G60 front brake problems. It's really
puzzling me to hear how others, inluding Dave Lawson, are more than happy
with the G60's on the track. Even though I've spent way too much money on
cryo-treated rotors, Pagid racing pads & a dual master cylinder unit, I
have had nothing but problems with the G60's.

After a few warmup laps, tire pressure adjustments and instruction laps
(my friend  showing me the proper line), we started running some solo
laps.  My friend - David M. - complained the car was pushing terribly and
resisting all his turn-in efforts. Still, he was running 1:56's  and said
the brake shudder/chatter through the pedal was not bad. (Interestingly,
last time we were at Pueblo with my 16" street Pirellis, he said the
handling was neutral, though we were slower.) I was a few seconds slower,
thought the car was pretty neutral, yet felt terrible brake pedal shudder.
Brake fade really didn't seemed that bad, but the pedal shudder got worse
as the brakes got hotter. Going into turn 1, the long front straight
helped to cool the brakes a bit and the shudder wasn't objectionable. But
by turn 3, the G60's were HOT and the shudder was very bad.

I decided we'd try running with the center diff locked. Our earlier laps
the diff was open, and the inside rear wheel would spin exiting the
tighter turns under  power. I noticed an immediate improvement with the
center diff locked, and my times gradually dropped, until by the time we
quit (prematurely), I actually turned a few 1:56's. David M. insisted he
still could not get the car to turn-in, and that tire pressure
adjustments, diff open/locked did not seem to make a difference (maybe
he's just not accustomed to driving such a "heavy" car on the track).
Regardless, he eventually broke into the 1:53's.

The day came to an early end when 1)the gas gauge took a serious dive, and
I thought I felt a cut-out due to fuel starvation under hard cornering,
and 2) we demolished a new Kumho. The left front tire, in which we were
probably running 50psi hot,  was cooked - the outer third of the tread was
completely gone to the point where the cords were exposed!!  Maybe the car
really was pushing as bad as David M. said. Yes, the track is run
clockwise and is the fastest turns are right-hand ones.

So, other than the tire failure and irritating brakes, it was a pretty
successful test day. David  M. thought that if we reduced  the understeer
and put some "real" brakes on the car, he could turn 1:50's.  I thought
the car was turning in fine, but the brakes were severly overheating.  He
agreed that when he starting using the brakes harder, the shudder was
horrific. Maximum boost was 13psi and fluid/exhaust temps were similar to
what Dave Lawson saw.   We succeeded in expending 14 gallons of fuel in
about 125 miles (did we do that many laps?), this on a car that actually
gets 24mpg on the highway!

We stopped at the alignment shop on the way home for advice on the
understeer condition and the decimated front tire. The mechanic, who
aligns many SCCA cars,  emphasized, "Well, I keep telling you we can set
this car up for the street or the track, but not both!"  He said the -1
degree camber in the front was the most he could get out of the car, and
the 0 toe was about the most toe-out he would recommend for street use.
His suggestions were to 1)dial-in more toe-out for the track only !?, and
2)replace the stock (actually UrQ) upper strut bearing and cap plate with
some type of aftermarket bushing/plate -- this to minimize front
suspension deflection and allow him to set the front camber more negative.

As to the G60's, my feeling is that with the clamping power of the dual
master cylinder unit and the Pagid racing pads, they are simply
overheating. We're going to try some cooling ducts and Porterfield pads
and see what happens. If that doesn't help, it's time to look into some
4-pot calipers. David M. seems to think I'm simply asking the G60's to do
way too much.

The Kumho's stuck well, though I'm having a hard time believing the left
front tire wasn't somehow defective. The asphalt at Pueblo is pretty
abrasive and the left front takes the brunt of the load, but the tire
looked ok until my last session on the track. The other three tires looked
decent at the end of the day.

Dave -- let's get together at Pueblo sometime. The track stays open all
winter, weather permitting. It's a pretty laid-back place, though, when I
went in August, there were some ex-Indy light cars testing there. It was a
pretty harrowing experiencing watching them blow by me on the front
straight and disappear rapidly.

Gary Kaklikian
86 4kcstq
86 5kcstq

Lawson, Dave wrote:

> On very short notice I was invited to join another ur-q owner and
> a quad-cam ford mustang cobra for an open track day at peublo
> motorsport park. It sounded like a great mental health day and a
> good reason to burn up some old R1's. The 2 ur-q's were loaded
> into the trailer and we headed south.
>
> It was a gorgeous fall day with the temperature about 85 F.
> We were the only ones there, 3 cars, 4 drivers, and a 2.2 mile
> 10 turn road coarse. The mustang was setup for SCCA T2
> competition, the ur-q's were street/daily drivers and setup
> as follows, 1983 models, single knock MC engines, K26 turbos. I
> was running about 12psi boost and the red ur-q was running 15 psi
> boost. The red ur-q has a 2 piece EM which has been ceramic
> coated inside and out, down pipe coated too. My ur-q has
> eibach/bilstein/delrin bushings and the 3.89 final drive,
> the red ur-q has h&r/bilstein and stock bushings and
> 4.11 final drive. Both had G60 brakes, I was running stock sway
> bars and the red ur-q has a larger rear bar. I was running old
> BFG R1's on the 15x8 wheels and the red ur-q had R1's on 16x8
> S4 wheels.
>
> Neither myself or my friend had driven this track before. The
> mustang driver has raced there in SCCA and PCA events. Our
> instructor/mentor for the day has logged lots of track time here
> over the past 10 years. He is a quattro fanatic, has a 91 200 TQ
> Avant and is building a new SCCA ITB coupe GT. He used to
> run pro rally back in the late 70's and early 80's. I hadn't been
> on a pavement track in a few years but it all started to come back
> after a few laps. My friend in the ur-q and I worked our times
> down to 2:02 and the mustang was running about 1:53. The ur-q's
> were very evenly matched, even with the difference in gearing.
> I was seeing 105 at the end of the front straight and the G60's
> did a good job of hauling the car down to ~65 for turn 1. The
> ur-q's performed great even though the temps were on the high
> side. I was seeing the coolant close to 250F, the oil temp on
> the LED bargraph was 140-150C and my EGT was 1400F.
> After a few sessions I down loaded the ECU codes and I got
> a 2141, I left my diagnostic notes at home and couldn't remember
> what it was and made a few phone calls. Turns out it is an error
> for max retard of timing due to knock. I swapped in another ECU
> with a chip with less aggressive (stock) timing and went out again.
> I still got a 2141. I ran the rest of the day with a lighter foot and
> somewhat short shifting. My ur-q ended the day by blowing off
> the vacuum line from some sort of damper for the fuel system.
> I shoved it back on so the car would idle and we loaded it back
> into the trailer for the drive home.
>
> Some observations. My car had very neutral handling at the limit
> with just a hint of understeer. I have been tracking my ur-q on and
> off for the past 8 years and I have never experienced any handling
> traits like Dave E mentions for cars with the "old" style suspension.
> I will keep looking. The G60 brakes worked great with, dare I admit,
> stock Audi pads and crossdrilled rotors. 5 year old hardened track
> tires are way better than any street tire, the car had tons of grip
> and not a peep from the tires. Driver experience plays a big role.
> I feel I was doing fine, but our guide went out in an ur-q and I was
> chasing him, he lost me after 3/4 of a lap. I wasn't willing to commit
> that much to keep up with him. He was running close to the
> mustang times with a 100 hp deficit. I need to follow through with
> my plans for installing a larger oil cooler and radiator. The red ur-q
> has more body roll than my ur-q. The ceramic coatings on the red
> ur-q lower underhood temps.
>
> Now it's time to get the ur-q ready for steamboat, we're expecting
> snow tomorrow, off with the track tires and on with the haka nrw's.
> -
> Dave Lawson
>
>