[In case you missed this on the ahhh...other Corvette Forum and ncrs.org. This version has been slightly edited for clarity, punctuation, and grammar. -Duke]
As promised, here is the report on my weekend with the Z06. The Torch
Red example I was supposed to have had a problem, so a Quicksilver Z06
was substituted, and, interestingly, this is the same car (VIN sequence
number 36) that Car and Driver used in their three car comparison with
the Viper ACR and Cobra R published in the current (Feb. 2001) issue.
Check out the license plate on page 55 - Michigan ECS 44. The odometer
read 8049 (page 54) while C and D had it, and was a bit over 12,000
during my watch. The car is obviously on at least its second or third
set of tires, and I suspect that the brake rotors have also been
replaced as they were not scored and barely had a ridge at the OD. C
and D ran the car on the big track at Willow Springs, and I know from my own
experience that only one day at the track will score the rotors.
Clearly, this car has been thrashed pretty hard for over six months,
but it drove like a brand new car! The upper portion of the dipstick
had built up varnish, so you know it was ridden hard and put away
wet - a lot, but the only minor fault I noticed was the steering wheel
cocked slightly to the left, and for all I know it could be within
factory build tolerance.
After running Mulholland from Pacific Coast Highway to the Rock Store on Saturday I reread
the Car and Driver article, and was totally confused. We don't seem to
be working from the same play book, or we must have tested completely
different cars! I'll quote from their comments, then give my own
impression. I made the run in "Competition Mode", which means the
active handling was on, but traction control was disabled. From the
coast to the Rock Store we only came up behind one vehicle, a SUV whose
driver slowed and pulled over to the shoulder to let us by, which earned
him two toots and two thumbs up. It's nice that there are still a few
courteous drivers out there who will voluntarily yield to faster
traffic.
Car and Driver said the Z06 only generated 0.93g on the skid pad and was
tail happy. Prior tests have been in the range of 1g. My suspicion is
that the tires were already cooked from prior heat cycling when they had
the car, and when the tires go off grip is reduced and oversteer
increases.
They mentioned "flat seats". I disagree. My butt felt like it was
sitting in a hole - a bit strange at first, but I got used to it. There
have been complaints about the seat's lateral support and lack of
adjustable side bolsters. I eventually found the seat comfortable and
supportive, but at the level of inertial forces this car produces,
anything short of a custom racing seat and six point harness is probably
inadequate at the track, but would not be very convenient for normal
driving.
"The steering is quick, but loads up massively in turns". - Car and
Driver
This statement certainly confused me. What I noticed as I pushed the
Z06 ever harder through the tight second gear corners on Mulholland was
that there is no progressive build up of discernible understeer and
steering wheel torque with increasing lateral force. Willow's Turn 2
and Turn 8 are taken at much higher speeds, and it's possible for a car
with speed sensitive steering to feel heavy at high speed. My MR2
feels like it's understeering heavily in Turn 8 with lots of self
centering steering wheel torque because steering boost is eliminated
above 80 MPH. The Corvette's Magnasteer II system provides
increasing steering effort with both increasing speed and increasing
lateral load, so this could combine to generate high steering forces in a
high speed high lateral load turn like Willow Spring's Turn 8.
Related to this was their comment under "Highs" that the rear end is
squirrely. I found the same thing, but, again, I think their comment
may have come from a set of shot tires. It's always been my experience
that once your tires are cooked, oversteer increases. The trouble with
bringing the Z06 out of second gear corners (in Competition mode) is
finding any traction as you add throttle past the apex. The car IS tail
happy, but there's only so much torque the rear tires can handle with
only 47 percent of the static weight. On Sunday I drove up and down the
switchbacks on Palos Verdes Drive East and had the same problem, but
then I tried third gear and was able to run much quicker and smoother.
Because second is so short I had to upshift on the short chutes between
switchbacks and then go back into second under braking. Believe me, at
the rate things are happening in this car the extra shifting makes for
a lot more work and more chances for error. With the massive torque,
accelerating past the apex in third is still mighty impressive, but you
don't have to struggle to find traction and fight the oversteer as
much. I might also blame this tendency on the throttle tip in program.
It would be nice to be able to reprogram it or have a couple of
different programs to choose from like the new M3. The throttle did not
feel very progressive in the upper half of its travel range.
I initially found the lack of discernible understeer and steering wheel
torque followed quickly by throttle induced oversteer to be
disconcerting, but as I pushed harder and realized the massive amount of
available grip and basic stability, my confidence built up. Overall
grip levels are equivalent to a well set up car with DOT legal racing
tires. The car has very quick response, but demands a driver with
equivalently quick reflexes. The rear breaks away quickly, but very
smoothly and is easy to catch with a bit of throttle modulation and
opposite lock.
The road had damp spots in shady areas and a fair amount of debris and
mud from Friday's heavy rain, so that made things a bit interesting and
demanded some caution and extra alertness. I let my copilot drive it
back down Mulholland, and he managed to get it crossed up within two
minutes of taking the helm on a damp patch (with both active handling
AND traction control engaged), but recovered nicely and did okay after
that. The new traction control is much less intrusive and is now a real
driving aid rather than a party pooper. I don't know if the active
handling ever intervened while I was driving. When it does a message is
displayed on the DIC, but given the rate that things happen in this car
on a tight, twisty road one hardly has time to look at the DIC. A
couple of times I felt the car was at the limit, and the active handling
was probably aiding with control, but it is very transparent.
Another interesting comment that C and D made - "...unsettling body
motion at high speed..." - probably has some merit. I found the damping
to be well suited to the suspension ride rates at the speeds we were
traveling on public roads, but I can see where more damping might be
required on a high speed track. So far there are no magic formulas or
even computer simulations to select suitable damping rates. It's a
function of road conditions and the speed range you are traveling. For
the same road conditions (bumpiness) you need more damping, particularly
rebound, at higher speeds. For example, more damping would be required
on Willow's big track than the Streets to control body motion. Take it
from Bob Riley who was quoted in a Car and Driver interview a few years
ago: "Ninety percent of setting up a [race] car is reading shocks".
Any serious driver's car needs adjustable damping rate shocks, like
those available from Spax.
Bottom line is that this is a very impressive sports car, but I think
we've reached the limit of power on a front engine rear drive car,
especially on a tight road or course. The locomotive-like torque (about
300 pound-feet as early as 1000 revs) can make for some grins, but can
be a chore to manage. I can't say anything about the high speed
handling characteristics. Prudence and my own sense of mortality
prevented me from running through the sweepers on Kanaan Dune Road at
triple digit speeds. The only way to sensibly evaluate this car at high
speed is on a big track like Willow Springs, and I did not attempt to
evaluate the car without at least the active handling engaged. Had I a
bit more time to familiarize myself with the car, I might have tried it,
but such an evaluation would be best done at a track like The Streets of
Willow Springs. If you screwup, the worse damage might be a rock chip
from spinning into the desert. On Mulholland you can take out a
guardrail and go off a cliff!
I also had a gripe about the brakes. They felt too sensitive and
overboosted, and I have this same complaint on most new cars including
my own cars when they were new, but they are now okay because they have
all been to the track to have their rotors scored. Once the rotors
score from a day at the track sensitivity is reduced to an acceptable
level, which makes it easier to execute heel and toe double clutch
downshifts, and the Corvette's pedals are suitably arranged. One more
minor gripe is the shift knob. I would prefer one that is longer and
curved toward the front so I can wrap my whole hand around it, but there
are plenty of aftermarket alternatives. The linkage is a bit heavy,
but you can't transmit nearly 400 pound-feet of torque through a Swiss
watch. Considering the beefy nature required for a box with this torque
capacity, shift effort is reasonable and the combination of box and
linkage readily readily accepted banged off shifts as fast as you like.
The new clutch used on all 2001 models is commendably light of effort
and suitably progressive.
Car and Driver described the FE4 suspension as "spine compressing".
Again, I disagree. It IS very firm, but suitably damped for normal
speeds and is livable as a daily driver if you're a serious sports car
guy. Driving up to Palos Verdes gave me an opportunity to test
suspension compliance and chassis rigidity through the Portuguese Bend
slide area. There is sufficient compliance to absorb most of the bumps
and dips at greater than normal speed on this very choppy section of
road, and it never bottomed or scrapped. It also proved that this
Hardtop's structure is immensely rigid, noticeably more so than the
Coupe I had last year. Even with the FE4 suspension this car feels
absolutely flex and rattle free.
There is noticeable "freeway hop" on certain sections of freeway, but I
didn't find it too objectionable. What WAS objectionable is all the
road noise and expansion joint thumping transmitted from the tires
through the rear suspension into the interior. The Z06 has less sound
insulation than the Coupe and Convertible, and the noise may resonate in
the trunk cavity, which is open to the cockpit. Perhaps an acoustic
divider would help here, or just turn up the stereo, but I never turned on the radio during the
entire weekend.
Ingress and egress, an issue that is becoming more important to me as
the years go by, is quite satisfactory - not as good as a big sedan, but
probably best in class if you've ever tried a Viper or F355 on for
size. I understand the F360 is much better, but haven't had the
opportunity to try it on. In normal street driving the Z06 is docile
and easy to drive smooth and granny style in traffic, and this is aided
by a slow throttle tip in for the first inch of travel. This will also
yield decent fuel economy (EPA ratings are 19/28), and on trailing
throttle at low revs you hear a nice burble from the exhaust with
muffled afterfires - probably the result of retarded ignition timing on
overrun to keep the converters hot. At higher revs this is not
noticeable as there is probably a fuel shutoff when you lift off.
The engine has uncanny flexibility. It idles smoothly at 750 and will
pull from this speed in the upper gears with nary a protest while
delivering the torque of a hydraulic lifter big block. At the top end
it feels more like a mechanical lifter special high performance big
block than any small block I've experienced, yet there is no noticeable
torque surge in the midrange. The torque curve is very flat, and it
pulls quite linearly from low to high revs. This is all accomplished
without variable valve timing and a multipath inlet manifold. When
these features do arrive on the LS engine, the torque curve will be
higher and even flatter than it is now. I can only imagine. There's
no need for five engine choices anymore. The LS6 covers this entire range,
and you can't help but fall in love with it. The rev limiter
intervenes at 6500, and it is very easy to hit in the lower gears. At
normal street and freeway cruising speeds the exhaust is quiet, which is
fine with me, but roars with authority when you boot the throttle. I
found it easy to defeat the 1-4 skip shift by just short shifting to
second at 2000 revs. If I wanted to pull away a little faster, I held
first gear to about 2800 revs. The skip shift is only activated if you
shift between 14 and 19 MPH and have applied less than 21 percent
throttle.
So after evaluating both a six-speed Z51 Coupe and the Z06, here's the
Corvette I want. Unfortunately, it will require a fourth model, but
could also be done by consolidating the Coupe and Hardtop into a single
model. First, I prefer the fastback/hatchback styling of the Coupe, but
don't like the removable targa top. The Corvette I want is the
hatchback Coupe with a fixed roof and a removable roof panel, like the
MR2, but just make it a magnesium framed SMC skinned panel. Glass
moonroofs are a waste - too hot and too heavy. Having sunroofs for the
past 25 years has made me an addict. Flipping the back up creates
excellent ventilation without the drafts suffered from open side windows
while allowing the option of near open air motoring; and with a
removable center roof panel you have the structural rigidity of a fully
closed car.
The LS6 engine is the obvious choice, and I think I'd select the FE4
suspension. The Goodyear Eagle F1 Supercar tires are definitely the way
to go over the runflats, but I'd like to evaluate them in combination
with the Z51's FE3 suspension. Also, as mentioned before, adjustable
damping shocks are a must. I don't mind crawling under the car to turn
a screw or knob when I go to the track.
The Z06 has a different gearset in the T-56. The architecture of this
box requires fourth to be direct, so they shortened first, second, and
third by ten percent. The downside is a big gap between third and
fourth. I think a better solution would be a shorter 3.73 ring and
pinion (all M6 models currently run a 3.42) with the standard ratios.
This way the overall first through third gearing would be about the
same, and fourth would also be ten percent shorter than the current Z06
setup and tighten up the 3-4 spacing; and the standard box' 0.75 fifth
with a 3.73 would allow the Z06 to achieve top speed, perhaps 180 MPH,
before it runs out of revs. The standard box' 0.50 sixth with a 3.73
would yield about the same overall gearing as the current 0.56 sixth and
3.42 combination. Sixth is what delivers the Corvette's excellent
highway fuel economy, and the Z06 will pull usably from less than 60 MPH
in sixth. I'm not sure why GM went this way on gearing, but the
gearset already existed and has been used in some Camaros, so the parts
were already designed an tooled.
There's been a lot of controversy about GM's mythical claim of zero to
sixty in four seconds flat. I tried a handful of launches and
understand why a "good" zero to sixty time is so elusive. A good launch
is a delicate balance between axle hop (too conservative) and lighting
the tires (too aggressive). Personally, I don't think zero to sixty is
a very useful measure of automotive virtue, particularly at this level
of performance, and a high powered front heavy car car like the Corvette
is going to be traction limited. Good launches will require lots of
practice and by implication lots of clutches, plus a sticky surface and
a bit of luck. If you do luck out and get a perfect launch, it should
deliver a feeling somewhat like what Colonel Stapp must have experienced
when he rode those rocket sleds back in the fifties.
Any car enthusiast would be thrilled with this car, but I really wonder
how many would have the skills to operate it safely at the edges of its
substantial envelope. Active handling, traction control, and ABS are
all aids to make up for small mistakes, but if you're just too fast into
a corner because you stayed on the power too long and didn't brake soon
enough or aggressively enough you're going to crash just as you would in
a car without microprocessor assists. I've never seen a correlation
between financial means and driving skills even with the availability of
commercial high performance driving schools. Likewise, if you're only
into zero to sixty and the quarter mile, you're missing the whole point
of this car and a whole other world of exhilaration, driving pleasure,
and personal satisfaction. If you acquire a Z06 without the intent of
taking it to any of the many available track events - not necessarily
wheel to wheel racing - then you are missing out on most of the fun
except bragging rights, which isn't worth much in my book.
The LS1-powered Coupe and Convertible with the Z51 package deliver
outstanding high end sports car performance at a bargain price while
being sufficiently comfortable and flexible to perform a myriad of
yeoman tasks expected of an daily driven car. The Z06 takes all these
virtues to a noticeably higher level without subtracting much of the
pleasant and easy nature of the other models, but to explore the limits
of its envelope including the higher levels of acceleration, grip, and
responsiveness, particularly on large radius high speed turns, you've
got to take it too the track.
Duke
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Thanks 
