2001 Corvette Z06 by Hib Halverson
Mid-12s on 30 More Horsepower
While the Z06 is really aimed at road racers and
autocrossers, the first thing some Corvetters will do with it is head
for the drag strip. After 12 years on top; the ZR1 gets booted off the
best-accelerating-stock-Corvette hill. Z06 is the quicker
"Zed". While Iíve not tested a production example on the
drag strip, at the Mid-Ohio preview, GM supplied quarter-mile numbers
run by development engineers in prototypes. Under ideal conditions, the
car went 12.6/114 with a four-flat, 0-60. Thatís quickĖdamn quick.
Even an average, production Z06 in the hands of an average driver on an
average track will probably take a stock ZR-1 by a couple of tenths. The
three, key enablers in the Zed-ought-six sending the Zed-are-one packing
is the new, LS6 engine, a new iteration of the Tremec, six-speed manual
transmission and the sticky Goodyear Supercar tire.
Americans, born and raised on conspicuous
consumption, like big, thumping V8s in their sports cars. John Juriga,
Integration Manager for the Corvette engine program at GM Powertrain
Division (GMPT), often says, "The engine is the heart and
soul of a Corvette." We like the way he thinks.
On June 11, 1996, General Motors previewed a totally
new V8 engine design to the automotive press. Known to engineers working
on the project as "Gen3," the roll-out version was the
high-performance, all-aluminum variant, RPO LS1, first used in the
LS1 was a home run right out of the box. It mixed
cutting-edge technology with proven pushrods and two-valves-per-cylinder
and combined that with state-of-art block, cylinder head and induction
system designs. The result was a 345 cubic inch V8 that produced one SAE
net horsepower per cubic inch, remarkable for an engine with eight-valve
heads and pushrod valve gear. It did that for less cost than an overhead
cam engine and with a design that, in iron block form, could be shared
with millions of full-sized trucks and SUVs. For two years, LS1 has been
on the Wards Auto World 10 Best Engine list. For more about the LS1,
point your browser at: www.idavette.net/hib/ls1c.html
In í97, I asked sources close to the Gen3 project
about iterations more powerful than LS1. One off-the-record answer was
something like, "Weíve got development versions running on dynos
at the 400hp level right now." By late-í98, the RPO
"LS6" had leaked out and the rumor mill churned. I still
chuckle at Internet speculation that LS6 had 450hp or was just an LS1
with different ECM calibration.
Finally, the Beacon of Reality cuts through the fog.
Itís not 450hp, but itís a hell of a lot more than a different ECM
calibration. LS6ís very core is unique. The LS1 had had
less-than-optimum high-rpm oil control, so GMPT set-out to improve that
with a special block. It was revised at the base of the cylinders to
improve "bay-to-bay" breathing. As the pistons move up and
down, they force air in-and-out of the spaces (or "bays")
beneath them. At high rpm, this reciprocating air flow is violent and
really whips up the oil. While the LS1 block has some machined openings
between bays, the LS6 block has larger "windows" at the base
of each cylinder that better accommodate bay-to-bay breathing. The
positive crankcase ventilation (PCV) system was also changed. Taking a
page out of the LT5ís book, the LS6 gets a valley-mounted oil
separator. This both reduces oil aeration and simplifies the PCV system.
All this improves oil control, reduces oil consumption, reduces
parasitic power loss and contributes to the LS6ís 500 additional,
A traditional way to make more power is put in a
bigger cam. The LS6 camshaft has more lift and more overlap. It gets the
valves open more, opens them quicker and runs to a higher rpm. LS6ís
also have better valve springs to tolerate more lift at higher rpm.
No doubt, the biggest performance change from LS6
comes with its cylinder heads. Changes in intake and exhaust ports
increase air flow in and exhaust flow out. A slightly smaller combustion
chamber ups the compression ratio to 10.5:1. Lastly, the water jackets
were altered for improved cooling performance.
LS6ís increased air flow required more fuel, so injectors with
additional flow capacity were used. The intake manifold was
revised to improve airflow by 10%. To compliment the increased
flow capacity of the heads and intake, the higher-capacity mass
air flow (MAF) sensor from the six-liter, light truck engine and a
revised air filter assembly are used.
Lastly, the LS6ís engine controls calibration
was changed to one appropriate for the additional air and fuel flow and
having a 6600 rpm rev limit.
either image for larger view.
So, whatís all this killer LS6 stuff get you? Well, power is up from
345hp@5600rpm to 385hp@6000 rpm. To put that in historical perspective,
the 1990 ZR1 was powered by the early LT5 which put out ten less
horsepower at the same power peak. Not only does LS6 give get a 40hp
boost at the top end, but it looses nothing in the low-end and
mid-range. Itís torque curve from idle to 3000 rpm equals that of last
yearís LS1. Z06 drivers get this extra performance while meeting
Californiaís low-emissions the vehicle (LEV) standard and with
projected, EPA "city test" fuel economy that improves a
mile-per-gallon. GM Powertrain gives us more power, better mileage and
the same LEV rating as last year. Seems like a great deal to me.
John Juriga offered up this sound bite, "The
LS1 already was the best overhead valve engine and the LS6 brings it up
another level. This is a very high-performance engine perfectly suited
for everyday driving. It's safe to say it is a benchmark for the world.
That the same exact heads are going to go on the 6.0-liter LQ9 used in
light trucks for 2001 says much about the LS6ís durability, as well.
"The LS6 V8 might be the best validation of a
simple philosophy: continuous refining of
existing technologies can be more cost effective and more satisfying to
the customer than developing new ones. Proof lies in the fact that its
predecessor, the LS1, already delivers the most horsepower available in
the automotive marketplace for less than $40,000."
This look at the technical side of the LS6 has been
brief. This fall, GM High-Tech Performance Magazine will publish
a feature article covering the LS6 in depth. Be watching for it.