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::
Callaway Sledgehammer Twin Turbo Pictures :: |
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Callaway Sledgehammer Twin Turbo General Info :: |
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Produced in |
1988 |
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Curb Weight |
1589kg / 3503 lbs |
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Length |
4483 mm / 176.5 in |
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Width |
1803 mm / 70.9 in |
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Height |
1186 mm / 46.7 in |
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Wheelbase |
2443 mm / 96.2 in |
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Layout |
Front Engine RWD |
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Drivetrain :: |
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Engine |
V8 LT1 |
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Displacement |
5.7 Liters 2733 cc / 348.8
cu in |
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Valvetrain |
xxx |
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Fuel Fed |
Dual Bosh fuel pumps feed
the system |
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Aspiration |
Twin Turbo |
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Gearbox |
6 speed manual |
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Callaway Sledgehammer Twin Turbo performance stats :: |
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Horsepower |
898 hp / 669.5 kW @ 6200 rpm |
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Torque |
772.2 ft/lbs / 1047.0 @
6200 rpm |
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Redline |
Unknown |
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Power to weight ratio |
0.56 hp/kg |
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0-100 km/h | 0-60 mph |
Roughly 3.9 to 4.0 seconds |
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0-160 km/h | 0-100 mph |
Unknown |
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400 m | 1/4 mile |
10.6 seconds |
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Top Speed |
254.8 mph / 409.9 km/h |
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:: Callaway Sledgehammer Twin Turbo Additional Info :: |
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SledgeHammer
Text of Article by D. Randy Riggs, Vette
Magazine, 1989
When the call came last October, I was
ready. It was time to jump in the
car,
make a banzai run to the airport and hop
a plane bound for Columbus, Ohio. As
the lone journalist invited to what is
normally a top-secret Callaway test
session, I felt a tremendous sense of
anticipation. I was about to witness a top-
speed attempt in a streetable Corvette
that stretched the limits of my
imagination .
In the Columbus Airport, I met Tim Good,
Callaway's chief engineer, and together we
drove off in a rental car up Route 33 to
Bellefontaine, just a short distance from
East
Liberty and one of the finest high-
speed facilities in the world, the |
Transportation Research Center, recently purchased from the state by
Honda. Just imagine a 7.5
mile oval with steeply banked
turns and straightaways so long it's difficult to see where they end.
At TRC, the Callaway group was about to make the first test of a project
car that had consumed
their time for the better part of six months and had occupied their
thoughts and note pads since
August of 1987, when the Callaway Top Gun Corvette blew away everybody in
a Car and Driver
shootout known as the Gathering of Eagles.
The Top Gun Callaway Corvette had run 231 mph on a hot August day,
spectacular to say the
least,but the car was not nice to drive. The No Smoking light hadn't even
gone out on the return
flight from the Gathering of Eagles when Reeves Callaway began making a
laundry list of things
he was unhappy with on Top Gun. Things such as absence of low-speed
drivability and A/C and
un-Callawaylike rough mannerisms. Reeves found himself asking no one in
particular, "Can I
build a real version of that car?"
During a meeting with Corvette chief engineer Dave McClellan, Reeves was
discussing the cover
of an automotive publication that featured his Callaway, with the cover
line, "Des Is Der Hammer."
In German, the word hammer is a neat way of implying significant power.
McClellan joked to
Reeves,"Das Is Der Sledgehammer!" The name stuck.
And over dinner, just before Christmas last year, Reeves told me he
thought it was possible to
build a Callaway Corvette with all the creature comforts of his standard
twin-turbo beauty, yet one
that would have the speed of a fast private aircraft, 250 mph. And he drew
out a formula on a
napkin that showed just how much power would be required to push a
slippery vehicle through the
air at those speeds, nearly 1,000 horsepower!
Then along came the impetus to build such a vehicle. The German magazine
Auto Motor und
Sport invited Callaway to the Nardo highspeed track in Italy to run a
top-speed contest against a
Porsche 959 and a Ferrari F40, supplied by their respective factories. The
only problem was the
deadline; Callaway, a small company, couldn't finish the car in time to
meet it, since a project of
this magnitude stretches both personnel and financial reserves.
In Italy, the run went off with driver supreme Walter Roehrl piloting the
factory Ferrari and
Porsche. The tricked-out Ferrari actually ran slower than a stocker, at
198 mph and the tweaked
959 went 210 mph.
As it turned out, Ferrari and Porsche were extremely pleased that Callaway
was a no-show.
By the time Callaway went to TRC in the middle of October last year, the
trip to Italy had been
canceled but the lofty goals still loomed on the horizon. Reeves was going
to build a Corvette with
250-mph capability, stable and comfortable at all speeds, avoiding the
nickel-rocket syndrome of
hard-to operate clutches, high interior noise, high driver-compartment
temperatures and fumes in
the cockpit.
Because of the Callaway performance image, Reeves feels that the company
needs to
demonstrate its capability time and time again, to let people know it is
here. A rolling laboratory,
such as this 250-mph car, would certainly drive home an image of Callaway
as the supreme
performance vehicle.
In June of '88, things got serious at Callaway. Most important the
financial aspect of the project
was approved. Chief engineer Tim Good then produced a project outline, and
he began putting
together the team for the project, now officially codenamed Sledgehammer.
In addition to Tim Good and Reeves Callaway, Elmer Coy was assigned as
project engineer, a
person Good describes as "remarkable", because he's a mechanical engineer
who knows how
electrons flow." Dave Hendricks became the project technician, while
Talbot Hack provided
additional engineering assistance, all from within the company.
Two people outside the organization had impressed Reeves during the year.
One was
Lingenfelter, an NHRA drag racing champion Reeves had met during the
Gathering of Eagles.
"When John's engine broke during a run, he went back to his shop that
night and next morning
he was ready to go again," says Reeves." I like that kind of dedication."
John was selected not
only to share the driving chores with Reeves but to build the engine to
Callaway's exacting
specifications as well. Lingenfelter Racing is located in Fort Wayne,
Indiana, and is known for
excellence in this realm.
Because Reeves wanted a serious aerodynamic restyle, he sought the
services of stylist Paul
Deutschman from Montreal, whose work he'd seen in several automotive
publications. Paul came
through with an absolutely stunning package. Tony Cicale of the Carl Haas
Team, which
constructed Mario Andretti's Indy effort, was consulted as an
aerodynamicist.
And, finally, Carroll Smith, a road racing professional who helped manage
Shelby's GT-40s to
LeMans victories back in the '60s and is author of Tune to Win, was
contracted for chassis
engineering.
The team used an '88 production Callaway as a base, car No. 51, to be
exact, and work began in
earnest. As Tim Good sums it up, "You can really do anything when you put
together the right
people."
To prove their point about street capability, the Sledgehammer had been
driven from Callaway
headquarters in sleepy Old Lyme, Connecticut, to the TRC facility in Ohio.
It was then driven
home after the tests were completed.
I first spotted the Sledgehammer in the hotel parking lot at sunrise, the
morning after I'd arrived.
Hard to believe a vehicle with such potential can be driven to the
hardware store. Yet there it was,
parked next to a Dodge van. And the styling was far better in the flesh
than anyone had
conveyed to me.
Even though the group had arrived in the wee hours, it was off to TRC
early on the morning of
October 20, for there was much to be done. Once at the facility, the
Sledgehammer got a going-
over from one end to the other, and it was here that one could begin to
appreciate the incredible
effort that had gone into the car.
The team began with a Bowtie block with four-bolt caps and a Cosworth
SIGMA finished crank,
cross-drilled to facilitate rod oiling for high loads. Clevite 77 bearings
were fitted. A Houdaille fluid
damper was used, in standard Corvette diameter, to clear discharge pipes.
Crower rods were also
fitted, along with Jesel roller rockers with a Jesel stud girdle. Crane
supplied the roller lifters.
Oiling is via an in-pan-style Barnes dry-sump system, which holds l0
quarts of Mobil l synthetic,
the brand specified in production Callaway cars. The tank fits in the spot
normally occupied by the
HVAC (heating/ventilation/air conditioning) system, now moved to the right
rear storage
compartment in a custom-built arrangement. Oil cooling is provided by
coolers mounted in the
nose on each side of the car.
Cosworth pistons were specially made for Sledgehammer. Jeff Roper,
experienced in running
Turbo Buick V6 motors at Indy, designed them, with Buick Indy motor
skirts. Speed Pro plasma
moly rings were fitted.
Cam Techniques supplied the camshaft. which was designed by Dave Generous.
Surprisingly, the
cam is not that aggressive, but very special to aid highway performance.
Brodix supplied the No.
12 heads, which were drilled and tapped to accept standard Callaway front
engine dress. The
heads were O ringed, copper gaskets were fitted, and studs, instead of
bolts, were used for
retention.
898 horsepower; 6200 rpm in fifth Overdrive equals 254.76 mph!
Callaway Corvettes are famous for their twin-turbo design, and that
concept carries through to the
Sledgehammer. Originally, they had planned to use a mirror image of their
current system, but
they dropped that plan in favor of a design that they could package on the
upcoming ZR1 (yes,
gang, a twin-turbo ZR1 will be coming from Callaway!).
Huge Turbonetics T04B-series turbos were used with R. Lee stainless steel
wastegates. The
wastegates can be controlled electronically, through an electronic
pressure regulator, or manually,
through a boost knob in the cockpit. Boost is set at 1.5 bar, or 22 psi.
Individual stainless
exhaust headers were built at Callaway.
The turbos' location is ingenious; they nestle just behind the front gill
panels, rearward of the
front wheels, one on each side of the vehicle. This location required some
amazingly clever
plumbing work, which runs through 4-inch holes cut in the frame rails.
Braces restore the structural
integrity of the frame. Callaway also fitted the largest-possible
intercoolers, which are fed by four
inlet openings in the restyled nose. Air exits the hood from two rear,
stylized outlets.
Callaway built their own distributor, as well as the fuel pressure
regulator, from billet aluminum.
Dual Bosch fuel pumps feed the system. They went with an English Zytec
engine-management
system, while Rochester Products custom-built special injectors with
sequential timing. Fuel rails
were Callaway's own. An MSD (Multiple Spark Discharge) ignition system
provides spark. Its claim
to fame is high power and proper spark under extremely high
cylinder-gas-loading conditions.
The module is located in the left rear storage compartment. As with all
Callaway Corvettes,
Champion Spark Plugs were used.
The Zytec is capable of controlling ignition and injector timing, and a
Toshiba laptop computer
was adapted to the system to allow adjustment of fuel and ignition on the
fly. It then records the
information and plays it all back after the car is parked. And here's the
best part. The engine
produces a conservative 898 horsepower on the dyno, more can be had if
necessary!
To keep everything cool, Hack engineered a huge copper/brass radiator with
a G&O core
mounted on a steep angle and fed through ample openings in the nose. It's
also supplemented
by two electric fans mounted on a fabricated bracket.
Because of the anticipated power delivery, Callaway left nothing to chance
on the chassis.
Goodyear was instrumental in supplying tires for the occasion: ZR40
Gatorbacks from the
standard production molds, but constructed more like a racing tire. Treads
were then shaved to
prevent heat buildup and chunking, while mounting was on standard Callaway
Dymag magnesium
rims. Goodyear even sent along tire engineer Reed Kryder, who monitored
temperatures and
pressures.
Koni supplied special shocks of standard Corvette design, but valved and
constructed for the task
at hand. Ride height is about one inch lower than stock, with 44 pounds of
air in the tires. Carroll
Smith then repositioned the lower control arms to control bump steer,
something a driver wants to
avoid while traveling over 200 mph.
Power delivery goes through a Doug Nash 5-speed built to GTO racing specs
and fitted to a
special overdrive unit through a special adapter. The output shaft is
shortened, along with the
drive shaft. The yokes, axles and Spicer/Dana rear axle unit are specially
constructed for strength
and durability. Behind the left rear fender grille are coolers for both
the axle and overdrive unit.
The right rear fender houses the A/C evaporator. Headers dump into a
huge-diameter system
that presently exits out the rear center of the car. Mufflers are by
SuperTrapp.
At TKC, the rear styling of the Sledgehammer wasn't completed and is being
finished at press
time. Because the car was hampered by a persistent misfire on the drive
out to TRC, the crew
checked a number of items before the car ventured out on the first
shakedown runs. And we're
talking superfast here, just imagine 135-mph warm-ups, speeds faster than
most cars are
capable of. Reeves was doing the driving, while Elmer Coy, strapped in
with helmet in place,
fiddled with the laptop computer. Elmer probably never dreamed an
engineering job would put
him in a 200-mph-plus seat!
There's tremendous pressure on the team when runs are scheduled. Top speed
sessions are
limited to costly half-hour segments, when TRC personnel clear the track,
put timing and
ambulance crews in place and put many people on hold until the passes are
made. And the
scheduling is done well in advance, so if problems develop you can't
cancel out just prior to the
session. Because of this, the crew worked hard and fast between runs, like
a well-orchestrated
Indy crew. And the pressure was on.
So just what is the Sledgehammer like to live with? Inside, the car is a
bit noisier than a standard
Corvette, but it's all there, stereo cassette, power windows, A/C and
additions include a leather-
covered roll bar and fire-suppression system cleverly concealed in the
storage area. Five point
restraints are in place for both passengers. Serious stuff.
Even the digital speedometer read to 255 mph, the highest number you can
generate with an 8-
bit microprocessor. (Ironically, when the car reached its ultimate top
speed, the speedo pegged
and began counting down!)
Smith, to see how the car was tracking at speed, had placed a piece of
tape on the top center of
the wheel. Because it was straight as an arrow, it was time to step down
on that pedal with a little
more authority.
Up to 198.6 mph and suddenly smoke appeared from under the car. An oil
leak began surfacing,
and at about the same time the misfire returned. The leak was minor,
traced to an oil adapter
housing in the drysump system. But the misfire was another story, so
Sledgehammer returned to
the garage.
New spark plug wires were made up, the ground wire was replaced, and a
small puncture was
discovered in a tire. Reeves had parked it just in time. It was also
discovered that one of the
rear axle output shafts was loose in the housing, so a spare rear was
bolted in place. Think it's
easy to go very fast? Think again.
The day had not gone well, and when we awoke to a driving rainstorm on
Friday morning, a sense
of gloom came over the group. The day would be spent working on the car,
which had again
misfired during a 130-mph run in the rain. Nothing would be proved on that
bleak Ohio autumn
day. To cap it all off, some of the team was coming down with the flu.
On Saturday, the weather broke, but it was cold and windy, and the car
continued to misfire. They
changed Zytec units, MSD units and virtually every component in the
ignition system. Reeves had
to fly to England, so Sunday would be a time to regroup. But the weather
forecast for the following
week was grim, and Monday graced the team with snow flurries and general
misery.
When Reeves returned from England with a severe cold, he handed over the
driving chores to
Lingenfelter. Tuesday came the breakthrough. The misfire had been traced
to three
contaminated A/C Rochester fuel injectors. One could feel promise return
to the air and the mood
became decidedly upbeat.
On Wednesday, a long hard week after arrival, it was time to turn
Lingenfelter and the now strong
running Sledgehammer loose. The first runs registered around the 220 mph
mark. Then Tim
Good noticed the dirt pattern around the front intake gills was flowing
out, instead of in.
Obviously, a low-pressure area had developed at speed, so the engine was
starving for air. Small
scoops were fitted to the gills, and out went Sledgehammer to the concrete
oval once again.
One can't imagine what a streaking 200-mph-plus car sounds like as it
flies by, just 100 feet
away. It's a giant whoosh, more noise coming from the air being displaced
than from the engine,
and this time it was some kind of whoosh.
The Sledgehammer disappeared into the distance and the walkie-talkie
crackled with the answer
to the question everyone had burned into their mind. How fast? 254.76 mph.
Das is der Sledgehammer. And how!
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SledgeHammer!
text of article in Sport Auto, Germany 1989, Klaus Rosshuber:
The ultimate sports car is 880 hp, is over 400 km/hr fast and costs
$400,000 U.S. These figures
are impressive by themselves. Now, Sport Auto drives Reeves Callaway's
Sledgehammer on the
streets and measures the sobering numbers this car achieves,
overwhelmingly an impressive
experience.
"If the Callaway Twin Turbo is a hammer then this car is a sledgehammer."
In this manner, Dave
McClellan concisely described the most ambitious development of the
Chevrolet Corvette, the 880
hp Sledgehammer from Callaway. Coming up with these names, the head
engineer of the
Corvette program was comparing this new Sledgehammer with the standard
Callaway Corvette,
which, with 390 hp, is also no wimp. The nickname stuck.
Reeves Callaway has defined, in a dominant manner, the final and ultimate
expression of the
legendary American sports car. He says, "of course the Sledgehammer is not
a production car, but
it shows in a spectacular manner our technical capabilities and proves an
880 hp sports car may
be used in a day-to-day manner, similar to any other Corvette." Callaway's
entry into the market,
dominated by the Ferrari F40, Porsche 959 and Lamborghini Diablo etc.,
appears in a relatively
discrete manner as far as this only U.S. sports car, is of itself,
discrete in a country where
toothpaste can only be had in tubes of giant proportion. This seems to
exactly fit the bill for what
is wanted.
Reeves Callaway, Corvette Tuner Enhancer, has good reason to smile. His
Twin Turbo Corvette
will blow off the collective European supercar field. The wind- tunnel
tested developed spoiler set
for the Sledgehammer should help minimize lift up to the 400 kilometers
per hour top speed.
Subtlety is the nice part of this package. The Sledgehammer has the
dimensions of an entirely
stock 88 Corvette. It is clad in a specially cut spoiler suit which the
Callaway organization will have
available off the self to other owners. Wheel style is the same as on the
normal Twin Turbo
Corvette, the only distinctive visiting card of the Sledgehammer is on the
end of the car that
people see most, the rear end. Four arm-thick special muffler pipes stick
out of the center of the
rear and for he who doesn't know what he is driving behind, he will hear
it. Driving behind this car
sounds like driving behind a race motor equipped Group C Mercedes, but
which race car will sit
idling comfortably at 800 rpms per minute? As promised, this, the most
powerful of sports cars,
may be driven at the national speed limit with composure and grace.
Driving like this, the driver can only guess what calamity can be let
loose once the right foot is
depressed. But who could be satisfied with just contemplating this idea?
To let loose this
horrendous reserve of horsepower there is a bit of highway in Old Lyme,
long forgotten by the
local sheriffs, upon the concrete slabs of which one can probe the
potential of the Sledgehammer.
The dash gauges confirm results achieved in previous road tests. "Be
extremely careful about
spinning the wheels and snapping the drive-lane," warned Tim Good as he
double-checked the
Simpson 6-point seat belt strapping him in. Good is Chief Engineer at
Callaway and the technical
father of project Sledgehammer.
Objects in the rearview mirror diminish as the coupe, with your sincere
writer behind the steering
wheel, endlessly accelerates. The merry burble of the Twin Turbo V8
changes as the rpms
increase to the sound of an orchestra of 100 hammer smiths accompanied
with a chorus of twin
turbos. What the tires can translate into forward motion results in an
acceleration experience
realized till now only by drag racers. The shot of energy transforms the
car into a bullet. A curb
weight of 1589 kilograms yields weight to horsepower ratio of 1.8
kilograms to each horsepower.
Instead of pulling wheelies, the car would rather perform a power slide of
sorts when this power is
applied. Howling like a guard dog, the first section of the concert is
ended as the wastegate
opens if the pressure is allowed to build up to 1.5 bar. With a deep
click, the shifter finds 2nd
gear and the process repeats itself 3 times with an unadulterated roar.
Most unfortunately, the
couple of miles of Old Lyme highway just aren't enough to repeat the
process for the 5th and 6th
gear of this beautiful ZF transmission. The speedometer eases down . We
finish our road test
having had the good fortune of not encountering the Men in Black.
Fortunately their handcuffs
are still rattling empty.
This road test revealed the extremely civilized manners of the
Sledgehammer.
A beefy roll cage protects its passengers . The package looses very little
of the comfort provided
by the production brethren. No wonder: Tim Good and his men have retained
the stock 3 stage
adjustable Delco (built under license from Bilstein) shock absorbers. The
springs for the car have
been made somewhat harder and the car's bodywork has been lowered 25
millimeters. The
philosophy seems to be, "if its good, use it and don't change it." This
bearishly powerful engine,
with its ship-motor-like 1047 NMS of torque runs with unusual evenness and
yields a very relaxing
and easy cruise for traveling. A 2 speed transmission would be totally
sufficient as long as one is
conservative with the gas pedal.
This Corvette handles with admirable neutrality in the curves and the rear
end has been beefed
up to cope with this copious torque. Nonetheless, a full stomp on the gas
pedal will put the car
into a definite drift . The precise steering and long wheel base allow
this to be a predictable and
handlebar phenomenon. Thoughtless applications of full throttle should be
strictly forbidden
such maneuvers will change this classy, refined dressage horse into an
unwieldy rodeo beast. In
this situation the whole road just isn't enough width to keep this bucking
Mustang in line. Yet in
such situations, the good design of the car proves its worth as one can
reign in on the car and
bring it back under control.
Credit for the sound handling of this power in the rear end, and
suspension in general, goes to
Carroll Smith who set the car up using special uniball linkage. In his 60
years, Smith has gained
experience in such successful ventures as Carrol Shelby GT 40 LeMans
entry. Back at home base
in the immaculate high tech factory of Reeves Callaway, the underhood
workings of the
Sledgehammer were revealed to your authors. The underhood area is packed
with all the neat
stuff that makes the Sledgehammer what it is.
Tim Good said, "the biggest problem we encountered was packaging all the
necessary materials
to develop this amount of power." A tour of the underhood topography
reveals what makes this
the super Corvette. The location of the 5.7 Chevy V8 block just about
nothing is in it's regular
place. In the normal location of the radiator one finds two huge
intercoolers, hand made from
aluminum. Fed by four openings in the front of the bodywork, the
compressed air looses 50°C as
it passes through these intercoolers. The homemade custom built radiator
lies horizontally
underneath the intercoolers, ducts feed outside air to this. In the front
left and right wheel wells,
one can find the two oiler coolers. Along the side, gill panels form the
entry for the induction air
just behind the wheel wells. The heavy duty ducting piping between the two
turbos is all hand
welded. Having passed through the hand made exhaust manifolds, the exhaust
gas encounters
Garrett TO4 Turbochargers which the Callaway team joined with compressor
from Turbonetics, a
TO4 B. Tim Good says, "only this way could we achieve the desired
characteristics of the engine
performance." Turbochargers are fitted with integral waste gates. The
exhaust system is all made
from stainless steel and uses no catalytic converters. In the rear of the
system one finds a
quartet of SuperTrapp mufflers. The underside of the car is heavily
protected with materials
against heat build up and subsequent damage; these are made with polyester
and aluminum.
The temperatures developed in the engine dictate a drysump design which
carries 9.5 liters of oil
through a homemade in-house designed and manufactured oil pump. The sump
tank is also
made in house. The engine long block itself has little in common with the
stock version. The block
is a NASCAR series Chevrolet special product. Cylinder heads are made by
Brodix. connecting rods
are hand balanced. The rods carry special Mahle pistons. The Camshaft is
made by Cam
Techniques with full roller gear.
"Thanks to the size of the turbo chargers, we experience no lag; the
secret lies in the contouring
of the camshaft," says Callaway Engineer Dave Auerbach. He's also involved
in the R&D of the
Aston Martin Group C Engine, and entrusted to the Old Lyme team by their
counterparts in Great
Britain. The engine is masterfully controlled by English manufactured
Zytech, whose ECM controls
ignition and fuel injection. For excellent performance using this system,
AVGAS is recommended.
MSD ultra high performance ignition system provides a big spark to each
cylinder. Tim Good says,
"using the MSD system we achieve complete combustion even in this very
pumped up
atmosphere." Favorable ignition conditions and turbo generated pressure of
1.5 bar, allow this
sort of power to be achieved.
The culmination of this power and engineering development, at which this
car proved itself to be
faster and superior to the European sports car collector, was tested in
Columbus Ohio at the
Technical Research Center (TRC). As in the glorious days of speed testing
at Brooklands,
Callaway continued the tradition of driving the car to and from the test
facility. Once they got
there, the car was equipped with specially made Goodyear racing tires on
its Dymag rims. The
"sneakers" on the car made drag specialist and Sledgehammer record driver
John Lingenfelter a
little safer at speed. The record was set in October 1989, 254.76 mph
which figures to exactly
410 km/h. Now we can report that it would be possible to confirm these
achieved numbers in the
Vaterland itself.
Arrangements could be made through Callaway importer Ernst Woehr from
Leingarten, making
some German man some $400,000 poorer, and bringing this, the fastest
street sports car in the
world, to Germany.
Callaway Official Site
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