Callaway Twin Turbo GTV6


 

 

Text from Car & Driver - October 1985

Callaway Twin Turbo GTV6 (Road Test)

 

The world of after-market specialty cars and automotive speed parts is slowly entering a new era. Caught between increasing pressures on the murky automotive gray market and the spread of state emissions inspections, many of the current paragons of automotive achievement will soon disappear. And we can't say that we'll be heartbroken to see some of them go. Not that we stand foursquare behind the EPA regulations, but we've tested all too many cars whose low-tech emissions devices have weakened their performance, compromised their reliability, and encouraged their owners to remove them and risk running afoul of the law. In this day of sophisticated engine-management systems and computer controls, compliance and performance need not be conflicting goals. Our point is well made by a special Alfa Romeo GTV6 modified by Callaway Turbosystems of Old Lyme, Connecticut.

'I'he Alfa's stock 154-bhp, 2.5-liter engine has been transformed into a hyperthyroid state by the addition of twin turbochargers and intercoolers. The resulting 230 bhp can hurl the Twin Turbo Alfa from 0 to 60 mph in a mere 5.9 seconds and slingshot it through the quarter-mile in 14.3 seconds at 98 mph. (In comparison, the standard GTV6 we tested last May reached 60 in 8.2 seconds, the quarter-mile mark in 16.1 seconds at 82 mph.) Top speed is limited to 140 mph by the 6300-rpm redline (a 10 mph improvement), though the engine will willingly pull well past that figure. That's enough performance to let the TwinTurbo Alfa keep pace with some of the quickest cars in the country. But the key difference between this car and most similarly modified machines is that the Alfa won't get its builder into trouble with the EPA.

 

The Callaway people have taken great pains to pacify the government by maintaining a clean exhaust while generating this elevated power. As hard as this is to achieve technically, it's even harder to achieve officially, because the emissions bureaucracy has no formal procedures for certifying aftermarket engine modifications. Callaway's engineers, however, went the extra mile to demonstrate to the EPA that their car was clean and their hearts were pure.

The first step was to design a turbo system that preserved the stock emissions controls yet still worked double time to pump out the ponies. Generating the power was the easy part. A maximum of 10.0 psi of boost is produced by two IHI RHB5 turbochargers, one mounted beside each of the V-6's cylinder heads. The two turbo’s inhale through the Alfa's stock Bosch L-jetronic fuel-injection system, and each blows its compressed output through a BMW 318i throttle body into an air-to-air intercooler. The two intercoolers are welded to a plenum chamber above the engine that feeds the stock intake runners. A Callaway Microfueler is connected to each throttle body to supply the additional fueldemanded by the engine's voracious appetite during high-boost conditions. A fabricated stainless-steel exhaust manifold feeds and supports each turbocharger.

Downstream of the turbos, the exhaust gases are directed to the original catalytic converter and exhaust system via heavily insulated plumbing. The insulation is very important because it retains the heat needed to warm the catalyst quickly to operating temperature (a critical requirement in the EPA's cold-start emissions test). This plumbing also houses the stock oxygen sensor, which keeps the air-fuel ratio in the optimal range for the catalyst. The only internal change is a reduction of the compression ratio from 9.0 to 7.6:1, which was accomplished by disassembling the engine and trimming the piston crowns on one of Callaway's numerically controlled milling machines. Since all of the stock fuel and ignition calibrations are unchanged and the emissions components operate normally, the turbocharged engine runs very much like the standard one until the boost comes in. Consequently, it has no problem passing the emissions tests. The difficulty was in proving it to the government.

 

 

To avoid any suspicion of tampering, Callaway contracted with an EPA-approved laboratory to perform the work. The lab started by installing the turbo conversion on a new GI'V6 and accumulating the 4000 miles required for normal EPA certification tests, following an approved driving schedule. The car was then run through an emissions test, and the results were compared with those of a standard GTV6. That meant dealing with emissions considerably lower than the nominal standards, because production cars are engineered with allowances both for the deterioration of their emissions controls over 50,000 miles and for car-to-car variability. The Callaway Turbo Alfa produced no more emissions than the stock car, and the entire process was carefully documented for submission to the EPA. Because there is no official procedure for aftermarket modifications, the EPA did not formally certify the car. However, the agency did agree that Callaway's approach provides a reasonable basis for assuming that the emissions controls of his Twin Turbo Alfas have not been tampered with. For prospective owners, what this means is that the EPA is not likely to come down on them, and that their Alfas should be able to pass state-run emissions tests with flying colors.

The one fly in the ointment is the California Air resources Board, which has its own procedures. Since California is such a large market, Callaway is now hard at work on satisfying the CARB's zealous air police. One reason for these extensive compliance measures is that Callaway intends to sell the cars through Alfa Romeo dealers. In fact, the program was initiated bv Alfa's American distributor in mid- 1983 to give the company's flagging U.S. sales a shot in the arm. The original intention was to sell the car as a regular Alfa model, but this plan was scuttled by the parent company in Italv, which was uncomfortable with the notion of a modified car being sold under its banner. Instead, Callawav Turbosvstems is buying the cars wholesale from Alfa, modifying them, and then marketing them through selected Alfa dealerships as Callawav Twin Turbos. Still, the Alfa connection bestows a certain legitimacy on the project,

At Alfas behest, two of' the modified engines were run through the factorv's standard 200-hour dynamometer durability test, and five prototypes have been flogged mercilessly to uncover any weaknesses. And just like any proper new car, each 'I'win Turbo comes with a warrantv supplied bv Callawav, it's good for twelve months or 12,000 miles. Furthermore, each dealer will be required to buy three cars at a time to prove that its interest in the Twin Turbo is serious. Such practicalities may reassure a potential buyer, but the sale will be clinched by the marvelous engine. The beauty of this turbo transformation is not only the enormous power it yields but also the ease with which that power is generated. Boost is available as low as 1500 rpm. Bv 2500, full pressure is buffing on the piston crowns, so constant shifting isn't needed to keep the engine on the boil.

This characteristic combines with the low standard gearing to give the Twin -Turbo the feel of a sprinter: it seems ever eager to run faster. Even in fifth, throttle response is virtually instantaneous; a driver could make a convincing case that a 5.0-titer V-8 is under the hood. Indeed, there are few visual clues to the contrary: the standard hood bulge has been replaced by a bold hood scoop to feed the intercoolers, subtle pinstripes adorn the car's flanks, and the rear side windows carry "Callaway 'I'win Turbo" logos. Inside, the only giveaway is a boost gauge under the dash. Our test car was also equipped with optional BBS three-piece modular wheels, 205/55VR-16 Goodyear Eagle VR tires, and a rear spoiler. Even though the changes are minimal, the G'I'V6 chassis has little trouble dealing with the newfound 76 bhp.

One reason is the traditional Alfa understeer, which helps keep the car from getting twitchy when the boost comes in. With 230, bhp on hand, though, tail-out drifts are inevitable if you keep your foot down. Fortunately, the big Goodyears break away and recover progressively; they improve cornering gnp as well, from the stocker's 0.75 g to 0.79 g. The steering effort, however, is a bit heavier, and the Twin Turbo doesn't track as truly over rough pavement as the stock car. Only at slow speeds does the chassis lose out to the boosted engine. A heavy foot in a tight turn will light up the inside rear wheel. A hard launch will produce so much wheel hop that you'll think the differential is being hammered through the floorpan.

The stocker also suffers from both problems, but they warrant extra care with the Twin Turbo. Under most conditions, though, the Twin Turbo G-fV6 is no more demanding than the standard car. Preserving the engine. calibrations has also preserved the Alfa's non temperamental nature, and the turbo car need not be driven in the fire-breathing mode at all times. That's important, because the Twin Turbo is meant to be a real car, not a hyper-expensive week-end toy. In fact, the basic car will sell for just under $24,000, and even a heavy option load will add only another three grand to the ticket. That's not cheap, but it's in the ballpark with the strong-selling Porsche 944 and Chevrolet Corvette.

The Callaway people hope that this Italian-American alternative to Porsche and Corvette will draw enough customers to meet their sales goal of between 100 and 200 cars a year. We do too, not only because we'd like to see a couple hundred more interesting cars in the world, but also because this car's success might encourage the legal approach to the high-performance business. And that would enhance the chances that cars like this will still be allowed into the market in the years to come.

 

 

 

Vehicle type: front-engine, rear-wheel-drive, 2 + 2-passenger 3-door coupe

Price as tested: $27,234

 

Options on test car: ............base Callaway Twin Turbo Alfa Romeo
GTV6. $23,994; BOS 3-piece wheels and Goodyear Eagle
VR tires, $2095; leather interior, $750; rear spoiler, $395.
 Standard accessories: power windows, A/C, tilt steering, rear defroster
 Sound system: none

 

ENGINE

Type .......................................... twin-turbgcharged and intercooled V-6, aluminum block and heads
Bore x stroke ..............................3.46 x 2.69 in, 88.0 x 68.3mm
Displacement ............................152 cu in, 2492cc
Compression ratio ....................7.6:1
Fuel system .............................. Bosch L-Jetronic fuel injection
Emissions controls ..................3-way catalytic converter, feedback fuel-air-ratio control
Turbochargers .........................2, IHI RHB5
Waste gates..............................integral
Maximum boost pressure ......10.0 psi
Valve gear ................................belt-driven single overhead cams
Power ........................................(SAE net) 230 bhp @ 5500 rpm
Torque.......................................(SAE net) 245 lb-ft @ 2500 rpm Redline 6300 rpm

 

DRIVETRAIN

Transmission 5-speed
Final-drive ratio 4.10:1
Gear.......... Ratio.......... Mph/1000 rpm .....Max. test speed
1 .........................3.50 ............5.0 ..........................31 mph (6300 rpm)
11 .......................1.96 ............8.9 ..........................56 mph (6300 rpm)
III .......................1.26 ............13.8 ........................87 mph (6300 rpm)
IV .......................0.95 ............18.3 ........................115 mph (6300 rpm)
v .........................0.78 ............22.3 ........................140 mph (6300 rpm)

 

DIMENSIONS AND CAPACITIES

Wheelbase ........................94.5 in
Track, F/R ..........................54.0/53.2 in
Length . . ........................... 171.2 in
Width ..................................65.5 in
Height .................................52.4 in
Frontal are...........................20.0 sq ft
Curb weight .......................2878 lb
Weight distribution, F/R..51.2/48.8%
Fuel capacity .....................17.0 gal

 

CHASSIS/BODY

Type unit construction
Body material welded steel Stampings

 

INTERIOR

SAE volume, front seat ............44 cu ft
rear seat:..................................... 31 cu ft
trunk space v................................7 cu ft
Front seats .................................bucket
Seat adjustments fore and aft, seatback angie
General comfort poor fair good excellent
Fore-and-aft support poor fair good excellent
Lateral support poor fair good excellent

 

SUSPENSION

F:... ind, unequal-length control arms, torsion bars, anti-roll bar
R: ..de Dion rigid axle integral with 2 diagonal trailing arms, transverse Watt linkage, coil springs, anti-roll bar

 

STEERING

Type ........................... ......................... rack and -pinion
Turns lock-to-lock ...............................3.7
Turning circle curb-to-curb ................32.8 ft

 

BRAKES

F:................................. 10.5 x 0.9-in vented disc
R.................................: 9.8 x 0.4-in disc
Power assist vacuum

 

WHEELS AND TIRES

Wheel size .....................7.0 x 16 in
Tires ...............................Goodyear Eagle VR55, 205/55VR-16

 

ACCELERATION ................................Seconds

Zero to 30 mph .....................................2.0
.............40 mph ..................................... 3.2
.............50 mph ..................................... 4.3
.............60 mph ..................................... 5.9
.............70 mph ..................................... 7.5
.............80 mph ..................................... 9.5
.............90 mph ..................................... 12.2
.............100 mph ................................... 14.9
Top-gear passing time, 30-50 mph .....................................8.0
.........................................50-70 mph .....................................6.1
Standing 1/4 mile .....................................14.3 sec @ 98 mph
Top speed ................................................140 mph

 

BRAKING

70-0 mph @ impending lockup ............179 ft
Modulation .............................................poor fair good excellent
Fade ......................................................... none moderate heavy
Front-rear balance ..................................poor fair good

 

HANDLING

Roadholding, 300-ft-dia skidpad ..........0.79 g
Understeer ...............................................minimal moderateate excessive

COAST-DOWN MEASUREMENTS
Road horsepower @ 30 mph .....................................5 hp
.....................................50 mph ....................................13 hp
.....................................70 mph .................................... 31 hp

 

FUEL ECONOMY

EPA city driving ..........................19 mpg
EPA highway driving ................. 25 mpg
CID observed ...............................21 mpg

 

INTERIOR SOUND LEVEL

Idle .................................................53 dBA
Full-throttle acceleration .............79 dBA
70-mph cruising ............................73 dBA
70-mph coasting ...........................72 dBA