We here at Motor Trend feel strongly about a vehicle’s fun-to-drive quotient; so much so that we have a fun-to-drive category in our Car of the Year scoring procedure. This Turbo firebird most certainly qualifies as fun to drive, but in an entirely different sense from, say, a CRX or MR2. Those cars are light, responsive, and willing. By contrast, the main ingredient of the Pontiac’s appeal is, pure and simple, power. Power that’s available at any engine speed, any gear. Just get your foot in it – and enjoy. We even found ourselves enjoying the freeway drone for a change, because of this Firebird’s ability to make chopped liver of anyone competing for those infrequent holes in traffic.
Where, you may inquire, does all this power come from? Well, indirectly, from Buick. Remember the Grand National Regal, followed by the GNX? The engine that was used to make the GNX such a killer at the dragstrip simply lost its lease on life when Buick division ran out of rear-drive platforms. Front drive just can’t cope with that kind of power, so the boys from Buick reluctantly had to put the engine on the shelf. Of course, there are many sharks cruising the murky corporate waters, and those of the We-Build-Excitement division saw a golden opportunity to put it to the Chevy Camaro guys. They wanted, and got the engine for their rear-drive Firebird. We have no information on what the Camaro guys said – we probably couldn’t print it, anyway.
In any case and for whatever corporate reason, the Buick turbo V-6 was assigned to Pontiac and was forthwith slipped into the 20th Anniversary Pontiac Trans Am, ever after to be known as the 20th Turbo. This did not happen, however, without a lot of engineering and testing. The Pontiac people decided they wanted the car to be covered by the full factory warranty (5/50), not the restricted one that applied when it was at Buick (12/12). This meant extensive testing, and testing, and more testing. All involved (Hydramatic division, B-O-C engine, etc.) wanted their particular test run, so the car underwent 50,000-mile durability, 20,000-mile accelerated powertrain durability, high-speed endurance, hot-fuel handling, water intrusion, skidpad tests, ad nauseum. In addition, the Pontiac engineers concentrated on the top 10 warranty claims from the Grand National program to further increase reliability of installation.
The most important criteria for extended durability turned out to be control of the exhaust gas temperatures. The maximum allowable temperature to achieve the desired durability was 1550 degrees F. Below that temperature…excellent durability, above it… not so good. Control of the EGT was a question of adequate fuel flow capabilities at full power, which meant oversize injectors and higher fuel pressure (large fuel pump. In addition, a little peak power was sacrificed to increase durability by choosing the smaller A/R ratio turbo from the GN engine and the larger intercooler from the GNX.
The basic engine is a 3.8 liter cast iron V-6 with pushrod-operated valves and roller cam followers. The cylinder heads come from the 3-liter V-6, chosen to give shorter exhaust ports (higher exhaust energy at the turbine inlet) and a more compact engine dimension. A Garrett AiResearch T2.5 turbo is the turbo of choice, with the wastegate under the control of the ECM. The “hot side” (turbine inlet) of the T2.5 is plumbed to the exhaust side of the engine with stainless steel exhaust tubing, required to cope with the extreme heat of the exhaust gases. The “cold side” (compressor discharge) of the turbo pumps through a fairly large air-to-air intercooler on its way to the combustion chamber via the aluminum intake plenum and runners. The intercooler removes some of the heat of compression to increase the charge density, and on arrival in the combustion chamber, the properly compressed, injected, swirled fuel/air mixture is ignited by Direct Fire injection. Ignition timing and sequential fuel injection are controlled by the ECM, which gets its information from both crankshaft and camshaft position sensors.
It should come as no surprise that horsepower equals heat. Pontiac engineers gave special attention to airflow into the radiator and used a new radiator with three plates assigned to keeping the automatic transmission cool. In the area of increased reliability, the turbocharger center bearing is liquid cooled, and an oil cooler/warmer has been included, which is larger than the cooler fitted on the GN engine. A special adapter allows the Modine cooler from the Corvette L98 V-8.
With all this going for it, we don’t have to tell you that this is a strong mutha engine. It produced more than one horsepower per cubic inch, but manages to remain tractable and docile – until called on to be otherwise. This power level is the equivalent of the 7.5-liter monsters of only 15 years ago, and points out the advantages of turbocharging, electronic ignition, and fuel control. Turbocharging, combined with up-to-date electronic controls, is a power-on-demand system, with small penalties incurred during partial throttle conditions. Turbo technology has given designers that latitude to use small-displacement engines, with their inherent fuel efficiencies, and yet extract large amounts of power – on demand – with high boost pressure. It also allows the power curve to be tailored to the designer’s wishes. This engine develops maximum power from 4000 to 4500 rpm.
The EPA rating had not yet been determined, but during its stay in our office, the average fuel consumption was over 18 mpg, and the car was driven at WOT (wide-open throttle) a lot more than at any other setting. This is quite a testimony to the benefits of smaller-displacement, low-friction engine philosophy. Driven sanely, we’re sure this 20th Anniversary T/A will return over 20 mpg.
With all this power on tap, the engineers chose the THM 200R-4 4-speed automatic transmission, calibrated to shift exactly at the engine power peak – 4500 rpm. It deals with the engine’s power with impunity, producing smooth, full-power upshifts all of the time and smooth kickdowns most of the time. There is one combination of partial throttle, 3-rd gear kickdown that tricks the system and causes momentary lack of concentration in the shift control. The result is a quick downshift/upshift – and then back down into the correct gear. Otherwise, we thought the engine/transmission combination meshed well, although a 5-speed manual (unavailable for a variety of reasons) would be tempting.
The chassis specified for the turbo V-6 powertrain is basically the Firebird GTA Level III, or WS-6, recalibrated for this application. The only changes required were a decrease in front spring rates to accommodate the lighter (by 127 lb.) V-6 and a new “deflected disc” shock that better handles small road irregularities like freeway bump strips. It does this by bypassing some of the shock’s internal valving under conditions of low shaft speed and light impact forces. Tires and wheels are unchanged from the GTA, 245/50ZR16 Goodyear Eagle Gatorbacks.
During the instrumented testing for this story, we were treated to the Turbo T/A in its element – the dragstrip. Maximum acceleration starts (drag racers call them “leaves”) are a walk in the park. Left foot hard on the brake, bring the power up slowly, car starts to creep sideways as engine torque overcomes rear-wheel brake torque, 3000 rpm, full throttle and release the brakes – you’re gone like a catapult shot. After initial wheelspin, the Firebird tracks straight, working its way up through the gears, ECM sniffing for ping, juggling boost and spark advance to hold the engine right on the ragged edge of detonation, boost gauge quivering at 15 psi, upshifts smacking you hard in the back. All too soon, the traps flash by and it’s over – 60mph in under 6 seconds, quarter-mile right at 14. As we mentioned earlier, a drive in this killer Pontiac is the most fun you can have with your clothes on.
The only real problem in producing good runs is to balance wheelspin at the start. Too much boost at brake release will simply send the tires up in a huge cloud of smoke; not enough, and the engine falls off the boost a little too much, affecting elapsed time.
Steady-state cornering (skidpad) performance was good, reflecting the firm suspension and 245/50 Goodyears. Maintaining a constant speed produces mild understeer up to the limit, definite understeer at the limit, and power oversteer if desired. In other words, the driver is able to control the attitude of the car with power. Altogether, an enjoyable concept.
The brakes on the 20th Anniversary Trans Am are an outgrowth of Pontiac’s Showroom Stock racing programs and are almost totally fade-proof in any normal driving. They use the same Repco calipers as fitted to the Corvette and a 12-inch vented front rotor with an 11.7-inch rotor at the rear. The car we tested had some mismatched brake pads and rotors in the rear, and the performance wasn’t up to snuff. Even so, the mismatched components only caused a little instability.
Driving the T/A over mountain roads is a real experience. The marvelous flexibility of the engine allows the luxury of loafing through the corners and just making the straightaways disappear. The engine rushes the car up to speed fast, and after a while, it’s easy to underestimate velocity because the competent sort of whoosh sound that makes it all happen is a little deceiving.
The Turbo Pontiac looks identical to the GTA with the exception of the front fascia emblem with 20th Anniversary logo, assorted “Turbo” emblems, and the available “Official Indianapolis Pace Car” decal, giving the owner the option of installing it or not. Pontiac engineers used simple analog instrumentation for the 20th Turbo, and the boost gauge lives integrally in the tach face. The seats are performance-oriented but could use a little more later al support and more fore-and-aft adjustment. They have four power and two manual adjustments, plus some adjustability for the headrest. The vehicle also has GM’s PASS-Key anti-theft system. Darn rear everything is standard, except for the hatch roof and Ventura leather seats.
If you haven’t guessed already, we like this sucker. It’s forceful, focused, and - we have to admit – imperfect, but it brings a real excitement to driving, an excitement that all too often missing lately in the corporate-think, insurance-wary world we live in. Make no mistake, this is a modern, sophisticated vehicle – usually that means boring – that’ll smack ya back in the seat like a 60s musclecar and gets 20 mpg. Like having your cake and eating it too."
GENERAL
Vehicle Mfr:.......... Pontiac Motor Division, General Motors Corp., Pontiac. Mich.
Body type:.......... 4-passenger, 2-door
Drive system:.......... Front engine, rear drive
Base Price:.......... $20,399
Price as tested:.......... $25,000 (est.)
ENGINE
Type:.......... Transverse V-6, cast iron block and heads, liquid-cooled
Displacement:.......... 3800 cc (230 cu in.)
Compression ratio:.......... 8.1:1
Induction system:.......... Sequential fuel injection, turbocharged, intercooled
Valvetrain:.......... OHV, 2 Valves/cylinder
Max. power (SAE net):.......... 250 hp @ 4300 rpm
Max. torque (SAE net):.......... 340 lb-ft @ 2800 rpm
Emissions control:.......... Catalytic converter, EGR, air pump
Recommended fuel:.......... Unleaded premium
DRIVETRAIN
Transmission:.......... 4-sp. auto.. O/D
Transmission ratios:.......... (1st) 2.74:1
(2nd) 1.57:1
(3rd) 1.00:1
(4th) 0.67:1
Axle ratio:.......... 3.27:1
Final drive ratio:.......... 2.19:1
CAPACITIES
Crankcase:.......... 4.7 L (5 qt)
Fuel tank:.......... 68.1 L (18.0 gal)
Luggage:.......... 878 L (31.0 cu ft)
Range (at EPA combined):.......... 590 km (360 ml)
SUSPENSION
Front:.......... independent, upper and lower control arms MacPherson struts, coil springs, hydraulic shocks, anti-roll bar
Rear:.......... Solid axle, torque arms, track bars, coil springs, anti-roll barhydraulic shocks, anti-roll bar
STEERING
Type:.......... Recirculating ball, power assist
Ratio:.......... 12.7:1
Turns (lock to lock):.......... 2.3
Turning circle:.......... 9.9 m (32.6 ft)
BRAKES
Front:.......... 305 mm (12.0 in.), vented discs, power assist
Rear:.......... 297 mm (11.7 in.), vented discs, power assist
Anti-lock:.......... Not available
WHEELS AND TIRES
Wheel Size:.......... 16 x 8.0 in.
Wheel type:.......... Cast alloy
Tire size & Construction:.......... P245/50zR16 steel-belted radial
Tire mfr. & model:.......... Goodyear Eagle ZR50 Gatorbacks
DIMENSIONS
Published curb weight:.......... 1575 kg (3464 lb)
Weight distribution, f/r:.......... 54/46%
Wheelbase:.......... 2566 mm (101 in.)
Overall length:.......... 4862 mm (191.6 in.)
Overall width:.......... 1838 mm (72.4.in.)
Overall height:.......... 1270 mm (50 in.)
Track, f/r:.......... 1541/1564mm (60.7/81.6 in.)
SPECIFICATIONS
Power-to-weight ratio:.......... 13.9 lb/hp
Drag coefficient:.......... 0.31
EPA (combined):.......... 20 mpg
MEASURED PERFORMANCE
QUARTER MILE
Time:.......... 14.18 sec
Speed:.......... 95.8 mph
BRAKING
60-0:.......... 142 ft
30-0:.......... 41 ft
SKIDPAD:.......... 0.84 g
SPEEDOMETER CALIBRATION
Indicated.......... 30..... 40..... 50..... 60
Actual.......... 31..... 39..... 49..... 59
