Retrospective: 1989 Pontiac 20th Anniversary Turbo Trans Am

By James Mackintosh, 25 March 2009

If you talk to a Detroit-muscle-loving gearhead, you'd think the small-block Chevy V8 is the be-all-end-all of American Performance. So here's a question: what is the fastest-accelerating stock F-body (Camaro/Firebird derivative) ever made?  If I told you that it had a 231ci V6 and a four-speed auto, would you call me a liar?

Well, if you would, you'd be wrong.  How about a quick number crunch: 4.6 seconds.  That's how long a 1989 20th Anniversary Trans Am takes to get to 60 miles an hour.  That's faster than an original Z28, a Firebird 455 S/D, ANY SLP FireChicken (sorry!), any LS1 SS or WS6, ANY LT1 ever...  that's also faster than a 911 Carrera 4S before direct injection, too.  So, what in the world causes a V6 3rd Gen Firebird to dust off it's boots so quickly and lay down the smackdown?

Turbo Trans-Am

In a word: Turbo.  A quick history lesson first, though.  In response to the gas crunch of the early seventies, Buick released a new kind of motor on the US public in 1978: the 3.8L Turbo V6.  It used a simple blow-through carb setup mated to a 3-speed automatic.  For the time, it was hot stuff: 175bhp and 275lb-ft of torque with a catalyst running on high-test unleaded meant it was quicker than most every other American car of the time.

Of course, a carb and a turbocharger go together like peanut butter and sushi, and the cars were a mess to drive.  3 gears weren't enough to properly take advantage of the Turbo Buick's narrow blown powerband, and lag was atrocious.  It was more of a novelty than an answer...  Until 1984.

1982 saw the introduction of the infamous Regal Gran National, which has been described as "the Darth Vader of cars."  Named after the NASCAR Gran National series (oh boy!), the '82 GN was available with a limp-wristed 4.1L V6 or the carb'd turbo V6.  The Gran National returned in 1984 sporting sequential multi-port fuel injection with electronic controls, and power jumped to 200bhp and 300lb-ft.  An '84 Gran National, on the antiquated and overweight G-body Regal chassis, could accelerate to 60mph in about 6 seconds flat - which was absurd for '84.

Another TTA

Through the next 3 years of production, the Gran National did nothing but get faster.  An intercooler was added  in 1986, bumping power to 235bhp and then 245bhp in 1987.  A regular Gran National could now dispatch the 60mph dash in 5.4 seconds, which  made it faster than the equivalent Corvette of the time - that's a story for another time, though.  What we're arriving at is the apex of the Gran National line before the RWD G-bodies went out of production in 1987, the GNX.  The GNX was an ultra-limited-production (547 produced) high-po version of the GN, paying homage to the hotrod GSX packages from the 70's.  Mechanical changes were numerous: a new Garrett exhaust-driven hairdryer with a quick-spooling ceramic impeller, an uprated intercooler, a retuned EEPROM (computer), high-flow dual exhaust bumped power from 247 to a claimed 276 and torque up to a meaty 360lb-ft.

There were other changes to the GNX (ladder-bar rear suspension for hard launches, reprogrammed trans with a special torque converter and trans cooler, special wheels, etc.)  What this meant was that in 1987, the only faster-accelerating car you could buy in North America was a Ferrari F40.  The Countach couldn't keep up, ditto the 911 Turbo or the Testarossa.  The GNX was badass on a whole new level.

20th AE Trans Am advert

Now, in 1988, GM discontinued the rear-drive G-body to be replaced by the awful front-drive W body, and that spelled the end of the Buick Turbo V6 program.  GM engineers were convinced a FWD transaxle simply couldn't cope with all the torque the turbo V6 made (they were right; the 4L85E can't even put up with the 280lb-ft the later Supercharged 231ci V6's made...) and performance Buicks pretty much died out.  So what happened to that badass GNX motor?

Why, it got shipped over to the Pontiac division to create some Excitement!   In 1989, the Trans Am was picked to pace the Indianapolis 500, and Pontiac needed a suitable car.  Only 1,555 20th AE Trans Ams were made, all pearl white with a tan interior.  3rd Gen F-bodies could already be ordered with a 231ci V6, so the swap wasn't too difficult - they just stuck a mildly modified GNX motor into a lighter, nimbler F-body chassis.

The engine received a few upgrades over the GNX: a new intercooler, tubular exhaust manifolds for faster spooling, tuned aluminum intake manifold, and a few other minor details like Trans-Am specific heads adapted from the FWD 3800 to fit between the strut towers, which had better exhaust flow and combustion chamber design.

1989 Pontiac 20th Anniversary Trans Am Turbo engine

The Turbo V6 was rated at 250bhp@4400rpm and 340lb-ft of torque @ 2800rpm, but let's be honest: that was only to make sure the 5.7L L98-equipped Trans Am GTA not look so bad.  Real output was well over 300bhp and closer to 400lb-ft of torque, confirmed at 301rwhp on a GM dyno.  The secret to the TTA's (Turbo Trans Am's) success: a Garrett Turbo and a hefty torque converter.  Your grandmother could launch one like a pro: just brake-torque it to build boost and lock the torque converter, and then slip off the brake and make sure it's pointed straight.  With a  curb weight of 3346 lbs, the TTA had a power/weight ratio of 13.4 lbs/bhp, which is quite powerful even by today's standards.

httpv://www.youtube.com/watch?v=FdVHICHIk1Q

The official factory claim for the TTA was 5.4 seconds to sixty and a top speed of 161; Car & Driver got the aforementioned 4.6 second figure.  In 1989, it was flat-out the fastest accelerating production car you could buy in America, and the sleeper factor was EXTREMELY high.  It just looked like a white Trans Am - easy pickin's, right?

TTA at dragstrip

The engines were assembled by PAS, Inc (Production Automotive Services) and final assembly was done in the F-body plant in Van Nuys, CA.  The only major interior difference was a turbo boost gauge integrated into the tachometer, "20th Anniversary" and "Turbo" badging, and other small geegaws.

The TTA was only around for a year, but it made an impression.  Car & Driver was  the only newsrag to publish a 0-60 time below 5 seconds, but others hovered between 5.2-5.5 seconds, which is still fast.  Quarter mile times ranged from 13.4 (C&D) to 14.1 seconds, depending on the publication.  They said at the time "this is a car for muscle-car mavens, pure and simple." Road & Track said "This 20th Anniversary Rocket can't decide whether to pace Indy or enter."

And as soon as it was here, it was gone.  Only 1,555 of them were made during the 1989 model year, and all found loving homes with turbostruck owners.  Pontiac never again tried the high-tech turbo approach with the F-body, which is a shame.  Hopefully they'll give it another shot again- GM's high-feature 24v V6 is perfectly capable of being turbocharged, and GM is going to need a competitor if Ford comes out with an EcoBoost V6-powered Mustang, like they should.  I'm just sayin'...

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