![]() The system relies on an accelerometer-type transducer bolted to the intake manifold to listen for vibrations characteristic of unscheduled combustion. This is why Pontiac has adopted a very sophisticated spark retarder, pioneered by Buick in its 1978 turbo Regal. A side effect of using a later spark to limit detonation is the fact that it also sacrifices power. It can be combatted by at least three means: by adding water injection, which Pontiac has avoided for a number of good reasons by enriching the fuel-air mixture, which is unfortunately contrary to efficiency goals and therefore used sparingly and by retarding ignition timing. ![]() Nine psi worth of overpressure is a rather ambitious undertaking for an engine certified to run on 91-octane fuel, and realizing this, Pontiac has taken several precautions to avoid the mechanical destruction all too common when a turbocharger blows an engine the wrong way. It heats the charge to maintain cold drivability, but once the cooling system reaches 217 degrees Fahrenheit, the thermostat shuts off flow to keep fuel-air mixtures as cool as possible. Instead, there's a water jacket surrounding the plenum chamber. Heat is also detrimental to a high-mass flow, so the normally aspirated 301 engine's exhaust crossover has been omitted from the turbo engine's intake manifold. ![]() All passages are as smooth in shape and as generous in area as possible to minimize power-limiting restrictions. Air is picked up by a four-inch-diameter duct just above the front air dam, flows unimpeded to the carburetor, where fuel is added, and then turns through 90 degrees in the plenum to enter the turbo compressor in a horizontal stream. 1979 Pontiac Firebird Trans Am Road TestĪ Rochester Quadrajet carburetor feeds the turbo's hungry mouth through a carefully designed cast-aluminum plenum chamber.From the Archive: Paris By Pontiac Trans Am.Though others have bolted the hardware together in almost exactly the same fashion as Pontiac did here (Buick's turbo V-6 comes closest), the Trans Am's new turbo V-8 does distinguish itself as the biggest of its kind ever to see large-scale production. ![]() The biggest engine this division builds, a 302-cubic-inch V-8 (labeled a 301 by marketeers), was originally conceived in 1977 as a smooth-running, fuel-efficient station-wagon mover, but with lots of redevelopment it's risen to the task at hand with turbocharging. Faced with two "easy" alternatives to kick off the Eighties-building stone-slow Firebirds or borrowing engines from another GM division-Pontiac avoided both, and instead allotted more than a few engineering dollars to discover some fresh horsepower. The turbo Bird must carry around its old, heavy body for two more model years in spite of the fact that all the medium-to-big engines fit for this sort of duty are out of production. We should all tip our hats to the engineer and bean counter who've joined forces to keep the Firebird flying high, even if it did take a little heat under its tail to maintain altitude. The decal fowl is now on a new flight plan- out of a rather primitive past to a future where speed and efficiency are precisely matched in importance. It's a turbocharger, installed by Pontiac to ruffle the Firebird's pinfeather and boost its potency to 205 horsepower for 1980. It's not gas distress that makes Pontiac's bird of performance burp fire all over the Trans Am's hood. From the October 1979 issue of Car and Driver.
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