1981 (FB)

By Manntis April 23, 2003

Known as an ‘FB’ type due to its VIN, the 1981 model (P815) appeared in August 1980. The rear and tail lights were redesigned eliminating the “Baroque depression”. The new urethane bumper covers not only updated the look of the car, they dropped the drag coefficient by .02 for a .34 Cd (equivalent to a 5 bhp gain!) and decreased front-end lift from 0.18 to 0.12.

The thermal reactor was gone. Instead, a “reactive exhaust manifold” attached directly to the engine served as a chamber to burn unburned hydro-carbons and carbon monoxide in the exhaust, with air pumped in through the exhaust port. Two catalytic converters were mounted in series behind the exhaust manifold, the second with two catalyst beds and air injection.

The new shutter valve cut fuel and air to the rear rotor, under deceleration (via engine vacuum), diverting the total air-fuel mix from the carburetor (still a 2-stage 4-barrel) to the front rotor. A “coasting valve” opened to allow fresh air into the rear chamber, preventing excessive vacuum. Spark plugs were replaced with four-electrode plugs with tile tips closer to the combustion chamber, and the trailing plug shutoff that had been used to keep HC high for complete bunting in the thermal reactor was eliminated as counterproductive with the catalysts.

The new lean burn system increased fuel economy by up to 20% (from 20mpg up to 24mpg combined city/highway), and catalytic converters allowed a leaner fuel/air mix. Power remained at 100HP, but a curb weight reduced by 85lb ( by elimination of the heavy thermal reactor ) improved acceleration, according to Mazda’s data, from 8.7sec to 8.6sec in a 0-60mph sprint. Ironically, the improved economy was accompanied by increasing the fuel tank from 14.5gal to 16gal.

Interior changes were led by the instrument panel. Gone was the clock, moved to the center console. The 3-function gauge to the left of the tachometer includes a separate voltmeter and an oil-pressure gauge. The fuel gauge was moved to the bottom of the tachometer, which no longer served as voltmeter. The color of lettering and dial needles were reversed on instruments as well, from orange needles with white numerals to vice versa.

The shift lever, shortened by 50mm, was moved 30mm closer to the driver and the boot was redesigned. The handbrake was redesigned as well, and the sun-visors provided with recesses in the headliner Shiny interior trim was eliminated.

The S model now had the 5-speed transmission as standard, along with the rear anti-roll bar (though reduced in diameter in response to previous complaints of tail happy handling). Also newly standard on the S were an electric remote fuel filler door release and intermittent wipers.

The GS got a new headlight reminder chime, ignition key light, map lamp, cargo area lamp, power mirrors on both sides, and a “dead pedal” for the driver.

The Leather Sport (LS) of 1980 (GX in Canada) was continued as the GSL, though with a host of new features. In addition to the new GS items, the GSL got rear disc brakes, a limited-slip differential, a rear window washer and wiper, cruise control, digital clock, audio upgrade, power windows, special seats, a removable sunroof, and raised white letter 185/70HR-13 tires on aluminum wheels. A 3-speed automatic was optionally available on the GS and GSL, and the sunroof and wheels standard on the GSL were options on the GS. Only the GSL, however, had the genuine leather upholstery as an option.

The Japanese variant RX-7 had rotor inspired aluminum wheels, and again Japanese and Australian RX-7 models were available as a 2+2 (in North America where rear-impact protection standards were higher the rear seats were deleted to make room for additional body bracing). North American markets received the lean-burning version of the 12A, whereas European and Japanese RX-7 owners have a slightly different engine.

• blended rear brake light strip
• Urethane bumper covers
• Shutter valve
• Coasting valve
• 20% better fuel economy
• Catalytic converters replaced thermal reactor
• New instrument panel
• Quartz clock in console
• Ignition key light, map lamp, cargo area lamp
• Power mirrors
• ‘dead pedal’
• Rear disc brakes (GSL)
• LSD (GSL)
• Rear wiper (GSL)

General Data
Models:	S GS GSL
Engine:	12A (1146 CC displacement) rotary 2 stage 4 barrel carburetor normally aspirated 100 bhp SAE net @ 6000 rpm 105 lb-ft torque @ 4000 rpm 9.4:1 compression ratio 21 mpg city/30 mpg highway
Transmission:	1st 3.674:1 2nd 2.217:1 3rd 1.432:1 4th 1.000:1 5th (GS) 0.825:1 Reverse 3.542:1 Final Drive 3.909:1
Brakes:	226mm (8.9 in) Vented Disc front 200 x 33mm (7.9 x 1.3 in) Drum rear Solid Disc rear (GSL only) Vacuum assist front-rear hydraulic split
Suspension:	Macpherson strut front w. 23 mm (0.91 in) anti-roll bar Watt linkage live axle rear w. 18 mm (0.71 in) anti-roll bar (GS only)
Steering:	Recirculating ball type 38mm (1.5 in) offset 33mm shaft diameter 15 degree distortion @ 7.2 lbs-ft torque variable overall ratio 17-20:1 3.7 turns (lock to lock) 31.5 ft turning circle
Wheelbase:	2420mm (95.3 in)
Wheels:	13″ alloy 110 mm bolt pattern
Track:	1420/1400 mm (55.9/55.1 in) front/rear
Body:	Unibody (monocoque) 6780 lb-ft torsional rigidity .34 Cd 4320mm (170.1 in)long 1670mm (65.7 in) wide
Vehicle Weight:	S (4 speed)   1065kg (2348 lbs) GS (5 speed) 1080kg (2381 lbs) GS (auto) 1097kg (2420 lbs) GS (auto) 1093 kg (2410 lbs) (Calif)
Acceleration	0-30 mph 2.8 sec 0-40 mph 4.3 sec 0-50 mph 6.3 sec 0-60 mph 8.7 sec 0-80 mph 16 sec

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Submitted on April 23, 2003 in Tech & Specs.

TAGS: FB, GS, GSL, LS, P815, RX-7, S, thermal reactor, VIN

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