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240 Landmarks TopGasoline and Natural Gas Engine > 12T (TGP) (lean burn engine)
 12T (TGP) (lean burn engine)
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Homogeneous lean burn technology was drawing attention in terms of coping with exhaust emissions and improving fuel efficiency. However, practical use was hampered by unstable combustion resulting from poor ignition performance of the fuel-air mixture. The key solution to this problem was a subsidiary chamber, called the turbulence generating pot TGP.
This 12T engine had a regular chamber and a TGP subsidiary chamber without an intake valve. By improving the fuel and ignition systems, the ignition performance of the homogeneous fuel-air mixture was improved, combustion was stabilized, and the mixture's lean limit was expanded.
On the nozzle hole that connects the main chamber and TGP, a two-ground spark plug was provided for igniting the fresh mixture flow generated during the compression process. In the TGP where a very strong flow is present, the fuel-air mixture burned quickly, and a strong flame was blown into the main chamber. This enabled quick and stable combustion of the homogeneous and lean fuel-air mixture. This system allowed the vehicle to be driven in the lean area at an air-fuel ratio between 16 and 18, allowing conformance with the 1976 emission gas regulations without a catalyst.
Fuel atomization and a homogeneous fuel-air mixture were achieved by a carburetor with a sintered alloy air bleed.
CO and HC not burnt in the combustion chamber were reacted in the exhaust system by detecting the warming up and driving states, and appropriately delaying the ignition timing. This lowered the maximum combustion temperature and reduced NOx.
If the negative pressure in the intake manifold increased sharply, liquid fuel adhered to the inner wall of the intake manifold would immediately evaporate, creating a rich fuel-air mixture. In response, air was introduced temporarily into the intake manifold (mixture control system).
The 1.6-liter Toyota lean burn 12T engine conformed to the 1976 emission gas regulations, and a liftback Toyota Corolla and Sprinter equipped with this engine were released in Jan. 1976.
The emission gas regulations of 1978 led to the development of the 12T-U engine which added an oxidation catalyst, EGR, and secondary air induction system (AS) to the 12T engine.
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Storage location:TOYOTA MOTOR CORPORATION, TOYOTA HERITAGE DIV., TOYOTA AUTOMOBILE MUSEUM (41-100, Yokomichi, Nagakute, Nagakute-cho, Aichi-gun, Aichi-ken 480-1131)
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Year manufactured:1976
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Manufacturer:Toyota Motor Corporation
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Classification:Mass-production product
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Current status:In storage: not open to the public
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Model / Manufacture
Model:12T
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Type:Gasoline
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Company name:Toyota Motor Corporation
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Usage:Conformed to emission gas regulations of 1976
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Installation model:Toyota Carina, Corolla
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Year of manufacture:1976~1978
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Specification
Cylinder arrangement, number of cylinders:Inline 4-cylinder
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Cycle / cooling method:4/water-cooled
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Valve type / number:OHV/
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Combustion chamber:Hemispherical
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Total displacement:1588 cc
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Bore x stroke:85.0×70.0 mm
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Compression ratio:8.5
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Mass (weight):141 kg
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Performance
Max. output:85 ps/5400 rpm
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Max. torque:12.5 kgm/3400 rpm
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Rate of fuel consumption:17.5 km/L
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Device
Intake system:Cross flow type
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Exhaust system:Cross flow type
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Points of interest, topicality:This engine used a unique and unprecedented lean burn method to dramatically improve ignition performance by admitting a homogeneous lean fuel-air mixture. It had an optimal layout, including subsidiary chambers, nozzle holes, and plugs.
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Features:It conformed to the emission gas regulations of 1976 without a catalyst by adopting a lean burn method that used a homogeneous lean fuel-air mixture.
A subsidiary chamber called the TGP was provided. A spark plug was set in the nozzle hole that connects the main chamber and the TGP for igniting the fresh mixture flow generated during a compression process.
Because a very strong flow was present in the TGP, the mixture in the TGP burnt quickly and a strong jet flame could be blown into the main chamber. This enabled quick and stable combustion of the homogeneous and lean mixture.
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Reference materials:Tadahide Toda, Hidetaka Nohira, Toshiaki Konomi, Shinobu Ishiyama, "Toyota Kihaku Nensho Enjin (12T) No Nensho Kaiseki", Toyota Gijutsu Vol. 26, No. 2, Oct. 1976
Shogo Sanda, Masami Konishi, Tokuhiko Nakamura, Eishi Ono, Toyokazu Baika, "Toyota Kihaku Nensho Enjin No Nensho Tokusei", Toyota Gijutsu Vol. 26, No. 3, Dec. 1976
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