1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Heres A Summary of whats in my ride.

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Old May 14, 2006 | 08:38 AM
  #1  
willie j spec's Avatar
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From: ground zero manhatten
Heres A Summary of whats in my ride.

Turbocharged and Fuel Injected 12A 1983

The Turbo was Japanese model only. The 12AT powered the Cosmo & Luce before it powered the RX-7. The 12AT was the first Turbocharged and Fuel Injected Rotary engine ever. The Turbo was revised to have four side intake ports. Each bank has one injector located in the intake port in near the port opening in the trochoid chamber. Because of this location ( which is a cross between manifold and direct-injection ) Mazda engineers call the fuel system Semi-Direct Injection. The injector is actuated by a electric current and satisfied the rotaries widely varying fuel demands, from 600rpm idling and 7000rpm full operation. Air and fuel mixing is prompted at lower speeds by an air bleed to the injector nozzle receptacle, at higher rpm by a mixing plate socket, an open sided plastic tube with twin perforated plates. The plates splash and squeeze injected fuel, aiding mixture atomization.

The fuel-injection control unit is an analog type made Nipon Denso; it works in conjunction with the Mitsubishi Electric digital emission-control computer. Fuel is injected once per intake stroke. simutaniosly in both chambers. As there is a 180° difference in the rotors' working phase. One chamber is injected at the beginning of the intake travel where the one in the other chamber gets fuel when it is almost 2/3 through the travel.



As the rotary has an internal "internal" intake ports ( each chamber takes in fuel and air one one side of the trochoid-housing and travels to the other side, where combustion occurs ) chamber filling and mixture strength become uniform between the two banks despite the staggered injection timing. Primary intake port timing is unchanged from the carburated 6PI engine: opening at 58° ATDC and closes at 40° ABDC. Opening of the secondary port is advanced to 32° ATDC. Closing remains at 40° ABDC. The single peripheral exhaust port opens at 75° BBDC and closes at 48° ATDC. Of interest the air-only secondary intake port and manifold are dual throttle valves. A second butterfly valve is located upstream of manifold, it opens slightly later then the lower one. The dual-valve arraignment prevents sudden air-pressure shocks and together with the semi-direct injection system, allows a smaller plenum chamber.



http://home.online.no/~arban/RX7.html
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Old May 14, 2006 | 09:43 AM
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ChunkyMonkey's Avatar
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Are you just giving us a history of the Japan 12a Turbo 7? Or, are there mods on top of your 7?....I can't wait to turbo my 1st gen.....
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Old May 14, 2006 | 10:18 AM
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willie j spec's Avatar
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From: ground zero manhatten
yeah a little history i suppose. and some facts on my ride i guess.

i also just made the transplant, i wanted to keep it a 12a and just happenned accross this motor, best $900 i spent on my car.
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Old May 14, 2006 | 01:32 PM
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Uhmm.... wtf... so you posted someone elses Rx-7 model summary and copied the Turbo 12a section?

If you want to give "A Summary of what's in [your] ride.", you really might consider talking about your ride, 'cause I'm pretty sure most people on here know what a 12a turbo is, where it's found, and definately know how it works...
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Old May 14, 2006 | 03:13 PM
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From: St Joe MO
Either way, that is the first details I have seen on the 12AT, interesting read.
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