Fitting a 20B engine to an FC3S RX7 (2nd Generation 1986-1991).
Transmission and engine mounts / Other engine mounting issues / Turbos, fuel system and exhaust / Engine management / Mazda's prototype 3 rotor RX7 / More information
This car is a 1987 FC3S RX7 TurboII (Second
Generation RX7), It's owner is Chito in Los Angeles, California, USA.
Transmission and engine mounts:
The original 13B TurboII transmission was used, with the
original transmission cross member bolted at all the same original places.
In order to fabricate engine mounts, the transmission was bolted to the engine and to the body, thereby leaving the engine unmounted
at the front.
Other engine mounting issues:
As the 20B is about 7 inches longer than the 13B TurboII
engine, the original radiator was replaced with an aluminium one
located further forward (and necessitates using some big electric fans).
Turbos, fuel system and exhaust:
Due to the complex layout of the 20B's original
sequential turbos, these were removed and replaced with a single large
550cc injectors have been used on the primaries and 1200cc injectors on the secondaries. Given that, the engine should be capable of 10 - 12 lbs boost with a little left over in injector capacity so it does not lean out.
The exhaust is custom made, with a 3.5 inch downpipe to a 3.5 inch Borla stainless steel resonator branching into two 3 inch pipes and two 3 inch exhaust, all made from stainless steel. Evidently it sounds great!
Two electromotive TEC1 engine management systems are used,
with two sets of three coils each, one spark plug per coil (the other
side of the coil is grounded).
Two crank angle sensors are used, which are 180 degrees apart, one for leading and the other side, trailing. These sensors were installed inside the original 20B crank angle sensor. (The 20B crank angle sensor is located at the same place where the 13B distributor is).
The TEC units manage the ignition timing as well as fuel injection, with the main computers mounted in the polished aluminium compartment and the coil packs mounted on the suspension tower (TEC II units combine the computer and coil pack into one unit).
Mazda's Prototype 3 rotor 2nd generation RX7:
Mazda's early multi rotor engines had problems due to
the design of the eccentric shaft. When this was overcome in the mid 1980s,
Mazda started to build them mainly for racing. However the engineers tried
several modified production cars with these engines.
The car pictured below was fitted with a naturally aspirated
3 rotor engine, which probably would have been a 13G 3 rotor engine (Note that
13G was never used in any production cars, however the related 20B was).
Thanks to Chito for the pictures and information about his conversion. His email address was email@example.com however I have since tried to contact him on several occasions without success.
Further reading and acknowledgements:
Other relevant reading at Craig's Rotary Page (Please go via the INDEX
Other relevant sites on the Internet (Please go via the LINKS
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