The Mazda FE DOHC (informally FE3) engine.
This is a high-spec FE5A tuned engine, 10:1 C/R. Stock power for this engine is 148bhp, but this one used to make 238 at 1 bar (15 PSI) with a piggyback controller. After the piggyback was damaged, the setup was swapped for an aftermarket ECU.
The old exhaust manifold was built to BPT specs, and didn't really fit the FE-DOHC head. A new exhaust manifold was constructed out of 38mm ID pipe bends, the result was a manifold that matched the earlier unit in critical dimensions, making the use of original downpipe possible, but had a proper clearance for easy access to mounting studs. Also the flow was considerably improved. Going from 15 PSI to 10 only decreased engine power from 238 to 228hp.
The exhaust system is 2.5" with a single free flow muffler. It was made from scratch.
The latest significant mod is switching from distributor ignition to direct ignition. Originally the system was meant to drive a coilpack of two double-ended coils, however it seems to run four coils connected in pairs fine. This arrangement enables zero-lag "misfire" system, which I doubt ever to use. It gives stronger spark than distributor system, which is better for cold (winter) starts and heavy acceleration, but eats plugs more rapidly too.
The NEW engine
I'm building a new engine to replace the well-served old one. The new engine will have the crank pulled from a 2.2l R2 diesel engine, for the benefit of forged construction and cross drilled oil galleries, which both are absent from the F2 (gasoline 2.2) crank.
The flywheel flange is 8-bolt instead of six, so either a stock diesel crank (heavy) or a custom order flywheel is needed.
The oil pump gear needs to be changed from R2 to DOHC model. It is either press or thermo fitted.