4 Rotor Turbo. Has anyone done or have one?

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Dec 20, 2009 | 11:16 AM

Arthur242630

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From: Redcar

4 Rotor Turbo. Has anyone done or have one?

Hi Everyone first post. I know it's prob been asked before but Has anyone done or have a 4 Rotor Turbo engine? I heard I'm prob wrong here so be gentle. I heard you need two centre sections off the 3 Rotor Cosmos engine and 1 FD3 engine and some customers engine bolts to cater for the extra length along with custom engine mounts. Could it really be that easy?

Dec 21, 2009 | 09:23 AM

Aaron Cake

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It's actually not that simple at all.

The major hurdle is the eccentric shaft. A 4 rotor engine must use a three piece shaft, otherwise the engine is impossible to assemble. As such a part is not produced outside of Mazda (good luck getting one from them) it must be machined separately. Any competent machine shop can of course do this, at a cost.

Center irons must be modified with support bearings for this shaft. 20B thick irons are a bit thick and would make for a LONG engine and shaft, limiting fitment as well as high RPM operation. The ports are also funky (find an image of a 20B center housing to see what I mean).

Regarding ports, 4 rotor engines made of stock Mazda parts must be peripheral ported to keep port sizes the same. Because if you just stack middle irons together, the inner two rotors have less port area as they are only fed by ports designed to be primary ports. This necessitates a custom intake setup as well, not that a side port 4 rotor could use a stock intake or anything...

Cooling and lubrication is not insignificant. The center irons must be modified so that oil can actually reach the bearings, and the easiest way to get enough oil flow and pressure is to go to a dry sump system. Otherwise you are asking an oil pump designed for a 2 rotor engine to supply more then twice the oil. Each housing must have it's own cooling pipes (externally) otherwise you have an engine that runs cool at the front, but insanely hot at the rear.

There are many, many, many issues that must be solved in building a 4 rotor. I'm not making this stuff up, as there is a 4 rotor shaft sitting on my work bench right now. All told, when this project actually gets completed (years...), I'll have about $50K into it. That is at the low side if a person is capable of doing most of the labour (the only thing I can't do is the machining of the eccentric). If you are farming out stuff and paying others for labour, figure between $75K - $100K all told.

Precision Engineering/Kiwi RE makes a kit with many of the hard parts needed to assemble a 4 rotor engine. They supply the eccentric, counterweight and modify the center irons. You are on your own for everything else. Last I checked, the price was $8K NZ from Kiwi and a little less from Precision.