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Honda K20C1 FK8 Auto-Engine Conversion

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Jul 9, 2022
I've been working on a Honda engine conversion for about a year. I chose the K20C1 FK8 engine, which was made available by Honda a couple years ago for off-road and racing use. It's an amazingly well engineered engine, currently used in Formula 3 racing and similar to what is sold commercially in the Honda Civic R-Type sedans. The baseline engine is rated at 306 HP at 6500 RPM with 195 ft-lbs of torque through most of that RPM range. Some key features include direct fuel injection, turbocharger, integrated (into the block) exhaust manifold, and variable valve timing (on the exhaust side only). Dry weight of the engine, including starter, alternator, turbocharger, fuel injection, and water pump is approximately 320 lbs. I had planned to de-rate the engine to 4500 RPM and 230 HP to enhance durability and avoid exceeding the maximum HP rating for the aircraft I'm building. The PSRU design is being handled by EPI Inc (EPI, Inc. Home Page), a company and designer who thoroughly understands the concept of torsional resonance and has extensive experience with PSRU design. The engine sold new with wiring harness and ECU for $9000 plus shipping. I couldn't be happier with the package I received and everything I've learned about the engine since purchasing one last January.

On the negative side, Honda provides absolutely no support for projects of this nature and I've really struggled to obtain the geometric dimensioning of key features such as the bell housing hole pattern and exact locations of engine mounts needed for PSRU design and installation in the aircraft. (I've been slowly building a 3D model in SolidWorks, similar to one I built for Honda's L15B7 engine -- Free CAD Designs, Files & 3D Models | The GrabCAD Community Library). After multiple trips to a CMM contractor and some help from others, that dimensioning is mostly complete.

Despite strong emotional ties to the idea of converting this engine to airplane use, I recently abandoned the project in favor of a Lycoming IO-360 engine installation. Friends convinced me that at my age (72), there was a good chance I'd never work through all the one-off issues a complex project like this involves. To name a few, layout and acquisition of radiator, intercooler, and oil cooler; new or modified intake manifold to allow space for the PSRU; sourcing parts, building and testing the PSRU once EPI Inc. finished the design; custom cowling; custom radiator cooling plenum; integration of the ECU into the overall aircraft electronics; aviation-grade wiring harness; etc. etc. There were also some concerns about overall weight and W&B issues for the particular airframe being built in parallel. That said, I still believe this engine has incredible potential and I have very high confidence in the suitability of the evolving EPI Inc. PSRU design. So, if anyone out there has an interest in pursuing the idea further, I'm happy to share what I've learned at no cost (and no warranty) -- engine modeling, sources for parts, planned PSRU design (detailed SolidWorks assembly drawing by EPI Inc.), etc. The engine, itself, is currently listed on eBay, along with a number of accessory parts. Anyone interested, please DM me and I'm happy to talk.


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