Building a 6 stroke engine

[rep_movsd]

I'm going to work on an experimental prototype engine, that will be a six-stroker -
i.e. An extra stroke after the power stroke that inducts only air (later I will be injecting water) to absorb residual heat energy and convert it to some mechanical work.

Thus I need an EFI that is capable of delivering 0 fuel on certain strokes. How hard is it to customize the FreeEMS firmware to do this? I have extensive low-level software development experience for the PC (C / Assembler / Device drivers) and some micro-controller experience.

At first glance I would assume the software changes should be quite simple, but I just need to know. This is the first time I am working with an EFI system.

Thanks in advance
Vivek

[pishta]

how big will the valves be to evacuate the water that is not compressable? Must be pretty big? I dont get it. Any updates? Is the air stroke always the 6th? That would be easy to decipher with a cam sensor or combo crank/cam sensor combo.

[Fred]

Thanks for bump, pishta.

To do this in a non-hacky way would be quite a challenge. To do this in a hacky way wouldn't be difficult, maybe.

The variables that deal with crank angles hold up to 720 degrees. They hold a bit more, but not 1.5x more and would overflow past that. So you need to upgrade the variable to 32 bits, which would be a pain, or change the scale of the variable, which would also be a pain. If you ever get the engine built and FreeEMS attached, post again and we'll figure something out for you.

Fred.

[rep_movsd]

I still need to get a donor motorbike for this.

Water injection I am not very keen on, since there are issues with creating corrosion and thermal stress.

All I would actually need is to count crank revolutions and turn off the injector on every other intake stroke, so technically not a 6 stroker, more like an 8 stroker.

Codewise I think I could manage, even if it involved lots of rewriting, what I have no clue about is how to interface with the fuel injectors and other sensors etc.

I think I will start by replacing the proprietary ECU of the bike with a FreeEMS and then once it runs reliably for a couple of Kilomiles, then start editing the code.

[Fred]

Sounds like a four stroke to me!

[rep_movsd]

Rather a hack on the fuel injection, for experimental purposes

[HD13]

Try using a fourstroke lawnmower engine, cheaper and simple.
I think that wil be first one for FreeEems.
When that works try a motorcycle or small car engine.

[Fred]

Motorcycles are easy or hard depending on how they're setup. Same goes for any engine type. Small stuff is challenging in some ways. The easiest engines to run are 4 cylinder or 6 cylinder japanese stuff like toyota, mazda, mitsubishi.

[rep_movsd]

I will be doing it on one of the new Royal Enfield Classic EFI - Even these new ones are simple enough for a Neanderthal to work with. The factory ECU is good, but can't be reprogrammed or hacked cheaply. At most the maps can be changed.

Meanwhile I also want to retro fit EFI to my old school iron barrel Enfield.

[sim]

how big will the valves be to evacuate the water that is not compressable? Must be pretty big? I dont get it. Any updates? Is the air stroke always the 6th? That would be easy to decipher with a cam sensor or combo crank/cam sensor combo.

I think the water being injected is in the form of tiny droplets. The idea is the droplets flash to steam and help to push the piston down on the sixth stroke.

This works on a four-stroke also, though the main reason to inject water in that case is to cool the intake charge.