Water injection on N/A engines

[ehb]

Hey guys,

I've been lurking here for quite a long time now. Unfortunately the development here at this stage is out of my league, so I won't be of any help code- or electronics-wise. I am however very interested in converting my 1980 Mini Clubman Estate from HIF44 Carb to FreeEMS some time in the hopefully-not-too-far future You guys are doing a great job, especially now that a good pace has returned.. Thanks for not giving up!

Now aside my introduction, I wanted to bring up a subject that's not so commonly implemented, but which I'm very curious about:
Water injection on naturally aspirated engines

I've given this some thought and a few calculations on my own, to see how much power/fuel saving could actually be gained. Hope you don't mind numbers.
The ratio water expands when converted from liquid to steam is about 1:1800. So 1ml of H2O will turn into about 1.8ltrs of steam.
I concluded that roughly 1g of fuel could turn about 16g of water (80°C, pre-heating assumed) into 28.8ltrs of steam (140°C, higher boiling temperature due to high pressure in combustion chamber).

Now the calculations get hard on my head, since I'm not dealing with VE tables all day like you guys (yet).
If my understanding is right, a 500cc 1cyl engine gets about 400ml of air at 80% VE. At stoichometric this would mean 0.035g of fuel per charge. If 30% of the heat could be used, about 0.18ml of water could be turned into 315ml steam.

I don't know, sounds enough for me to be worth a try. I would think something like that could happen too, enhancing the gasoline flame front, cleaner combustion too.

Don't get me wrong, I'm not very eager to try this on my Mini, but for example power generator units could profit from this, if it works as intended.
Of course I have concerns about vapour blow-by at the pistons, or corrosion from superheated steam, fouled plugs, and a ton of other things. Still the idea is chewing up brain time, so I needed to get it out for public review

What I'd love to see to make this happen with FreeEMS is a second VE table for the water injector. This could be useful for other applications too, like switching between LPG and gas (or mixing both?). I haven't looked at the code, neither would I understand it. So I'm just humbly asking to maybe keep this feature in mind.

Thanks for reading, now input please. Anyone ever used water injection on N/A engines?

Greets from Germany, Stefan

[longracing]

It's worth checking out this site http://www.aquamist.co.uk/

Water injection is useful on a high-compression engine where high octane fuel is not readily available. The main advantage is the reduced detonation. There are bigger improvements on turbo/supercharged engines. Using higher pressures will atomise the water a lot better, being able to map the amount injected will improve the efficiency of the system. Some of the moisture can get into the oil but should evaporate when the engine is at operating temperature. Some of the engines that used older systems showed signs of ring errosion when pulled down for rebuilds. The newer systems use less water & have better control.

It would require one of the PWM outputs.

[ehb]

Thanks for the aquamist link! I see the hardware is pretty well figured out, this system does seem interesting: http://www.aquamist.co.uk/cp/sys2c/sys2c.html

(@Fred:) Would it be possible to have different maps for the injector PWM outputs, hardware-wise? If yes, is it a big hassle to implement it in the firmware, or is it completely off the way FreeEMS was designed?
Just for future thoughts, no begging intended (yet)

[BenFenner]

Water injection is used to reduce detonation. Most naturally aspirated engines will be able to reach or pass MBT by adjusting ignition timing before they detonate on high octane pump fuel. This means there is not usually any power to be gained by water injection.
If you've done something else like raising the compression ratio or something, then it can be of benefit.

If you want to read a bunch of sillyness, I've got this: http://www.sr20-forum.com/all-motor/196 ... ngine.html

[Fred]

Water injection is used to reduce detonation. Most naturally aspirated engines will be able to reach or pass MBT by adjusting ignition timing before they detonate on high octane pump fuel. This means there is not usually any power to be gained by water injection.
If you've done something else like raising the compression ratio or something, then it can be of benefit.

If you want to read a bunch of sillyness, I've got this: http://www.sr20-forum.com/all-motor/196 ... ngine.html

What he said ^ :-)