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This is a general query about 2 stroke engines. In my teens I owned a 2 stroke motor cycle and noticed at night it used to run smoother. I picked up somewhere that it was due to more moisture in the air at night. Is this a correct and is this the reason that some WW2 aero engines had water injection?
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Night time air is generally cooler than in the day. That means that air is denser so more molecules of oxygen are drawn in on each inlet stroke. If sufficient fuel is available, extra oxygen means more power.
I think that water injection is used to reduce inlet temperature but it will also add more oxygen.
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I remeber the same re two stroke bikes.
Cool air is denser however damp air also benefits the combustion process by slowing the combustion and allowing a more efficient burn and thuis more energy to be obtianed from the fuel, i.e. it increases the thermo dynamic efficiency of the engine. ECU controlled engines will benefit further from damp air or water injection in that the moisture reduces knock (pre ignition) allowing the ECU to further optimise the ignition / injection timing.
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Oh right so it wasn't my imagination then. If water optimises efficent burnt burn and lowering emissions is todays requirements then could water injection be a further refinement to that end? Motor manufactures might balk at the idea due to cost but in the end all these mods become cheaper with economics of scale. After all its not as if it's a new discovery. I've since read that some WW2 fighters had it to cool the turbo charger down.
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Also, if it was an air-cooled engine, the cooler night-time air would help regarding keeping the engine temperature down a bit. Air-cooled 2-stroke engines tended to 'lose their edge' as they approached full working temperature.
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There have been a few a water injected engine projects and they do work but they take there toll on the engine. the pots stay cleaner but valve seats and lips errode and the life of the engine is shortened. The test vehilcles also discovered that they really needed to stop injection 2 mins before shutdown to aviod water contamination of the bores and the oil or there was real metal to metal contact on cold start. I played with this in the early 70's, Ok I'm old, well old ish, on an Austin Cambridge engine sure cleaned the engine out, free decoke if you wound the cc per stroke up. I had to change the oil afer 2000 miles due to emulsion in the rocker cover, that's cam cover for the young ones on here who do not know what a push rod is. Regards Peter
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Peter D i did the same on a marina 1300 in the 70's and got the same results as you.
i also practised with a torque tube made of cardboard but it caught fire.
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There have been a few a water injected engine projects
For our final year thesis in the late1950s a group of us were initially assigned to design a six-stroke engine which would have water injection at round about the start of the 5th stroke. Unfortunately it was cancelled.
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L\'escargot.
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> ... the rocker cover.........
If you really want to be pedantic, in the manufacturing trade a rocker cover/panel is whar most people call a sill.
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L\'escargot.
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in the manufacturing trade .........
Correction ~ replace "trade" with "parlance".
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L\'escargot.
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I sold the Austin after about 110K miles and bought a 1.8 Marina Estate from the same guy I bought the Austin Cambridge from. Both were his private cars and he was the transport manager for a major utilities company in S. Wales. Regards Peter
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ECU controlled engines will benefit further from damp air or water injection in that the moisture reduces knock (pre ignition)
2 stroke engines tended to have their spark quite well advanced, so anything that helps to reduce knock would be noticed more than on a 4 stroke.
It's the reason why they sound lumpy at idle, and one reason a freewheel is fitted - it's not pleasant on the overrun! The other reason for a freewheel is for lubrication of course.
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I noticed the same thing with my RS turbo, it would fly in misty conditions although, sods law, i couldn't see very far
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Aim low, expect nothing & dont be disappointed
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Manic 1970's 2 strokes always felt quicker in dark, rainy nights because a crash was always that much nearer :-0
A Mach 111 must have been virtually unrideable in the wet, not enough revs and the plugs foul, enough revs and the front is waving in the air with the back wheel pointing somewhere else, particularly if shod with an Avon Speedmaster or similar. And a nice grabby drum brake on the front would add to the fun.
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My brother had a Suzuki RG500. Now there was a mad bike. Unfortunately I was too young to ride it at the time but I went pillion a few times.
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>>I think that water injection is used to ... but it will also add more oxygen.
Eh?????? How???
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>>I think that water injection is used to ... but it will also add more oxygen. Eh?????? How???
Discombobulation.
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