water injection = Higher Efficiency?

[ar5boosted]

Originally Posted by teoman

I takes 2.2 MJ to vaporize 1 kg of water.
1 kg of gasoline has about 46MJ of energy.

Havent had a look at all the steam table pressure graphs yet, but purely from an energetic point of view, every unit of water by mass cancels out about 0.05 units of fuel.

Energy is used up to vaporize the water. After that both n2 and h2o compete for the thermal energy and expand.

I have my own observations on Water-Injection, developed from years of continual operation.

Whilst it takes energy to vaporise the water, it was heat energy that the engine was going to throw away anyway.

Adding water will simply convert extra heat that is there and not really wanted into kinetic piston driving energy so that the heat is not flushed out the radiator and muffler as it is on a normal car.

So you can win in fuel efficiency using water-injection.

[teoman]

Yes it could be possible to win in fuel efficinecy. But i like to fully understand what is going on. Then i feel that i can tune it so that i can maximise the benefit.

Unfortunately that energy is not useless waste energy. Its function is to heat up the air and make it expand.

But with the water phase change if you can get the same gas pressure but cooler, you have less losses.

For example how much water is ideal?

For 20 units of water to 1 unit of fuel by mass theoretically you are producing steam at ambient pressure. So the engine will not run.

All the academic publications i have read seem to suggest that %20 water to fuel is the most beneficial.

But those are lab tests. And in real world consitions with changing load and rpm ine may need different rates.

If i can understand the theory behind the anectodal evidence i believe i can create the best setup.

[Fingie]

when it rains heavily or when the air is otherwise moist, my car's MPG improves noticeably. I am curious into this.

[George Tyler]

I agree we need to understand what is going on. We could do a before /after test on engine heat rejection, if less heat is going out the radiator or exhaust then we should be able to quantify it too. doing this would be a bit complicated though.
If you consider the combustion chamber temperature, and particularly the valves and piston, in normal operation will be hot enough to make some stream. There was a design once for a steam engine with internal steam generation, cylinder head was heated and a thin gap was created radially in the head that injected water was forced into by the "compression" stroke and turned instantly into steam. I think there could be a bit of this happening.
Of course, the engine is cooled in the process.

[ar5boosted]

Originally Posted by George Tyler

If you consider the combustion chamber temperature, and particularly the valves and piston, in normal operation will be hot enough to make some stream..

Inside the combustion chamber it's definitely hot enough to make steam.

You want to make steam as water expands 1800x when it turns to steam.

This will give the engine extra torque, so much so it's like adding extra cylinders. You feel it straight away.

[toc]

Simple approach is to add an injector into the intake after the airflow meter and calculate a pulse width based on current fuel injection pulse width (be it 0.2 times or less)?
Tune the injection time based on real world findings..

Is that a dumb idea?

[ar5boosted]

Originally Posted by toc

Simple approach is to add an injector into the intake after the airflow meter and calculate a pulse width based on current fuel injection pulse width (be it 0.2 times or less)?
Tune the injection time based on real world findings..

Is that a dumb idea?

Sounds ok to me. I've been told by the background neighsayers that the injectors will rust. However, Injectors are cheap and plentiful at the wreckers and I bought one for $3 to test how long it would last but got distracted.

Using spray-nozzles is problematic for various reasons. 'Limiting' is a better description, however that's what I used and could get it to work in a somewhat approximate system.

I based water input at a constant rpm of about 1,100 rpm on my Mitsubishi. Slightly above idle and slightly below accelerating values, but I was satisfied with that.

[t vago]

Injectors for E85 should not rust.

[teoman]

Thanks for dropping by tvago.

I have the setup sorted out.

I a using an arduino a canbus shield and an injector.

[t vago]

Originally Posted by teoman

Thanks for dropping by tvago.

I have the setup sorted out.

I a using an arduino a canbus shield and an injector.

Good! Have you seen any improvement in fuel economy with your setup?