lower egt and turbine power

[Metal_Dave]

I tried searching for some key words but didn't find what I was looking for.

My question is, if water injection lowers egt, does this adversely effect power to the turbine? I haven't thought too hard about it so maybe I'm forgetting something, but won't the turbine loose power if there is less heat in the exhaust? Or is the lower heat compensated by the energy in the hot water vapor? Does the turbine extract power from the vapor?

I could probably answer this myself if I spent some time flipping back through my thermo book... but if somebody knows offhand or can give me a link to where this issue is discussed, it would save me some trouble.

Thanks.

Dave

p.s. This is my first post. :D

[hotrod]

Your right, if you get carried away and reduce EGT's too much you might see a small drop in drive energy for the turbine. Water Injection and especially with Alcohol in the mix, produces more exhaust gas volume. Even though it is slightly cooler, the energy is not reduced to any significant degree.

Larry

PS welcome to the forum.

[Richard L]

I agree to what has been said.

If you treat the engine as a gas powered motor, it doesn'r really matter what kind of gases pushes the pistion down, it will turn the crank.

In steam engine, the pressured gas in generated by superheated steam and released to the combustion chamber and perform the mechanical coversion.

Gasoline/diesel engine is a short cut to the steam engine - fuel, air and ignition is all done within the engine itself.

In a water injected gasoline engine, water behaves almost the same as a steam engine, liquid water is vaporised to steam during combustion and the volume increase contribute to the final compression ratio and in turn increase the cylinder pressure and hence torque (power per rpm).

If the combustion does not produce enough heat to effectively converting the water to stream, you will see a power drop because the partally vaporised water will absorb the combustion energy but not enough to affect the compression ratio, this is the time when you see an decreace in egt and some loss of power.

In the ideal WI powered engine, the egt should be over the normal permitted temperature and then allow the water to use that excess heat to lower the egt to a safe level - you will then have more power at a correct EGT, turbo spoonling up time should improve as well.

In almost all power tuning strategies, gasoline is used in place of water when a rich mixture is being used.

In my opinion, if you can run the ideal A/F ratio for your engine and ignition timing to obtain highest EGT and use water to bring it backdown to a safe level, it will be the best way forward - just my opinion.

If you need more informatiopn have a read on the following link:
http://www.aquamist.co.uk/info/documents/turbowhitepaper/title.htm