Turbo Chubby parts

Bruce nacelp at bright.net
Tue Dec 11 13:52:14 GMT 2001


From: "Bernd Felsche" <bernie at innovative.iinet.net.au>
> According to the people who make some money from it,
> (e.g. http://www.aquamist.co.uk) there are several locations where
> you can introduce water injection for a variety of benefits. There's
> no "perfect" location. Upstream of the intercooler is best for
> vapourization, adding to the effectiveness of the intercooler
> (charge density) and distribution from a single jet.

Owww, so since they do it for monwy they must know all the answers.

> The closer you inject to the inlet valves, the greater the
> proportion of droplets and from a single injector, the greater the
> chance of imbalance. A port water-injector minimises vapourization
> but droplet sizes need to be very small. Distributing the right
> amount of water to each requires careful tuning and/or management.
> > what do I want?  I think that I want vaporization for increased
> > economy & atomization for power.  Warm, tepid or cold?
> The _least_ amount of water necessary will provide the maximum
> amount of power as water vapour displaces oxygen. It's better to
> have tiny droplets of water until the valve closes for compression.

<sigh>, again an instant reply without thinking things thru.

> > exactly what it "does" is still a mystery to me & the topic of a
> > major debate that I don't think that we have got to the bottom of.
> Evaporating the droplets in-cylinder doesn't reduce the total oxygen
> present even when the droplets evaporate and absorb energy during
> compression (six to seven times the amount of heat as for the same
> mass of gasoline).  The water vapour acts as a "buffer" to the flame
> front, not only obstructing it at a molecular level, but also to
> reduce hot spots by absorbing some of their heat.
> The Gasoline FAQ indicates the degree to which water content in the
> air (humidity) reduces an engine's Octane number requirements. Order
> of magnitude is 4 g water per kg of air reducing ONR by one point.
> (The relationship is not entirely linear.)

Getting to sound like trvia pursuit.

> With a high charge temperature and without becoming saturated, one
> could add 40 to 60 g of water per kg of inlet air, depending on
> initial ambient conditions. That's an AWR of between 25:1 and 16:1
> for an ONR of between 10 and 15 points.
> Too much water and the flame front slows too much as the reagents
> take longer to "find" each other, resulting in less torque.
> Determining what is "too much" will take some tuning time. Accurate
> knock detection and some means of measuring torque under controlled
> loads are a distinct advantage.
> Well, that's one theory anyway.

Yep, good old theory,  sure beats getting ones hand dirty, and actually
seeing what is going on.  Yep, tuning, does take time, and EXPERIMENTION.
Bruce

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