Water injection.

[Bernd Felsche]

Nicholas Parker writes:

>Hi,  I have personally filled one of those plastic Coke bottles to 100psi.
>It 99.9% full of water (to minimise injury to myself!) It's damn amazing how
>huch those things can take!! On a more sensible note, for my mist injection
>system I used a 250psi, 12v tyre compressor with a 'pressurised garden
>sprayer' bottle, you know, the ones that have a manual pump built in, but I
>removed the pump and put in a tyre valve, so it plugs right in to the
>compressor!

Unfortunately, the capacity of such a small bottle won't last long
under maximum-load conditions. I calculated a while back (1996 or
thereabouts) that a 2-litre engine at 6000 rpm would use around
10 litres of water to get to 100% RH at inlet temperature on a hot,
dry day. Much more if supercharged. And you want to inject even more
water.

Approx 300 kg of air in one hour, take-up about 30 g/kg of water/air
(dependent on ambient RH)  --> 9 kg (i.e. litres - near enough) required.

Lack of a compressor isn't such a big limitation; it's the duty
cycle the thing has to operate under. I bought a cheap air-horn
"compressor" to use as an airflow source with a venturi feed to
spray water (as in a spray gun). Spray works fine - mists well with
the correct jets. Would be OK in principle for use in a pre-filter
misting chamber.

Unfortunately, the unit isn't designed to run for very long (i.e.
low duty cycle) - the internal vanes (of course I opened it up!) are
made of some polymer composite which will probably wear out after a
short time if not lubricated. The whole unit gets quite warm after
about a minute or two.  It's also quite noisy - draws 8 amps.

So at this time, I'm "stuck" trying to find the right technology.

Does anybody have specifications for airflow from an auxiliary air
pump used for catalytic convertors? I reckon I could swipe one from
a New Beetle without it being noticed. :-)

Q Why would you want to do this?
A To drop the octane number requirement as much as 8 points.

10 litres capacity is probably sufficient for road car use - you
only get away with 6000 rpm for an hour if you're cruising on the
Autobahn or similar. The non-evaporated condensate can be collected,
filtered and recycled - so you don't have to meter the amount of
mist you generate.

Two other benefits for road cars; on hot days, the evaporation cools
the charge. On cold days, you can pre-heat the water and use the
warm mist to help pre-heat the charge air for better fuel
vapourization.

-- 
Real Name: Bernd Felsche
    Email: nospam.bernie at perth.DIALix.com.au
     http://www.perth.dialix.com.au/~bernie - Private HP
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