A superb octane-improves and ancillary coolant is that oldie but
goodie water injection: humidifying the combustion air.
Contrary to what would be expected from the fact that water
vapour is a product of combustion, its presence before the fuel
is burnt stimulates more complete burning. Several benefits,
easily added to a wide variety of engines, can flow from this
odd fact. Few if any commercial kits are on sale in N.Z., but I
have invented an extremely simple, cheap rig for DIY
water-injection, which I disclose here with full instructions.
Also I seize the opportunity to gush on, as enthusiasts tend to
about obsecure technologies with which they have fallen in love.
As this is not a technical journal but an enthusiasts' club mag,
I will become autobiographical to some extent.
History
The essential idea was developed in the first decade of the 20th
century. The original purpose was cooling. By 1910 some engines
which had been water-cooled were simply produced without
water-jackets after addition of "internal cooling", as
water-injection was first called.
Those engines had compression ratios around 4:1 and phenomenon
of pre-ignition (knocking, pinking) was unknown. Later however
this became the main reason for water injection, which turns out
to give spectacular octane improvement, allowing CR as high
13:1. By the end of World War II many aero engines used
water-injection. German versions use water-methanol mixtures,
partly because straight water would freeze in winter. The Wright
Cyclone, a main U.S. aero engine, tested with water and
methanol-water (the two liquids being miscible in all
proportions, unlike methanol & petrol), showed 50:50 best (as
had the Germans). The results were summarized as "high savings
in fuel cost - 52% at 100% power, decreasing to 25% at low
cruise powers … pure water is approximately equal to fuel when
used as an engine internal coolant at high power." Water gained
the Corsair (flown by some Kiwi pilots in the Pacific) 350bhp on
its normal maximum of 2100bhp - a 17% increase. These were
supercharged engines, so the result may not translate readily to
normal aspiration.
Another alcohol, infamous ethanol, was similarly mixed with
water before injection, but was not as good. When Renault
attached Formula1 with twin turbos cramming several atmospheres
of boost into Gornini's 1500cc V6, thy readily achieved 450bhp
but burned holes in pistons. Then a Kiwi mechanic recalled
water-injection; a reliable 550bhp won the championship. The
Saab turbo works rally car at one period had a water tank as big
as the petrol tank.
Some modern gas-turbine aero engines use water-injection for
maximum power at takeoff. Various naval and railway
external-combustion rigs are improved by steam injection.
Practical Experience
My main motive initially was to facilitate use of the low-octane
petrol which was the only unleaded petrol available in N.Z.
Troublesome, even dangerous, solvent effects have shown imported
half-aromatics 96-octane petrol to be a far inferior way,
compared with water to resist knock.
Many standard motors can benefit from water injection. Over the
past decade I have done many thousands of miles, and a small
amount of dynamometer testing, mostly on the Renault "Sierra"
motor (which powered the models 8, 10, 12, and some versions of
the 4 and 5). Power, economy, emissions and cooling are all
improved by a water:fuel ratio as low as 5%. At 8.5:1 CR,
knocking is abolished even if ignition is advanced 30 .
Certainly, water is a much better octane-booster than lead: more
effective, vastly cheaper, and incomparably healthier.
Friends have tested my water kits on Solex, Stromberg, Zebnith,
SU, Toyota, Nissan, etc., carbs. Results have been generally
good but unaccountably varying. One reason which I have not
published a formal account of this testing is that the
scientific mind's craving for regular patterns is frustrated by
the puzzling extent of variation between different engines.
Although no general rule-of-thumb promises can be formulated the
indications are that water-injection is well worth a try. Here
are a few reports on experience with my water kits. (1) Mercedes
Benz 280 (Solex carb). On a windless day, cruising at the speed
limit, the return from Tauranga to Auckland used 14% less petrol
than the outward journey had without water. (2) Renault 10,
1108cc During several trips between Auckland and Wellington, I
has been in the habit of cruising around 1/3 throttle (just off
the power jet), 50-55 mph, 45-40mpg. With water:fuel at 5 - 10%,
on this same journey , I took to cruising at 3/4 throttle or
more (65-80mph) - and still got 44mpg. Back down of the power
jet, the old cruising regime gave 53mph. (3) Toyota Starlett 11
Torque at low revs was so increased that the mechanic at first
thought the owner had slipped in a bigger motor. Making god play
with the extra power, the mathematician owner achieved petrol
savings of only 4%. (4) Leyland A70-powered house-truck (Solex
carb) The 1966321 motor, CR 6:1, could cruise this heavy vehicle
comfortably at no more than 45mph. Having settled onto this
cruising condition, with stable temperature etc., the former
military aviator barked the order for his wife to remove the
clothes-peg from the plastic water pipe. Their heads were pinned
back onto the quilted headboard, their facial features hideously
distorted by massive g-forces; able to move only their eyeballs,
they beheld in the rear-vision mirrors blue smoke billowing from
the rear tires as, at un-changed throttle, The Silver Snail
spurted up to 55mph. And the coolant temperature dropped
slightly. "She climbs hills noticeably further before losing
speed in any given gear." More torque was available at low revs.
With water:fuel at 25%, fuel consumption was improved about 15%,
despite the faster cruising.
Saving one litre of fuel in every seven, and getting a broader
useable power band, on the cheaper low-octaine petrol, for
neglible capital & running costs, is a very good deal. Sure,
turbo charging it isn't; but the price is right, and you'd be
assisting public health. My guess is that slow-revving motors,
like the A70, will achieve good gains with water; and certainly
any motor with CR around 10:1 or higher will benefit; "in
between", so to speak, are recent motors which are already
fairly efficient, CR around 9:1, on which the benefits will
probably be less marked. Anyway, it's very easy to try!
