Is there much or any benefit with water injection for detonation? Can it be used to allow higher compression ratios?

Yes there is a benifit; it would allow higher compression ratios.

Mix ethonal with the water or use windshield washer fluid and it will help support combustion.

Good luck.

Jim Burch

From Willard W. Pulkrabek's book

http://www.amazon.com/Engineering-Fundam...8159&sr=1-3

following page

Considering the millions of dollars spent each year by less educated owners on so-called
'cold air intakes'
with washable filters that are only slightly less restrictive
(typically 3 inches of water out of 404 inches total air pressure, and this compared to a paper filter with more pleats/area only just for a short period after proper washing, not after even 3,000 miles of road use)
it has always seemed a great shame
that the benefits of water injection
were not better understood
and that newbies be directed toward kits like the Spearco,
Snow Performance,
English Aquamist, etc

The fact that Buick found out the hard way that some owners of water injected and supercharged factory engines could not be trusted to fill their water reservoirs may be one reason water injection kits never caught on.

It is little known
that water injection is as good as
Exhaust Gas Recirculation (EGR)
at reducing NOx pollution
but when used has a fuel economy benefit
( up to 6%)
because a higher compression ratio can be used.

If you want to be sobered by another 'government waste' number,
calculate the dollar amount
of what saving 6% of all the gasoline
used in the USA
since the passage of the Clean Air Act in 1971 would be.

It is in the hundreds of Billions of $.


It is even sadder that lower level engineers at the EPA Labs in RTP North Carolina know and understand this, but their politically appointed bosses wouldn't have a clue about how to calculate it.

From the Aquamist site:

I still have an old vacuum operated unit that I got in 1978. We were running a 50/50 mix of ethanol and water with a small amount of lubricant. It worked well.

My uncle used a windshield washer pump with a throttle position sensor (potentiometer, variable resistor) to adjust flow. He claimed over 20mpg on the highway with a 70-ish Riviera.

I saw the aquamist site. I think their kits are geared towards boosted applications. What is out there for N/A setups?

Quote:

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From the Aquamist site:

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Alcohol injection for n/a engines hasn't really caught on because it really isn't that sensible for most people to do. If you're running too high of compression for pump gas, what are you going to do, run the alch injection all the time? I don't know how big those tanks are or how much real driving you could get doing that. That's why it's so big for the boosted guys, runs only on demand(boost). Not saying it's a bad idea, it'll do exactly what you want it to do, just not the most convenient thing out there for most applications considering race gas and even avgas is readily available.

Well I figured that it might be able to run only under load as well. I'm thinking timing reduction for cruising and toluene for racing...

Compression Ratio and Manifold Absolute Pressure (MAP) are linked.

You can run very high compression ratio on a fuel of limited octane rating,
as long as you keep the MAP below the detonation level.

"You can run an engine with a lot of squeeze on pump gas if you just keep your foot out of it"

To go above the level of MAP where detonation occurs,
one strategy is to both cool the intake air
and also enrich the air to fuel ratio.

A 50/50 mixture of alcohol and water atomized and sprayed into the intake air does both.

As the left hand side of the first graph
(by DA Gruden, an engineer at Porsche in the 1970s)
below shows,
you can get the advantage of better fuel economy with a static compression ratio as high as 15 to 1,
if you enrich the A/F when running high MAP at full throttle to something like
8.8 air to fuel ratio
(14.6 times 0.6 = 8.8)

If you don't want to use much water/alcohol mixture in daily driving,
you set up the engine to 'cruise' at a MAP enough below full throttle that detonation does not occur on the fuel octane rating you are using,
then turn on water injection only during
'emergency passing power'
where MAP is anywhere from 65 to 80% of full atmospheric pressure.

The second graph from a Japanese engineer
shows that this strategy can improve fuel economy by 6 to 7%
when MAP is held at a modest level
that just keeps detonation away
when at 'cruise' on the highway
or when accelerating at less than full throttle.

Kobayashi's graph that shows compression ratio versus part throttle fuel economy in the bottom section:

Where does ignition timing come in to this discussion? When water is used can the timing be bumped up? Is this where the better gas mileage comes from?

Pacifica and DaytonaTurbo:

From the small amount of reading I did, it appears that water injection usage is up to 20% of the amount of fuel used. Less, or perhaps none at all under part throttle/cruise.

Dodgeballs:

Off the Aquamist site there is small forum that has a section for naturally aspirated engines. Check it out: http://www.aquamist.co.uk/phpBB2/viewforum.php?f=14


DMERC and 360view: If anyone were to give this a go, you guys get my vote to see whether this will work or not.................

Here's a system geared towards high compression engines that uses vacuum signal to determine how much water to inject.



http://www.snowperformance.net/product.php?pk=7

Aussie opinion that water injection is the first of 5 ideas worth re-thinking:

http://autospeed.com/cms/A_111302/article.html

No graphs and charts, but my dad used it on his HP 289 with 9to1 compression to avoid detonation. Worked well. He didn't mix alky into it, just straight distilled water. I would suggest a bit of top end oil if you don't get the engine fully hot on each drive. Maybe some water soluible oil in the mix, although that would not be when you want to introduce oil!

I saw this alot in the late 70s early 80s in motorhomes... Trying to eliminate the pinging uphill and under loads... This was when unleaded gas and newer formulas were just being introduced.. As far as I remember it worked very well.. Newer technology and computers have fixed most of it....

it's something I've thought about for a "high efficiency" type of build-- high compression, short duration/high lift cam, and water injection to control detonation....