Water Injection by ported suction only.

[mde00]

Hi all,
I had recently come across this article on a DIY water injection system by Robert Mann. (

http://www.dave-cushman.net/misc/mannject.html)

It is very simplistic. From what I understand more water is needed at higher engine loads to allow the water to deter detonation. This system uses a fictitious method of simulating engine load and varying the amount of water intake by using the ported vacuum signal from the carburetor with no other external input. Correct me if I'm wrong but ported vacuum could be compared to a throttle position sensor when used in this application, not a direct indication of load. But pretty close. I have the system installed in my 4.2L, I6 NA jeep engine; I am also using a Motorcraft 2100 carb. So far the system is running smoothly with 25 degree initial advance. The article says to install it in the vac. advance line however the line just ends up filling with water and screws up the advance signal. Luckily this carb has two ported vac signals. So I have one dedicated to the water intake. Here is my question. By using clear vinyl tubing I can see that the carb essentially sucks in liquid rather than water vapor or atomized water. I am worried that the water being sucked in the carb above the throttle valve is flowing in rather than being atomized. Ultimately causing uneven distribution of the water to all cylinders. I cannot see the port where the water is being introduced so I have no idea. Do you think that the air velocity in the carb is enough to atomize the liquid? I know spray injection systems spray water above the venturi's however they are expensive and seem to do the same thing as this system. Also is five percent water to fuel ratio a good place to start for this kind of system? My only way of judjing water consumption is based on filling up both water and fuel tanks and then comparing the volume used for each tank of gas. This is my first post. I have been using this forum as a resource for a long time now. Great insight.
Cheers

 

[FoMoCoMoFo]

I see a couple of problems,
You appear to be confusing ported vac. with venturi vac.
ported vac. is the same as manifold vac except the throttle has to be opened past the port, so no vac advance at idle.
some 2100s have a venturi vac. port higher up the carb. that could give you the sort of vac signal that your after.
BUT, that ported vac. and venturi vac are both fed from the right/passenger side of the carb only, and neither is located well for good atomization or distribution.
Good luck.

 

[mde00]

I see what you mean. I did a little more reading and found some good explanations and the different carb vac. systems. Thanks for your input. Your right the venturi vac. signal is what I am looking for. There is one port on the passenger side of the 2100 the pulls about 5" Hg at idle maybe this could be it. I'll have to do a little more investigating and in the meantime unhook the system I had installed.
Thanks

 

[Bribyk]

Why is water necessary for an NA Jeep engine? Are you running higher compression? I've only heard of water injection on high-boost cars...

 

[mde00]

From what I've read it helps only to deter detonation when the timming in increased above normal. With more timming I get better performance and higher compression. Not even close to the amount that a turbo or super provides. So I was only trying to find a way to increase the timming without the negative effects of detonation. But the ported vac. signal I was using is totally wrong for this application which I think is way inferior to the mister or atomiser spray used in main stream water injection systems.
Cheers

 

[Bribyk]

Are you already running high octane gasoline? If not, this may be more expensive (depending on how much you drive) but safer for your engine. I'm a little worried about flooding or water left in the manifold and cylinders after shutdown.

 

[patprimmer]

If the water tank is below the discharge nozzle when the car is parked at the worst angle, water into the cylinder will not be a problem. The only potential problem from water running in is hydraulic lock which can very easily break internal engine parts. Small amounts of water are always there as after all hydrocarbon plus oxygen burn to make carbon dioxide and water.

Increasing timing will not necessarily make more power unless your current timing is knock limited on the fuel you are using.

This subject has been discussed in detail many times before. Please do a google search of the site rather than rehash it all again.

You really only want water flow at low manifold pressures, so systems that depend on manifold vacuum or air speed are not verry effective. The best systems have an electric powered pump and switch that senses manifold vacuum and rpm to metre the water flow.

The correlation between required water and fuel usage will be very poor as it will depend entirely on manner of use.

Regards

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[70AARCUDA]

...there's ALSO the very real (...and probable!) problem of running out of water and subsequent "over-lean" condition! Especially, when you "think" there's water available for that "hard" load situation!