DIY water injection

[hasa68mustang]

I was wanting to know what works and how well. I was considering making a DIY water injection system but wanted to know what would work. I know you need a hobbs switch to turn it on, and Ive heard shurflo pumps work well. Im watching one on ebay thats rated at "2.8GPM; 12V, 7 amps max; pressue 45psi" would that be sufficient? I ask because al of the kits are well above 100 psi that I see on ebay. I had some pages in my bookmarks but lost em all. anyone have any info to add?

 

[grocery getter]

i've seen some tips on DIY kits. i'll go back and try to find them.

Are you going with an intercooler also ?

 

[Bort62]

Why mess with Water Injection?>

Propane is self pressurizing, readily avaliable, and will cool the intake charge just about as well, if not better.

 

[hasa68mustang]

i've seen some tips on DIY kits. i'll go back and try to find them.

Are you going with an intercooler also ?

I was thinking about it. and not necessarily "water" injection, could run meth, or alcohol or 50% of either, or some of the other better cooling liquids discussed on here.

 

[matt1967]

Why mess with Water Injection?>
quote] ever see the inside of a water injected motor? Extremely clean.

 

[Bort62]

Propane has the added benifit over any of the others mentioned in that an expanding gas absorbs a large amount of heat.

Propane self pressurizes to about 150 psig IIRC, and expanding that to around 10 psig or whatever your boost pressure is will suck a lot of heat out of the incoming air charge.

Propane is also about 110 octane and will push your mixture ratio towards the rich side, which will help with detonation as well.

Water or alky or any other liquid is only going to suck out as much as it takes to equalize temperature. Off the top of my head I can't tell you what the relative heat absorbtions are, but I could figure it out if I get bored.

I would guess that for an equal mass rate of water or propane injected, the propane will lower the temperature of the air charge more.

But I could be wrong. Ill figure it out at work tomorrow.

On the plus side with propane, it is a trivial installation. Small latern style propane bottle, small solenoid valve like a nitrous valve, (there are other industrial valves out there that are cheaper)a little bit of plumbing, and a nitrous injection nozzle.

Hook the valve up to your pressure switch and off you go.

or just to a WOT switch.

On the downside, water is free - but you gotta pay to play

 

[hasa68mustang]

propane is rediculous here, not like up north where people use it to heat and such.

 

[Bort62]

Rediculous there? I live in Mojave. In case you don't know where that is, there is a desert of the same name

A little coleman propane bottle is going to be the same price no matter where you go. No need to buy it by the gallon at the gas station.

About 3 bucks.

Im not sure how much it contains, but Ill find out tomorrow and post. Definately enough for a day at the track.

 

[Bort62]

Okay, here it comes.

If you make the following assumptions ...

Airflow into your engine of 600 CFM (at boost)
Intake air temperature of around 70 C (post Turbo)
Water temperature of 17 C
Propane self pressurized at 17 C
Boost of 14.7 psi

Flowing at equal mass rates, propane blows water away... I'm not exactly sure what a sane mass rate is, but .01 kg/s is .6 kg a minute, or about a pound a minute. One of those little propane bottles is a pound.

That would drop you about 10 degrees C on your intake air temperature.

If you were to use water at the same rate, 1 lb is about 1/8th of a gallon or 1 pint, or 2 cups.

That would give you a drop in temperature of about 5 degrees C.

Now, if you added enough propane to change your mixture ratio from 14:1 to say 10:1 at the above conditions, that would be about:

Mass flow of the air at that point is about 1 lb of air per second. At 14:1 that means that for every 1 lb of air you have ~1/14 lb of fuel. To add enough fuel to that to increase it to 10:1 then you get the delta of 1/14 and 1/10 which is about .03 lbs.

So .03 lbs/sec of propane would be needed. That puts you at about .014 kg/s of propane.

According to my model... that would lower your intake temperature about 13 degrees C. That's not bad...

I probably made some errors in here as I was doing it in my head. Please point them out

I will take a closer look at my thermodynamic model tomorrow and see if it makes sense... but I think it does.

 

[Bort62]

To give a perspective to cost, on this hypotheical engine we would get about 45 seconds of WOT out of 3$ worth of propane.

In that time you would have spent 45 * .01 = 4.5 lbs or about 2/3 a gallon of gasoline.

So instead of spending 1.50$ in fuel at the track, you've now spent 4.50$

Worth it?

I think so.

 

[XFlow_Fairlane]

not for me as I don't have a track only car. $4.50 for every 45 seconds of wide open throttle on the street gets pretty pricey. so does get stuck on a power tune with no propane. Propane is for trucks in my book

 

[Silver Shadow]

Take a look at this...
http://www.better-mileage.com/water4.html

 

[hasa68mustang]

not for me as I don't have a track only car. $4.50 for every 45 seconds of wide open throttle on the street gets pretty pricey. so does get stuck on a power tune with no propane. Propane is for trucks in my book

Same here. The car is a weekend cruiser.

 

[Bort62]

You are burning that Much in gas anyways at full throttle for that time period your spending about 2$ in gasoline alone. The propane replaces some of the fuel.

Besides, 600 CFM @ 15psi boost is a pretty rowdy engine. I just pulled that off the top of my head.

That would probably come out around 700-800 hp.

so figure for a wild boosted street 6 about half of that.

So a minute and a half out of your propane tank

And how often do you spend at full throttle? 45 seconds is a LONG time.

And besides, you could buy it in bulk and refill it at home. A gallon of propane is like 2.19 here and that is 4 lbs. So its really like 50 cents a pound.

So about 2$ in gasoline and 50 cents is propane for a minute and a half of full throttle. Its really cheap as hell if you are the slightest bit smart about it.

 

[Bort62]

Take a look at this...
http://www.better-mileage.com/water4.html

That website is talking about something else entirely. It has nothing to do with cooling the intake charge.

Injecting steam will actually heat the intake charge - and it says so right in the article.

 

[XFlow_Fairlane]

I like water.....it shouldn't burn if there is a leak ifI do everything right. plus I can refill on the road and not at home. just much safer all around for me. I think there is a reason rally cars use water and not propane.

 

[Bort62]

Im sure there is a good reason to use water, it just depends on what your priorities are.

There is how ever no question that propane is a better cooling choice.

You just have to weigh the pro's and cons

 

[XFlow_Fairlane]

one nice thing about water is that it won't change your AFR. if you dump in propane on a simple hobbs switch your mixture will be pretty crappy (WAY rich then going lean later on) water has little to no effect on combustion process. while they both could really use their own ECU to vary the rate injected water is the one that will not screw with your mixture.