Water injection has been used to prevent detonation since at least WWII. We've got an 02 WRX, and it's absolutely painful to put the expensive stuff in the tank. Where we are it's so expensive that we've been known to hit the $50 credit card cutoff before getting the tank full. We've stepped down to mid-grade, but some performance is lost due to the computer detecting knocking and lowering boost and probably ignition advance. It runs on 87, but then the loss of power is quite noticable, and it stats to affect drivability.

I know they make water injection kits for subies, but they are expensive and seem to be targeted at boostaholics. All I want to be able to do is run the cheap gas.

So here's my idea. A sealed reservoir, filled with distilled water. From the bottom of the reservoir, a tube will go to the intake of the compression side of the turbo, through a metering orifice. A hose from the top of the reservior would go to the outlet of the turbo, the boost side. The boost pressure would force water out of the reservoir , into the inlet area of the turbo which would be at atmospheric pressure. At no boost, no water flows. The more boost, the more water. It seems like the turbo would do a good job of atomizing the water, and evaporation of the water would probably even help cool the intake charge. It has an oem bypass valve, so when the throttle valve closes the pressure on both sides of the turbo is roughly equalized.

Is there any reason this wouldn't work? Could it damage the turbo? Could it damage the engine? Would it somehow negatively effect gas mileage enough to counteract the savings of using cheap gas?

There are quite a few "boostaholics" injecting H20 (and alcohol on occaion) pre turbo... You can end up w/ puddling in the intake, and the bigger droplets from the intake walls can damage the turbo blades...

Realistically, the difference between good gas (ok crappy California 91 octane) and the cheap stuff is 4 bucks per tank. Is it worth the trouble and potential damage for 4 bucks a tank?? (20cents difference per gallon x 20 gallons)

BJH

Trust me.. the way my finances are right now, $4 a week is a big deal. It shouldn't take much water to bring 87 up to 91, does anyone know how to calculate that? If I can find a way to minimize risk to the turbo, I might just have to give this a try.

The water doesn't burn, so in this sense it won't "boost" the octane rating of your gasoline. If it did, the station owners wouldn't be getting fined for topping the storage tanks with a garden hose.

The water injection setups I've seen are on supercharged cars. WI is used to cool the intake charge (make it more dense), and the volume of water is very small. It does do a nice job of cleaning carbon build up.

Now ethanol injection is a different matter, since ethanol is flammable, but I'm not a fuel formulation expert so someone else will have to chime in on mixture ratios...

water will not increase the octane of gasoline. no way no how. What it will do is to reduce the combustion temperatures and reduce the tendency of pinging. it will also reduce the amount of air and fuel you take in because it will be displaced. Will you see an increase in HP because of timing? who knows. maybe. Yoy might have to crank the boost up higher to get the same hp.

If it were me I'd be very careful jury rigging water into your turbo system. Lots of thing could go wrong if you get it wrong.

$4 a week is not a lot of money. How much were you planning to spend on your water inection system?
If money is that tight you should think twice about putting your foot in it. You could probably save at least $10 a week by staying out of the boost altogether and driving slower.

The water and ethanol injector raise the thresho9ld for predetonation, they do not increase octane. Put the right gas in and don't be so cheap, well short run cheap, long run $$$$$$$$$$$$$.

How about some toluene or other octane booster? Probably would be a wash on cost though

It may not technically boost the octane, but it boosts the "effective" octane. Octane is just a measure of how ignitable the gas is. The higher the octane, the harder it is to light. Of course they can't mix the water in at the station, because gas and water don't mix. It has to be mixed with the air as it's going in to the engine.

I was intending to spend about $20 on the water injection sytstem. No fancy electric valves, no pressure sensors, just nice and simple.

Search for water injection on the net. There are many sights with either kits or how to articles. Most use a high pressure pump to atomize the water as you inject it. You also don't want to inject it before the turbo. 20,000rpm turbine blades don't like to hit things, even if it is only water.

I ran my Suby (the one in the 914) on 87 gas in the beginning - believing that I'd be able to tune it for lower octane gas. It just ran rough. I bought a bottle of octane booster and it ran noticeably smoother straight away. On 91 it just purrs.

If there is financial hardship - I'd guess you'd save more by capping the boost on your motor (take out the boost controller solenoid and run it at minimum boost (7 or 8 pounds) by plumbing the compressor side straight to the waste gate. (This should be a very easy and very reversible operation - I'm not sure if it will cause a check-engine light or not though....)

Anyways - this should make more of a difference. The areas of the fuelling map where the engine is under a lot of boost are the areas where it runs richer than stoke. You'll notice some lack of the old grunt, but you'll probably save more money this way than by running cheaper gas. Also - if you drive 65, and quit accelerating like a madman - you'll also probably be able to get a few extra miles per gallon.

That is exactly how they used to do it. I have an old turbo book that shows the exact setup on a turbo Corvair. It should work fine. Just use clean water and start out with a very small orifice. If you use to much water it will start to condense (it can even freeze) in the intercooler. Make sure the tank you use can take the boost pressure. Also make sure to use a large diameter hose to "charge" the tank or it will take to long to start the water flow and it will keep going after the boost is gone.

At the shop I used to work at (the shop was just down the road from you in Pismo Beach) we had a car with a centrifugal supercharger that used a windshield washer pump and a simple hobbs pressure switch - the water went directly into to the impeller and cooled the charge air to below ambient.

Your lucky you only fit $50 a fillup - my truck takes $125!

Trade the WRX for a 2.5RS, the money you get in the trade will buy a LOT of 87 octane gas. The 2.5 is fast, it gets better gas mileage, and it runs on 87...

I agree...
why take the risk of damaging a 30K investment over 4$?

trade it in..

buy a 1990 camry if you have to, or put the 914 project on hold... but don't cause 6k damages over 4 bucks

brant

I had a Focus that I turbo'd and used aquamist water injection for a time. It will cool the intake charge, and allow more timing, less pinging. Its also a bother. I had to pump alot of liquid into the car with 6psi no intercooler. I was runing washer fluid, as that is part H2o, part alcohol, and would not freeze here in WI in the winter. I'd go thru a gallon jug with every fill. I had problems with the pre filter for the aquamist pump clogging, and the pump burning out. After 3 pumps, all on warrenty thank goodness, I switched to an air to water intercooler and had much better results. Upped the boost to 10psi, no pinging, more performance, all good.

Does water injection work? Sure.

Is it your magic bullet? Probably not.

Is it bad to inject prior to the turbo? Not if you like buying new turbos.

I've seen some pretty brutal photos of turbo blades looking like they were sandblasted after a water injection set up as you propose. It sounds simple- boost pushes water in to the system, but I'd not go that direction. Been there, done that, it only sort of worked.

Now this is the sort of thing that says "hey, don't do that!"

$30k investment? Hah! salvage title.. $12.5k a couple years ago. I'll keep my eyes out for a good used stock turbo cheap. If I ever find one and have it in hand, then I'll experiment. You guys have talked me out of it... FOR NOW! MOOOOOOOHAHAHAHA!

note to self...

NEVER..... never... never buy used car from Royce.

Yeah, you might have to weld on it at midnight in a hotel parking lot!

Whatever happened to CptTripps, anyways?

Yeah, it's a double-edged sword... You inject the water, and the intake charge is cooled somewhat like an intercooler does, and that increases the charge density, probably making up for the room the water makes, but it depends on a lot of things. Then the water vapor in the cylinder takes up a significant amount of the heat from combustion, lowering efficiency a tad. When they say that water injection effectively increases octane, it's basically true. Water injection is for increasing the amount of air and fuel you can cram into a cylinder.

Consider that WWII planes used water for when they needed extra power; they didn't use it to increase the range they could fly by constant injection throughout the flight. I'd be mostly concerned with those little drops of water eroding my compressor. Doesn’t sound good. At any rate, I wouldn't use my daily driver, or a car I cared about too much to experiment with water injection hacks.

Consider a couple hundred bucks a year to be a sporty car tax. It's not bad, but if it's going to kill you, it's probably time to downgrade.. You'll save on fuel, you'll save on insurance, and the savings will be much more tangible than 20 bucks a month.

Besides, everyone knows the best water injection method for a Suby is to have a slow head gasket leak.