If I wanted to build a very high compression engine, would water injection be a way to prevent knock, rather than adding an octane booster, such as Torco?

If so, are there any good units out there already designed for our engines, or is it still a "homemade" market?

 

A water/ethyl alcohol spray injection system was used on military aircraft engines years ago to provide air charge cooling and higher density. There is a horsepower gain but I have no idea on who makes a system or how much water/alcohol mix should be injected. Old time mechanics used a dribble of water into the carburetor as a way to clear carbon deposits in combustion chambers. The trick was to put in enough water to clean the engine but not enough to make it stop suddenly.

Charlie

 

There was a kit available from B&M the Transmission people. It was brought out way back in the early 80s when unleaded gas and lack of real high octane gas became a reality.
As was mentioned this was developed for WW11 fighter planes with High Compression engines to get by with lower octane fuel. What it actually does is the atomized water cools the incoming mixture so it does not "pre-ignite". This stops the fuel from igniting from heat in the cylinder as the piston comes up for compression stroke. Hot spots such as carbon deposits will actually ignite a mixture as it compresses. High Octane fuel is compounded to ignite at a higher temperature than lower octane fuel, the water injection cools the mixture.
By the way this is the reason why High Test is no advantage in a low compression designed for regular ( 87 octane) engine.
Barrier

 

What about the Meth kits from ECS, Snow Performance & Cooling mist?

 

I have a friend who makes these systems for other cars and has been doing this for some time with great success. PM me for more info.

 

I run a water/meth kit on my supercharged viper. As I understand it, the water doesn't necessarily prevent knock. It cools the intake charge by pulling heat. The methanol portion is what helps with the knock. Methanol has a (I believe) 109+ octane rating, allowing you to run more timing, or in your case, more compression, especially on standard pump gas.

On a side note, I live in MN, the hot thing here is to convert the car over to E85. One of the local shops here has done a lot of testing, and has found cooler temps, more power, and the ability to fill up at the pump with 105 octane E85. It's about .50 cheaper than super unleaded too.

Call Bart at Hi-tech 763-712-9088. Tell him Brian said to call. They are converting my 11.75 to one ZO6 over soon.

 

100 or 110 Octane

 

This is why I asked. Conventional wisdom says that for every point of compression raised in an engine, power is increased by about 4.5%.

So by simply milling the heads to get raise compression by two and a half points, I could get a 10% increase in power boost - and that boost is a across the entire curve. Throw in a little water injection to prevent knock, and I should be good to go.

Anything wrong with that reasoning? Assuming I get an increase of 40ft/lbs of torque across the board - while that may not sound like much, the fact that the increase in not peaky, rather being evenly distributed sounds nice. Getting an increase of 40 ft/lbs at extremely low RPMs sounds very attractive. Furthermore, I wouldn't have to buy expensive additives - just water. I could always carry a couple bottle of Evian just in case I run out.

 

Couple of thoughts: Back in the early 60s GM produced two cars with Turbos. The Olds Jetfire with 215ci Al.V8 , and the Corvair Monza Turbo (??) they both came with a water injector although they used a "special" liquid that contained alcohol so it would not freeze, this could be purchased at a GM dealer. I suppose that was a solution for the detonation they were getting with the Turbos.
The LT1s of the 90s used a cylinder head first cooling system which enabled Chevy to raise the compression by cooling the heads and intake area so lower octane fuels would work with the increased compression. They also had the Optispark ignition controlled by computer and knock detectors.
The only problem I see is the correct amount of water spray you would need.
I still have the B & M kit I bought but never used, I just have to find it, I'll take a look this week, maybe some answers there.
Barrier

 

would that alky kit work good on a normally aspirated 11/1 compression engine? maybe let you advance your timing a little bit? ??

 

But I am not talking about 11:1. I am talking about 13:1 or greater.

 

You may want to ask the boys in the FI forum. Alot of them are running meth/water injection. ECS's sells a kit from alky control that seems to be rather poplular.

 

It's all fun and games till something fails, and it will.

 

Julio from Alkycontrol.com who makes the kits ECS sells is a great guy to work with. His kits are based on using a MAP sensor, I'm not sure if there would be a way to have it spray without having a boosted engine. Hundreds of TurboBuick guys running his kits as fast or faster than they were running with C16. You may try contacting him to see if he could alter one of his kits for a non FI application.

Muncie; Did you move!? Saw you location says IN!?

 

Are you saying that high compression is more hazardous than forced induction? That doesn't seem right.

 

Yepperz. Took a job a little farther east in the land of snow and humidity. I never really appreciated how wonderful NM climate is to your car's mechanicals/electrical until I moved here. I'm seeing surface rust on things I never would have dreamed....poor, poor car

 

If you can't make the AlkyControl kit work on your car NA, the CoolingMist kit will read a MAF signal and work off that -- probably your best bet for an NA car. Oh, I don't think I'd bother spraying just water into an NA motor, you'll likely get significantly better results spraying actual methanol. Just a guess.

 

As noted above, water injection has been used successfully in the past by lots of folks to control detonation. The methanol is generally added to prevent freezing, but the addition of water will supress detonation without the alcohol.

Water injection works by slowing the flame speed and reducing the peak temperatures, both of which significantly reduce the tendency of the engine to detonate. There have been tests showing that at really high compression ratios you can burn as much as half the gas (but then you are injecting almost as much water as gas) as compared to a more "normal" engine. So the use of water injection as a detonation supression system can be a good thing.

Remember that you only want the water injected at high manifold pressures, and using a MAP sensor to control the flow rate is a good way to do it. You don't want to be injecting water when you don't need it, it does you no good and actually hurts the efficiency.

I used to have a BMW 2 liter that we built with 13:1 CR. That was in the "good old days" when real Sunoco 260 was available and unless you were opening the throttle wide open below 3500 rpm it wouldn't detonate at all. It was making almost 200hp and still got better than 30mpg on the highway at 75mph... I also did some research in college using a variable compression ratio engine (with knock sensors) and saw first hand what water can do. Based on that experience I am still (and Smokey Yunick was) a big believer in high compression ratios.

With the technology available today, the detonation sensors on the cars and the ability to program an injection system, it would be pretty easy to progam a system to inject the right amount of water to control detonation in one of our cars. You would have to put it on the dyno, read the map sensor, knock sensor and watch the timing. When the computer started to pull back timing (based on the knock sensor), you could add water until it got back all the way to the proper advance. Do that for several rpm points and draw up a curve and set the water flow to that (or a bit more for hot days) level and you should be fine. Note also that as you go up in speed, the percent of water (in relation to airflow) will actually decrease, since speed and higher induction losses actually reduce the volumetric efficiency. Where you really need more water is at lower RPM and wide throttle openings.

Although it is a hassle to refill the bottle from time to time, I am suprised that the big auto companies haven't gone to higher CR's and added water. It wouldn't cost much, probably $20/car, and the gas mileage would be a lot better. I just figure that most folks wouldn't want to always be adding water to the bottle and also have to add a shot of alcohol in cold weather... Still, with the price of gas today, if you said "hey, you can have 20% better fuel mileage, all you have to do is fill up this little water bottle once a month, would the consumer be willing to do it. I would bet that a car that "burned water" would be a hit... Heck, even my lowly winter car has a warning light for low washer level, and with today's "drive by wire" throttle systems you could limit limit manifold pressure to a "safe" level when the bottle is empty.

A bit long winded, but just my thoughts on this.

 

Try FJO's water/ it is a killer system.....

 

A very informative thread. Thank you very much.

Also, thanks to everyone who chimed in. It has been very helpful and you have provided a lot of good leads.

I just wonder if I am missing something here because it seems like an obvious no brainer to me. Raise the compression, inject water and enjoy the new power and fuel efficiency.

One thing I'd like to have answered though, is whether bumping the compression up a couple of points is detrimental to our engines. Someone above mentioned this. It doesn't seem nearly as harmful as FI, but I might be missing something.

The only downside I see to bumping the CR is the possibility of greater piston blow by.