I'm going to some up what you need to know, in my opinion. After I've expounded these two points, I'll then tell you the most important factors. If I told you those first, you'd go bonkers! All this inane babble is to underscore two things.
Firstly, no-one uses alcohol or water injection on a stock compression engine unless its turbo charged. There is no point because unless you need to have a higher fuel octane to run a stock 8:1 compression, water or alchohol is useless. It won't do anything at all. But even when an anti-detonation injection (ADI) system is set up, such as for the one Oldsmobile tried on there ill-fated Turbocharged Jet Fire F85, the maintenance is never done correctly. That system was never tended to with the right additive in lots of cases. Despite an 800 mpg methyl-alcohol consumption, compelte nonggs would shove anti-freeze or gasoline in the reservoir with suitibly horrific results. So today, its a brave car marker who employs an ADI system. There are none that sell any such system from the factory, and, I predict, they never will. It's not a petrochemical conspiracy, it's a fact of life.
ADI systems are never tended to properly, and can only be used where either compression or turbo/supercharger boost is raised!
Secondly. An engine with ADI can run any compression up to ~12:1 with enough water, and up to ~14:1 with the right alcohol mix. And it is certainly possible to run on 89 octane at that level. All you do is add metal to the head and raise that compression ratio. The benefits are instant. Part throttle economy improves, the torque increases, and , in the case of alcohol, the peak power increases proportional to the compression increase. With just water, the peak power goes up slightly, but as soon as the water is introduced at wide open throttle, the power levels off, as water is quelling the flame. With alcohol, the flame front is enrichened, and power increases. This is wounderful because you can run stock pump gas, and get high octane performance. The mpg's improve at part throttle when no alcohol or water is used by a large amount. As long as the system is checked fro operation on a regular basis and stocked full of fluid, it will work just like a EFi system, but supply a resistance to detonation under all conditions.
Righto, some background to shore up what I've said.
Maximum power is limited not primarliy by valve size, cfm or work rate, but by how much power you can get before detonation sets in. That is when the fuel air mixture in the chamber expands under intense heat and presure. We call it an explosion, but it is not, and can happen when hard edges of the combustion chamber, plugs or exhast valve heat allow the temperature to rise enough. Here is some vital info you need to know before fitting an Anti-detonation Injection (alcohol or water) system which operates via knock sensor or wide open throttle.
The simple rule of engines is that HP=PLAN,
where P=pressure, how much combustion chamber pressure the engine design can carry.
L = Load, the amount of work the engine can carry without granading
A= Area of the piston
N= number of cyles, or rate of work.
Some of those things are influenced by the compression ratio.
If you raise the comprssion from say, 8:1 to 13:1, the power will increase proportionally
if the engine won't detonate under load. If it does detonate at a lower level of compression, then that becomes the ideal compression ratio.
Case 1: Say your stock 200 cube 1981 Mustang runs on 89 octane, and has a stock comprssion of 8:1. Power was 83 hp.When the engineers raise the compression, they find the 200 engine cannot hold more than 10:1 after the engineers fiddle with the ignition curve, optimise the cam advance, use different head chamber shapes etc. They do everything bar changing the cam, running EFI, or water or alchohol injection. 10:1 is therefore the maximum compression under load the engine will handle under a 89 octane fuel. The power is now 100 hp. But that leaves no margin for error if you accidently put 83 in it, or run it to overheating, or advance the ignition. So most auto makers err on the side of caution, and may tell the engineers to just run it at 9:1 for safety sake. The engine ends up with 90 hp instead
Case 2: In the bad old days of 105 octane pump gas, the auto maker may have just elected to run hi test fuel for the above car, and get 10:1 comprssion ratio performance all the time. Gas was cheap, and hi-octane was everywhere! The engine would do 100 hp, but with a huge factor of safety under load. The engineers then consider raising the compression again....bringing us to ....
Case 3: Here, they find 13:1 is quite ok with hi-octane. The power is now almost 130 hp. But the engineers realise ther is no factor of safety. They are delighted at the part throttle economy, responsiveness but are finding that the combustion temnperatures are now getting too high, and that the emission gear needs upgraded air injection to lower the NOx levels. So they forget this option. Besides the customer whould have to fill up at the airport with illegal leaded plane fuel, or carry a can of VP Red around just to fuel it in the 1980's onwards!
The above cases are exactly why all car markers are now running EFI engines with full management systems. They are just trying to get the most out of 89 octane, in a way that will raise performance without raising emissions.
Water or alcohol injection does all a high octane engine does, with just a head change!
