Water Methanol MW50

[Ian]

Hi All,

 

I was wondering if anyone was using the equivalent of MW50 or MW30 or water/oil injection to provided greater knock margin and cooling on engines. Water 99% 1% oil was most effective however it could freeze.

NACA provided the following in the 1943  https://ntrs.nasa.gov/api/citations/19930091835/downloads/19930091835.pdf

I know that there is a STC'd version was/is available but it sounds a little pricey for what is a simple system.

A few benefits are;

• lower head temperatures at higher power settings
• Lower fuel consumption
• Increased knock resistance allowing lower octane fuels or higher compression pistons.
• removal of engine deposits

 

It certainly seems simpler and less work than many other modifications.

 

 

[Bruce Tuncks]

How is it injected Ian ? Is it injected into the inlet plenum ?

I find the idea attractive.

[Ian]

Injection into the inlet plenum works. There are some pretty simple systems out there that just use windscreen wiper pumps and a light to let you know that water levels are low.

You could also go for the STC version which is about $15000 or an off the shelf automotive system.

 

I've been playing with an arduino to provide better gear up landing warnings. However it occurred to me that a very similar system could automate the whole shebang as well however YMMV. Simple rules like > 80% power turn on injection are reasonable.

Water's pretty cheap octane improver. This paper suggests the following formula where w = water and f=fuel flow.

So if you wanted to standard 91 octane rated fuel in an engine which expects 98 you could inject a water to fuel ratio of .42 and have the added bonus of the heads running significantly cooler.  There's also the benefit of the cost savings. 91 is about $1.57, 98 is about $1.73 and avgas is current about $3.08 in Canberra at the moment. 

The main reason to include methanol/ethanol in the mix is as an antifreeze so if you're flying in conditions where icing is a concern it's a good idea.

The key point to remember is that you only need to do this at low altitudes and higher throttle settings, so the water tank can be reasonably small depending upon your flying.

 

In an ideal world it would be good if there was a combination of engine management system and a higher pressure pump connected to an injector to keep the water fuel ration in the right zone. Some car fuel injectors are stainless and can work for this purpose.

 

The main risk is additional water making it's way into the sump. But normal combustion products include water and it should only really be used in takeoff and climb. Cruise and landing temperatures should clear any excess moisture.

But in comparison to the damage and costs that high temperatures and detonation create it's a very manageable risk.

[Old Koreelah]

15 minutes ago, Ian said:

Injection into the inlet plenum works. There are some pretty simple systems out there that just use windscreen wiper pumps…

My second version is based on a $28 windscreen washer kit. It operates only at full throttle, so I only have to top up the 4 litre tank after several take-offs. It sprays directly into the carby mouth. I’ve gradually increased the spray rate in ground testing until it’s getting more water than fuel. Still hasn’t put out the fire!

 

15 minutes ago, Ian said:

The main reason to include methanol/ethanol in the mix is as an antifreeze so if you're flying in conditions where icing is a concern it's a good idea.

After all the efforts to keep ethanol out of my fuel, I’ve been using straight rain water. Because it only operates for a minute or so at full throttle, I doubt icing will be an issue.

15 minutes ago, Ian said:

 

 

[Ian]

Good to see it's being done.

How are you finding head/exhaust temperatures, engine sound etc?

[facthunter]

Water Meth will give you a significant power increase as well as keep engine temps down. Alcohol in the inlet is used for de ice and anti ice mostly on bigger radials combined with hot air from the engine.  Nev

[turboplanner]

What are the dyno test results?

 

[Bruce Tuncks]

Good stuff guys. I agree that it is only for take-off that the extra cooling is required, so the weight of the water should not be a problem.

It was real interesting how NACA once seriously considered using the water in ordinary exhaust gasses ... While a hydrocarbon burning in oxygen must produce water, I had no idea that the weight of water so produced could exceed the weight of fuel burned. Not for us lot tho.....  too heavy and complex for the savings.

[facthunter]

I've only mentioned that about FIVE times. Put the atomic weights in the equation to see that there's more water than hydrocarbon and don't run your engine for short periods and leave it sitting afterwards if you want a reliable engine.  Nev.

[Old Koreelah]

3 hours ago, Ian said:

Good to see it's being done.

How are you finding head/exhaust temperatures, engine sound etc?

Can’t find my notes, but at least 10C reduction of CHTs and EGTs were quite even. There is no indication of when the water injection stops as I back off the power, other than a clear rise in head temps.

 

On climb, there are three ways to keep CHTs under control: open cowl flaps, ease off power...or go full throttle!

[Ian]

8 minutes ago, Old Koreelah said:

On climb, there are three ways to keep CHTs under control: open cowl flaps, ease off power...or go full throttle!

Just thinking, given the cooling and anti-knock effect. Its sounds like a lean efficient climb be achievable? Using fuel for cooling has always seemed a bit extravagant.

 

Also have you looked at the internals of the engine through a borescope, the water is meant to keep everything very clean.

[Old Koreelah]

2 hours ago, Ian said:

…Also have you looked at the internals of the engine through a borescope, the water is meant to keep everything very clean.

That’s the main reason for the water; years of AvGas has deposited lots of stuff, on top of the carbon buildup from running slightly rich. Air-cooled 4 strokes are only a short step up from 2 strokes in relying on over-rich fuel to cool the hot bits.

[facthunter]

AIr cooled 2 strokes are really fuel cooled at times. I used to get really clapped out Chev engines which were full of carbon and get them hot and pour water down the carbs with them running at mid range revs on no load. The engines were mostly cleaned of the carbon in quite a short time, Nev

[Ian]

21 hours ago, facthunter said:

I've only mentioned that about FIVE times. Put the atomic weights in the equation to see that there's more water than hydrocarbon and don't run your engine for short periods and leave it sitting afterwards if you want a reliable engine.  Nev.

Is anyone using active extraction of water from the engine case? Ie an air pump going from the engine case to water absorbing beads to stop corrision?

[facthunter]

The normal way to achieve this is by running the oil temp above 85 c. The water meth is transient and unless you have a lot of blow by I doubt you'd have any issue if it's only on at full power. Motors run a bit cold will cloud the oil. You can see it on the dipstick and you will get corrosion as it will absorb sulphur and other undesirable products of combustion.  It will normally take about 45 minutes of flight to reach equilibrium temperature.  Nev

[Ian]

I was thinking something like this. It removes the residual humidity and lowers the risk of corrosion.

https://www.aviationconsumer.com/maintenance/engine-dehydrators-engine-saver-prevails/

[facthunter]

You could also recondition the oil the same way. Synthetics can operate at over 100 degrees C so any water will quickly be evaporated from the oil. Hotter parts like pistons and crankshafts will help remove water  from the oil also as it circulates but you may get some condensation in the cooler parts.  Hydrocarbons make water when burned. A tired engine (poor piston ring sealing) allows more combustion products to get in the oil. Older engines deteriorate faster than new ones. Nev

[Ian]

On 04/09/2022 at 11:39 AM, Old Koreelah said:

My second version is based on a $28 windscreen washer kit. It operates only at full throttle, so I only have to top up the 4 litre tank after several take-offs. It sprays directly into the carby mouth. I’ve gradually increased the spray rate in ground testing until it’s getting more water than fuel. Still hasn’t put out the fire!

Have you noticed any changes at all in the oil or anything else?

From an installation point of view how would you rate the difficulty out of 10? A couple of photos would be nice if you have the time?

[facthunter]

My experiments with clapped out engines  I've added copious amounts of water and the motor keeps running as long as the throttle is well north  of idle. If you just use it at high power with methanol  at a rate less than the fuel flow you aren't even doubling the amount of water the motor is handling normally. I'd be more concerned about some finding it's way into the carburetter and causing potential problems there inject after the carb but not far. I've flown turboprops with water meth and that increases the power by a considerable margin and keeps turbine temps down as well compared with what would happen if you just increased fuel flow. Nev

[Old Koreelah]

4 hours ago, Ian said:

Have you noticed any changes at all in the oil or anything else?

Nothing adverse noticed; remember the water is only being injected during full power TO and climb, so only a minute or so.

It’s main purpose is to keep head temperatures under control, but hope it will also clean out the carbon.

4 hours ago, Ian said:

From an installation point of view how would you rate the difficulty out of 10? A couple of photos would be nice if you have the time?

Sorry Ian, can’t take pix; I had a fall onto concrete that resulted in a new hip being fitted, so climbing into plane is verboten for another month or two. Can’t drive and SWMBO is already overloaded with all my jobs, so won’t be asking her to take me to airport.

Installation is dead simple: mounted reservoir as low in cockpit as possible (so it doesn’t syphon) and ran fine tube into air filter box, where it mates up with a spray nozzle pinched off my wife’s ironing bottle.

 

Connected pump’s (+) wire to main bus, ran (-) to an alloy strip riveted to side of cockpit, where throttle lever will earth it only on full throttle.

3 hours ago, facthunter said:

…I'd be more concerned about some finding it's way into the carburetter and causing potential problems there inject after the carb but not far.

Agreed Nev. Next version will inject into a hole drilled in the carby-manifold rubber. I also plan to install a variable control on the panel (next to the CHT gauge) so I can much about with the mixture, plus a few other features.

[pluessy]

If you add the water after the carburetor or throttle, keep in mind that the high vacuum at low idle will suck the water up from about 5m below. You might need a solenoid or use a peristaltic pump (cheap off eBay). Proper water/methanol injectors have a minimum pressure valve as part of the injector body that only opens when the supply pressure exceeds a certain limit.

Methanol is added for a number of reasons already mentioned (anti-freeze, power) but also to prevent algae growth in the bottle and lines. Especially important if any lines or the reservoir are open to light.

[Old Koreelah]

12 minutes ago, pluessy said:

If you add the water after the carburetor or throttle, keep in mind that the high vacuum at low idle will suck the water up from about 5m below.

That doesn’t seem to happen with my setup; I guess the fine spray nozzle in front of the carby mouth doesn’t see enough pressure drop for it to require a shut-off valve.

[lee-wave]

The emissions of  petrol driven internal combustion produces about 15% of H20.   If the engine oil does not reach optimum temperature the oil emusifies in the oil and can cause internal corrosion surprisingly quickly.  Modern multigrade engine oils with additives can minimise the effects.   But I follow the general rule of an oil and filter change every 20 hours or 6 month whichever comes sooner..  

Also if I know the aircraft is not going to fly for a while I run the carburettor dry turn the prop over a dozen or so times and then park it.   before the next flight I would turn the prop over a dozen times or so, fuel cock open ,fuel pump 10 seconds, full choke, throttle completely closed. The motor fires up instantly....every time...

[facthunter]

Your % is wrong. Take the equation for combustion and use the atomic weighs for each ingredient and you'll find there's more H2O mass than Fuel Mass.  Your ADDED water meth will be less than the water made and if it's only injected at full throttle and the rings seal as they should you should have no real issues much above the normal. Oil can go  cloudy without water being injected if the engine OIL runs too cold. Nev

[Ian]

The key problem is that the airspace in the crankcase is moist regardless of whether you use water injection. Yes it may result in the exhaust stream being going through the block and existing via the breather beingslightly more humid however there is a significant amount of water either way. Steam passing over hot components won't condense so condensation occurs for a short period after starting and once the engine turns off and the crankcase cools. Condensate in the oil will evaporate after extended runs and exit via the breather. 

This is why systems which actively ventilate the crankcase with dry air after parking should reduce internal corrosion for planes which are kept sitting for extended periods.