Water Injection

[TBill36]

Has anyone experimented with water injection. Everything I've read indicates it's beneficial to combustion, improves fuel economy, and most importantly lowers EGT. I would think it would be relatively simple to install something for cruise only RPMs. I'm in South FL and see 800 F for long periods of time at cruise in the summer. I've posted this questions several times over the years on boatdiesel with no response.

 

[Ski in NC]

Post a link to some of the literature that describes the benefits. New one on me.

 

[READY]

I would expect if it had merits and no downside either the trucking industry or the engine manufacturers would adopt it. I think it might be snake oil.

 

[O C Diver]

I remember this from back in the 70s when many cars were struggling with ultra lean carburetors to raise exhaust gas temperatures for the catalytic converter. Seem to remember a kit that misted water in the carburetor above a certain RPM.

Don't remember any of it being used on a diesel.

Ted

 

[High Wire]

Doubt anyone on here would risk their propulsion engine on such experiments. Way, way, way, too expensive.

 

[rslifkin]

Water injection does work for some purposes. But it's rarely seen outside of a last-ditch performance effort. Below that level, you can usually do other things to gain most of the benefit without the complexity of water injection, inconvenience of keeping the system filled, etc. I remember there being at least one potential downside to it as well, but I'm blank on what it was.

 

[denverd0n]

If water injection was really a good idea, why would we go to so much effort to REMOVE water from our fuel!?!

 

[rslifkin]

If water injection was really a good idea, why would we go to so much effort to REMOVE water from our fuel!?!

Water misted into the intake under heavy load is different from liquid water being fed through injection pumps, injectors, etc. And also, water in fuel can easily feed in mostly water at idle causing an engine to run badly or not at all.

 

[High Wire]

Is Race Trawler an oxymoron?

 

[OldDan1943]

IM feeble opinion, it is a pipe dream.
At one time, there was a brief movement to wean a gasoline engine off of gas to water. Obviously that didn't work.
Just because it works in the lab with the engine on a dynamometer does not mean it will work in the real world.
I would recommend you avoid this and avoid picking up a hot horseshoe too.

 

[Shrew]

To me there is a difference between manufacturing based on legitimate R&D and DIY modification based on a scientific paper. There is no gurantee that the engines we have were designed to handle the theory we're discussing.

They've shown combustion engines modified to run on used cooking oil, but that doesn't mean you can pack your Corvette full of bacon grease and run around town.

 

[Portage_Bay]

The concept and limited application has been around since at least WWII. If it were effective in general use it would be widespread, but it isn't, so it's not.

Here's a Wikipedia article on water injection.
https://en.m.wikipedia.org/wiki/Water_injection_(engine)

And the part relevant to diesel engines
"A 2016 study combined water injection with exhaust gas recirculation. Water was injected into the exhaust manifold of a diesel engine and, by opening the exhaust valve during the induction stroke, the injected water and some of the exhaust gas was drawn back into the cylinder. The effect was to reduce NOx emissions by up to 85% but at the cost of increased soot emissions.[14]"

 

[KnotYet]

Water injection is normally used in a modified engine to keep temperature below the
threshold of damage. It is commonly mixed with methanol to enhance the effect.
Most users will inject it only during high load conditions as it isn't needed otherwise.

I wouldn't consider water injection desirable if your EGT is only 800 degrees F.
That's not that high as long as it is within the engine mfgr's operating range.
The guys using water injection are seeing much higher temps albeit for a shorter time.

 

[Xsbank]

Water injection (water/methanol) was commonly used on large piston aircraft engines during takeoff. The addition of water made a huge increase in horsepower output as it lowered egt and made for a very dense fuel charge. The system was cranky though and some operators removed the system, resulting in much lower payloads and much longer take-off runs.

In a similar goal, the WOT setting on an aircraft engine was entirely to dump huge amounts of raw fuel into the cylinders to prevent premature ignition. A movement to use reduced throttle/power on takeoff on piston engine aircraft that were not fully loaded could result in detonation and much reduced engine life, the opposite effect desired.

Definitely not needed on a trawler engine. For no other reason that your typical trawler owner is frightened of WOT.

 

[Shrew]

The concept and limited application has been around since at least WWII. If it were effective in general use it would be widespread, but it isn't, so it's not.

You've reminded of the gasifiers for cars in Europe during WWII as well.

 

[DDW]

I have installed and used water injection on turbocharged gas engines. It was the only way to keep them together. We tied it to boost pressure, would come on above a certain manifold pressure. It lowers peak combustion temperature and would inhibit (actually completely eliminate) carbon buildup on the piston hand head.

A friend of mine did some research on it using the research engine at a major university. A research engine is an instrumented super tough, variable compression ratio, variable boost pressure engine. He added water injection to it and got it to produce the highest BMEP the professors had ever seen from the engine.

Whether is it worth the trouble (honestly is isn't that much trouble) just to lower EGT that is already under limits is debatable. You would be able to measure the effect, but probably not the benefit. The EGT might drop from 800 to 700, but until you've done 5 rebuilds each way, how do you know you've accomplished anything?

 

[Ski in NC]

Water injection in a boosted gasser and on a boosted diesel do very different things. Need to be clear about what type engine is being discussed to keep the conversation clear.

 

[Comodave]

I would not risk a $20K+ engine on it. If it was a good idea the manufacturers would be doing it.

 

[DDW]

Water injection in a boosted gasser and on a boosted diesel do very different things. Need to be clear about what type engine is being discussed to keep the conversation clear.

Actually I thought the effect was similar. But have no experience with diesel.

 

[TBill36]

Thanks for the replies. What got me thinking about this was from about 15 years ago where Tony Athens (very respected on boatdiesel back then) had a technique to wash your aftercooler by injecting a dawn-water mixture followed by water at WOT. The concept basically steam cleans your aftercooler. I started reading about what the hot rod truck diesel guys were doing with the methanol water injection. Water being used to keep the increased heat from the methanol to cool the egt and supposedly improve combustion. So in my mind a mild water injection would be a good thing as most high output diesel engines are killed by heat. Not necessarily in the trawler world, but more in the sportfish or motor yacht world where there is more demand on turbo-aftercooled diesels where the aftercoolers get clogged up and lead to higher EGT. Water injection would not only help keep the aftercooler cleaner, but keep egt lower. I was just curious to see if anyone had looked into it or experimented with it.

 

[Ski in NC]

Actually I thought the effect was similar. But have no experience with diesel.

Water injection on a boosted gasser is to reduce detonation, a very real problem (WW2 aero engines). Detonation is a non-issue on a diesel. Yep, it could reduce EGT, but 800F is fine on most engines.

As far a keeping aftercoolers clean, they should be kept clean the old fashioned way. As in, clean them. Once clean, air filter should keep dirt from building up. Oil mist just goes through.

Spray water up stream of turbo and it will be instantly vaporized by the heat of compression while at power. What your are really doing then is reducing O2 content of the charge air. And once cooled in aftercooler, there is condensation there all the time getting blown in with charge air, so there is already water injection.

Different world with the hot rod crowd, like tractor pulls. They are getting like 1500-plus hp out of block meant for 300, they have to do all sorts things to keep chunks from flying out.

 

[DDW]

My understanding is it reduces detonation in gassers by lowering peak temperatures, and slowing the speed of combustion. Beyond allowing increased manifold pressure it allows advanced spark timing which raised BMEP. Detonation isn't an issue in diesels, but injection timing certainly is, advancing it is the most often used tuning change - until the engine blows. Slowing the burn rate delays the engine blowing. I know that the auto and diesel cycles are thermodynamically different, but the mechanical problems of containing the explosions without failure are somewhat similar.

Without any water injection, there is no more water in the manifold that was there in the ambient air to begin with. But yes, any water vapor is displacing air and therefore oxygen, also water vapor is less dense than air so it displaces more than its share.

Methanol injection is a whole different thing.

 

[FF]

"Water injection (water/methanol) was commonly used on large piston aircraft engines during takeoff. The addition of water made a huge increase in horsepower output as it lowered egt and made for a very dense fuel charge. The system was cranky though and some operators removed the system, resulting in much lower payloads and much longer take-off runs. "

Actually the water injection did not ADD power , it ALLOWED higher power settings with out pre ignition or detonation.
THe alcohol did add some power , but it was mainly to keep the water tank from freezing at altitude.

I was power plant officer for 3350 engines with Uncle Sam

Actually water injection is a very good technique to get rid of carbon deposits on gas engines.

Simply find an old "Flit" hand pumped insect sprayer and with the engine warm from a run ,spray water down the intake as you open the throttle .

About 2000 RPM the engine will stumble , after 5 min , if you have left a sheet of newspaper under the tail pipe you will see chunks of carbon removed from the combustion chamber.

Works well, with no harm to the engine.

 

[markbarendt]

Has anyone experimented with water injection. Everything I've read indicates it's beneficial to combustion, improves fuel economy, and most importantly lowers EGT. I would think it would be relatively simple to install something for cruise only RPMs. I'm in South FL and see 800 F for long periods of time at cruise in the summer. I've posted this questions several times over the years on boatdiesel with no response.

Water injection is an old idea.

There are two general reasons people consider it.

1- To 'de-carbon' the combustion chamber of an old/worn engine.

This requires very little precision. Essentially just pour it (water or maybe ATF) into the carburetor/air intake of a fully loaded running engine at a rate that does not stall the engine.

This is an act of desperation and borders on the practice of witchcraft.

2- To cool/change the mass of the air going into the engine.

As I understand the history, in WW2 piston engine aircraft were able to make a tiny bit more power when flying through rainy conditions.

This requires a high precision delivery system to avoid problems.

This is rooted in real physics and practical experience, but, I'd bet a nickel that you won't be able to measure the difference on your boat.

An easier way to get this done is to pipe your engine intake air from the outside through an insulated duct. If it 80 outside and 100 to 120 in the engine room that is a significant change that really can change things.

 

[Lepke]

I originally trained on radial aircraft engines a long time ago. Water injection increases the compression ratio because water doesn't compress much. It was used to temporally increase hp in an emergency. It's very hard on the engine. WWII radial engines went 100-400 hours between overhaul. That meant new cylinders/head, piston and rings.

Using water injection in a diesel would put some water in the oil just like soot. Using it continuously would put a lot of water in the oil. Engine components aren't designed for resistance to water let alone emulsified oil.

 

[alormaria]

I originally trained on radial aircraft engines a long time ago. Water injection increases the compression ratio because water doesn't compress much. It was used to temporally increase hp in an emergency. It's very hard on the engine. WWII radial engines went 100-400 hours between overhaul. That meant new cylinders/head, piston and rings.

Yes, my father used to work on P-47s that had water injection for emergency use only. If the throttle had been shoved far enough forward to engage water injection, the engine had to be torn down.

 

[Greg S]

Any of you trawlers old enough to remember Popular Mechanics magazines? Back through the 1950's in the adverts there were carburetors and add-ons that you could buy to inject water into your car engine.
Guy I knew, dead of old age decades ago, claims to have designed some of these. We laughed at him but he insisted it worked. ALL of these dissappeared from the magazines. Can you say conspiracy theory? There were claims that the auto manufacturers or oil companies made them dissappear.

 

[markbarendt]

Any of you trawlers old enough to remember Popular Mechanics magazines? Back through the 1950's in the adverts there were carburetors and add-ons that you could buy to inject water into your car engine.
Guy I knew, dead of old age decades ago, claims to have designed some of these. We laughed at him but he insisted it worked. ALL of these dissappeared from the magazines. Can you say conspiracy theory? There were claims that the auto manufacturers or oil companies made them dissappear.

They were still being made and sold in the '70s. My Dad's business was in auto parts and we actually sold them.

Fighting detonation was one of the selling points, staying tuned longer too.

That was back in the days of points and condensers and tune ups every 3000 miles were the norm. Whether it was 'snake oil' or not, lots of people were looking for ways to stretch the time between tune ups.

Alas electronic ignition, fuel injection, and computers solved those big issues.

 

[FF]

"Alas electronic ignition, fuel injection, and computers solved those big issues."

Also solved by higher octane being made available at the local gas pump.

Aircraft gasoline (Purple) was 115/145 octane but still could use the added power from water for a short field take off.

In the 1960's the 3350 could do 1,000 hours , 1500 hours got a commendation for the plane captain 2,000 hrs rared a party .
*****


Some diesels have a setup that uses Ether as an alternate fuel to help start at very low temperatures. I have often thought the system could be used at shutdown to shoot preserving oil (fogging oil) into the cylinders.

Yes, most diesels will still sort of run on this fluid , but they stop quickly when the spray stops .

Many folks think engine preservation is not needed as they will be using the boat "next week", but some next weeks are a month or more apart.

 

[stroutmail]

There is merit, but probably not an aftermarket add on

Water injection has been used since before WWII in high performance gasoline engines. My Father was a Plane Captain Mechanic and many military planes used water injection to achieve higher HP.

It has also been studied for use in diesel engines to reduce emissions and NOx

https://dieselnet.com/tech/engine_water.php

It has many risks if the water is injected incorrectly, so probably not an aftermarket item.