Academic Question - Alcohol/Water Injection

S

Soldmy66

Famous Member
I would like opinions, academic only since I have no intention of doing this in the near term, of using alcohol/water (or windshield washer fluid) injection that would trigger only occur at conditions under which full load was being placed on the engine - as a means of controlling detonation -- thus running a higher effetive compression ratio than might otherwise be tolerated on pump gas. This would occur only at (or immediately prior to) the point of detonation.

Extra points - in a fuel injected application - could a 2nd set of injectors be used with alcohol/water for this purpose?

Again - this is just spitballing intended just to have some fun - so lets keep attacks to a minimum, please.
 
Ok, you could NOT use the petrol injectors for the job, corrosion and lack of internal lube (although petrol has limited lubricating property) would soon cause a failure, a better system is to inject a fine mist pushed through a small orifice at high pressure. There are such systems used for boosted application, and in the case of a positive displacement blower, the mist helps with sealing as well as cooling. IMO I would only use this with boosted applications, and not alcohol, only clean water. No NA engine should detonate ever, if it does something is wrong, fueling, heat, too much compression, etc. Another alternative is No2 injection into the airstream in limited amounts to reduce intake temps, but this has its own problems. The LPG injection system, as used in our ecoLPi falcons injected the LPG as a liquid, this has a strong cooling effect due to the change in state of the LPG, this allowed the engines to make more power than its petrol brothers. Riccardo did some research on this many years ago for the WW2 effort. read High speed internal combustion engines by him if your interested.
 
What i have picked up from the show engine masters is straight alcohol is better for cooling and combustion. This may also allow more timing. Otherwise if there is pinging its either its running too lean, timing is too far advance or both.
 
InlineDave87 said:
What i have picked up from the show engine masters is straight alcohol is better for cooling and combustion. This may also allow more timing. Otherwise if there is pinging its either its running too lean, timing is too far advance or both.
Click to expand...
Ive been ocassionaly watching engine masters, IMO they have dumbed it down for the masses. The main issue I have is that their dyno tests are always done, A without any accesories, B no air filter, C no silencing, D only a WOT, E they start at about 3500rpm, most street engines are operated at partial throttle most of the time. The tests are so short that that no issues are likely to appear. I know its an "entertainment" but really a bit more detail would be nice. A discussion of engine operating would be nice. And they never seem to go anywhere other than USA based donks. As to alcohol as a for cooling, of course its better, its a hydrocarbon, with a high latent heat, its going to be a fantastic internal coolant, and its an oxygenated fuel, theres an OH on the end of its chemical formula, that makes a big difference. If you can find one, Ricardo's books is very informative, even though it was written many years ago.
 
aussie7mains said:
The LPG injection system, as used in our ecoLPi falcons injected the LPG as a liquid, this has a strong cooling effect due to the change in state of the LPG, this allowed the engines to make more power than its petrol brothers.
Click to expand...
I'm off point yet say I understood lpg had less 'oomph' (embodied energy) than gasoline. Anyway,
seems you got the answer, 66?
More I'd say B4 stopping, timing can B set for optimal performance (no injection needed) and even advanced/retarded during engine running w/modern tech, totally avoiding chance of minor detonation.
Some use water spray thru carb/throttle body to 'decarbonize' combustion chambers ("clean"). Good to see you again~
 
LPG does indeed have a lower heating value than petrol, this is why you use more of it to get equivilant torque, in the case of the ECO LPI system in the Falcon, the cooling effiecency makes up for the torque loss usually associated with LPG vapour systems. IT does NOT make up for the lower HHV, which usually results in about a15% increase in consumption, I get 21-23 litres/100km in my rig. Water has been used as a decarbonisation method for years, but in modern engines its uneccessary. The modern diesels with cooled EGR can have problems of carbon on the intake side. To totaly get rid of knock you can use knock sensors and controlled timing, but this is very sofisicated software to get this to work, not for amatuers.
 
"...sensors and controlled timing, but this is very sofisicated software to get this to work,..."
yup'n today's mechanics wrk w/this'n VVT, the rest of it, daily.

Looks like ur there "66"? Get what ya need?
 
chad said:
"...sensors and controlled timing, but this is very sofisicated software to get this to work,..."
yup'n today's mechanics wrk w/this'n VVT, the rest of it, daily.

Looks like ur there "66"? Get what ya need?
Click to expand...
They work with the sensors etc, but I can tell you the software involved to make it work IS very sofisticated. (spelling?) When I worked for Westport on the CNG engines we had a couple of engineers writing software to do this, they were using a crankshaft chopper wheel to try and detect when the engine knocked, it took them about a year to get it to work, and even then its wasn't foolproof. The sensors mounted on the blocks might be easier, but i doubt it. VVT would be easier to work with. Keep in mind most of the trades people only skim the surface of the ECU programme, the nitty gritty is down deep and much more complex. Ive played around with a Wolf 3D system about 15 years ago, they had written the software, this made it fairly easy to manipulate the injector on times and ignition timing through a hand held pad, or on the PC. It took me a while to get things running OK, but I was only tuning by the "seat of the pants" I had no dyno other than the road. Westport took about 1 week to map all the operating charts for one CNG engine on an engine dyno, even then the final tuning was done on the road.
 
"...I worked for Westport on the CNG engines we had a couple of engineers writing software to do this..."
Very cool, what yrs was that?
Thnx~
(BTW: the dash bd computer on our 8 sec car allows U to play w/all of this).
 
chad said:
"...I worked for Westport on the CNG engines we had a couple of engineers writing software to do this..."
Very cool, what yrs was that?
Thnx~
(BTW: the dash bd computer on our 8 sec car allows U to play w/all of this).
Click to expand...
I started with an Australian company called AEC in 2004, it went down the pan in 2011 and was bought up by Westport at that time. I stayed with them till 2014 then I retired. Around 2018 they closed up the Australian factory. Theyre still going in Vancouver Canada. We had developed our own CNG injection system for spark ignited conversions of bus and truck engines. We had our own injectors and ECU for this. They re fiddling about with Hydrogen now.
 
"...fiddling about with Hydrogen now...."
Ka Boom !
? Universe's most plentiful element ?
 
Soldmy66 said:
Extra points - in a fuel injected application - could a 2nd set of injectors be used with alcohol/water for this purpose?
Click to expand...
Yes, and an optimal method, but the entire WI system must be resistant to corrosion, of course. All 2001+ US trucks for example, have been required to use injectors to allow high % alcohol fuels without corrosion, and so they can work well for WI or WMI. Likewise for pumps or regulators etc. I have three Ford/Denso XL5E 200cc/min injectors firing upstream in my turbo 5L project for the water content, vaporization (plus anti-puddling and even distribution), and charge cooling. They were tested for almost 3 months separately immersed in water-only, and blends of ethanol and methanol with zero issues.

As WI has been around going on 100 years, there is a ton of info and experience out there. There are many options for control today, depending on the scheme of use, timing, and percentages required, which can have substantial advantages over fixed-volume misting systems. I am currently preparing to test ratio-metric WI, which applies a % relative to the fuel being injected, and one of several control schemes available in inexpensive aftermarket EFI and WI controllers. A huge benefit to WI is that the engine is not de-tuned to avoid detonation, and full efficiency timing can be applied. A huge detriment is the hassle of maintaining liquid in the tank.

If you are after academia, I would suggest some aspirin and pulling the original NACA study reports for water injection. Attached is only one of the later reports to get a taste. Extensive and deep stuff with lots of implications. Spoiler alert - methanol in water was simply to prevent freezing in the originally-envisioned high-altitude supercharged aircraft cold environment. That said, and separate from how water alters the combustion process far beyond delay of cylinder pressure or cooling as many assume (exhaust temperature is hotter with WI); alcohols can provide additional octane and cooling in the intake. So, additives have different effects and purposes. Depending on your reasons and requirements, water-only, added ethanol, methanol, or others can provide specific advantages for specific issues or benefits. Have fun!
 

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Thanks for that! Just read the whole thing. Other than having to invert the fuel/air ratios into what I'm used to- really interesting. Incredible how much later in the downstroke the peak cylinder pressure occurred! Wow that's a big torque boost on the same fuel. Impressive.
 
"...specific advantages for specific issues or benefits..."
sounds ike what the boss did w/his puterized dash &
starlette drag car to get to eight five, six. 8 injectors
right @ the cylenders, 3 or 4 placed thru out the intake
and 'after turbo' air stream.
 
One thing I took note of in the publication: there was no economy or power benefit of water injection except at very high loads. So much for street use, it's not worth it for normal driving.
 
True, and WI does not fix anything that isn't crippled or excessive. However, there is economy or power benefit if there is a hurdle to overcome, or an advantage made for it. Random examples are poor fuel grade (low octane) where full torque can be restored for better power or economy; engine mods to increase cruise compression (cam timing or pistons, etc); charge stuffing such as EGR to raise cruise compression and heat, and so on. It's not magic; it's a tool.
 
FWIW and complelely unrelated to my original post -- My Dad flew a B-26 in WWII. The B-26 used a pair of Pratt & Whitney R-2800 twin-row, 18-cylinder, air-cooled radial aircraft engines, each with a displacement of 2,800 cu in. Each engine incorporated a single-stage centrifical supercharger and Pratt & Whitney added water-methanol injection for takeoff and to give emergency power in combat. The water-methanol injection was referred to as "Anti-Detonant Injection" (ADI) system.
 
my dad wuz on em too (over China) from India. No
what that means? They hada use this very system
to get over the Himalayas (1 is 29,000 ft) in non-presser-
ized craft. (Open air vehicles) 8^ 0
(pre-jets. Today they get to 6 or 7 mi hi w/in 10 min off runway)
 
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