Landracing Forum
Tech Information => Water/Methanol Injection => Topic started by: Blue on June 28, 2008, 09:39:25 PM
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OK, I appreciate that there is a lot of history behind water injection making power and keeping motors from blowing up at high power densities.
That said, what the water really does is cool the incoming charge, retard the burn rate in the combustion chamber to reduce pre-ignition, and provide an additional quantity of working gas for the engine to expand and produce pressure. In any installation and technique listed here, we need to separate these three effects.
I could go into a long explanation of the physics and my own experience with large bore engines, but it would be better to have you guys talk about your own experience within these three categories.
Specifically, cooling the intake charge without affecting anything else has advantages and effects equivalent to running on a cooler day. Retarding burn rate to reduce pre-ignition (as opposed to detonation) is a separate effect that requires a higher amount of water. Reducing pre-ignition through TBC's, smoothing sharp edges, or other chamber effects has to be compared to water injection without the penalties of injection. Last, the best use of water is to absorb excess heat where we know we simply have too much heat in the combustion chamber and need to stuff some more inert mass in there (beyond the nitrogen in the atmosphere) to absorb it and push the piston down instead of melting it.
All of this has to be understood independent of the addition of methanol (a fuel) and all of its issues.
LSR has lots of good information, and lots of mythology on water injection. To understand when and how much water to inject, we have to separate all these effects and turn the mythology into fact.
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OK, I appreciate that there is a lot of history behind water injection making power and keeping motors from blowing up at high power densities.
That said, what the water really does is cool the incoming charge, retard the burn rate in the combustion chamber to reduce pre-ignition, and provide an additional quantity of working gas for the engine to expand and produce pressure. In any installation and technique listed here, we need to separate these three effects.
I could go into a long explanation of the physics and my own experience with large bore engines, but it would be better to have you guys talk about your own experience within these three categories.
Specifically, cooling the intake charge without affecting anything else has advantages and effects equivalent to running on a cooler day. Retarding burn rate to reduce pre-ignition (as opposed to detonation) is a separate effect that requires a higher amount of water. Reducing pre-ignition through TBC's, smoothing sharp edges, or other chamber effects has to be compared to water injection without the penalties of injection. Last, the best use of water is to absorb excess heat where we know we simply have too much heat in the combustion chamber and need to stuff some more inert mass in there (beyond the nitrogen in the atmosphere) to absorb it and push the piston down instead of melting it.
All of this has to be understood independent of the addition of methanol (a fuel) and all of its issues.
LSR has lots of good information, and lots of mythology on water injection. To understand when and how much water to inject, we have to separate all these effects and turn the mythology into fact.
Eric,
I and many others find your knowledge and information sharing to be among the best, I find that often when I cannot understand what a person posts the first time I read it is due to one 1 of 3 reasons.
1. Words and meanings are often misspelled so badly that you cannot take the writer seriously.
2. The writer used big words/nomenclature to try to "impress" the readers with their command of the English language.
3. The writer is a very knowledgeable person and is willing to assist/dumb it down to a level that is more understandable to the masses and I thank you for that as I do not desire spending time to look up meanings/terminology to decipher what the writer is trying to convey.
Thank you again,
John
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Noonan, I'm definitley for "dumbing it down".
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Noonan, I'm definitley for "dumbing it down".
Amen. :-D
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Blue & Others
We have used water injection in the 222 car for years. As i have posted for before [ and am sure you know] if it was't for water injection in ww2 aero engines, we would be speaking German. From information in my aero books i learned they were injecting about 40% water-methanol to the fuel rate. I have since read up to 100% in some cases. We used 20% because their water is 5o%methanol. Janes aircraft books 0n ww2 engines has specs.on most engines, one spec is were they picked up 8% hp with water injection alone. Water injection or anti detonation injection [adi] allowed them to increase boost pressures and make more power.Most racers don't know the history of these great engines if they picked up one these books they would be impressed and humbled.
I have a graph that shows how Ricardo picked up brake mean effective power by increasing water injection and boost from the maximum of 237 bmep at the riches setting max power level, to 290 bmep which was the limit of the dyno.
Hope to have bvillrcr take a photo and post it here.
JL222
PS Ricardo also was able to lean the engine back to less than the fuel rate at full rich and maximum cylinder pressures fell and the gross heat flow to the water system fell to the same level at 170 bmep without water injection.
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Gee...this is an old one, but interesting never the less.
So let me see if i understand:
Water injection has 3 ways to help
1 cooling the charge to the cylinder - making it denser therefore allowing better filling of the combustion chamber.
2 retarding the burn rate - which seems to be the same as increasing the octane rating of the fuel.
3 absorb excess heat - ?
I understand number 1. As water is vaporized it absorbs heat in order to change from liquid to gas (swamp cooler effect) . this cools the charge making it denser.
Can anyone explain 2 and 3.
What is the mechanism that is slowing the burn rate?
3 seems to be suggesting that by replacing some of the combustion charge in the cylinder with inert gas the heat will be reduced. But won't power be reduced as well? (this is what an EGR valve dose)
The reason I ask is I am planing my assault with my 1980 Chevy monza, which at the moment runs a B&M 144 roots type blower on a small block 350ci engine. It is a street car and uses pump gas @ 6lbs of boost. I am going to convert it to a race only car and want to up the boost to the max possible (of course).
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Fheckro...seems like #1 is acomplishing #2. As far as reducing flame speed I'm not 100% sure but I've read that the higher
the temp the faster the reaction [ this was not about engines ] but it seems it would apply.
Ricardo tested the results of water injection and steam seperatly and there were benefits to both.
We just installed a new water injection system on the 222 car [Alcohol Injection Systems] and while talking to the owner [salesman] he mentioned a turbo car that was streching the valves at Bville, same problem we were having and hope to solve from water injection + get all the other benefits
Their also installing a system on a pro-modified nitros car to slow down the flame speed.
Water injection would be a good way to cool the intake on your roots blower. My charts show 189 deg. at 6lbs at 45% efficiency, 153 deg at 65% ...286 deg and 220 deg at 12 lbs these temps are on a 70 deg day.
JL222
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I've asked in another thread if water injection is helpful for a normally aspirated engine, but got no response. Anybody care to chime in, and if so, what would be a target ratio of air/fuel : water?
I've read where water injection can cost power because the cylinder volume has less air/fuel mixture.
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JL,
"My charts show 189 deg. at 6lbs at 45% efficiency, 153 deg at 65% ...286 deg and 220 deg at 12 lbs these temps are on a 70 deg day."
Can I get a copy of those charts?
I have no idea what max boost will be but I'm thinking it would be somewhere around 20.
Thanks
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If you use Gulf Coast water, you will probably be too rich.
Will
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JL,
"My charts show 189 deg. at 6lbs at 45% efficiency, 153 deg at 65% ...286 deg and 220 deg at 12 lbs these temps are on a 70 deg day."
Can I get a copy of those charts?
Thanks
This might help you.
Tom G.
http://www.stealth316.com/2-adiabat1.htm
http://www.stealth316.com/2-turbotemp.htm
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JL,
"My charts show 189 deg. at 6lbs at 45% efficiency, 153 deg at 65% ...286 deg and 220 deg at 12 lbs these temps are on a 70 deg day."
Can I get a copy of those charts?
I have no idea what max boost will be but I'm thinking it would be somewhere around 20.
Thanks
Sent personal message. Looks like your a little new to this so look for [my messages] that's you in the blue bar were
[ home is], to sent a message to me, click on the pm icon above ignore on my post, or reply through pm.
20lbs is 394 deg at 45% efficiency 294 deg at 65% and 264 deg at 75% and all the numbers are figured at 14.7 atm.
JL222
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got it , thanks
Tom,
"Compressors usually operate in the 55-75% efficiency range" <----in context with paragraph about turbo chargers.
do you know what the efficiency range of roots style blowers is?
Fred
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Fred,
Don't take this to the bank, but as I recall standard GMC type 6-71 blowers are very efficient at low blower speeds. It is when you start to speed them up to make more boost, say over 15 lbs. their efficiency starts to rapidly drop, and they start creating lots of heat.
It has been years since I stayed up to date on GMC style superchargers. Nowadays you can get Hi Helix rotors installed in them, different configuration openings in the case, both top and bottom, etc. I am sure the latest super trick Roots style blower is much more efficient, than the old style GMC takeoffs.
If someone else has better information feel free to jump in and correct me.
Tom G.
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I think some/most of the inefficiency of a low helix roots blowers is the air rushing in as the lobes separate at the top and rushig out as the lobes mesh at the bottom . Roots and screw blowers work on the same principle . High helix is a compromise between low helix inefficiency and screw blowers size and need for high rpm .
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I've asked in another thread if water injection is helpful for a normally aspirated engine, but got no response. Anybody care to chime in, and if so, what would be a target ratio of air/fuel : water?
Definitely helpful if you're trying to run a high(er) compression motor on a fuel with a lower anti-knock index (pump gas for instance). Typical water:fuel ratio for n/a applications is 10-15%.
I've read where water injection can cost power because the cylinder volume has less air/fuel mixture.
If this were really true I probably wouldn't have a job. :-D
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I've asked in another thread if water injection is helpful for a normally aspirated engine, but got no response. Anybody care to chime in, and if so, what would be a target ratio of air/fuel : water?
I've read where water injection can cost power because the cylinder volume has less air/fuel mixture.
I've got to learn how to take fotos and post, my chemistry book [ typical effect of temperature on gas volume at 1 atmosphere] two of the 5 examples
300 deg kelvin =-----570 ml volume
V2=VI X T2 DIVIDED T1
610 deg kelvin ==== 1180 ml volume
This shows that as air is heated [supercharged in our case] the volume increases but its just expanded air with no extra oxygen molecules and when it is cooled it shrinks, again no extra molecules but it is denser. the shrunk air from cooling [water injection--intercooler--alcohol] allows more air and molecules to be packed into the same space.
This is why roots style blowers [they heat air more than turbos or centrifugals] are so much better when ran on alcohol than gas.
JL222
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This is a subject that has many twists and turns.
The usual rule of thumb for NA engines is to start at water injection rates of about 10%-20% of fuel flow. As mentioned above, ADI used in WWII aircraft like the Pratt and Whitney R2800 engine used about 50% of fuel flow, with a mixture of 50% methanol and 50% water, and in extreme cold conditions they also had a mixture of ethanol, methanol and water, if I recall correctly it was about 60% alcohol by volume.
http://www.enginehistory.org/Frank%20WalkerWeb1.pdf
Water vapor actually assists in the combustion process, as it facilitates conversion of carbon monoxide to CO2. In lab tests you can take a mixture of dry carbon monoxide gas and oxygen and it is nearly impossible to ignite, but add just a bit of water vapor and it ignites easily. This is one of the pathways that water injection uses to help make more power.
It cools the fuel air mixture by evaporation and due to the high specific heat of water (how much energy it takes to raise a water droplet one degree compared to a similar weight of gasoline). It also takes considerably more energy to evaporate the water droplet, to gas (steam) than it does to evaporate the gasoline droplet.
This means that during the compression stroke the fuel air mixture does not heat up as much due to compression, so the work that used to be spent fighting rising pressure due to heat in the cylinder is spent evaporating the water alcohol mist. This gains engine power by reducing compression losses.
The water does slightly retard the effective ignition due to its cooling effect but in many engines that moves the time of peak cylinder pressure slightly later in the combustion stroke closer to its ideal 12-14 degrees after top dead center for maximum power recovery. Also during the burn phase the water gives back the energy that was invested to evaporate it. It lowers peak cylinder pressure (cooling effect during compression and higher heat capacity), but the steam generated during combustion stretches out the pressure peak so although the peak cylinder pressure is slightly lower the total effective pressure goes up because the pressure does not fall as fast as the piston descends down the cylinder due to waters high specific heat (it has to expand more to cool off the same amount as a normal fuel air charge).
The slightly lower peak cylinder temperature, lowers heat stress, and heat losses to the cooling system, and helps keep valves alive at power levels that would melt them without the water injection.
The evaporative cooling as the fuel air water mist enters the cylinder also increase volumetric efficiency of the engine as the fuel air charge heats up less as it passes the hot head of the intake valve, and cools off hot spots like spark plug electrodes and any other possible sources of pre-ignition.
All these effects allow you to produce more useful work out of the same or even more fuel than you could burn before without killing the engine due to high heat loads.
Larry
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Hotrod...that reference article about Frank Walker and his work on water injection is one of the best I've ever read.
It's a must read for anyone interested in water injection and clears up alot of myths.
150 in [60 lbs boost] and 3800 hp wow!! Also testing for 100 hrs at full military power :-o
Hey guys if somebody says water injection doesn't make any power, just say how much you wana bet :-D
JL222
P.S. Wish I knew all about the hydraulic drive for the superchargers on that E model.
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Yes and that is on an engine that started out rated at 2000 hp, which gives good field validation to test results by NACA that water injection was capable of increasing MEP and power up to 160-180% of gasoline only power on supercharged aircraft engines of the day.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930093187_1993093187.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930091074_1993091074.pdf
The primary limit to engine power for most internal combustion spark ignition engines is knock limits imposed by fuel octane and heat limits posed by combustion temperatures. If you don't melt it you break it due to detonation. Water injection attacks both of those problems at the same time, by internal cooling and raising the effective fuel octane very substantially. That is where most of the power gain is. By increasing the effective fuel octane you can stuff more fuel and air into the engine than is physically possible on gasoline only.
Larry
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For anyone worried about water/meth affecting engine durability, I ran a Snow Performance kit on a TRD Supercharged Tacoma 3.4L V6 for 140,000 miles. It still ran great when I traded it for my Dodge Ram. In the North in the winter, WalMart sells -30F windshield washer fluid. I would stock up on it, because it worked great and was cheap. I ran an overdrive pulley and the 4x4 Extra Cab truck would run mid 14's, though the suspension was not up to handle the power. I also have installed water meth on a turbocharged Sisu 8.4 L diesel in a working 38' Lobster Boat. This is one of the Northern Bay 38's that I build. It draws 4 feet of water, weighs 18,000 lbs and is 13' 8" beam. With the stock 410 hp diesel we were able to get 35 mph. By adding water meth and some careful tuning we got 41.5 mph and were able to beat smaller boats with 750 hp diesels. I'd say if you are running a boosted motor, water meth is your friend. If the economy was better, I'd trade my hemi Ram in on a Cummins and talk to Matt Snow about a water meth kit.
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You can still read this - just page down to the bit of rudeness posted by some troll.
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Roots blowers accept the charge radial to the rotor OD, separate it into two streams, which are conveyed in the concave (female) lobe spaces around the inner wall of the case on both sides, to discharge 180° away. The convex/concave inter-lobe volume is not a factor, but only permits both sealing the rotors to prevent backflow, and prevents interference. All compression (if any) is induced by resistance in the manifold.
Screw blowers (Opcon AB, Sprintex, Autorotor) appear similar, but the principle and flow path are very different. The intake is axial (not radial) to the rotors, with the charge volume contained entirely between the male and female rotors (which is zero at tangency in a Roots). As the charge is passed lengthwise down the case by the helix angle (like Archimede's screw pump), the inter-lobe volume shrinks causing internal compression. Finally, at the "blind" end the lobes rotate apart and expose the charge to the exhaust port.
Spambot?
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Panic has been on this forum for along time.
Tom G.
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A spambot always has a live link to another website in the signature area.
Pete
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my experience is the water injection only works in lower boost application..... now if your talking aircraft stuff yeah it would probably work in higher boost especially at altitude where their is no oxygen ... i feel it is a band aid... if your using it to slow burn race then your head squish and piston dome isn't right... if your using it to keep valves from stretching get a bigger stem size or a different supplier.... if your using it to fix a problem then fix the problem right... W I can have too many variables.... man up for the expensive stitches not the band aid.... let me add this, so yer only gonna get so much stuff past an intake port... so if you displace some of that air fuel area with 2 parts hydrogen than that's good right? humm.... don't you 4 stroke guys wanna run in the 12 to 13 AF range? I mean fuel and oxygen makes the heat and heat is power so.... yeah yeah we can beat this dead horse around for a while..... black/white, Ford/Chevy, Yankees and Raiders still suck..... tonic water with my Gin please!
Kent
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"expose the charge to the exhaust port" -- the exhaust port?
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Stan,
My advice to you is to ignore the subject of exhaust ports - as we know your problem is on your INTAKE side.
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"expose the charge to the exhaust port" -- the exhaust port?
Blower Stan Blower. LOL.
Tom G.
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if you were to inject water into the ex port or ex pipe on a turbo setup, the instant steam would spool up the turbo quickly and possibly out of the boost operating range
kent
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Spambot?
It's those clever rejoinders that make these visits such fun. The fastest reaction is entirely composed of:
1. ignorance
2. personal ad hominem attack
That was so helpful, and contributes a great deal to the discussion.
sabat: please, remind me - exactly where did I copy this from, and to whom should it be attributed?
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my experience is the water injection only works in lower boost application..... now if your talking aircraft stuff yeah it would probably work in higher boost especially at altitude where their is no oxygen ... i feel it is a band aid... if your using it to slow burn race then your head squish and piston dome isn't right... if your using it to keep valves from stretching get a bigger stem size or a different supplier.... if your using it to fix a problem then fix the problem right... W I can have too many variables.... man up for the expensive stitches not the band aid.... let me add this, so yer only gonna get so much stuff past an intake port... so if you displace some of that air fuel area with 2 parts hydrogen than that's good right? humm.... don't you 4 stroke guys wanna run in the 12 to 13 AF range? I mean fuel and oxygen makes the heat and heat is power so.... yeah yeah we can beat this dead horse around for a while..... black/white, Ford/Chevy, Yankees and Raiders still suck..... tonic water with my Gin please!
Kent
kent... read reply #16 and maybe you'll understand how to get more through an intake port. If increasing hp from 2000 to 3800
doesn't convince ya that water injection works... nothing will, and those test were done on earth at 60 psi boost.
Low pressure only, how about 175 psig and 3 gal min. [ Turbochargers by Hugh Machinnes pg 118] 3 stage turbos and no room for intercoolers.
The 222 engine would melt at 12...13 air fuel so a big NO.
JL222
P.S. better make that a double
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my experience is the water injection only works in lower boost application..... now if your talking aircraft stuff yeah it would probably work in higher boost especially at altitude where their is no oxygen ... i feel it is a band aid... if your using it to slow burn race then your head squish and piston dome isn't right... if your using it to keep valves from stretching get a bigger stem size or a different supplier.... if your using it to fix a problem then fix the problem right... W I can have too many variables.... man up for the expensive stitches not the band aid.... let me add this, so yer only gonna get so much stuff past an intake port... so if you displace some of that air fuel area with 2 parts hydrogen than that's good right? humm.... don't you 4 stroke guys wanna run in the 12 to 13 AF range? I mean fuel and oxygen makes the heat and heat is power so.... yeah yeah we can beat this dead horse around for a while..... black/white, Ford/Chevy, Yankees and Raiders still suck..... tonic water with my Gin please!
Kent
kent... read reply #16 and maybe you'll understand how to get more through an intake port. If increasing hp from 2000 to 3800
doesn't convince ya that water injection works... nothing will, and those test were done on earth at 60 psi boost.
Low pressure only, how about 175 psig and 3 gal min. [ Turbochargers by Hugh Machinnes pg 118] 3 stage turbos and no room for intercoolers.
The 222 engine would melt at 12...13 air fuel so a big NO.
JL222
P.S. better make that a double
Really? How rich do you run that car and on what type of fuel(unless you don't want that publically known) ?
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Fast-Evo... A8C ..118 octane AF :-D What AF you run?
JL222
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I run in the high 11's to low 12's.
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I'm going to try it on a blown Caddy flathead, with about 12lbs boost. I don;t have room for an intercooler, so this intrigues me. I'd be happy To provide with/without dyno results. I realize this is not on the same level as a lot of you guys, but they should be good, realistic, unbiased results.
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I'm going to try it on a blown Caddy flathead, with about 12lbs boost. I don;t have room for an intercooler, so this intrigues me. I'd be happy To provide with/without dyno results. I realize this is not on the same level as a lot of you guys, but they should be good, realistic, unbiased results.
I've observed that roots blown engines [ on gas] with no intercooler or water injection don't go any faster than the unblown guys.
JL222 :cheers:
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Yep, I've noticed the same thing! Sometimes not as fast.
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I don't remember where the thread about alcohol in gasoline - and the potential need for removing said alky - is located. If one of you would be so kind as to freshen my memory - I'll post the response that Rick Gold (ERC) sent along. He discusses it in good detail and I'd like for all to be able to read it.
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4 barrel Mike can find it. He finds everything.
DW
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4 barrel Mike can find it. He finds everything.
DW
Gee, thanks (I think :roll: )
While on a very short coffee break, only finding slim pickings. The most appropos is this ECTA forum thread (?) which I did NOT take time to read thoroughly: http://www.landracing.com/forum/index.php/topic,6531.0.html (http://www.landracing.com/forum/index.php/topic,6531.0.html)
Mike