Water/meth injection on a high compression engine

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xstfudonniex
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Water/meth injection on a high compression engine

Post by xstfudonniex »

It seems to make sense, build an 11:1 or 12:1 and use water/meth to reduce detonation and make it driveable on pump gas, but i cant seem to find much info on it.
Is there a reason this is unpopular?
pros and cons?
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Post by rustbucket79 »

Definately not worth the hassle unless it's a 5% street/95% race deal where it will run race gas, but even then not worth the hassle over running straight race gas.

An engine built to run on a specific octane that you plan to use will be a much happier camper/non tempermental combo than a hopped up (compression) that you're trying to run on insufficient octane with a bandage. (water injection)

Translation, it isn't easy to find the information you're looking for because it isn't worth the effort over just building the correct compression ratio engine in the first place. :wink:
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Re: Water/meth injection on a high compression engine

Post by GuysMonteSS »

xstfudonniex wrote:It seems to make sense, build an 11:1 or 12:1 and use water/meth to reduce detonation and make it driveable on pump gas, but i cant seem to find much info on it.
Is there a reason this is unpopular?
pros and cons?
Theoretically,and all things being perfect,using a water/meth injection system should be an ideal way to go for a performance application,even in a mostly street driven car,but you dont seem to hear of anyone doing this.
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Post by F-BIRD'88 »

With the development of affordable digitial electronic water flow control systems this is becoming more and more viable and popular as an alternative to high octane gasoline for high compression ratio N/A motors.
There are quite a few companies popping up wiht systems for N/A applications.

Wether it is the right thing for you to do, depends....

Will not make the same exact power as high octane fuel or Alcohol in a high compression motor but it does get close.

You couldn't have google searched very hard. The concept as a whole that pertains to supercharged applications is all relevant to a high compression N/A application.

The only down side is you have to fill the water injection reservoir and service the spray nozzle tip and inline filter, once in a while.

Many people use common "Winter formula" Windshield washer fluid as a convenient water injection "boost fluid". The stuff that does not contain much or any detergent is best. Typically blue and labled as winter formula. Shake it, if it foams up a lot, its not the right stuff.
Its mostly Methanol and distilled water. You can spike it with more Methanol to bring it up to optimum 50-50 mix.

if you don't mind mixing your own and filling the bottle and a bit of preventative routine maintance to avoid trouble, it can work well for you.

If you're going drag racing, its probabily not worth it so much. Just install a secondary fuel system with under hood fuel cell and pump to run race gas in while racing.
Then back the spark timing off for street duty on pump gas.
But for road racing or street driving it is a viable way to skin the cat.

Can also be very effective in controlling combustion speed and excess heat in Nitrous oxide applications. Dame, gave away another speed secret. [-(
Last edited by F-BIRD'88 on Wed Dec 17, 2008 8:41 am, edited 1 time in total.
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Post by illfish »

Most of the time people use it as a crutch for an improperly designed engine for their application. An 11:1 small block with efficient aluminum heads can run on pump gas without injection. 12:1 is pushing it but can be done without it. There is a company that is used by alot of the Mustang guys. Saw it in Pro 5.0 or Muscle Mustangs. Mostly used in blown applications to keep the heat down and prevent pre ignition. Might want to check your build sheet if you need it.
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Post by Brad »

The is some good technical info on www.aquamist.co.uk about water injection.
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Post by cablebandit »

i have a 10.4:1 c/r 408 ls1 running 7-12psi

on the street it runs 93 pump + meth injection at 7 psi boost
on the track i run race gas + meth injection.

meth with pump gas is for octane
meth with race gas is for the intake air temp reduction
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Post by Ron C. »

Actually it's pretty popular if your in the right circles.
http://www.alcoholinjectionsystems.com/
These guys seem to know what there doing.
I run a system that I designed myself....it works when you get it right.

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Post by Unkl Ian »

http://www.landracing.com/forum/index.p ... board=26.0

Definitely more popular in certain circles.
Please help make Speedtalk a Troll free zone.
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Post by FastFourierTransportation »

Even more popular in old piston-engine aircraft. ;)

These two graphs show the change in the "ideal" air/fuel ratio for knock suppression. As you can see, the hotter the intake charge, the richer the mixture wants to be.

The red line is fuel only. The blue is fuel + water. The green is fuel + 70/30 meth/water.

Notice how fuel + water is the only combination which does not lose a LOT of knock-resistance at higher temperatures in the stoichiometric range. Also notice how sensitive the meth/water mixture is to heat! It's a perfect graphical example of why methanol has a high RON, but not a high MON, and why the difference between those numbers is called "sensitivity". You can see the sensitivity of the gasoline as well, which is appropriately less than methanol/water.

150 degree intake temperatures:
Image

250 degree intake temperatures:
Image

------

I hope these graphs give someone else the same insight they gave me into why different air/fuel ratios, and water vs. methanol preferences, worked for some engines and not for others. Also, it shows why some tuners are understandably skeptical of water/meth injection, and especially skeptical of just water.

The real benefit of straight water is not the huge increase in outright power potential, as there's only about a 10-15% increase in peak knock threshold even with a lot of water injected: the benefit of just water is in the 20-50% increase in detonation threshold around 13-14:1 air/fuel ratio.

Think of it this way: water is a gas saver ... it will allow you to make about as much, or more, power at 13-14:1 than you'd normally be able to make at 10-12:1.

On naturally aspirated engines, the higher compression acts more like the "high temp" graph here due to the increase in adiabatic compression. Since many N/A engines do not run nearly as rich as their turbo/supercharged counterparts, a little water should go a long way.

Another good application for just water is when you turbocharge/supercharge an engine, but can't deliver enough fuel for 11-12:1 air/fuel ratio. Water injection would allow you to make just as much power without as much fuel.

Fun stuff!

-Adrian
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Practical Engineering is finding new and better ways to copy other people's designs.
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Post by Guest »

This is off topic and on the money. How about adding a few more syllables to the word meth? It wont make you any faster but it will help your tune up and delivery! METHANOL.
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Post by FastFourierTransportation »

Guest wrote:This is off topic and on the money. How about adding a few more syllables to the word meth? It wont make you any faster but it will help your tune up and delivery! METHANOL.
Last time I checked, I used the word "methanol" twice in that post (see below), and if you're going to be critical of me using an abbreviation, can you at least SPELL correctly?! :roll: The word "won't" has an apostrophe; it is a contraction.
It's a perfect graphical example of why methanol has a high RON, but not a high MON, and why the difference between those numbers is called "sensitivity". You can see the sensitivity of the gasoline as well, which is appropriately less than methanol/water.
I hope you don't go around pointing out whenever someone says "TNT" instead of TriNitroToluene, or how about when someone buys "gas" instead of "gasoline"? "Nitro" instead of "nitromethane"? "Nitrous" instead of "Nitrous Oxide"? :lol:

This won't make you any faster, but it will help your tune up and delivery: next time you want to be a smartass, don't forget the smart part. :wink:

-Adrian
A theory without experiment is like a painter without sight, but an experiment with no theory is just a 4 year old with paint.

Practical Engineering is finding new and better ways to copy other people's designs.
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Post by Tuner »

It’s the PC police. They’re here to help us. No abbreviations allowed with a potentially offensive alternative definition. If someone wants to be a crank, you can’t say that anymore. That’s going to be a tough one in this crowd. When the agents of change sweep the internet to find where crank and meth are being used this joint will be one of the first to receive a visit from the ebony helicopters.

Good lick on morphing the old NACA graphics and providing some insight. I’ve had people I thought were smart until they told me, “that stuff’s too old, it’s obsolete, there’s better ways now,” and this one really got me, “they used Avgas for those tests, it doesn’t apply to my engine because I use racing fuel.” What good does it do to give a kid a book if all he does with it is eat the pages?
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Post by FastFourierTransportation »

Tuner wrote:Good lick on morphing the old NACA graphics and providing some insight. I’ve had people I thought were smart until they told me, “that stuff’s too old, it’s obsolete, there’s better ways now,” and this one really got me, “they used Avgas for those tests, it doesn’t apply to my engine because I use racing fuel.” What good does it do to give a kid a book if all he does with it is eat the pages?
That's what I love about the scientific research NACA did: it was real science. If the data collection methods are sound, scientific data never becomes obsolete. The conclusions based on that data may change as more data is collected, but the data will always be good. :-k

The other thing is that time alone never makes a scientific experiment obsolete. New information can change how you interpret the data. But, if there is no relevant new information, the age of the experiment is completely irrelevant. :mrgreen:

Just as long as the PC police don't try to confiscate all our rods. :-S
A theory without experiment is like a painter without sight, but an experiment with no theory is just a 4 year old with paint.

Practical Engineering is finding new and better ways to copy other people's designs.
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Water Injection

Post by 73c34me »

Apreciate this topic. I have a brand new old stock Edelbrock Vari Injection system that I have been interested in trying. Anyone have info on this old unit. Seems to be well thought out, but the pump is quite small compared to current offerings.
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