Water injection

General engine tech -- Drag Racing to Circle Track

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tresi
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Water injection

Post by tresi » Wed Jun 13, 2018 3:33 pm

An old trick that has met with success and failure. I'm told the main problem with some of the cheesy kits of the 70's and 80's is they don't inject near enough water. I'm hearing it takes about 10% of the fuel volume, is that by volume or weight? Is this the same ratio for water/methanol? Is this 10% figure way off?

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Re: Water injection

Post by F-BIRD'88 » Wed Jun 13, 2018 4:10 pm

Water/methanol 50-50 (Can be) UP TO about 30% of the total fuel volume at WOT. It replaces the (excess) fuel normally used to cool the combustion chamber, while also cooling the intake charge air and being very "high octane" supresses detonation.
You use as much as you need. Remember methanol is a (high octane) fuel, soo...

remember also the water displaces air fuel (volumetric efficientcy) and too much cooling drenches the fire.
And it does not "burn".. but methanol does.

ya the lil 70's era water injection kits are too dinky and have poor metering and spray injection quality.
i forget if it is by volume or by weight.
I am going to say by weight (mass)

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Re: Water injection

Post by F-BIRD'88 » Wed Jun 13, 2018 4:15 pm

Very effective for roots supercharging on pump gas.
The lil B&M blowers (and anything non intercooled) really love water/methanol injection.
X2 if the motor has a high compression ratio too.

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Re: Water injection

Post by grandsport51 » Wed Jun 13, 2018 4:47 pm

Well you can study the NACA studies here http://naca.central.cranfield.ac.uk. Also look
At this reference which is more modern https://shopeurocompulsion.net/blogs/te ... r-injecton
Either way you are correct you have to inject
A lot more water than we used to in the 70s

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Re: Water injection

Post by F-BIRD'88 » Wed Jun 13, 2018 5:27 pm

A very good article..
One point specific to roots suprcharging on a car.
A car is not a airplane, so....
Supercharger heat soak.....
Aby body who has messed with a lil B&M blower on the street
Will tell you about the performance effect of super charger heat soak. The first pass is fine but as you make each successive drag pass, the blower case heats up.
All that hot air from the hot supercharger DECREASES charge density and invites detonation.
Not on the NACA tests that the air inlet temp is held stable at 158F... You cannot do this on the street in the real world.
But with water methanol injection which deos cool the charge air and COOLS the blower too, You eliminate/control blower hot soak and get much better average NET charge air temps
You get much better overall performance and reliability with the water injection, especially if you want to make lots of power by driving the blower faster to make more power on pump gas on the street ( and while drag racing).
A airplane does not have this problem at 30,000 feet and 300+ MPH.
Water methanol injection is very effective at controlling/eliminating the problem of roots blower heat soak.

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Re: Water injection

Post by joe 90 » Wed Jun 13, 2018 5:50 pm

Methanol belongs in the fuel tank.

It's only purpose when mixed with the water is to stop it from freezing.
Ethanol is better at that job and it's not toxic.

The 50/50 water methanol thing, it's fairytale stuff, made up by the marketing people.

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Re: Water injection

Post by F-BIRD'88 » Wed Jun 13, 2018 5:56 pm

near 100 YEARS of real world use says different.
50-50 water methanol is better than just water alone.

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Re: Water injection

Post by Truckedup » Wed Jun 13, 2018 5:58 pm

F-BIRD'88 wrote:
Wed Jun 13, 2018 5:27 pm
A very good article..
One point specific to roots suprcharging on a car.
A car is not a airplane, so....
Supercharger heat soak.....
Aby body who has messed with a lil B&M blower on the street
Will tell you about the performance effect of super charger heat soak. The first pass is fine but as you make each successive drag pass, the blower case heats up.
All that hot air from the hot supercharger DECREASES charge density and invites detonation.
Not on the NACA tests that the air inlet temp is held stable at 158F... You cannot do this on the street in the real world.
But with water methanol injection which deos cool the charge air and COOLS the blower too, You eliminate/control blower hot soak and get much better average NET charge air temps
You get much better overall performance and reliability with the water injection, especially if you want to make lots of power by driving the blower faster to make more power on pump gas on the street ( and while drag racing).
A airplane does not have this problem at 30,000 feet and 300+ MPH.
Water methanol injection is very effective at controlling/eliminating the problem of roots blower heat soak.
Yes, airplanes are different none used Rootes superchargers :D I have a lot of engineering articles written by Allison as they developed the 1710 V12 aircraft engine...Some dual stage supercharged engines were running 90 inches of boost, about 35 psi..Allison found straight water suppressed detonation as well as mixed 50 % with alcohol..
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Re: Water injection

Post by F-BIRD'88 » Wed Jun 13, 2018 6:01 pm

This is why there is SO MUCH mis information.
A car is not a airplane.
And in the allison tests on that specific engine
the water may have supresed detonation as well as water + methanol BUT is is not as POWERFULL.
Water DOES not burn and displaces AIR fuel which make the motor less volumetric efficient.
When you have a HUGE CID aircraft motor is not that important.

If you want to go fast with a non intercooled roots blower
on pump gas use 50-50 water methanol injection.
yes it goes in a tank. It is also very safe at a 50-50 mix.

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Re: Water injection

Post by tresi » Wed Jun 13, 2018 6:07 pm

Interesting but limited to boosted applications. Surely water injection can benefit N/A applications as well

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Re: Water injection

Post by F-BIRD'88 » Wed Jun 13, 2018 6:14 pm

re water injection and N/A applications:

It is much harder to control metering because the amount of water needed changes on the fly depending on conditions.
With a supercharger there is ALWAYS a lot of EXCESS heat that needs to be absorbed by the vapourization of the water.
When you run out of available HEAT, vapourization STOPS.
Liquied fuel will not burn. (poor combustion)

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Re: Water injection

Post by joe 90 » Wed Jun 13, 2018 6:22 pm

F-BIRD'88 wrote:
Wed Jun 13, 2018 5:56 pm
near 100 YEARS of real world use says different.
50-50 water methanol is better than just water alone.
You haven't read the links?

Report no 756?

http://www.riceracing.com.au/resources/ ... ection.pdf
From the 1940s. They had to cut the testing a bit short due to the dyno, it couldn't handle the extra power.

http://digitalcommons.mtu.edu/cgi/viewc ... ntext=etdr

If you read that the answer is just the same, they should have used a smaller engine with less power to start with.



As I said, the 50/50 thing(there's never any mention of total volume to fuel) is for the ricers......You always get what you pay for and water is free so it's no good.Methanol , you need to buy so it's better?

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Re: Water injection

Post by F-BIRD'88 » Wed Jun 13, 2018 6:26 pm

water is not free. especially distilled water.
More crap. use 50-50 water methanol injection.
You will go faster farther for less net cost.

Us normal consumers have a cost effrctive good choice for "boost fluid". it is the basic winter formula windshield washer fluid.
usually Blue. The stuff that DOES NOT have any detergent or glycol in it. It is about 30-35% methanol mixed with distilled water. You can then bump it up to 50-50 by adding a bit of methanol to it. if you need to.
you can buy spoiled methanol ( that has absorbed a bit of water) cheap too.

Shake the bottle. If it is blue winter formula and it does not foam when shaked it has no detergent. and likely no glycol either in it. Do not use the summer stuff.

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Re: Water injection

Post by Truckedup » Wed Jun 13, 2018 6:36 pm

F-BIRD'88 wrote:
Wed Jun 13, 2018 6:14 pm
re water injection and N/A applications:

It is much harder to control metering because the amount of water needed changes on the fly depending on conditions.
With a supercharger there is ALWAYS a lot of EXCESS heat that needs to be absorbed by the vapourization of the water.
When you run out of available HEAT, vapourization STOPS.
Liquied fuel will not burn. (poor combustion)
I was simply offering additional information based on actual engines on the dyno and in service... In the case of the aircraft engines, the water was only injected above a certain manifold pressure...At any rate, do publish your information from water/alcohol on your engines... I did use a modern system on a modified N/A GMC 302 inline 6 about 10 years ago...I had to use about 10 percent compared to fuel flow to limit detonation..I tried both water and water methanol and noticed no difference...Of course this was a high compression vintage engine making about .75 HP per cubic inch and not a more powerful supercharged engine..
Last edited by Truckedup on Wed Jun 13, 2018 6:38 pm, edited 1 time in total.
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Re: Water injection

Post by joe 90 » Wed Jun 13, 2018 6:37 pm

Well you obviously haven't read the links because it'll take you hours or days.

In my part of the world water is FREE.
It's also clean so you don't need distilled water.
BUT
If I want to use distilled water it's also free.
That's because in my part of the world it's legal to make your own moonshine for your own consumption which many people do including myself.
So when the still isn't distilling alcohol (heads and tails used in the water tank) it can distill water.

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