water injection pre turbo

[Forcefed6]

Little bit of a thread dig here...

Justin.... What sort of setup do you use, like High pressure pump, type of water jet you use, and maybe the size of it. Also, what type of mixture do you suggest would be good for a pre-throttle injection?

Do you have any results from running the water injection, and not running it... Like from from 1 dyno ramp to the next?

I am considering fitting a setup, and just trying to find what people have actually found themselves before I am fully sold on the idea.

[abently]

Even the best nozzle can get a partial block and the day it does is the day it water jets your compressor wheel...hardly worth the risk when a post turbo setup is so easy these days.

Why not put a 45 degree bend on the intake piping to the Turbo Intake ?

[abently]

Pre-turbo WI: Compression in a turbo is usually adiabatic. This means that the air is heated as it is

compressed, which takes power from the shaft and requires removing through an intercooler. If you inject

water before the turbo, then you can move compression to near isothermal, so very little heat is added, and

less power is taken from the turbine to compress the air for the same boost level. You can loose the

intercooler and therefore suffer less pressure drop between compressor and inlet. All of which gives you the possibility to get more power out the same turbo.

Water has a very high latent heat of vapourisation, but once you have reached the saturation pressure in air, then you gain no more cooling at that point. However Dalton's law comes to the rescue at this point and if you bung in some other miscible fluids, say methanol and acetone, then each has its own saturation pressure, and you get an accumulative cooling effect. A little petrol would do the job if you added a second injector for it.

Bill

This is why pre-turbo WI is superior to post Turbo injection.

[twentyEight]

Why not put a 45 degree bend on the intake piping to the Turbo Intake ?

That would be just as bad as when the nozzle jets like Justen suggested the water would hit the wall of the bend and build up as a coating which would be a more solid form than the spray to begin with...

[Hen]

Pre-turbo WI: Compression in a turbo is usually adiabatic. This means that the air is heated as it is compressed, which takes power from the shaft and requires removing through an intercooler. If you inject water before the turbo, then you can move compression to near isothermal, so very little heat is added, and less power is taken from the turbine to compress the air for the same boost level.

Bill

I partly agree and partly disagree with the above. Yes, compression is usually adiabatic, and adding water can change this to basically isothermal.

This ISN'T because less heat is added though. The same amount of heat is added to the air and water mixture, it's just that hopefully all this heat is used to evaporate the water. As mentioned, water has a huge latent heat, so it takes stacks of energy to change it from liquid to vapour.

So basically you get a cooler charge, but you're still taking the same energy out of the turbine to compress to the same boost level.

Hen

EDIT - I have to admit I didn't wade more than a few paragraphs into that quote though.

[thechuckster]

fwiw: when my pre-carbi water injection system used to kick in there was a noticeable slowing of engine acceleration, followed by a stronger surge than before the injection kicked in.

personally i prefer the newer and smaller turbo with its much reduced lag (even tho i'm no longer getting as much boost) as it eliminated my reliance on the water injection for charge cooling.

I also wondered about the effect that a denser charge of air+fuel+water (instead of air+fuel only) hitting the compressor blades would have on acceleration of the turbine as the engine and turbine accelerate into regions of higher boost, e.g. there must be more energy required to push the blades thru the denser air-charge and compress it so thus there would be a (slight?) reduction in compression efficiency?


re: thick water droplets - my water sprayed thru the carbi so the throttle and variable venturi tended to eliminate large droplets - but the compressor blades were quite clean & polished compared to one from a EFI engine.

[JustenGT8]

Water injection is good no question.....no way i would be running 20-22psi on a 10:1 comp engine without it

Pre turbo injection may have some advantages to post turbo but nothing presented that demonstrates it and certainly nothing that quantifies it...just theory and anecdotals. Whereas the damage pre turbo injection can do is well proven.

Just a matter of making your choice and living with the consequences.

[abently]

.....no way i would be running 20-22psi on a 10:1 comp engine without it

Sorry but I have to disagree with that over generalisation. Too little information....especially static CR with no cam timing details not to mention boost with no Turbo details either...

Pre-Turbo WI is known to move the surge line to the right of the Compressor Map depending on droplet size.... but Pre-turbo compressor Wheel damage is history and anybody still damaging their comp wheels from it is just being cheap and nasty.

There are nozzle systems out there able to produce droplets as small as 10 microns, we are talking about droplets smaller then fog itself, droplets smaller then what OEM Air paper filters filter out, get a grip of yourselves people and grow some nads.

QED

[JustenGT8]

WTF, pull your head in mate...i said no way "I" would be running that boost on my comp....and if you cared to check my engine is stock internals so no big cams etc etc.

As for the rest i don't disagree but still no back to back REAL world data presented to quantify the advantage. Also, the risk of a blocked nozzle is very high in my experience and the fancier the nozzle the higher the risk....as i said previously, the day it produces less than optimum spray is the day it water jets your compressor wheel goodbye. With post turbo you may have reduced performance and that's about it.

[big_zop]

...as i said previously, the day it produces less than optimum spray is the day it water jets your compressor wheel goodbye. With post turbo you may have reduced performance and that's about it.

And say hello to detonation too if youre relying on the water injection and it fails - pre or post turbo wont save you there.

On another note, have you got some way to monitor the water injection performance to protect your engine incase it fails - or just a knock sensor and ignition retard from there? Also, how does it work as i dont think you would have the need when not on boost or the capacity to hold enough water to run constantly and where is it injected?

[JustenGT8]

You can run a line pressure sensor to check for a blocked filter but i don't.

Many ways to control WI but mine is a realtively simple boost/rpm referenced signal from the ECU. I have sized my jets to deliver peak flow at peak torque and as demonstrated it' works well. As for tank size a 5 litre tank would be more than sufficient for 95% of applications....off road long distance racing is about the only thing i could think you would want a bigger tank for.

[merc-blue]

Justen,
Do you have details on your setup in a thread?if not im requesting you do,
Im very tempted to run water injection (post turbs) in my 4AGTE build,

Im struggling to find any real info on seting it up PROPERLY. just alot BS.

I want to run 4 injectors but agains truggling to find proper injectors as opposed to a sprayer that constantly sprays when there is line pressure and its controlled on/off bassed on TPS
Not a closed loop system that when things start tolook ugly it keeps sprayig water air fuel and boosting and getting uglyer

[vinno]

just a thought about the pre turbo water injection..

heated water under presser readily vapourises (obviously), and so if a pressurised system is already being used then if it was heated it would be more likely to atomise..

obviously this is kind of contradictory as the whole idea is to cool the system but surely there must be a compromise considerring the main problem is the lack of atomisation..

not really sure wat i'm talking about just thought i would throw it out there..

cheers
vinno.

[JustenGT8]

Justen,
Do you have details on your setup in a thread?if not im requesting you do,
Im very tempted to run water injection (post turbs) in my 4AGTE build,

Im struggling to find any real info on seting it up PROPERLY. just alot BS.

I want to run 4 injectors but agains truggling to find proper injectors as opposed to a sprayer that constantly sprays when there is line pressure and its controlled on/off bassed on TPS
Not a closed loop system that when things start tolook ugly it keeps sprayig water air fuel and boosting and getting uglyer

PM sent (10 char)