Post combustion water injection???
12-21-2007, 09:02 PM
#1
Post combustion water injection???
So I was thinking about this, and was thinking if you where to inject water right before the turbo as a form of anti lag. I was watching my EGT's the other day and just sitting idling they where around 600* which is more then enough to instantly turn water into steam. The extreme amount of expansion should really boost exhaust volume and help spin up the turbo quickly. I think this could really help guys with big turbos or manuals if it was set for a quick shot when you first stab the throttle. Any thoughts??
12-21-2007, 09:13 PM
#2
It could do something. It would have to make the air dinser, or thicker. Should drive the turbo better. Actually I was thinking of that for this high altitude lag/ boost loss. Even though the water it's selfe may not increase power, it should produce more boost, and supress det.
12-21-2007, 11:17 PM
#5
The whole idea of it, is to not make more power or reduce detonation, it would solely be to reduce lag and make it build boost faster. Maybe I'll have to throw something together one of these days. I think I have enough stuff laying around. I don't really need it with my setup, but could help people running bigger, more laggy turbos. IDK, just a thought I had.
12-21-2007, 11:40 PM
#6
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The only problem I see is the increased pressure in the exhaust is going to come closer to equalizing the pressure in the cylinder on the exhaust stroke. You may loose some power to pumping losses. It may make up for the lost power as the boost builds faster and you can phase the water out. Good idea, have you heard of anyone trying it before?
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12-22-2007, 05:41 AM
#9
Concerning OP...
I'm not so sure you'd see the results you would be expecting. I'd have to do some research to confirm this but the expansion ratio of water into steam is around 1,500 it's original volume which I don't think is close to the expansion characteristics of fuel. You would need to inject quite alot of water-mist (comparatively) to see enough expansion to help with the lag. But if you were to inject x amount of water into the exhaust you would also inadvertently be cooling your exhaust gases which would increase it's density but reduce it's volume and therefore losing pressure which will effect flow across the turbine negatively.
They claim heat is a turbo's best friend because of the expanding nature of hot gases, and cooling that exhaust would be counter productive. In order to find out if it would be viable you would have to research how much heat loss you would incur compared to how much pressure you would gain by the expanding steam and see which one counter balances the other better. If I remembered a fraction of the equations I learned in school I might be able to help more.
On a side note/precaution...
From working on steam engines...A sure fire way to destroy any turbine is to hit it with regular un-superheated steam. You will kill the life of a turbine instantly in some cases. You would need to create superheated steam which is steam that is heated to a temperature higher than the boiling point corresponding to its pressure. Meaning it cannot exist in contact with water, nor contain water, and it resembles a perfect gas. If the steam is not superheated it will contain small H20 molecules. Once that un-superheated steam hits the turbine blades it can pit them and in most cases shatter the turbines themselves. You gotta realize those blades travel anywhere between 60,000rpm - 120,000rpm and a water molecule hitting something at that speed will almost certainly obliterate it. Granted at idle your turbo is spinning nowhere near that but it would still have a negative effect on the surface of the turbine blades.
I would have to look through my old engineering notes to find the formula but, the temperature at which steam becomes superheated is dependent on two things, Heat and Pressure. The higher the pressure the less heat is needed, and inversely the lower the pressure the more heat is needed. You'd have to figure out what the pressure is inside the hot pipes at idle as well as the temperature and figure out if that is enough to instantly superheat steam.
Just a few things for you to think about
Last edited by Spoolin; 12-22-2007 at 03:28 PM.
12-22-2007, 09:28 AM
#10
You would need to inject quite alot of water-mist (comparatively) to see enough expansion to help with the lag. But if you were to inject x amount of water into the exhaust you would also inadvertently be cooling your exhaust gases which would increase it's density but reduce it's volume and therefore losing pressure which will effect flow across the turbine negatively.They claim heat is a turbo's best friend because of the expanding nature of hot gases, and cooling that exhaust would be counter productive. In order to find out if it would be viable you would have to research how much heat loss you would incur compared to how much pressure you would gain by the expanding steam and see which one counter balances the other better. If I remembered a fraction of the equations I learned in school I might be able to help more.
