pre-charger water injection

[Brutus]

When using water injection it is advised to inject ~15% water. For pre-charger water injection it is recommend keeping the water/fuel ratio on 25~30%. Why? Does some of the water pour out of my air intake? I suppose not. Well then, is some mist coming out of my intake? Never noticed. So where does it go? Isn?t it all sucked into the engine with the airflow :?:

[Slump]

It is, but some of the water will be "used up" (well, from a heat absorbtion standpoint) in the cooling of the blower and charge immediately after discharge. You still want some liquid water to make it into the combustion chamber. That's why you inject extra water.

This does have the effect of displacing oxygen, though, with all that extra water vapour.

[Brutus]

No, it can?t be used up. A little warmed up, yes. But I?ve been told that chilling the intake charge is just a side effect of water injection. The main cooling comes from the latent heat, when the water evaporates in the combusting chamber. That?s clear if you consider that the specific heat is 4.18 KJ/kg/K against the 2256KJ/kg latent heat.
What?s not exactly clear to me is why you inject proportional so much more water pre-charged.
And, at what point becomes oxygen displacement an issue?

[Slump]

My point was that the hot blower is going to turn some portion of that water into steam. The blower (at least my Eaton) is well over 100*C after driving for a while, and the output temps of the blower are in the 200*C range.

Further, it has to travel further before it gets to the combustion chamber.

So, to ensure that you still have some liquid water, you need to inject more water then you would if you were injecting post blower.

The point of injecting pre-blower (at least for me) is to help cool the blower and prevent heat soak in the blower.

[Brutus]

Wow 200*C! Didn?t know the M45 gets that hot. :shock:
BTW. You are using a 67.5 pulley & FM link, right? Okay, now I understand what you mean.
Fuel cut is probally at ~7500RPM. Underdrive alternator pulley is 145mm (not sure about that). So 145/67.5x7500=16100RPM. Nice setup. 11psi? I guess you get a deltaT about 110*C according the Eaton info.
Sure it will be pretty hot. Hope you don?t mind I took the liberty to make some small calculations. But please tell me. Will the temp. rise above the 100*C with just the 72.5 pulley and a 6950 fuel cut? What do you think? Thanks.

[perry190]

I've been running WI for about 6 months now with no major problems (that Richard couldnt sort out :wink: ) but have recently started fitting a charge cooler kit

as below (not my car)



As you can see, I'm a bit restricted as to where to now put my jet. The piping is quite thin aluminium and so not best suited to a bend location.

space and 'flat' wise the easiest loaction would be pre-IC, also the last bend after the IC is almost on top of the plenum etc so a little worrying (and I'd have to drain the charge cooler etc and remove the heat exchanger to drill it)

dont really want to 'suck it and see' as I'll end up with a hole in my pipe if the chosen point is no godd.

what the suggestions of the knowledgable ones on here? Richard?

thanks in anticipation
Perry