Boost rise pre-blower water injection

[Darknight]

Our team runs in a very restricted class and the cars are equipped with superchargers.

My question is if I injec water pre blower, would this raise the boost level???

The reasoning is that water would effectivly better seal the blower and therefore would raise the boost slightly. 0.5psi would be a blessing.

[Richard L]

I ahve seen many supercharged installation where water was injected before the blower and seeing 1psi increase over 6 psi is quite normal.

We have not yet looing closely into the reason behind it. Some believe the increase is due to volume increase by the water vaporisation and other think it is caused by the tip seal effect.

If anyone knows other effects, please post to this thread.

[masterp2]

This definately sounds like an experiment for Gelf. He just needs to add a boost sensor reading to his charts and do a pre/post turbo comparison.

I have been studying the chemistry on this idea, and it something I want to do with my diesel. So far, here is what I think. Conventional misting, post-IC, likely is very inneficient for evaporization (especially for the water in the mix). I just don't see how, with so little time and the large drop sizes, that much of it can go to lowering charge temps in Latent heat of Vaporization (LHOV).

Some facts:

Meth has 4x the vapor pressure of water (much more volatile)
Meth has half the LHoV of water.

It feels much colder on our hand though, doesn't it?

Net: In the temps and pressures we are using, Meth cools twice as effectively as water, becoming a vaprous fuel in the process. Water cools but has so little time to do so. So I believe most water isn't used until it gets to the cylinder, where it flashes to steam.

Using the turbo, and the heat that is created across it, to evaporate the mix, would be much more effective, if charge saturation (lowest charge temp) is the goal. Also, when referencing "saturation", the amount of meth that can be absorbed into the air, is not affected by how much water is in the air. They are independent processes, each affected only by temp and pressure.

But next we have to worry about how much solution to evaporate across the turbo, if there is an intercooler. A 100% saturation across the turbo, will be condensate at the lower IC exit temp. This RADICALLY lowers IC efficiency, because now a lot of the IC's effort is wasted, recondensing water (which is just LHoV backwards). Plus liquid in the IC is a boundary efficiency killer.

A 60% saturation across the turbo might be 95% at the IC exit, that would be better. Now you can overinject as much as you want in a seperate stage post-IC.

Interesting that meth predominates in the vapor state over water. It means that an 80/20 mix will evaporate in almost exactly the same proportions (4 parts meth evaporate for every part water). If you want more meth in the vapor and more (liquid) water, when the charge enters the cylinder, then use a 60/40 mix, or 50/50.

Simple experiment. take meth and water and mix it in 2 proportions, same total volume. One 80/20 and one 50/50. Set both samples outside. The 80/20 should be gone first, and its smell should remain the same throughout the evaporation. The 50/50 should evaporate last (take the longest) and the smell toward the end, with little left in the container, should be very light, mostly water.

[masterp2]

Ooops, only just noticed you have a suoercharger application. :oops:

[hotrod]

I think it would help for two reasons;

First a blower is a postive dispacement pump, for a given rpm, it can only move so much "volume", by cooling the charge entering the blower it will move more air (mass) at the same rpm. Since air mass is the important factor its a good thing. I found a web page some time back that mentioned an experiment that Kenny Bell ran to prove that intercooling before a blower increases air flow but intercooling after a blower has no effect on mass flow, only higher density due to cooling but lower boost and a minor gain due to improved detonation resistance.

On the sealing, there is good reason to say yes to that. For years in drag racing they injected the fuel ahead of the roots blower to both cool it and to act as a fluid seal. They had problems with the idea only because of the explosive nature of Nitromethane. If the engine back fired through an intake valve, it would blow the entire top of the engine off, because you had the intake manifold and pressure side of the blower full of fuel air mix.

That should not be a problem for a water injection system as water methanol mix is much less explosive than nitromethane. One other solution to the blow up problem was to put blow out reliefs in the pressure side of the blower manifold. If it back fired and the fuel air mix ignited, the high pressures would blow out special safety disks rather than lift the intake manifold and blower 30 ' in the air.

The extra cooling also allowed them to run tighter clearances in the blower which also helped reduce leakage past the rotors.



Larry