Pre or Post Turbo?
 

I'll try this again.

What are the most criticals aspects of a well designed mist injection system?
1. nozzle placement pre or post turbo? I've heard post turbo to avoid damage to the blades, but I've heard from a guy who installed the nozzle pre turbo over three years ago and he says absolutely no problems with the blades. Apparently, pre turbo is supposed to provide better vaporization of the atomized water particles.
2. Is the nozzle orifice diameter more important than pump pressure, or is it the other way around?
3. What's the minimum boost required to take advantage of the mist system?
4. Are there different design methods which enable the water pump to respond to varying boost levels?

I'm sure I've missed a few.

I would also like to know the benifits/problems of post and pre-turbo as I'm ready to hook up my 6.5TD chevy

In theory being able to inject pre-turbo would be a good thing. I think most just avoid it from the bad experiences in the past. I would use it to absorb heat during compression. I would not use it to improve atomization. Your jet/nozzle should be doing the atomizing and the better the atomization the less likely you will do blade damage or unbalance the cylinder with water droplets on the blades.

The combination of pump pressure, flow and the results at the orifice as a result are what you are looking for. It is no one item but how they work together.

Boost is not required for WI to be a benefit. Any engine that has to be run unduly rich to prevent knock would benefit. This would include high compression NA applications. Generically - if you have to run 93 octane fuel at lower than 12.5:1 AFR you have high enough cylinder pressures whether from CR or forced induction to benefit from WI.

There are numerous production and DIY methods of varying the flow. Some do so with high speed solenoids that work like fuel injectors others use variable voltage at the pump.

Talking about Engines with Intercooler you have to think also about placing the nozzle very near to the IC. that would help also temperatures to go down more than normal.

Just in order to run more power... but also to reduce mixture consumption by having the same power

Regards

Prometeus

Pre turbo is not a very good idea.
Good: It's a good way to use a cheap low pressure pump and a simple anti-siphon check valve.

Bad: The main problem is you are using the turbo to atomize the water. This is VERY hard on the turbo. It's just like sandblasting the turbo blades, they will dull down and wear out. Using WI you are likely to start injecting at/near full boost. The turbo is spinning at 100,000rpm+ by this time and the effect of a stream of dense, cold water into the compressor is intese stress on the blades and shaft.

Go for the quality install and get a good 100+psi pump, solonoid valve, and atomizer then install it post-intercooler.

Well, RR did just that with all the fuel carburretted straight into the the centre of the Merlin's 10" diameter supercharger impeller.. 25C reduction in post compression temps, 60 Nett BHP gain, 6 mph increase in speed on the Spitfire.. never once read anything about impleler damage

Very nice gains!, you need a small orifice jet and to inject into the centre of the turbo, ages ago on here there was a pic of a turbo with blade damage due to WI but there`s a thread going on here at the moment discussing it all with smaller jets in use.

I`m half tempted to try a 0.3mm jet on each turbo to see how it reacts, but that would mean buying another pump etc and it`s not financially possible at the moment.

that is the key. Spray turbo center mass. Compressor impingement damage results when a large low velocity particle collides with the sonic velocity blad tip. Spray the center, and you have very little velocity differential.