capillary tube to expansion valve

I am in the unenviable position being in charge of retrofiting a "no name" split unit domestic air conditioner (9000 BTU) for advanced control within an R&D project
The unit comes with adjustable speed compressor (inverter) but has a fixed capillary tube instead of an adjustable expansion valve. I want to have the valve controllable too, so I need a bypass of sorts. The controller will have an overview of the system, balancing compressor speed and valve opening.
I would appreciate some advice on the following:
1. Is this conversion feasible? Would it possibly make the system unstable, e.g. end up with moist refrigerant entering the compressor?
2. what type of expansion valve? There are "thermostatic" and "electronic". What would be continuously controllable, e.g. my algorithm may request 25% open. If they can both do the job I'll go for the cheaper
3. I've read in this newsgroup that the compressor may need retrofiting too for a "a hard start kit" whatever this is :)
Alternatively I would need an experienced HVAC engineer to do this conversion for me, in the area of Bangor wales UK
thanks nikos
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It has lot to do with what are you really looking for precise temperature control precise RH what is your end project, end product your end achievement. Tony

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English isn't your first language is it?
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my objective is to make the thing run more efficiently through advanced control, ie. consume the least possible energy for a certain cooling task
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wrote:

So your trying to re-invent the wheel.
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wrote:

cooling you room cooling your six pack cooling part for the satellite cooling part for your dragster some how I have feeling that you are hiding something tony
And yes "KJPRO" English isn't my first language So??
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