Sounds good to me Bruce.
I don't think I would bother with the throttle positioning sensor though. Once the engine is up to temp, as long as the water flow is not too great it will happily ingest it.
I'm presuming the engine runs constant speed and an unloader just kicks the compressor in and out?
That being the case, speed is more important than load. I have tens of times poured water down the inlet of a diesel Engine at substantial flow rate and I wasn't running along side the vehicle at the time! :0)
As long as the revs are up and the flow rate of the water is not over powering, It will be fine.
Yes, You can pump a lot more water through under load but that is not required here. A small, constant ( more or less) flow will work fine. I use the word constant as in when the engine is running over hours rather than just a squirt from a bottle at the end of each run. If one times it to run 10 Min every hour, that would be constant to me rather than the batch pumping. I don't doubt that works, I have done it myself many, many times, I just believe a more protracted application for engines doing longer hours like vehicles and gennys would work even better. The constant application I see as more of a preventative in stopping buildup rather than an antidote once it has occurred.
If one has an engine they pull out the shed and use occasionaly, Sure Give the thing a spray, that the most practical thing to do and would be fine. If you are running the thing 4 hours a day most days, then there is greater ease in setting something permanent up and the justification in run time for it.
In all honesty, I like pumps. I like to pump water for WI and I like to Pump Fuel for burners. Pumping eliminates a lot of problems and the BIG advantage is it gives you wide and precise control. I don't suggest it much because most people say " I don't want to make things complicated".
To me complication is doing too much that is not necessary and gives no benefit.
Putting in a pump and a speed controller/ timer/ whatever is very simple and it affords a LOT of advantages over gravity and other methods.
I look at the risk. Pump fails, No WI. Big deal. not going to explode because the WI stops. You have 100 hrs of run time to get another one before it matters. Go back to your squirt bottle in the mean time and it's still OK. Despite what people say, Nothing is Bullet proff at all so you do what suits your Mindset and what suits your abilities and knowledge to apply.
If you were going to have a solenoid and a temp sensor you could drip feed the water in easily because it won't run till the engine is running and up to temp. May be easier than using a pan and getting that to work Whatever suits one's prefrances.
A lot of people make a big thing out of the engine filling with water. It's NOT a big deal at all unless you leave it for a week+.
I have done it on a number of occasions.
Firstly, unlike popular Opinion, I don't believe there are too many conventional (pull or electric) starters out there that have the ability to turn an engine hard enough to bend or brake anything with the engine Hydrolocked. Couldn't say home many small engines I have taken crank Nuts off by packing the cylinder with rag through the plug hole to lock them up and then put a 4ft bar on the end of the spanner to move the net. NEVER damaged an engine like that yet.
When you see the engine is full of water, you pull the injector or spark plug and push the water out. Spin it up a bit to clear it and that's it.
Check the oil and if it's not over saturated, reinstall plug or injector and off you go.
An amount of due Diligence is required with these things. If one needs it to be fool proof because they are too foolish to disconnect something when they are going to leave it for a long time or fail to take obvious precautions, well that's different but chances are if one is that distracted, they'll fk something up anyway. :0)
The thing that gets me with the simple Obsession is people only tend to apply it to DIY. If you said that Driving a car from the '50s was better than a modern car because there was less to go wrong. People would say you were an idiot and site all the comfort, saftey and convenience as well as reliability a modern car affords. ( You and I with Mercs may be an exception!) They are very happy with all that " Complication" but then say Oh no it's too much when you suggest putting a timer or a sensor on a stationary engine. I don't get it myself.
Like your Idea with temp sensors and solenoids, I don't think it's a complication, I simply think it's using some simple technology to get a better result than not applying those systems or methods... which have inherent problems of their own.