2 solenoid valve questions. Voltage (12v vs 24v) and Cv (.3 vs .7)

I’ve read that 12v solenoid valves can have problems during voltage drops, which 24v ones are less prone to. Is this a common problem? Lots of teams seem to use the SMC line carried by Vex and WCP and they only sell the 12v models. I would think they would carry the 24v models if this was a problem.
Second. The valves seem to cluster around Cv values of .3 and .7, give or take. I understand that punchers and big cylinders will need the .7Cv and tiny cylinders only need the .3Cv ones, but are there any guidelines or a calculator to estimate what Cv is needed for cylinders that fall in between.
We are trying to standardize our pneumatics, which are a hodgepodge right now, and are having trouble with this.

The airflow you need, might depend somewhat on how the cylinder is used, as well as it’s size.

If you are going to standardize, go with the biggest size you can legally use, that you can afford and will work with the rest of your robot plans.

The following screenshot from the CTRE PCM User’s Guide shows a little more detail about the 12V vs. 24V situation, see Notes 1 and 2 below the table:

Based on some quick research, I have found both SMC and Festo spec +/- 10% Voltage fluctuation as acceptable. Anecdotally I know that these ratings are a bit conservative, but beyond that is where you may see issues, especially under times of high current draw/low voltage (pushing situations, end of the match, etc.).

With regulated 24V, there’s reduced risk of your solenoids not firing properly at the extremes, but I also don’t have a lot of evidence, anecdotal or otherwise, of teams having major problems with 12V solenoids not firing. If anyone does, I’d be interested in hearing about it.

Useful Cv calculator!
https://www.swagelok.com/en/toolbox/cv-calculator

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