Many members here seem to lean towards the “more power is better” side of the spectrum. If you happen to be one of some who stand proudly on the “do more with less” side (like me), however, then this post is for you, especially if you’re stumped in your tuning quest to attain consistency of your PCP’s shot-to-shot performance after dropping its regulator pressure.
When you dramatically increase the horsepower on a car but neglect to strengthen its chassis to compensate for the increase stress, you’re going to end up with a very large lawnmower, or at the least, a car with a schizophrenic performance character. Conversely, when you drop the regulator pressure on your high-power PCP without addressing other important parameters, you’d end up with … well, a hotdog minus the sauerkraut, if you will.
Needless to say, adjustment of a regulator by decreasing plenum pressure to increase shot count with the desire of retaining consistency throughout the entire shot range also requires changing the compression and decompression rates of the Belleville washers to ensure quick reaction times—for both opening and closing. In most high-power setups, regulators are tuned to quickly decompress when the exhaust/plenum valve is open and quickly compress to shut the valve at a relatively fast plenum-recharge rate at a given setting, thus making available metered, consistent air for subsequent shots. However, the entire dynamic is altered when only lowering plenum pressure by reducing the gap between the valve seat and piston orifice. A sluggish recharge cycle is typically the outcome, resulting in a shot string having a wide variance, the extent to which is dependent on how quickly each shot is taken. That’s because the Belleville washers’ tension is too high for the now-lowered plenum pressure that the washers are holding the valve seat open for a longer duration, as if they’re fighting against the air pressure trying to squash them flat (and thus prevent unregulated air from entering the plenum). The tension will eventually be overcome and the piston orifice will seat itself on the delrin/peek seal, but the time it takes to do so is extended compared to when the regulator was set up for a higher plenum pressure (regulator creep can also be an effect of this). Essentially, the setup has become dynamically unbalanced (like in the car example stated above), and you can observe this if your PCP is equipped with a regulator pressure gauge—the needle will return to the set BAR number slower than it did before the adjustment as the pressure of the unregulated air drops closer to the set BAR pressure, though not necessarily equalize to it just yet.
To restore balance to the new setup you would need to decrease the tension by a little bit by removing a Belleville washer—or two, depending on how low of a plenum pressure at which you’re setting the regulator—so that the regulator’s valve is still able to open quickly to refill the plenum yet close immediately thereafter (about a second’s time) following a shot. Of course, this should be done to match your PCP's current hammer spring's tension rate for maximum consistency and stable performance over the entire usable shot range. By doing the above you'll be able to take subsequent shots and not have to wait too long for the plenum to recharge … and have your hotdog the way you like it too.
Cheers!
When you dramatically increase the horsepower on a car but neglect to strengthen its chassis to compensate for the increase stress, you’re going to end up with a very large lawnmower, or at the least, a car with a schizophrenic performance character. Conversely, when you drop the regulator pressure on your high-power PCP without addressing other important parameters, you’d end up with … well, a hotdog minus the sauerkraut, if you will.
Needless to say, adjustment of a regulator by decreasing plenum pressure to increase shot count with the desire of retaining consistency throughout the entire shot range also requires changing the compression and decompression rates of the Belleville washers to ensure quick reaction times—for both opening and closing. In most high-power setups, regulators are tuned to quickly decompress when the exhaust/plenum valve is open and quickly compress to shut the valve at a relatively fast plenum-recharge rate at a given setting, thus making available metered, consistent air for subsequent shots. However, the entire dynamic is altered when only lowering plenum pressure by reducing the gap between the valve seat and piston orifice. A sluggish recharge cycle is typically the outcome, resulting in a shot string having a wide variance, the extent to which is dependent on how quickly each shot is taken. That’s because the Belleville washers’ tension is too high for the now-lowered plenum pressure that the washers are holding the valve seat open for a longer duration, as if they’re fighting against the air pressure trying to squash them flat (and thus prevent unregulated air from entering the plenum). The tension will eventually be overcome and the piston orifice will seat itself on the delrin/peek seal, but the time it takes to do so is extended compared to when the regulator was set up for a higher plenum pressure (regulator creep can also be an effect of this). Essentially, the setup has become dynamically unbalanced (like in the car example stated above), and you can observe this if your PCP is equipped with a regulator pressure gauge—the needle will return to the set BAR number slower than it did before the adjustment as the pressure of the unregulated air drops closer to the set BAR pressure, though not necessarily equalize to it just yet.
To restore balance to the new setup you would need to decrease the tension by a little bit by removing a Belleville washer—or two, depending on how low of a plenum pressure at which you’re setting the regulator—so that the regulator’s valve is still able to open quickly to refill the plenum yet close immediately thereafter (about a second’s time) following a shot. Of course, this should be done to match your PCP's current hammer spring's tension rate for maximum consistency and stable performance over the entire usable shot range. By doing the above you'll be able to take subsequent shots and not have to wait too long for the plenum to recharge … and have your hotdog the way you like it too.
Cheers!
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