The front portion of the Nerve body consists of an integrated LPR (low pressure regulator) that supplies the air supply for the solenoid. The LPR is designed to take in air from the main valve, drop the pressure, and send it to the solenoid via the solenoid insert (discussed later).
The design purpose and benefit of using an LPR on this type of marker is discussed on the Design & Theory page (in the Related Links section)
The LPR is a miniature pressure regulator with an adjustment knob at the front. It is adjusted the same way as the vertical regulator; screw the endcap tighter for more pressure, out for lower. The LPR can be used to fine-tune the velocity in combination with the input pressure. Additionally, there is a tight balance between the dwell setting and the LPR pressure entering the solenoid; increasing one can be compensated by decreasing the other, and vice-versa. For detailed instructions on how to set the marker's pressure and dwell, check the Setting Electronics & Pressure page in the Related Links section.
LPR Extender:
Around May/June 2005 the original LPR setup was upgraded to the version visible above. The previous setup involved the LPR being directly screwed into the body instead of attaching using the silver extender piece as shown on all the diagrams on the site.
The purpose of the LPR extender is to add volume to the valve's dump chamber and help sustain a consistent velocity at high rates of fire. The LPR itself is exactly identical, except for the two extender components that add volume.
The LPR extender is included as a free factory upgrade from Smart Parts to markers that don't have it installed. It also comes with the factory upgraded valve poppet.
LPR Diagrams:
Below is shown a diagram of the LPR and extender components. I haven't made a diagram with the original non-extender components due to the parts being free.
Solenoid Insert:
LPR air pressure send back into the marker on its way to the solenoid is directed there through a component called the solenoid insert. This is an aluminum rod fitted with a pair of o-rings, and a mesh filter on the end to keep dirt and debris out of the valve.
The solenoid insert is accessible through a hole in the rear of the marker body, hidden under the bolt carriage backplate.
When removed, the insert length is visible:
The insert is threaded 1/4-28 at the rear and has a 1/8" hex head to allow removal from the body. The Nerve solenoid insert is not compatible with a Shocker insert.
Located around the end of the insert are two 1x3-mm ID o-rings. These are required to be installed or the marker will leak from the rear.
Solenoid Insert Airflow: 
Provided here is a cutaway diagram of a Nerve body, highlight on the solenoid insert and the associated solenoid.
Airflow enters the Nerve body around the LPR section at the front, and enters up into the solenoid insert chamber through a port in the front. Air is then routed toward the insert where it enters the filter (not shown) and exits through the porting in the side of the insert shaft (this is between the two o-rings. From this point pressure passes around the ram piston housing and enters the solenoid through the bottom. The outside o-rings on the piston are required to be in working order or this air may leak into other portions of the marker and prevent firing, or cause leaks (refer to the Troubleshooting page)
LPR Tester:
During normal operation you will be able to increase or decrease the solenoid pressure from the LPR, however you won't know what it is set to specifically unless you install a gauge to do so. New Designz sells an optional gauge adapter which will allow you to test the marker out while viewing the solenoid pressure.
Pictured above is the NDZ LPR adapter. To use this component you must remove the bolt assembly from the rear of the marker, unscrew and remove the solenoid insert, and screw the gauge into the empty solenoid insert chamber. An o-ring on the adapter piece seals the pressure from leaking.
You will be able to increase and decrease the LPR pressure at will and view the exact amount through the gauge at the back. When decreasing the pressure you will need to fire the gun once before the pressure will actually go down (this is a function of how the LPR works).
You can also test the marker out using paint over a chronograph however it requires a few extra steps. Before you install the LPR tester on the rear of the marker, remove the bolt from the bolt carriage and slide it down into the body. Use a small allen wrench or other tool to rotate the bolt around so the bolt pin sits inside the hammer. At this point you can install the LPR tester and pressurize the marker, and it will cycle the bolt as normal.
You can see above the larger gauge I installed on my tester, for use in the shop.
Although you can cycle the marker using this setup above, NEVER bring the gun out onto the field and play with it in this disassembled condition. The Nerve is not meant to be cycled without the bolt carriage installed, so using the marker without it is a recipe for disaster.
Overview:
· All Nerves use a low pressure regulator (LPR) to drop the solenoid pressure.
· A balance between LPR pressure and dwell must be used to gain the best performance out of your Nerve.
· Current LPR setups utilize a volumizer (extender) to add volume to the Nerve dump chamber.
· The solenoid insert rod is used to bring LPR pressure to the solenoid.
· An LPR tester must be used to verify the pressure of the solenoid, for fine-tuning and experimentation.
Related Links:
· Firing assembly
· Design & Theory
· Setting electronics and pressure
· Leaking/Shooting troubleshooting