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The Terminator
Engine/Tuning
PPRV cutaway
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<blockquote data-quote="Black306" data-source="post: 11002284" data-attributes="member: 4780"><p>Unfortunately, it had been almost 3 years since I messed around with PPRVs to remember whether or not the barrel moves. From what I recall, it doesn't. There should be a matching grove in the cylinder for the barrel's ring. If you still have that cut away, could you please remove the barrel and take a pic of the cylinder? Even if that barrel moves, I can see that only affecting spring seat pressure and maybe fuel flow through the small nipple causing a reduction in flow rather than a quick drop.</p><p></p><p>The PPRV is definitely a check valve and key to quicker starts. Some people going with an aftermarket hat install aftermarket check valves to help with starts.</p><p></p><p>I believe helping over pressure while running is the misconception. There is no "blow off" feature. As designed, the relief valve on the PPRV would remain closed due to pump and spring pressure. So if the pumps were running at 100psi, the rails will see 100psi. The relief valve doesn't open until the pumps are commanded to reduce pressure and pressure in the lines is more than pump and spring pressure. I believe that it is the small hole in the nipple that helps reduce the speed of pressure spikes. When going with aftermarket pumps that flow more fuel, the hole becomes inadequate and causes excessive spikes resulting in hesitations.</p><p></p><p>However, I believe you are correct on not worrying about fuel pressure after shutting down without a PPRV. If the system doesn't hold pressure when shut off, there is no increase of fuel pressure due to heat. :beer:</p></blockquote><p></p>
[QUOTE="Black306, post: 11002284, member: 4780"] Unfortunately, it had been almost 3 years since I messed around with PPRVs to remember whether or not the barrel moves. From what I recall, it doesn't. There should be a matching grove in the cylinder for the barrel's ring. If you still have that cut away, could you please remove the barrel and take a pic of the cylinder? Even if that barrel moves, I can see that only affecting spring seat pressure and maybe fuel flow through the small nipple causing a reduction in flow rather than a quick drop. The PPRV is definitely a check valve and key to quicker starts. Some people going with an aftermarket hat install aftermarket check valves to help with starts. I believe helping over pressure while running is the misconception. There is no "blow off" feature. As designed, the relief valve on the PPRV would remain closed due to pump and spring pressure. So if the pumps were running at 100psi, the rails will see 100psi. The relief valve doesn't open until the pumps are commanded to reduce pressure and pressure in the lines is more than pump and spring pressure. I believe that it is the small hole in the nipple that helps reduce the speed of pressure spikes. When going with aftermarket pumps that flow more fuel, the hole becomes inadequate and causes excessive spikes resulting in hesitations. However, I believe you are correct on not worrying about fuel pressure after shutting down without a PPRV. If the system doesn't hold pressure when shut off, there is no increase of fuel pressure due to heat. :beer: [/QUOTE]
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