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The Terminator
Engine/Tuning
PPRV cutaway
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<blockquote data-quote="Black306" data-source="post: 11001074" data-attributes="member: 4780"><p>Here is my take on the subject.</p><p></p><p><a href="http://www.svtperformance.com/forums/engine-tuning-214/281209-frps-6.html#post7581013" target="_blank">http://www.svtperformance.com/forums/engine-tuning-214/281209-frps-6.html#post7581013</a></p><p></p><p>Using Aaron175617's images.....</p><p></p><p>Here is what happens when things are running normal.</p><p></p><p><img src="http://westcoastmustangs.com//temp/pprv_example_1.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Pumps are pumping, fuel is being used at a reasonable rate, little bit is being dripped back into the tank through the small nipple, and the flow is going through the larger, straight shot valve.</p><p></p><p><img src="http://westcoastmustangs.com//temp/pprv_example_2.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Something has caused a pressure spike. Normally, the pumps running hard during a WOT, high RPM run and the throttle body shuts closed. ECU reacts by significantly reducing the duty cycle of the fuel injectors. Pumps keep pumping, pressure spikes through the system, and the ECU hasn't reacted. Fuel is still going through the straight shot valve and more is leaking though the small nipple due to increased pressure. Because the pumps are still creating pressure, that pressure is being applied to the side valve keeping it shut.</p><p></p><p><img src="http://westcoastmustangs.com//temp/pprv_example_3.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Computer basically goes 'oh crap!' and needs to bring fuel pressure down by cutting the pumps. As the pumps are reducing speed and pressure on the pump side of the PPRV is reduced, fuel flow doesn't pass through the straight shot valve. Instead, it pushes open the relief valve on the side and passed back through the pumps. Any pressure between the pumps and PPRV will also have some fuel come out of the small nipple.</p><p></p><p><img src="http://westcoastmustangs.com//temp/pprv_example_4.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>The ECU has WAY over reacted and shut down the pumps completely in an effort to get fuel pressure under control. Cars with bad hesitation issues will actually see 0psi if they datalog. Problem is that the spring holding the side valve is designed to maintain about 67psi. Pressure will only be reduced further through the injectors. You can't really see a steady ~67psi cause the injectors are always working and reducing pressure in the system between. If the PPRV was used in a controlled environment, you'll see it holds 67psi +/-7psi.</p><p></p><p></p><p></p><p></p><p>Why they designed it that way, I have no idea. I'd like to pick the engineer's brain on that one.</p><p></p><p>I would have done something like this....</p><p></p><p></p><p><img src="http://westcoastmustangs.com//temp/pprv_example_5.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Block off the chamber between the inlet and small nipple so no fuel can pass. Open up the small nipple hole to allow a lot more fuel to pass. Set the spring pressure so that fuel pressure can be raised to 39psi (delta) plus actual boost (say 20-25psi). That means it'll blow off at roughly 59 - 64 psi. Setting it up that way might also help FRPS damages. Only down side I see is that if the side valve were to fail, then fuel pressure couldn't be maintained. However, that type of failure would be similar to a return style fuel system FPR (Fuel Pressure Regulator) failing, which is relatively rare.</p></blockquote><p></p>
[QUOTE="Black306, post: 11001074, member: 4780"] Here is my take on the subject. [url]http://www.svtperformance.com/forums/engine-tuning-214/281209-frps-6.html#post7581013[/url] Using Aaron175617's images..... Here is what happens when things are running normal. [img]http://westcoastmustangs.com//temp/pprv_example_1.jpg[/img] Pumps are pumping, fuel is being used at a reasonable rate, little bit is being dripped back into the tank through the small nipple, and the flow is going through the larger, straight shot valve. [img]http://westcoastmustangs.com//temp/pprv_example_2.jpg[/img] Something has caused a pressure spike. Normally, the pumps running hard during a WOT, high RPM run and the throttle body shuts closed. ECU reacts by significantly reducing the duty cycle of the fuel injectors. Pumps keep pumping, pressure spikes through the system, and the ECU hasn't reacted. Fuel is still going through the straight shot valve and more is leaking though the small nipple due to increased pressure. Because the pumps are still creating pressure, that pressure is being applied to the side valve keeping it shut. [img]http://westcoastmustangs.com//temp/pprv_example_3.jpg[/img] Computer basically goes 'oh crap!' and needs to bring fuel pressure down by cutting the pumps. As the pumps are reducing speed and pressure on the pump side of the PPRV is reduced, fuel flow doesn't pass through the straight shot valve. Instead, it pushes open the relief valve on the side and passed back through the pumps. Any pressure between the pumps and PPRV will also have some fuel come out of the small nipple. [img]http://westcoastmustangs.com//temp/pprv_example_4.jpg[/img] The ECU has WAY over reacted and shut down the pumps completely in an effort to get fuel pressure under control. Cars with bad hesitation issues will actually see 0psi if they datalog. Problem is that the spring holding the side valve is designed to maintain about 67psi. Pressure will only be reduced further through the injectors. You can't really see a steady ~67psi cause the injectors are always working and reducing pressure in the system between. If the PPRV was used in a controlled environment, you'll see it holds 67psi +/-7psi. Why they designed it that way, I have no idea. I'd like to pick the engineer's brain on that one. I would have done something like this.... [img]http://westcoastmustangs.com//temp/pprv_example_5.jpg[/img] Block off the chamber between the inlet and small nipple so no fuel can pass. Open up the small nipple hole to allow a lot more fuel to pass. Set the spring pressure so that fuel pressure can be raised to 39psi (delta) plus actual boost (say 20-25psi). That means it'll blow off at roughly 59 - 64 psi. Setting it up that way might also help FRPS damages. Only down side I see is that if the side valve were to fail, then fuel pressure couldn't be maintained. However, that type of failure would be similar to a return style fuel system FPR (Fuel Pressure Regulator) failing, which is relatively rare. [/QUOTE]
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