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The Terminator
Engine/Tuning
All Kenne Bell Guys In Here Please!
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<blockquote data-quote="BOOOOST" data-source="post: 446563" data-attributes="member: 8188"><p>The reason they aren't getting any fuel pressure increase is simple:</p><p></p><p>The factory Cobra calibration will shorten injector pulse width to reduce fuel flow, and if the pressure is above 39psi, the pcm reduces fuel pressure. It senses that fuel pressure is raised beyond a specific threshhold. It constantly attempts to regulate fuel pressure to a mere 39psi, even at WOT. At 20psi total boost, the stock injectors become only a 20# injector (40psi - 20psi inlet manifold pressure forcing fuel back into the injector = 20psi effective pressure). At 40psi there would be no fuel whatsoever exiting the injector. Adding 8psi of boost drops the injector rating from 42 to 37#'s. At 20psi boost the injector is a 31#. This 11 #'s of fuel lost to the back pressure of boost will feed 168 hp! And there is no regulator to increase fuel pressure with boost. Therefore, the best solution is to raise fuel pressure with a BAP and modify the chip fuel strategies for a safe consistent AF ratio from 8-20psi. This is why it is important to have a tuner who understands how to tune the parameters in the pcm to keep the computer from pulling fuel, or lowering pulse width.</p><p></p><p>The Lightnings do not require a BAP or larger injectors up to 500 rwhp. After that 50# injectors and the BAP is recommended.</p></blockquote><p></p>
[QUOTE="BOOOOST, post: 446563, member: 8188"] The reason they aren't getting any fuel pressure increase is simple: The factory Cobra calibration will shorten injector pulse width to reduce fuel flow, and if the pressure is above 39psi, the pcm reduces fuel pressure. It senses that fuel pressure is raised beyond a specific threshhold. It constantly attempts to regulate fuel pressure to a mere 39psi, even at WOT. At 20psi total boost, the stock injectors become only a 20# injector (40psi - 20psi inlet manifold pressure forcing fuel back into the injector = 20psi effective pressure). At 40psi there would be no fuel whatsoever exiting the injector. Adding 8psi of boost drops the injector rating from 42 to 37#'s. At 20psi boost the injector is a 31#. This 11 #'s of fuel lost to the back pressure of boost will feed 168 hp! And there is no regulator to increase fuel pressure with boost. Therefore, the best solution is to raise fuel pressure with a BAP and modify the chip fuel strategies for a safe consistent AF ratio from 8-20psi. This is why it is important to have a tuner who understands how to tune the parameters in the pcm to keep the computer from pulling fuel, or lowering pulse width. The Lightnings do not require a BAP or larger injectors up to 500 rwhp. After that 50# injectors and the BAP is recommended. [/QUOTE]
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