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<blockquote data-quote="SecondhandSnake" data-source="post: 16413118" data-attributes="member: 116684"><p>Got out for a datalog session and found my issue. It's fuel pressure. I've got 40psid key on engine off, dropped to 38psid cold idle, by the time I got cruising down to 36psid, and all the way down to 32psid on acceleration.</p><p></p><p>Fault Tree Analysis (FTA) time. For the most part it boils down (no pun) to either insufficient pump performance or insufficient regulation.</p><p></p><p><u><strong>Pump- </strong></u></p><p><strong>Insufficient current/voltage</strong> - unlikely. 10ga wiring and 13.5V steady.</p><p>Insufficient output - calibration sheet from the factory shows it should flow far more than I need, even at 50% DC, as mentioned above. Mechanical issue is still possible. Could try running at 100%DC, though that's more likely to overheat the fuel, but sure as hell is going to give me enough volume/pressure.</p><p><strong>Insufficient fuel feed</strong> - Fed from a sumped tank, a <12" long -10AN line, at sump level, half a tank full, Earl's 100 micron filter. Biggest issue could be overheating of the fuel due to the high volume being returned, and would agree with pressure decaying over time. Pump wasn't whining like it was aerated/cavitating. I wouldn't think that it would put enough heat in the fuel in a less than 10 min drive with a deadhead regulator, 50% DC, half a tank, and returning below fuel level in the far corner of the tank, but who knows. I might see if I can put a thermocouple in the sump to monitor the temperature.</p><p></p><p><u><strong>Regulation-</strong></u></p><p><strong>Poor vacuum reference </strong>- Shows fine at atmospheric pressure, engine off, and rail gauge pressure, not delta pressure, drops when engine is on generating vacuum. If anything you'd think that would mean too much pressure at idle and still being spot on when going WOT as IMP approaches atmospheric. I will note I removed the stock vacuum tree and plumbed my own using 3/16" line. The FRPS, boost gauge, wastegates, and FPR are all teed off the lower manifold.</p><p><strong>Poor configuration/hardware issue</strong> - Deadhead setup, -10AN supply, -8AN return. It's then -10AN all the way from the regulator to a -10AN Y block and still -10AN to the rails. I haven't seen anyone else see issues with a deadhead setup like that.</p><p></p><p>Anything I'm missing?</p></blockquote><p></p>
[QUOTE="SecondhandSnake, post: 16413118, member: 116684"] Got out for a datalog session and found my issue. It's fuel pressure. I've got 40psid key on engine off, dropped to 38psid cold idle, by the time I got cruising down to 36psid, and all the way down to 32psid on acceleration. Fault Tree Analysis (FTA) time. For the most part it boils down (no pun) to either insufficient pump performance or insufficient regulation. [U][b]Pump- [/b][/U] [b]Insufficient current/voltage[/b] - unlikely. 10ga wiring and 13.5V steady. Insufficient output - calibration sheet from the factory shows it should flow far more than I need, even at 50% DC, as mentioned above. Mechanical issue is still possible. Could try running at 100%DC, though that's more likely to overheat the fuel, but sure as hell is going to give me enough volume/pressure. [b]Insufficient fuel feed[/b] - Fed from a sumped tank, a <12" long -10AN line, at sump level, half a tank full, Earl's 100 micron filter. Biggest issue could be overheating of the fuel due to the high volume being returned, and would agree with pressure decaying over time. Pump wasn't whining like it was aerated/cavitating. I wouldn't think that it would put enough heat in the fuel in a less than 10 min drive with a deadhead regulator, 50% DC, half a tank, and returning below fuel level in the far corner of the tank, but who knows. I might see if I can put a thermocouple in the sump to monitor the temperature. [U][b]Regulation-[/b][/U] [b]Poor vacuum reference [/b]- Shows fine at atmospheric pressure, engine off, and rail gauge pressure, not delta pressure, drops when engine is on generating vacuum. If anything you'd think that would mean too much pressure at idle and still being spot on when going WOT as IMP approaches atmospheric. I will note I removed the stock vacuum tree and plumbed my own using 3/16" line. The FRPS, boost gauge, wastegates, and FPR are all teed off the lower manifold. [b]Poor configuration/hardware issue[/b] - Deadhead setup, -10AN supply, -8AN return. It's then -10AN all the way from the regulator to a -10AN Y block and still -10AN to the rails. I haven't seen anyone else see issues with a deadhead setup like that. Anything I'm missing? [/QUOTE]
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