TheMonaLisa Posted July 22, 2016 Share Posted July 22, 2016 My fuel pressure fluctuation issues have me stumped as well as TWO of the most respected tuners on this forum. Been trying to solve this for a year now... Pressure has +/- 10psi swings during full throttle within 300 rpm span from 5500 rpm to redline. Pressure swings are monitored with an AEM fuel pressure gauge and verified with an AEM wideband as the swings directly affect the air fuel ratio. The problems became visible last year when I installed the AEM gauges along with DeatchWerks 850cc injectors and 65C pump at the same time. Below is a list of parts I've replaced trying to solve the problem: fuel pump fuel pump sock all 3 fuel pump housing o-rings and 2 o-rings on fuel pump neck fuel filter upgrade to sit fuel pressure regulator relocated fuel pressure regulator vacuum source verified voltage and current going to the fuel pump is correct Car runs great otherwise and boost pressure is solid. VF52 turbo I truly appreciate any input you might have. Truly at a loss of what to do next. Link to comment Share on other sites More sharing options...
utc_pyro Posted July 22, 2016 Share Posted July 22, 2016 On your pressure transducer, what's it's output range? If you can get it down to ~1v with a voltage divider, you could capture the pulsation with the audio input of a laptop. With that you could do an FFT on it and get the the frequency of the oscillation to get a better idea what's going on. Link to comment Share on other sites More sharing options...
TheMonaLisa Posted July 22, 2016 Author Share Posted July 22, 2016 I'm not positive about the output range of the pressure transducer but I know the gauge itself has a 0-5V analogue output for data logging. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
utc_pyro Posted July 22, 2016 Share Posted July 22, 2016 That'd work. Most laptops can take a 1Vrms signal in the line in. That comes out to 2.8v ish p-p so a 1/2 divider would be fine. Your profile says you're an ME so I presume you took circuits at some point and can figure this out. http://www.build-electronic-circuits.com/wp-content/uploads/2013/08/voltage-divider.png Vin is from your gauge logging output. Make R1 and R2 the same value, probably 1K ish. Add a ~4.7uf capacitor inline with Vout to filter out DC. That will be spliced into a 3.5mm audio cable to ether L or R. Make ground the same for everything. Record it with audacity or the like and then do a spectrum graph or FFT (depending on what functions the program it has). Link to comment Share on other sites More sharing options...
TheMonaLisa Posted July 22, 2016 Author Share Posted July 22, 2016 Thanks for all the direction. I can build this circuit in no time at all. Gonna try downloading Audacity tonight. Much appreciated Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
JmP6889928 Posted July 22, 2016 Share Posted July 22, 2016 Turkeylord did a complete loom rewire of the electrical feed lines to the fuel pump. Look here and see if it is something that may help: http://legacygt.com/forums/showthread.php/upgrading-your-fuel-pump-wiring-4th-gen-213570.html?t=213570 Link to comment Share on other sites More sharing options...
TheMonaLisa Posted August 20, 2016 Author Share Posted August 20, 2016 Bought an AEM320, gonna give that a go. Apparently the 65c and 300c have lost their credibility lately. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
TheMonaLisa Posted August 20, 2016 Author Share Posted August 20, 2016 Turkeylord did a complete loom rewire of the electrical feed lines to the fuel pump. Look here and see if it is something that may help: http://legacygt.com/forums/showthread.php/upgrading-your-fuel-pump-wiring-4th-gen-213570.html?t=213570 I have the DW hardwire kit on hand. Just haven't installed it yet. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
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