Fuel Pressure Drop - has anyone successfully implemented ADM FPCM on a '14 Chevy SS

[Mach Schnell!]

I searched the old threads on fuel pressure drop on supercharged LS3 / E38 ECM - and possible solution with ADM FPCM... but found no final answer. Has anyone successfully implemented the ADM FPCM on a 2014 Chevy SS? (This car from the factory has the ZL1 fuel pump but not the ZL1 FPCM.) If so, were any other hardware changes required? And what specific parameters have to be changed in the tune file in hptuners? My SAE fuel pressure signal drops from nominal 58 psi to 40 psi or less at WOT/ high RPM (at highest flow rate). I am still fairly close to my targeted 11.4 AFR (about 11.5-11.6) on both L/R wideband sensors, but don't like living dangerously. A screenshot of my data log is attached. (I don't have the ADM FPCM - but am considering it as a solution.) Thanks in advance.












Screenshot (339).jpg

[realsquash]

I searched the old threads on fuel pressure drop on supercharged LS3 / E38 ECM - and possible solution with ADM FPCM... but found no final answer. Has anyone successfully implemented the ADM FPCM on a 2014 Chevy SS? (This car from the factory has the ZL1 fuel pump but not the ZL1 FPCM.) If so, were any other hardware changes required? And what specific parameters have to be changed in the tune file in hptuners? My SAE fuel pressure signal drops from nominal 58 psi to 40 psi or less at WOT/ high RPM (at highest flow rate). I am still fairly close to my targeted 11.4 AFR (about 11.5-11.6) on both L/R wideband sensors, but don't like living dangerously. A screenshot of my data log is attached. (I don't have the ADM FPCM - but am considering it as a solution.) Thanks in advance.
Screenshot (339).jpg

How much boost are you producing? What's your max injector duty cycle? I don't think the ADM FPCM is going to do anything remarkable in your setup.

EDIT: 8 psi according to the screenshot?

[Mach Schnell!]

Boost is only about 8 psi. Max injector duty cycle is about 69% on 65lb/hr injectors.

[etm351]

What is the pulsewidth or duty cycle doing on the injector thats what i would worry about the most, the drop in fuel pressure isn't all bad if the injectors aren't going up and down to compensate. The duty cycle on the pump needs to be increased but i am not sure if there is a place to do that in the tune.

[JBZ]

How are you increasing voltage to the fuel pumps? With the fpcm it throws more voltage at it. Alot of guys with stock pumps run out of fuel pressure with increasing injector size, boost and/or e85. There are a number of ways around this but normally the fpcm will increase voltage (not like a boost referenced system 1.1, 4.1 or what ever) in 3 different setpoints for lack of better term and voltage to match.

Fpcm could help if your not already increasing voltage to the pumps in 3 stages vs boost, this is all assuming your using a returnless shstem. There are a few other options...one being a bandaid, get a bap with a hobbs switch. You may also consider getting better than stock zl1 pumps, a few options there or get a complete boost referenced return style system.

Try to log requested or desired fuel pressure. That should tell you if your asking for an increased voltage. You will see that increase with load and fuel pressure to match...even if it is dropping as load increases...i didnt notice that in your log.

[realsquash]

The only thing you're risking by operating like this is if one day the fuel pressure drops even lower than 40psi and you run out of injector duty cycle and the engine goes lean. If you want more fuel pressure then jacking up the pressures in the tune aren't going to help you at all (you should be able to run up to 65psi IIRC). The FPCM isn't going to do much/anything for you, either.

[Mach Schnell!]

Thanks for the replies, realsquash, etm351, and JBZ. I was already logging some additional signals from the same run and have plotted those in the new attached screenshot. The "Requested Fuel Pressure" is always 58 psi, it never varies. The "Fuel Pump Commanded DC" is always 99.6%, so I did not plot it. Unfortunately I wasn't logging "Desired Fuel Pressure", however that is different (?) from "Requested Fuel Pressure". I also wasn't logging actual Fuel Pump DC, but will in the future. I cleaned up the plot and have shown the Fuel Pressure signals together, "Requested", actual "Fuel Pressure SAE" and "Injector Delta Pressure". It is noteworthy that under vacuum, injector delta pressure > Fuel Pressure SAE, as expected. But in boost (I have 2 MAP sensors, both are plotted) sometimes, as in the screenshot, the Injector Delta Pressure > Fuel Pressure SAE which does NOT make sense. I have plotted IFR (Injector flow rate), and have a dashed reference line at 72 lb/hr. IFR drops is nominally about 75, but drops to 72 at full boost, low RPM, then drops to 68 at full boost, high RPM (max flow), and then increases to 80 lb/hr about the WOT when in DFCO mode (min flow). So it seems that the FPCM is holding pump voltage fixed. Clearly there is no boost referencing the MAP. I log the channel "Fuel Pressure State" which clearly goes through "low", "normal", and "high" flow states, but these don't appear to cause any change in pump output, as I understand they do with the ZL1 FPCM. Thanks for the help! (If the forum site allows posting a large file, I could post the log file)

(edit: I added Injector pulse widths for each bank which are about 13 ms max, consistent with the 67% DC and 20 ms period.)

Screenshot (376).jpg

[Mach Schnell!]

From a suggestion by austinb on ssforums, I increased the Fuel System Min Voltage from 13.5 to 14.5V for the lower half of the table. Interestingly the fuel pressure SAE didn't change - it must be capped in FPCM firmware at 58 psi, the IFR (injector flow rate) didn't change, but IDC (injector duty cycle) and MAF are both up together (both now shown on gauges in my screenshot), with AFR at targeted 11.4. Screenshot attached.

BTW... another datalog (not shown) of a slow, lengthy commute (>1 hour) with Fuel System Min Voltage set at 14.5V... and after 30 minutes or so the voltage dropped back to ~13.6 V. Thermal issue?

Still no explanation why delta pressure can ever be greater than fuel pressure SAE under boost. Not physically possible. Data in channel table left side of screenshot.

I have a ADM FPCM on order to give it a try.
Screenshot (416).jpg

[JBZ]

what are you actually seeing on your MAP in KPA. the only way this can exist is if your map is wrong, not scaled right or you don't have a high enough map sensor for the boost your seeing. without seeing an actual log or tune file its hard to say. but im sure you already know that delta = fuel pressure - boost/vacuum. your PCM thinks your in vacuum still...a little over 2 psi and your still pulling on the injectors even if your pushing against them with 8 psi of boost.

I don't really know which PSI boost to use since you have 3 listed in your graph and they all read differently. but if your actually seeing 8.3 lbs of boost your in the delta P range of 32.9 PSI

[Mach Schnell!]

what are you actually seeing on your MAP in KPA. the only way this can exist is if your map is wrong, not scaled right or you don't have a high enough map sensor for the boost your seeing. without seeing an actual log or tune file its hard to say. but im sure you already know that delta = fuel pressure - boost/vacuum. your PCM thinks your in vacuum still...a little over 2 psi and your still pulling on the injectors even if your pushing against them with 8 psi of boost.

I don't really know which PSI boost to use since you have 3 listed in your graph and they all read differently. but if your actually seeing 8.3 lbs of boost your in the delta P range of 32.9 PSI

JBZ - I have 2 MAP sensors: The RED font in the chart (and the top MAP gauge) labeled "MAP boost" is an aftermarket, properly scaled 4-bar absolute pressure sensor installed on the lower side of manifold, on same port as supercharger bypass valve actuator. The YELLOW font in the chart (and the bottom MAP gauge) labeled "MAP stock boost" is a GM ZR1 3-Bar MAP Sensor -P/N 12592525, scaled with published linear & offset terms = 312.5 kPa and -11.25kPa. I replaced the stock GM 1.2 bar sensor with this one, on the Whipple mounting location at back of lower side of intake manifold. The sensors agree with +/- 0.2 psi across the full range. On the left side of latest screenshot posted above, you can see the "Intake Manifold Absolute Pressure" reading is 22.8 psi, this minus 14.5 psi (sea level atm pressure) is my boost, which is reading 8.3 psi on the gauge (ZR1 sensor).

(The 3rd MAP signal on the chart in WHITE font labeled "MAF boost" is a math function, a virtual pressure gauge, where I calculate boost pressure from engine displacement, RPM, MAF, IAT, gas constant, and an assumed constant volumetric efficiency of 0.87, using appropriate units - reasonably agrees across most of the range with the other two real pressure sensors +/- 1 psi or so).

So I am still at a loss why the wrong delta-P under boost conditions. Note that when manifold pressure is BELOW atmospheric pressure, the delta pressure shown in hptuners is about right. It must have a SIGN problem associated with the Manifold pressure when under boost conditions.

Thanks for you help.

[schpenxel]

Post a log

[Mach Schnell!]

Post a log

Schpenxel- Log file is very large so not sure if can post, so here is a link to my dropbox folder if that's OK: https://www.dropbox.com/sh/d6hnqtn1b...yFWWeU2ha?dl=0
The tune and log files are in the folder. To view all the charts and gauges, the layout, channels, charts, gauges, graphs, several MATH functions are necessary and are there as well. There is a screenshot too.
Go to time: 06:55:03.259

Thanks

[DSteck]

Your pump just simply can't move the volume required at the pressure you want. A new FPCM that's asking for more pressure isn't going to make that stock pump move anything extra. Shoot me a PM... We have done a couple SS setups that work.

[realsquash]

If you want to do it the right way shoot me a PM.

[JBZ]

Its weird that it would have the same pumps as the zl1, with stock zl1 boost pressure and cant keep up. Other than variable voltage from the fpcm what other reason would it not be able to keep up? Are the fuel line smaller?

[Mach Schnell!]

Your pump just simply can't move the volume required at the pressure you want. A new FPCM that's asking for more pressure isn't going to make that stock pump move anything extra. Shoot me a PM... We have done a couple SS setups that work.

Thanks, will PM

[Mach Schnell!]

If you want to do it the right way shoot me a PM.

Thanks, will PM you

[Mach Schnell!]

Its weird that it would have the same pumps as the zl1, with stock zl1 boost pressure and cant keep up. Other than variable voltage from the fpcm what other reason would it not be able to keep up? Are the fuel line smaller?

Screenshot (419).jpg

I don't know if fuel line size differs from ZL1, or if there is another restriction in the line dropping more pressure (with respect to ZL1) at high flow rate.

I ordered ADM FPCM and will give it a try.

[Mach Schnell!]

I tested "Supercharger Fitted" setting at WOT today, albeit carefully with spark advance limited to 10 degrees. Bottom line is that with that parameter enabled, then "Injector Delta Pressure" is approx. equal to "Fuel Pressure SAE" minus MAP boost signal. Of course the "Fuel Pressure SAE" signal drops just the same as before. I have attached (1st) screenshot of my tune file settings on engine/torque management/supercharger tab. I also attached (2nd) screenshot of quick WOT test this morning with time stamp marked at max rpm 2nd gear: SAE Fuel Pressure 41.4 psi, Injector Delta Pressure 34.1 psi, "MAP Stock Boost" (the integrated 3-bar MAP that the PCM sees) 7.9 psi, my secondary MAP sensor 7.3 psi. IFR (Injector Flow Rate), the alarmed red gauge, reads 62.3 lb/hr and IDC (Injector Duty Cycle) 76.6%. AFR 4% too rich Vs 11.4 target.

Compare that to WOT run today with supercharger NOT fitted setting - (3rd) screenshot attached. SAE Fuel Pressure (same) 41.4 psi, Inj Delta Press 43.5 psi (wrong), IFR 68 lb/hr (same), Inj Duty Cycle 70.6. AFR ~ 2% rich. Higher MAF signal than "superchargerfitted" tune run.

So the "supercharger fitted" setting works to reference boost, but of course does nothing to compensate the inadequate fuel pressure at high flow rate. And since I have my tune roughly dialed in for the non-MAP-referenced Inj Delta Pressure, changing to a method that references MAP under boost, such as by using this "supercharger fitted" setting, would require some tweaking.Screenshot (428).pngScreenshot (426) max rpm.jpgScreenshot (425).jpg

[schpenxel]

There is a manifold boost patch that will do the same thing.

Obviously there are other issues on this one, but that's something I would do regardless on any FI application.