Fuel Pressure & differential constantly changing

[Cake]

Hi Guys,

Any ideas what my issue could be. Every time I start the car or idle , could be at a robot or stop sign. the fuel pressure is different. I set the differential to 50 psi. So it randomly changes even though the vacuum is pretty constant. Example. I start the car fuel differential is 52.5 psi and vacuum is -8. When I get home again and look its 50.5 and -8 vacuum.  I have changed fuel pump and fuel pressure regulator and its still doing the same thing. Any ideas what i can check next?

[Adamw]

I would be most suspicious of the reg.  Is it a good name brand one?  Some of the Chinese ones I have seen are absolutely terrible.  

[Cake]

Hi Adam,

Both were decent. First one was a aeromotive 1000hp compact efi. The new one looks like a A1000 from aeromotive. If you have a moment could you have a look at my map and see if there is something in the settings that blatantly wrong.

 

[Adamw]

Basic set-up looks ok, assuming it is a 150psi fuel press sensor.  Does the MAP match BAP when the engine is off? 

[Cake]

I'm pretty sure it is a 150psi fuel press sensor. It looks like the bap and map are also the same. Are they any inputs or values if wrong could cause this? I will then recheck that they correct.

 

I have the Flex fuel sensor after the regulator could that cause any issues?

[Adamw]

In traditional fuel equation, Diff Fuel Press = Fuel press - MGP.

MGP is MAP - BAP.

Since your MAP and BAP both match each other with the engine off it would be a pretty fair assumption that both are accurate (BAP is factory calibrated).  

So the fuel press sensor is the one I have least confidence in, but it appears to be giving realistic values so my feeling is the variable differential the ecu is reporting is probably real.

[0x33]

I had issues with fuel pressure sensor reporting some funky values. Turns out it was a knock off 150psi pressure transducer, replaced with a KA sensor and diff fuel pressure was rock solid. 

[Cake]

Thank you ill get the sensor wiring checked out and then sensor tested. Just one more thing on the  settings wise. If I look at the Injector dynamics values. it states its at fuel temp 52 degress C, would setting the base fuel pressure and the other fuel compensations tables at different temps cause these issues?

 

 

Basic Specifications

Nominal Flow Rate – 1065cc/min @ 3.0 Bar (43.5 psi) Using Gasoline at 52 Degrees C (125 Degrees F)
Maximum Differential Fuel Pressure – 10.0 Bar (145.0 psi)
Fuel Compatibility – Compatible With All Known Fuels
Electrical Connector – USCAR

---

ID1050x Dynamic Flow Data

Fuel Pressure			Offset			Slope
(psid)			(µsec)			(cc/min)
	8 Volts	10 Volts	12 Volts	14 Volts	16 Volts
40.0	1920	1410	1115	920	790	1020
43.5	1955	1425	1125	925	795	1065
45.0	1970	1435	1130	930	800	1085
50.0	2025	1475	1160	955	825	1145
55.0	2080	1515	1190	980	845	1205
60.0	2140	1540	1215	1000	860	1260
65.0	2195	1560	1225	1010	855	1305
70.0	2255	1575	1235	1015	850	1350
75.0	2340	1610	1250	1020	850	1390
80.0	2440	1655	1265	1020	850	1420
85.0	2555	1705	1280	1030	855	1455
90.0	2680	1765	1315	1045	865	1490
95.0	2815	1825	1355	1075	880	1530
100.0	2960	1890	1405	1110	900	1565

[Adamw]

1 hour ago, Cake said:

it states its at fuel temp 52 degress C, would setting the base fuel pressure and the other fuel compensations tables at different temps cause these issues?

No.

[koracing]

On 5/20/2021 at 12:09 AM, Cake said:

Hi Adam,

Both were decent. First one was a aeromotive 1000hp compact efi. The new one looks like a A1000 from aeromotive. If you have a moment could you have a look at my map and see if there is something in the settings that blatantly wrong.

 

I've had plenty of issues with the compact aeromotives to the point I won't sell them.  The standard 13109 is a solid unit.  The phrase "looks like" also does not mean "is" in this day and age of knock offs.