2018 Tahoe DI 5.3 "My funny gdi test mule"

[nmstec]

It's terrible, but it's my test mule.

[AndreyB]

Here's where they've placed it and it still smells like a mechanical HPFP to me. Still interesting that they have two dedicated wires to ECU so this one might be peak-hold control.

Looks like we shall measure resistance?

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[nmstec]

High Pressure Fuel Pump

The high fuel pressure necessary for direct injection is supplied by the high pressure fuel pump. The high pressure fuel pump is mounted on the rear of the engine under the intake manifold and is driven by a three-lobe cam on the camshaft. This high pressure fuel pump also regulates the fuel pressure using an actuator in the form of an internal solenoid-controlled valve. In order to keep the engine running efficiently under all operating conditions, the engine control module (ECM) requests pressure ranging from 2 to 15 MPa (290 to 2, 176 psi), depending on engine speed and load. Output drivers in the ECM provide the high pressure fuel pump control circuit with a 12 V pulse-width modulated (PWM) signal, which regulates fuel pressure by opening and closing the control valve at specific times during pump strokes. This effectively regulates the portion of each pump stroke that is delivered to the fuel rail. The high pressure fuel pump is normally closed and will not deliver an increase in fuel pressure when the control solenoid is NOT powered. In the event of pump control failure, the high pressure system is protected by a relief valve in the pump that prevents the pressure from exceeding 21.5 MPa (3, 118 psi).

[mck1117]

Yeah, that's not a BLDC, that's exactly the same setup as @AndreyB's VW. IIRC these also have a 3 lobe pump drive cam lobe at the back of the cam.

[nmstec]

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[mck1117]

some useful information about a 2015-2020 GDI GM 5.3

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[ssmith]

That leading edge table is really interesting. Way more linear than I would expect. Maybe they're just ignoring the non-linear area of the lobe. Also interesting that the lobe is 130 degrees, not 120. Guess the lobe is asymmetrical.

That one table basically combines the cam profile table and pump compensation table in RusEFI. It is simpler to just have one table, and if you're an OEM with full access to the design specs, you can just build the one table and tune it on the engine dyno. For the rest of us trying to figure this out in our garage, I think having the separate tables is more helpful, though maybe I'm projecting. With a perfect model, cam profile and injector info should be reasonbly close; the compensation table can therefore be lower resolution and determined with some road testing. How do they handle it when the PI control says to go above 0.46 cm^3 of fuel? Just cap there or keep adding degrees linearly?

I wonder what base angle is. The angle of the bottom of the lobe? Or the top? When you get around to trying to start it, try 222 (702 + 240[one lobe later] - 720[one full engine cycle]) and 112 (702 + 130[full lobe width] - 720[one full engine cycle]). For the cam profile, grab the one from the VW (basic sinusoidal) though it's probably more like a quick accel at peak/valley and somewhat linear in between (based on what we're seeing with the table above).

[mck1117]

Since mark asked, here's the table for the lift pump control:

edit: it looks like it's mechanically regulated, and this table is just to keep things just barely flowing through the regulator or something

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[nmstec]

Since mark asked, here's the table for the lift pump control:

edit: it looks like it's mechanically regulated, and this table is just to keep things just barely flowing through the regulator or something

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According to the snippets above they do say the FPCM does control the fuel pump according to ECMs fuel request. Dead head system.

[mck1117]

According to the snippets above they do say the FPCM does control the fuel pump according to ECMs fuel request. Dead head system.

this has a return line https://www.rockauto.com/en/moreinfo.php?pk=8445428&cc=3438971&pt=10147&jsn=462

is there a regulator in the filter or something?