How Gen V Direct Injection works

The all conquering supercharged LT4. Drawing by David Kimble

GM’s Gen V engines use direct injection which requires a proper fuel supply. There’s a lot of misunderstanding about the fuel delivery system because most enthusiasts are not familiar with PWM (Pulse Width Modulated) style fuel pumps.

The Overview:
For daily driving, you would normally see the engine target the stoichiometric AFR (Air Fuel Ratio) of 14.7:1 (also referred to as Lambda), if you have a wideband gauge hooked up. However, with 10% ethanol in most pump gas today, you see the program setup for 14.1:1 to account for that blend. When you step on the pedal and go wide open throttle (WOT), the vehicle goes into what is called “PE Mode” or “Power Enrichment Mode” looking for values approximately 12:1. This defers to another table that has modifiers of your aforementioned stoichiometric AFR values. The Mass Air Flow (MAF) tables and the Dynamic Airflow (VE) or volumetric efficiency tables that provide the basis for the manipulated fueling requested, taking into account factors like injector size in lbs/hr, the requested fuel line pressure and the Start Of Injection (SOI) which tells the injector when to fire.

Cross-section shows the direct injection of fuel into the combustion chamber

How it works:
The system uses two fuel pump technologies. The low side in-tank pumps are the pumps in the fuel tank that are controlled by the Fuel Pressure Control Module (FPCM) also called Fuel Pump Pressure Module (FPPM) for power output to the high pressure fuel pump which then supplies the fuel rails. The system requests approximately 50 PSI during normal driving and jumps up to approximately 72 PSI when going WOT.

The High Pressure Fuel Pump (HPFP) is located under the supercharger on the valley of the engine, in-between the cylinder heads. The high pressure pump has command technology which references it’s position as the plunger rides up and down on a specifically ground lobe on the camshaft to pressurize the fuel as it goes through the pump producing up to 2,900 psi fuel pressure (similar to diesel technology).

Factory bent high-pressure lines in the plenum. High Pressure fuel pump is shown right above the flex plate between cylinders 7 & 8.

The pressurized fuel enters the CNC (Computer numerical control) bent fuel lines and travels to the rails, and then enters the injectors. These injectors, unlike previous years port injection are located in the cylinder head with the tip projecting into the combustion chamber. Since the engines are direct injected, the fuel is fired into the cylinder from 1,500 -2,900 PSI on the intake stroke for a very short period of time (5 mil-seconds). The injected fuel will vaporize before the piston reaches top dead center (TDC), which allows for much more predictable fueling and more accurate/higher target AFRs . The benefits are less wasted fuel, better fuel delivery and a better AFR potential which results in increased mileage and reduced emissions.

For more detailed information on Gen V fuel delivery issues please ready my recently updated Gen V installation guide located here:

Speartech ’69 C10 with LT5

click on the photo for the link to Speartech’s page

“Our Gen 5 harnesses and control systems are designed to be used with the factory Gen 6 Camaro ZL1 fuel pump and in-line fuel pressure sensor which is available from your local Chevy dealer or from Rick’s Tanks who makes fuel tanks ready to go with the pump for various popular swap vehicles. If you don’t want to use the factory fuel pump and in-line pressure sensor, we can set the harness up for use with a regular high-flow fuel pump to be used in conjunction with a vacuum referenced fuel pressure regulator, just let us know.

The Gen 5 LT1 is GMs latest small block set to replace the LSX series of engines which have been around since 1997. With direct injection and VVT, it’s a whole new design and we have stayed ahead of the curve by developing a harness package for this new engine. You have all of the familiarity of our 24x and 58x hook-up design for the all new GM Gen 5 V8!”

Lokar Automatic Electronic Sport Shifters

written by Larry Cleeton (

The GM Supermatic trans controller supports manual up/down electronically, but as usual the Chevy Performance documentation was quite sparse.  It describes the wires, but not what to do with them.  I knew the dual calibration selector was simply a digital in signal to the controller that you ground to select calibration B.  I assumed the manual shift enable/up/down wires would be the same but wasn’t sure. I finally found the answer deep in the Help part of the calibration program you can use on the controller via a USB cable. Of course the old program wouldn’t run on 32 bit Windows. Fortunately Chevy Performance has a download of the latest version that supports 64 bit Windows. Then I found that the program won’t start without being connected to the trans controller. After that I finally found in the program help the following:

2.2.5 Cal A/B Wire

This wire is part of a 4-way connector using terminal “B” of the connector. A neat feature of the TCU is the ability to change to a completely different calibration at the flick of a switch. This is accomplished by hooking this lead to a dash/console-mounted toggle switch. Run the other switch pole to a ground. The default position (off) will be the Cal A setting. When switched on (grounded), the TCU will change the TCU to operate from the Cal B calibration.

NOTE: The TCU is already pre-programmed with an “A” and “B” calibration. The only difference is higher line pressure (firmer shifts) in the “B” calibration verses the “A” calibration.

2.2.6 Manual Shift Connector

The TCU is configured such that it’s possible to have fully manual upshifts and downshifts at the flick of a switch like a bump stick. This works by first activating the manual mode with one switch to Terminal C. Once activated, the transmission can be bumped up (Terminal B) or down (Terminal C) through the forward gears via an On-Off-On momentary rocker switch.

  • Terminal A (brn/white wire) – momentary ground for bump down
  • Terminal B (brn/ wire) – momentary ground for bump up
  • Terminal C (brn/red wire) – Toggle switch to ground to activate manual mode

Caution: Be aware that serious engine damage could occur due to over-revving if downshifts are made at too high of vehicle speed. The TCU cannot override your input while in the manual mode.

’71 C10 Firetruck

For the complete story click here

Nice clean installation

This is the latest version of the LT4, you can tell by the taller intercooler/supercharger top which is thicker and is straight across. The earlier version was thinner up front and kicked up slightly in the rear. After the first version came out there were issues with overheating on tracked Z06 cars that went into limp mode. To solve this issue GM designed larger intercooler bricks that necessitated a thicker cover for the supercharger.