Stock Injectors vs Magnuson Kit Injectors

[Mark-HD]

Thanks for your help. Your original e-mail got me on track and now after reading a lot more I had figured out I needed to start with the injector setup. I just ordered my Lt's so I'm waiting till I get them installed...I was getting a some conflicting info on the injectors. This file will help a lot.

[JR-Vette]

They are not 53 lb/hr
they are 47.5 lb/hr

The ZR1 has a fuel pump controller and a 3 phase fuel pump
Low pressure is 58 PSI, average is 72 PSI and maximum is 87 PSI

As engine load and boost changes the FPCM commands fuel pump pressure changes
The higher the pressure is from the 58 PSI make the injectors flow more then the 47 lb/hr.
So you can do the math of what the real injector flow of 47 lb/hr flows when the fuel pressure increases but the injectors on their own is 47 lb/hr in other engines with standard GM fuel rail pressure of 58 PSI

Originally Posted by E85LSX

I just looked at a ZR1 stock tune, at 59psi they have the injectors flowing 53lb/hr. That sounds close enough to me.

Please tell us why you want to know which injectors you have so we can better help you.

You can not tell by the Magnuson tune which injectors are included in the kit. There is a good chance the magnuson tuner has "raped" the IFR table and other injector tables to work around a MAF curve that is not properly calibrated. The MAF curve is actually not changed at all in the maggy tune.

If they are in fact ZR1 injectors I will gladly send you a stock ZR1 tune which you could copy all the injector parameters from and start tuning the car correctly.

[Mister HP]

We do have a Motro 60lb hr shorty injector , with the correct USCar terminal for LS3 engines currently available if anyone is looking for them.

Ed

[E85LSX]

Originally Posted by JR-Vette

They are not 53 lb/hr
they are 47.5 lb/hr

The ZR1 has a fuel pump controller and a 3 phase fuel pump
Low pressure is 58 PSI, average is 72 PSI and maximum is 87 PSI

As engine load and boost changes the FPCM commands fuel pump pressure changes
The higher the pressure is from the 58 PSI make the injectors flow more then the 47 lb/hr.
So you can do the math of what the real injector flow of 47 lb/hr flows when the fuel pressure increases but the injectors on their own is 47 lb/hr in other engines with standard GM fuel rail pressure of 58 PSI

I guess the size of the inejctor really depends on the pressure you are rating them at. . .

At 4bar (58psi) the ZR1 injectors flow about 53lb/hr

And why would you want to do the math to figure out what the ZR1 injectors flow when the data is published in every ZR1 stock tune? Calcultaions will get you close but real world flow testing is the only way to know exactly what an injector will flow and I'm sure GM flow tested the ZR1 injectors before using them.

[robertway]

Originally Posted by E85LSX

The injector parameters were raped to achieve the desired A/F ratio. The car is running MAF only as speed density is disabled in the tune. In this case the correct way to achieve the desired A/F ratio is to calibrate the MAF transfer.

So, after correctly characterizing the injectors you will want to (and have to) tune your MAF transfer.

Many different parameters in the tune are based on airmass, this is why it is critical to have the air flow model correctly calibrated.

I just sent the tune, enjoy.

Any chance you could elaborate on what it means when the "IFR table is raped". I see a lot of stuff over at the HPTuners site about table raping, PE and IFR tables but haven't found a definitive thread on what it is. I too am about to embark on trying to learn to tune bit by bit so any background info helps.

Thanks in advance

[E85LSX]

Originally Posted by robertway

Any chance you could elaborate on what it means when the "IFR table is raped". I see a lot of stuff over at the HPTuners site about table raping, PE and IFR tables but haven't found a definitive thread on what it is. I too am about to embark on trying to learn to tune bit by bit so any background info helps.

Thanks in advance

When someone "rapes the IFR or PE" they are changing the values in these tables to achieve their desired A/F ratio because the MAF transfer or VE tables are not tuned correctly(or whatever airflow model the computer uses).

In this specific case the IFR is raped to compensate for an incorrect MAF transfer. (I don't know how true this is but I think I read that Magnuson can't change the MAF transfer in the tune from stock. . . because of some emissions or CARB related bs)

The IFR table is not something you tune! The injectors have a specific flowrate at different pressures, pulsewidths and voltages ect. these are known values that are just plugged into the computer

The real problem with raping these tables is that the airflow is not correct and many other parameters in the computer rely on airflow (like timing for example).

[JR-Vette]

Originally Posted by E85LSX

I guess the size of the inejctor really depends on the pressure you are rating them at. . .

At 4bar (58psi) the ZR1 injectors flow about 53lb/hr

And why would you want to do the math to figure out what the ZR1 injectors flow when the data is published in every ZR1 stock tune? Calcultaions will get you close but real world flow testing is the only way to know exactly what an injector will flow and I'm sure GM flow tested the ZR1 injectors before using them.

We all know GM always uses a smaller injector as that means the PCM can spend less clock time sending less commands for pulse width with longer on times leaving more clock time for other functions and PCM has better, smoother control with smaller injector/longer ON times thus PCM has to command injectors on less.

A 52 lb injector / 545 cc/min would handle 832 flywheel HP ( 754 HP at 80% duty cycle) so no way would GM use that for 640 HP when that would make 52 lbs way too big for all NON WOT conditions

It is the 3 stage fuel system that allows the 48 lb stock LS9 injectors to flow better for non WOT at 58 PSI rail pressure and instead of larger injectors the fuel pump controller under load will increase pressure from 58 to 87 PSI

That makes a 48 lb injector then flow like a 53 lb injector (848 HP) and not that the injector itself is 53 lb/hr

If in fact the injectors were 53 lb at 58 PSI then at maximum rail pressure which is 87 PSI is now 58 lb/hr flow which handles 928 flywheel HP with a 80% DC

No way GM would use 53 lb injector for 640 HP

Point is the design is correct as GM's fuel 3 stage controller is increasing rail pressure as load increases making a smaller injector flow more rather then older systems where we only had a single stage fuel pump and reason a injector that would flow more with a constant 58 PSI rail pressure

[E85LSX]

JR-Vette please let this 47vs53lb/hr thing go. . .

Saying the vette injectors flow XXlb/hr and not telling us at what psi is absolutly useless
I will post a screen shot of the stock ZR1 IFR vs pressure table later tonight to help you understand. Also, injectors are commonly rated at 3bar (45psi) even though our Chevys use a 4 bar system (I kno the vette has variable fuel pressure though)

Finally, telling us what hp different size injectors will support is rediculous. The hp different injectors will support relies heavily on the type of fuel being used, the type of motor (blower, turbo, NA), the number of injectors and the delta psi across the injector

[JR-Vette]

Being I tune Corvettes 7 days a week I do not need to wait to see a screen shot, I will save you the time and here it is

Injector Slope Filename = Stock_2010_LS9.LS2

MAP kpa 252 244 237 230 222 215 208 201 193 186 179 171 164 157 149 142 135 128 120 113 106 98 91 84 76 69 62 55 47 40 33 25 18
Flow Gm/sec 1.90 2.03 2.17 2.29 2.40 2.47 2.59 2.71 2.80 2.91 3.01 3.10 3.19 3.27 3.34 3.41 3.49 3.56 3.62 3.69 3.75 3.81 3.88 3.94 4.00 4.05 4.11 4.18 4.24 4.30 4.36 4.42 4.48

3 stage fuel pump from 58 to 87 PSI
http://teamzr1.com/temp/zr1f.jpg

Check GM specs for the LS9 and you'll see the injectors themselves are 48 lb/hr rated at 58 PSI fuel rail pressure.

Fuel Pump

The electric fuel pump is a screw type pump which is located inside of the modular fuel sender. The electric fuel pump operation is controlled by the FSCM and 3 phase control module.

Electronic Returnless Fuel System (ERFS)

The electronic returnless fuel system is a microprocessor controlled fuel delivery system which transports fuel from the tank to the fuel rails.
It functions as an electronic replacement for a traditional, mechanical fuel pressure regulator. A pressure vent valve within the fuel tank provides an added measure of over-pressure protection.

The electronic returnless fuel system (ERFS) is a demand based system which uses a fuel pump driven by a dedicated controller, the fuel pump control module (FPCM).

Desired fuel pressure is commanded by the ECM and transmitted to the FPCM via a GMLAN message. A liquid fuel pressure sensor provides the feedback the FPCM requires for Closed Loop fuel pressure control.
For the GMX 245 SS application, the FPCM drives the fuel pump control module relay, also referred to as the fuel pump delivery control module, to control the brushless, 3-phase fuel pump.

Fuel Pump Control Module (FPCM)

The fuel pump flow control module (FPCM) is a serviceable GMLAN device mounted on the left, rear corner under the rear compartment floor panel carpet of the vehicle.
The FPCM receives the desired fuel pressure message from the engine control module (ECM) and drives the FPCM relay to control the 3-phase fuel pump, located within the fuel tank, to achieve the desired fuel pressure. A liquid pressure sensor provides fuel pressure feedback to the FPCM.

The FPCM provides a control enable input to the FPCM relay to turn the 3-phase fuel pump ON and OFF. The control enable input is switched to ground to turn ON the pump. The FPCM also sends a 400 HZ pulse width module (PWM) signal to the FPCM relay to control the fuel pump speed by varying the duty cycle of this signal.

Fuel Pump Control Module Relay

The fuel pump control module (FPCM) relay is a serviceable device mounted on the left, rear corner under the rear compartment floor panel carpet of the vehicle. The FPCM relay communicates with the FPCM via CAN serial data. The FPCM relay diagnostics are reported out via the FPCM.
The FPCM relay controls the brushless, 3-phase fuel pump by providing variable, continuous PWM speed control. The nominal current supplied to the fuel pump is 15 amps, with a maximum limit of 25 amps.

Fuel Pressure Sensor

The fuel pressure sensor is a serviceable 5-volt, 3-pin device. It is located on the fuel feed line forward of the fuel tank, and receives power and ground from the fuel pump control module (FPCM) through a vehicle wiring harness. The sensor provides a fuel pressure signal to the FPCM, which is used to provide Closed Loop fuel pressure control.

Fuel Sender Strainers
The strainers act as a coarse filter to perform the following functions:

• Filter contaminants

• Separate water from fuel

• Provide a wicking action that helps draw fuel into the fuel pump

Fuel stoppage at the strainer indicates that the fuel tank contains an abnormal amount of sediment or water. Therefore, the fuel tank will need to be removed and cleaned, and the filter strainer should be replaced.

In-Line Fuel Filter
The fuel filter is located on the fuel feed pipe, between the fuel pump and the fuel rail. The electric fuel pump supplies fuel through the in-line fuel filter to the fuel injection system.

The fuel pressure regulator keeps the fuel available to the fuel injectors at a regulated pressure. Unused fuel is returned from the fuel filter to the fuel tank by a separate fuel return pipe.

The paper filter element (2) traps particles in the fuel that may damage the fuel injection system. The filter housing (1) is made to withstand maximum fuel system pressure, exposure to fuel additives, and changes in temperature. There is no service interval for fuel filter replacement.

EVAP Lines and Hoses

The EVAP line extends from the fuel tank vent valve to the EVAP canister and into the engine compartment. The EVAP line is made of nylon and connects to the EVAP canister with a quick connect fitting.

Fuel Pressure Regulator

The fuel pressure regulator attaches to the fuel return pipe on the fuel sender assembly. The fuel pressure regulator is a diaphragm-operated relief valve.
A software bias compensates the injector on-time because the fuel pressure regulator is not referenced to manifold vacuum. The injector pulse width varies with the signal from the mass air flow (MAF)/intake air temperature (IAT) sensor.

With the engine running at idle, the system fuel pressure at the pressure test connection should be between 240-265 kPa (35-39 psi).
With the system pressurized and the pump OFF the pressure should stabilize and hold. If the pressure regulator supplies a fuel pressure which is too low or too high, a driveability condition will result.

Fuel Rail

The fuel rail consists of 3 parts:

• The pipe that carries fuel to each injector

• The fuel pressure test port

• Eight individual fuel injectors

The fuel rail is mounted on the intake manifold and distributes the fuel to each cylinder through the individual injectors.

Fuel Injectors

The fuel injector is a solenoid device that is controlled by the ECM.
When the ECM energizes the injector coil, a normally closed ball valve opens, allowing the fuel to flow past a director plate to the injector outlet.
The director plate has holes that control the fuel flow, generating a dual conical spray pattern of finely atomized fuel at the injector outlet. The fuel from the outlet is directed at both of the intake valves, causing the fuel to become further vaporized before entering the combustion chamber.

The 48 lb/hr fuel injectors will cause various driveability conditions if the following conditions occur:

• If the injectors will not open

• If the injectors are stuck open

• If the injectors are leaking

• If the injectors have a low coil resistance

Engine Fueling

The engine is fueled by individual injectors, one for each cylinder, that are controlled by the ECM.
The ECM controls each injector by energizing the injector coil for a brief period once every other engine revolution.

The length of this brief period, or pulse, is carefully calculated by the ECM to deliver the correct amount of fuel for proper driveability and emissions control.
The period of time when the 48 lb/hr injector is energized is called the pulse width and is measured in milliseconds, thousandths of a second.

While the engine is running, the ECM is constantly monitoring the inputs and recalculating the appropriate pulse width for each injector.
The pulse width calculation is based on the injector flow rate, mass of fuel the energized injector will pass per unit of time, the desired air/fuel ratio, and actual air mass in each cylinder and is adjusted for battery voltage, short term, and long term fuel trim.
The calculated pulse is timed to occur as each cylinders intake valves are closing to attain largest duration and most vaporization.

Fueling during a crank is slightly different than fueling during an engine run. As the engine begins to turn, a prime pulse may be injected to speed starting.
As soon as the ECM can determine where in the firing order the engine is, the ECM begins pulsing the injectors. The pulse width during the crank is based on the coolant temperature and the engine load.

The fueling system has several automatic adjustments in order to compensate for the differences in the fuel system hardware, the driving conditions, the fuel used, and the vehicle aging.

The basis for the fuel control is the pulse width calculation that is described above. Included in this calculation are an adjustment for the battery voltage, the short term fuel trim, and the long term fuel trim.

The battery voltage adjustment is necessary since the changes in the voltage across the injector affect the injector flow rate. The short term and the long term fuel trims are fine and gross adjustments to the pulse width that are designed in order to maximize the driveability and emissions control.

These fuel trims are based on the feedback from the oxygen sensors in the exhaust stream and are only used when the fuel control system is in a Closed Loop operation.

Under certain conditions, the fueling system will turn OFF the injectors for a period of time. This is referred to as fuel shut-off.
Fuel shut-off is used in order to improve traction, save fuel, improve emissions, and protect the vehicle under certain extreme or abusive conditions.

In case of a major internal problem, the ECM may be able to use a back-up fuel strategy for limp in mode that will run the engine until service can be performed.

Sequential Fuel Injection (SFI)

The ECM controls the fuel injectors based on information that the ECM receives from several information sensors. Each injector is fired individually in the engine firing order, which is called sequential fuel injection.
This allows precise fuel metering to each cylinder and improves the driveability under all of the driving conditions.

The ECM has several operating modes for fuel control, depending on the information that has been received from the sensors.

Starting Mode

When the ECM detects reference pulses from the CKP sensor, the ECM will enable the fuel pump. The fuel pump runs and builds up pressure in the fuel system. The ECM then monitors the MAF, IAT, engine coolant temperature (ECT), and the throttle position (TP) sensor signal in order to determine the required injector pulse width for starting.

Clear Flood Mode

If the engine is flooded with fuel during starting and will not start, the Clear Flood Mode can be manually selected. To select Clear Flood Mode, push the accelerator to wide open throttle (WOT). With this signal, the ECM will completely turn OFF the injectors and will maintain this stage as long as the ECM indicates a WOT condition with engine speed below 1,000 RPM.

Run Mode

The Run Mode has 2 conditions: Open Loop operation and Closed Loop operation. When the engine is first started and the engine speed is above 480 RPM, the system goes into Open Loop operation.
In Open Loop operation, the ECM ignores the signals from the oxygen sensors and calculates the required injector pulse width based primarily on inputs from the MAF, IAT and ECT sensors.

In Closed Loop, the ECM adjusts the calculated injector pulse width for each bank of injectors based on the signals from each oxygen sensor.

Acceleration Mode

The ECM monitors the changes in the TP and the MAF sensor signals in order to determine when the vehicle is being accelerated. The ECM will then increase the injector pulse width in order to provide more fuel for improved performance.

Deceleration Mode

The ECM monitors changes in TP and MAF sensor signals to determine when the vehicle is being decelerated. The ECM will then decrease injector pulse width or even shut OFF injectors for short periods to reduce exhaust emissions, and for better (engine braking) deceleration.

Battery Voltage Correction Mode

The ECM can compensate in order to maintain acceptable vehicle driveability when the ECM sees a low battery voltage condition. The ECM compensates by performing the following functions:

• Increasing the injector pulse width in order to maintain the proper amount of fuel being delivered

• Increasing the idle speed to increase the generator output

Fuel Shut-Off Mode

The ECM has the ability to completely turn OFF all of the injectors or selectively turn OFF some of the injectors when certain conditions are met.
These fuel shut-off modes allow the ECM to protect the engine from damage and also to improve the vehicles driveability.

The ECM will disable all of the eight injectors under the following conditions:

• Ignition OFF--Prevents engine run-on

• Ignition ON but no CKP signal--Prevents flooding or backfiring

• A high engine speed--Above the red line

• A high vehicle speed--Above the rated tire speed

• Closed throttle cast down--Reduces the emissions and increases engine braking.

The ECM will selectively disable the injectors under the following conditions:

• The torque management enabled--Transmission shifts or abusive maneuvers.

• The traction control enabled--In conjunction with the front brakes applying

Clearly then when pump controller commands 87 PSI the flow only then BECOMES greater then 48 lb/hr.

[E85LSX]

JR-Vette awsome post, can you please copy and paste even longer articles in this thread. . . Surprised u even have time to copy n paste being that ur tunning vettes 7 days a week lol

this thread is now dead. . .

[Total_Perf_Eng]

Knowing you tune Corvettes for a living, I would truely hope that you know that a 52lb injector behind a boosted car making 700+ rwhp, on a non-return style system is suicide.


Here is a well know calculation:

At 800 flywheel horsepower, with a BSFC of .5, and a max duty cycle at .80, on the industry standard of 3 bar (43.5psi), NOT factoring into consideration injector head pressure from boost, you need a 62.5lb injector. Convert that to 4 bar (58 psi), and your slightly over 70lb injectors (On an LS based motor running at 4 bar).

Anyone can reverse calculate their injector needs by knowing a few basic calculations.

Im not trying t debate, but saying a 52lb injector would work up to 700+rwhp, on a boosted application, is asking for major fuel issues. Unles that is you dont have an issue running your injectors static. There is not one tuner I know that would run 52's on anything over 625rwhp. Even thats pushing it.

Originally Posted by JR-Vette

A 52 lb injector / 545 cc/min would handle 832 flywheel HP ( 754 HP at 80% duty cycle) so no way would GM use that for 640 HP when that would make 52 lbs way too big for all NON WOT conditions