Question on direct injection fuel system.

[Crazy AWD]

My car has a high pressure direct injection fuel system that can actually inject up to three times per combustion cycle (something about getting the optimal fuel mixture in the cylinder). Will the 0-3 injections per cycle affect the IDC function? Or is it still just a matter of injection/time? Would I be better off tapping one of the ignition coil negative triggers instead?

Tahnks!

[Richard L]

What car do you have. The HFS-6 need to be reconfigured by use to take full advantage of the your fuel system. Direct injection, as multi-jet or three-stage injection is great with W/A injection, even it injects three times during a combustion cycle, it only accounts for 30% of the conventional Fuel onjection system. The injection duration is very short.

[Crazy AWD]

2009 BMW 335i

[Richard L]

Why do you want to tap into the ignition coil negative? It will destroy the unit for sure.

Can you tell me where are you located?

I am trying to identify the type of direct injection system used on this car. I believe ot is one of the followng:

1. Low pressure common rail - with piezo furl injector
2. High pressure common rail, with solenoid vaevb injectors.

Can you help me which is which? I know the chgange-over period is between 2007.

[Crazy AWD]

Originally Posted by Richard L

Why do you want to tap into the ignition coil negative? It will destroy the unit for sure.

Not main power for the coil, the low voltage trigger for the coil. I din't know if what I really needed was one pulse per cylinder cycle. Didn't know if the 1-3 pulses per cylander cycle would make the HFS-6 think the moater was running at a hier speed.

Originally Posted by Richard L

Can you tell me where are you located?

Texas...CDT

Originally Posted by Richard L

I am trying to identify the type of direct injection system used on this car. I believe ot is one of the followng:

1. Low pressure common rail - with piezo furl injector
2. High pressure common rail, with solenoid vaevb injectors.

Can you help me which is which? I know the chgange-over period is between 2007.

High pressure common rail, with piezo injectors.



More info:



It is the outward-opening piezo-injector that renders possible spray-directed direct
injection and thus the overall innovations of the N54 engine. Due to the fact that only this
component ensures that the injected fuel spray cone remains stable, even under the prevailing
influences of pressure and temperature in the combustion chamber.
This piezo-injector permits injection pressures of up to 200 bar and extremely quick
opening of the nozzle needle. In this way, it is possible to inject fuel into the combustion
chamber under conditions released from the power cycles limited by the valve opening
times.


The piezo-injector is integrated together with the spark plug centrally between the inlet
and exhaust valves in the cylinder head. This installation position prevents the cylinder
walls or the piston crown from being wetted with injected fuel. A uniform formation of the
homogeneous air/fuel mixture is obtained with the aid of the gas movement in the combustion
chamber and a stable fuel spray cone.
The gas movement is influenced on the one hand by the geometry of the intake
passages and on the other hand by the shape of the piston crown. The injected fuel is
swirled in the combustion chamber with the boost air until a homogeneous mixture is
available throughout the compression space at the point of ignition.

Injector Design and Function
The piezo-injector essentially consists of three sub-assemblies. The expansion of the
energized piezo-element lifts the nozzle needle outwards from its valve seat. To be able
to counter the different operating temperatures with comparable valve lifts, the injector
has a thermal compensating element.

The nozzle needle is pressed outwards
from its tapered valve seat. This opens up
an annular orifice. The pressurized fuel
flows through this annular orifice and forms
a hollow cone, the spray angle of which is
not dependent on the backpressure in the
combustion chamber.

Injection Strategy
Injection of the fuel mass required for the operating situation can take place in up to three
individual injections. Which option is used in the relevant operating situation is
dependent on engine load and speed. Here, the actual time resulting from the engine
speed available for metering the fuel is an important framework quantity.
A special situation during the operation of any engine is the range in which a high load
occurs at low engine speed, so-called "Low End Torque" operation. In this operating
situation, the required fuel mass is metered to the engine in three individual injections.
This results in a highly effective mixture formation which in the final analysis has the
effect of both increasing power output and saving fuel.
In order to bring the catalytic converters up to operating temperature as quickly as
possible, the N54 engine has a catalyst-heating mode for when the engine is started from
cold. In this mode, combustion heat is intentionally introduced into the exhaust train and
not used first and foremost to develop power output.
The point of ignition is moved to 30? (crankshaft degrees) after TDC. The main quantity
of the required fuel is injected before TDC and mixed with the boost air. The piston is
situated after TDC in its downward travel such that the air/fuel mixture is already expanding
again, which reduces the ignitability of the mixture.
In order to ignite the mixture reliably, a small residual quantity of fuel is injected 25? after
TDC and this guarantees an ignitable mixture at the spark plug. This small fuel quantity
therefore provides for ignition of the residual charge in the combustion chamber.
This operating mode is set by the engine-management system after a maximum period
of 60 seconds from engine starting but is terminated if the catalytic-converter response
temperature is reached earlier.

[Crazy AWD]

Somewhere around 3.5K RPMs I get a 100% duty cycle off the injector negative (I have a multi-meter that will read duty cycle, Hz, etc...). This ECU switches BOTH the negative side and the positive side of the piezo injector. I?ll have to get back under the engine cover to check, but perhaps the ECU is leaving the negative grounded longer than it is supplying current to the positive side?

If true... So I would need to flip from the injector negative to the injector positive and change the PWM MODE polarity solder link? Assuming that the injector positive is just 12v and not some other insanely high voltage.

[Richard L]

Thanks for the wealth of information on the last two posts. With your help, I can learn to retrieve theinjector signal much quicker.

There are two types of piezo injector based system. If you have help me identify them first, we can go deeper.

1. High pressure common rail, piezo injector acts like a normal solenoid valve.
2. Low Pressure fuel is fed into the piezo injector at about 40psi. When the multi-staggered piezo element is energised, push iong the fuel into the combustion at a very high pressure.

The piezo injector are fired using a switch-mode power supply, generating a rail voltage of around 300-400 volts. Power is fed to the Piezo element is in a semi-resonant state during firing. Piezo electric behave more like a capacitor/inductor than a resistor.

Is the Controller is made by siemens/VDO?

You are correct that the piezo injector is switched on both rails. It is more involved than altering the +/- PWM mode. Lets try "PWM(-)", wire to the -ve side the injector and let me know if you see an sign of detection on the green led. (I am referring onto the green wire of the yellow harness). The blocking diode on the HFS-6 is good for 600Volts.

[Richard L]

Your second post.

>3500 rpm, you see a full ground signal, it appeared that the (-) switch is fully driven to ground. I wonder if you can obtain a scope to see the waveform before it hits 3500rpm.

Therare two options you can try:
1. Switch to PWM(+), green wire of the yellow harness.
2. Rather switching the polarity of the PWM trigger mode, use the yellow wire. It is desiogned for Common rail diesel of FSI injectors. It detect +ve pulse durations.

[Crazy AWD]

OK, I hooked my meter up to the injector positive... saw about a 2% duty cycle at idle and somewhere around 40% duty cycle at WOT on a flat road (couldn't really go passed 60mph). Voltage was anywhere from 0V (during off throttle coasting) to almost 200V.


Would you recommend I start by removing the green negative wire and connect the yellow wire to the injector positive as a first try?
Or would you recommend changing the contact on the board and then moving the green wire to the injector positive as a first try?

[Richard L]

I would continue to use the green wire, still using PWM (-), wire it to the injetcor (+)