14CUX Injector opening time

[pibby]

Engine is controlled by the14cux. My understanding is it is batch/bank fire for each side of the engine. To quote from RAVE “the ECM having received data from the sensors produces pulses, the length of which will determine the simultaneous open time of each bank of injectors in turn, which will govern the amount of fuel injected.”

So if we look at the injector bank for cylinders 1/3/5/7 will the single pulse that is generated by the 14cux be of equal time across each injector on the bank. To give an example, when the bank is fired will all injectors open for say 3.4ms for the pulse or will they have different open times say 3.2/3.5/3.5/3.4 m/s?

Using software to view the injector opening time I can see they are often of different duration for the same bank. I was wondering whether this is just a timing issue (to do with the software to have enough time to read and then display the open time) or whether the opening times are meant to vary? If it is the latter then what logic and what input is the 14cux using to derive such? I have attached the wiring diagram and at face value it appears each injector on a bank should receive a pulse of the same duration.

The other thing I was trying to understand is what is the trigger/event the 14cux uses to send the injector pulse to each bank and are the pulses to each bank sent at the same time and if so then does each bank receive the same pulse duration information? Within this cycle of pulses to the injectors how does the 14cux know not to pulse the injectors when one of the cylinders is near to the top of its compression stroke? Does it use the coil/ignition module for reference? If it does use the coil then is it just a lucky dip for this session the engine is running as to which cylinder will be first in line to receive a spark as part of the ongoing cycle until the engine is stopped and started again?

Hope I didn’t confuse the reader with too ‘tongue tied’ a question!

Thanks.

[BigJon]

The 14CUX does not control the injectors sequentially. They all "fire" at the same time for the same pulse width.

It doesn't matter where in the stroke the pistons are as the fuel / air charge entry to the combustion chamber is controlled by valve timing.

[pibby]

BigJon - At face value that is what I assumed would happen. But I’m not sure this is how the 14cux is doing it. with the car idling there are definitely different pulse widths on the same bank and also differences between the banks. A couple of months ago I bought this up with an lpg installer who is the lead technician in Australia for a certain range of lpg hardware distributed/installed Australia wide and he said it is not uncommon to see different injector opening times on a bank for a bank fire injection. He also said he has seen plenty of cars which operate one bank richer than the other (and confirms it by swapping the injector banks and still gets the same side running richer.)

If the banks fire at the same time then I assume the separate feeds to each bank are for the NAS spec which has lambda feedback. I understand the different injector opening times between the banks when running the NAS spec as I have installed the oxy sensors and run the NAS spec. but when I revert to the aust spec I don’t understand why there are differences between the banks. And this comes back to the original question – I still don’t understand why there are differences within a bank when at face value, just like you say BigJon, I would expect them to be the same. Has anyone who has software which allows them to view the injector opening times by cylinder seen the same thing for a 14cux?

Oh, still not sure either – anyone know what the 14cux uses as the trigger to fire the injectors?

what I am seeing with the injector opening times is really testing the little knowledge I have so that’s why I am asking such basic questions!

[Blknight.aus]

the injectors open in groups

what your reading is the timing change between different cylinders in accordance with the adjusted loading for each "firing pot" so if pot 1 out of 1357 needs an injector opening of 3.2ms all of 1357 recieve a 3.2ms spurt of fuel if on subsequent turns the ECU decides that pot 7 needs 3.4ms of fuel then again all 4 get 3.4ms of fuel.

timing comes from the reluctor ring in the dizzy from memory, I'll dig out the manual for you later.

[pibby]

Blknight – that would be great. Btw, what manual are you referring to? I have rave which includes the workshop manual but was unable to find the answer in there.

In your example you mention for ‘round’ 1357 injector/pot one gets 3.2 m/s so for round 1357 they all get 3.2 m/s but how does it make the jump to then give injector/pot 7 3.4 m/s and the other 3 injectors 3.4 m/s in a subsequent round? I was assuming it gives out the pulse for the 4 injectors/bank at a time so when the open time is adjusted the new open time would commence at (in your example) injector/pot 1.

If the injector firing timing comes from the reluctor ring in the dizzy does that imply the 14cux doesn’t know what cylinder/injector it is using as the first cylinder to receive the new open time from the 14cux, the 14cux just sends the same open time to the 4 injectors on that bank and it doesn’t know where in the firing order it is (eg cyl 5 is next to fire), it just knows when the spark events are occurring not what cylinders they relate to?

Thanks.

[bee utey]

Goodness, what questions. On average the engine gets to burn about the right amount of fuel regardless where in the cycle the piston is. You know, carbies used to work too. Precision isn't what your ECU is about.
There is NO position sensor on your engine. So it gets some fuel each stroke, regardless if it's half of one injection pulse and half of another. This is what Land Rover considered to be good enough. The connection to the negative of the ignition coil just lets the ECU know how often to bung a bit of fuel in.
There are engines that fire all injectors in one go, such as the VN V6 Commydoor and the 5 cyl VW bus, they seem to work well enough for their era. It's only emission requirements and faster computers that allowed real time cylinder-by-cylinder mixture monitoring and sequential injection.

[Blknight.aus]

Blknight – that would be great. Btw, what manual are you referring to? I have rave which includes the workshop manual but was unable to find the answer in there.

In your example you mention for ‘round’ 1357 injector/pot one gets 3.2 m/s so for round 1357 they all get 3.2 m/s but how does it make the jump to then give injector/pot 7 3.4 m/s and the other 3 injectors 3.4 m/s in a subsequent round? I was assuming it gives out the pulse for the 4 injectors/bank at a time so when the open time is adjusted the new open time would commence at (in your example) injector/pot 1.

If the injector firing timing comes from the reluctor ring in the dizzy does that imply the 14cux doesn’t know what cylinder/injector it is using as the first cylinder to receive the new open time from the 14cux, the 14cux just sends the same open time to the 4 injectors on that bank and it doesn’t know where in the firing order it is (eg cyl 5 is next to fire), it just knows when the spark events are occurring not what cylinders they relate to?

Thanks.

I'm pretty sure I have a copy of the generic concepts of the different styles of fuel injection management systems, its not outright for a specific system but covers the basics for fault finding various styles of system.


your getting the grasp of it now, the 14cux essentially only has the ability to control 2 injectors, the mapping for the other 6 are basically paralleled to one of those 2 injectors. its similar to how your indicators work. you have one switch that can either turn on the left turn lights, the right turn lights or have them all off. When you decide to turn left you turn on the left turn lights and they all blink together for as long as you decide they need to be on for ditto for a right turn.

for some stuff thats a lot better than the generics in my books try these links

Rover 14CUX Hot Wire Mass Flow EFI: Service and Troubleshooting (http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm)
Fuel injection (http://www.g33.co.uk/fuel_injection.htm)
http://www.topsail.org/goodies/LR_Fuel_InjectionSystems.pdf

[Richard93Vogue]

Great thread guys!

I am enjoying reading these very informative conversations as I continue to investigate the best way forward in converting my Rangie to direct injection.

I have a question, might be a no brainer but here goes; will (or do) any of the aftermarket computer systems for a 14cux rover provide the capacity to make them into a sequential firing order instead of batch/group firing?

Several installers that I have spoken to regarding my project have raised concern about this issue, but it appears Pibby that you are running yours as a batch firing lpg system?

[Richard93Vogue]

And with a little bit more searching of various forums I find the answer to my own questions...beeutey has already said that the group firing is considered acceptable for this application.

Thanks

[PhilipA]

The rev signal is taken from the coil.


will (or do) any of the aftermarket computer systems for a 14cux rover provide the capacity to make them into a sequential firing order instead of batch/group firing?


AFAIK there are several aftermarket systems that are "sequential" eg Haltech, Motec , and several others.

However the reading that I have done suggests that sequential is mainly used by car makers to meet emission regs at low revs and that all non piezo setups revert to batch over 3K RPM, because the opening and closing time of conventional injectors takes too long to inject fuel into single cylinders at high revs.
The Megasquirt site has something on this.
This has now probably been superceded by direct injection with piezo injectors but that is a whole different ball game.

[Richard93Vogue]

Thanks for that Phil.

What I am musing over at the moment is whether I 'must' install a new computer system for injected gas or not.
I figure, in my non-tech mind that I don't need to as any new installation will have it's own brain and will be able to use the injector pulse signals from the existing engine.

Do you know of any Landrover people in this area (Hunter Region) who are able/experienced in doing gas injection on a 3.9?

Thanks,
Richard.

[PhilipA]

Do you know of any Landrover people in this area (Hunter Region) who are able/experienced in doing gas injection on a 3.9?



Sorry no.
But I think you will run into the same injector opening /closing time with gas injectors. AFAIK that is why they are batch.

I am a bit confused about your concern on gas injection. AFAIK, all systems have their own ECU and take a "base" injector duration from the 14CUX, which is then adjusted either by an o2 sensor or tweaks to the map. I have looked at the installation instructions for the UK Marelli System and I have a copy here if you want it. Just PM me with your email address.
Regards Philip A

[pibby]

richard - yes you must install an ecu to control the injected lpg hardware and its setup. i have attached the configuration manual for the system on my car (elko). as you will see, there are a number of parameters to set up and things to configure. they are a lot more involved than the mixer type. some say not worth the extra expense (or trouble). bee utey on this site is very pleased with the mixer installs he does which have the lambda control for the lpg system.

[myboat]

gidday have fittd over 200 hundred gas injected cars and discos and range rover it does not matter what it ie the gas ecu requires a pulse either from a igntion coil or better still off the pulse side of the injector which has been cut for the gas injection

hope this helps

bruce