Thread: 14CUX Injector opening time

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.

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!

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.

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.

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.

Originally Posted by 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.

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
Fuel injection
http://www.topsail.org/goodies/LR_Fu...ionSystems.pdf

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?

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