Thread: 14cux compatability

So different ecu's must have slightly different fueling maps then? I'm just trying to understand the differences between ecu's. For there to be differing part numbers relating to different models and engine sizes they obviously can't be exactly the same.

The plugs look fine to me. I know the engine suffered a holed piston before I bought it, although it also had a major overheating problem when I got it due to a shagged radiator, now fixed and runs fine with no overheating under load or idling for hours and doesn't lose coolant.

Only one piston suffered and the PO fitted a new (second hand) piston to repair the problem, plus supplied a recon radiator when I pointed out the massive leak.

This rangie was a UK import, brought to NZ in '95 and has a green tune resistor and no cats. From what I can tell it's a high comp engine, (based off the vin number and being UK spec).

I didn't think the 3.5s had the 14CUX injection system. Did they have the older flapper system so the ECU would be different.

No all Disco 3.5 had 14CUX.

On the subject of running a 4.6 the limitation is not the injector size as the same size injectors are run in a Ford 4.4 V8 as in Mustangs.

The limitation is the limit of duty cycle programmed into 3.9 14CUX of about 70% of the injector potential flow.

I do not know about whether a 3.5 has a different setting on the eprom than a 3.9. The 14CUX has many tunes in the one chip governed by the tune resistor.
Perhaps you should email the bloke in UK who does the upgrades to 14CUX to run a 4.6 ie removes the 70% injector duty cycle limit among other things. He should be able to tell you.
His name is Mark Adams. Google it and all will be revealed.
Regards Philip A

My 3.9 is running the injectors at full speed at high rpm to maintain 12:1. Good to know that is only 70% duty cycle.

AFAIK they run the same pressure as 14CUX, as I have swapped in Bosch Yellow top( In both Gen 11 and Gen 111 as fitted to Mustang) and the car (RRC 3.9 ) has run correct mixtures.

In fact before I added O2 sensors they were slightly richer at idle than the old Lucas, according to Ward at Graeme Cooper who dyno'd the car. This was with a standard Fuel pressure regulator.

This would not be the case if they ran at a higher pressure.

Regards Philip A

I saved this from when I was modifying my 3.9 back in 2008 . Luckily it still seems current
IMHO it is one of the best summaries of the 14CUX.
It agrees with us both in that you can get more power by increasing the fuel pressure a little , and the last sentence states that the injection feeds no more fuel after 4500 revs in a Range Rover, ie the duty cycle of the injectors is locked ( at about 70% AFAIK)
Fuel injection
I don't know without a great deal of research what the flow rate pressure is, but I do know that yellow top Bosch were rated at 18.5 lbs per hour and the Lucas green stripe were rated the same 18.5 lbs per hour.

That the yellow tops run correct mixtures in a 3.9 suggests to me that they are rated at the same pressure, or the mixtures would be out.
Regards Philip A