Thread: Binary File for EPROM in 14CXU Computer

freestyler - there's a write up i've read which says there are approx 5 fuel maps in the 14cux. you change the resistor in line with the ecu to determine which fuel map it uses. in philipa's post he shows how to do this and advises which is the NAS resistor to use. i read and also found that if you pull the resistor out altogether then by default it uses the closed loop fuel map.

with the injected lpg system they rely on the petrol ecu. so in your case the map on your 14cux is the aus map which has no feedback. you will find it isn't quite right for your motor either - i'm assuming the 14cux is for the 3.9 motor whereas you have a 4.4. so at idle and lite throttle it will be running rich (as it will be sucking more air than a 3.9) then there will be a transition point where it goes from rich to lean with the higher throttle openings. there is no feedback so it hasn't got a clue what's going on.

by putting in the oxygen sensors and wiring them back to the 14cux and changing the resistor you then have closed loop fuelling (please see philipa's write up).

this is important for the injected lpg. these work by getting a petrol map then making a lpg map from it. you hook up a laptop with the lpg software on it which is connected by cable to the lpg ecu which is spliced into the petrol injector wiring (this is how it knows what the petrol injectors are doing and can cut them off when running on lpg). to collect a petrol map you just drive around and the lpg ecu takes the readings of petrol injector opening time vs vacuum (it has it's own manifold pressure sensor). once you've covered a wide enough range of throttle openings and rpm, the lpg software has some swanky algorithims which give you a first cut of a lpg map. you then proceed to drive around on lpg adjusting this lpg map till the car drive correctly.

this bit is my interpretation of what's happening so please don't quote me! the algorithim is based on the petrol readings being correct ie the correct petrol ecu/map running the vehicle. in your case (and mine) it's not. hence the algorithim the lpg ecu uses ends up generating a poor lpg map which you then have to spend a lot of time fine tuning. sure you can get the motor running ok but i found there wasn't enough resolution in the software to get the map just right.

when you run closed loop the petrol map becomes perfectly suited to the engine which is in the car to feed in enough fuel to run lambda 1.0. so when you hook up your lpg software the algorithim works on the petrol map. so you end up relying on the processing power of the 14cux which is reading the oxygen sensors but also is reading the afm/tps/temperature etc to get the initial fuelling close to right in that millisecond when you bang on the throttle.

i have two led's from jaycar on my dash which tell me if each bank is running from lean to rich. i used these to tweak my lpg map when i used to run open loop. now i run in closed loop i can see my fuelling is working and corrects itself.

probably the best way to explain the difference is using the led's. when running open loop and you accelerate the led's would go to either end of the gauge (rich or lean) then eventually come back to running approx stoich. it was very hard to get fuelling that accurate under continuous throttle positions. under closed loop, with a proper petrol base map the led would shoot up to rich momentarily then come back to stoich. the better your map the less the led's go to the outer ends of their readings. from memory correctly functioning oxygen sensors should cycle at 300 ms or thereabouts which you can see in the led's (each is about say 10 individual led's in a row).

so to do this you will need to source a cable and software.

the closed loop injected lpg map relies on the work done by the land rover engineers in the 14cux not me playing around with my lpg software. i know which one i prefer!

hth,
brett.

The O2 sensors arrived last week and I got them in and hooked up this week end. Initial indications are that they are working well. I have to take my quad in for a service and saftey recall today see how it goes on a longer trip pulling a trailer. Tim