3.9l EFI motor questions

[walker]

Since I have to buy a new motor for the Rangie I am looking at getting a 3.9l EFI one.

I have been told that there are older (not very good) EFI systems and newer (better) EFI systems. I know the 3.5l EFI used the older system and the 4.0l used the newer system.

Can someone tell me if the 3.9l uses the older or newer system of EFI & what is the difference?

[PhilipA]

The 3.9 efi uses the newer system which is an adaptation of the Bosch LE Jetronic generally called 14CUX.
It has a Mass Airflow meter (MAF) instead of the Bosch 'flapper'. it has starting enrichment by the ECU lengthening the duration of the injectors, rather than a cold start injector, and it has a stepper motor for idle compensation for the aircon etc.
In USA etc it has closed loop with o2 sensors but in Australia has no feedback loop.
It is generally a strong robust system, and is/was the most popular system in the World.
the 4.0 used the the GEMS system which is a very modern system with direct fire ignition.
The 14 CUX is very reliable, but now being old may have poor contacts , and malfunctioning sensors. Most sensors are cheap with the exception of the MAF, and It is suicide to run an oiled airfilter such as a K&N as it fouls the MAF
The only real consideration that makes fitting a 14 CUX a bit difficult is that it has an elctronic Vehicle Speed Sensor (VSS) which increases idle if the car is moving to prevent stalling as the car stops. If you were to retrofit you would have to somehow fit a VSS . there are specialists who can fix this for you.
I am assuming you wish to fit to an injected 3.5, as it is much more expensive to set up an injection fuel system on a carby car.
Regards Philip A

[walker]

Thanks Phillip. I am planning to buy a complete motor. In fact I will probably buy a complete car and pull out everything I want. style_emoticons/<#EMO_DIR#>/laugh.gif style_emoticons/<#EMO_DIR#>/laugh.gif

At the moment I have the basic Carby 3.5 which is now DEAD!

I will upgrade to at least a 3.9l EFI plus put in a ZF auto at the same time. I have been told to go to EFI I will also need a new tank & high pressure fuel pump & lines. I have been quoted $4500 for everything (3.9l complete motor, ZF auto, transfer case & fuel tank pump & high pressure lines). However I can also pick up a complete car for this price or less.

I assume if I buy a complete motor then the VSS will be fitted so I don't have to worry??

Also to get my technical facts straight, did the 3.5 EFI differ from the 3.9 EFI because they were not direct injection, or not high pressure throught the lines or what was it? I just remember someone explaining it but can't remember.

[PhilipA]

The 3.5 injection (14CU)was Bosch L jetronic, which was just an earlier cruder injection. Operating pressure is the same at 2.5 bar. Thats why I said it is cheap to upgrade a 3.5 injection to 3.9 as you can use the pump ,lines etc.
It is the same principle as a 3.9 so I don't understand high pressure vs low pressure. Just the 3.9 injection is much more accurate and sophisticated as it replaces mechanical devices with electronic devices. Flapper to MAF, cold start injector to control from ECU, cold start timer to electronic control, addition of stepper motor.

The VSS replaces the speedo cable. I guess its up to your negotiating ability if you have it included but its not usually with eithe ra motor or with a transfer. But the VSS itself is not the major issue.You would need to get an electronic speedo from a 3.9 if you want to be as per standard, but you may be better to buy an after market signal generator as the loom for a 3.9 will be different to a 3.5 and loom changeover is a very labour intensive job..
Regards Philip A

[101RRS]

Just be aware that the 3.9s in the Disco 1 (pre update) is different to the 3.9s in the Disco 1 (post update). The obvious difference is that the post update uses a serpentine belt where the earlier 3.9 has various belts. I am not sure what ather differences there are but some people have said their are other some (aircleaner/EFI?) - certainly the 3.9 in the pre updates was a bit more economical than the post update.

Someone else might be able to tell you the differences.

Gazzz

[51jay]

Originally posted by walker
Since I have to buy a new motor for the Rangie I am looking at getting a 3.9l EFI one.

Apologies for butting in but I'm looking at selling my 93 chipped, supercharged 3.9L efi with ZF and transfer case in order to change to diesel. If you'r interested this gives you everything you need in a package, except for the fuel pump. style_emoticons/<#EMO_DIR#>/biggrin.gif

[rovercare]

What sort of coin are you looking at for the blown 3.9 and some more details on injectors, engine management, rising rate reg? Dyno figures etc would be appreciated

[walker]

Originally posted by 51jay

Apologies for butting in but I'm looking at selling my 93 chipped, supercharged 3.9L efi with ZF and transfer case in order to change to diesel. If you'r interested this gives you everything you need in a package, except for the fuel pump. style_emoticons/<#EMO_DIR#>/biggrin.gif

No appologies needed. style_emoticons/<#EMO_DIR#>/biggrin.gif PM sent

[51jay]

Originally posted by rovercare
What sort of coin are you looking at for the blown 3.9 and some more details on injectors, engine management, rising rate reg? Dyno figures etc would be appreciated

Geez! I don't know, I imagine the injectors would be standard,as would be the fuel regulater. The piggyback chip would be to take care of the fuel and ignition curves. It's a Unichip. I will be taking it down the Gold Coast sometime this nonth to get it tuned and dyno ed so will find out then. I wouldn't expect it to be boosting any more than 1 Bar.
I've only had the RR a few weeks, but I bought it with the intention of swapping in a diesel.

[p38arover]

Originally posted by 51jay
I imagine the injectors would be standard,as would be the fuel regulater.

They may not be. When my 3.5 was bored and stroked to 4.6 (back in the late 80's), the original injectors wouldn't flow enough fuel (neither would the early EFI electronics). The injectors were replaced as was the electronics.

Ron

[p38arover]

Originally posted by PhilipA+--><div class='quotetop'>QUOTE(PhilipA)</div><div class='quotemain'>the 4.0 used the the GEMS system which is a very modern system with direct fire ignition.[/b]

I think the 4.0 used in the Disco 2 used the Thor engine with the Bosch EFI. I think the GEMS was only on the P38A.

<!--QuoteBegin-PhilipA
It is suicide to run an oiled airfilter such as a K&N as it fouls the MAF[/quote]

Hmm, I note that the breather from the rocker cover on my LPG P38A was moved from the throttle body and moved upstream. I had better check that it is after the MAF sensor. This is to stop the sump filling with LPG.

Ron

[PhilipA]

The green injectors on a 3.9 are quite big at 22.5lbs per hour,(vs Commodore at 18lbs) and are used in the 4.6.
Even with a supercharger on a 3.9 , I would think they are big enough if an adjustable fuel pressure reg is used.
The only thing a Unichip cannot do is increase the total injector duration at full throttle on a 14CUX, so to increase full throttle flow you have to increase fuel pressure or put in bigger injectors
OK, maybe I should have been more precise. The FIRST 4.0 was a GEMS in 38A and then Motronic in Thor engine in both 38A and Disco 2, but it as still 3950CC the same as a 3.9.
Regards Philip A

[walker]

I was speaking to MLR today. the Disco 2 uses the Bosch EFI system.

I am starting to think I might change my mind. The rangie is only an off-roader so does not get driven a lot. My thoughts at the moment are to try to get a 4.6l short motor and keep it on carby for the time being, along with the 4speed manual box I already have. Then maybe next year when I save up a bit more I will put the ZF in.

Any comments on doing this :?