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mitch8198

Landrover 3.9 V8 with Atom

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Hi everyone

We have a couple offroad 4wd trucks fitted with the Landrover 3.9 injected V8. We run into constant issues with high idle speed, rich running, cold starts and very poor fuel economy, all of which are difficult to diagnose in the field without proprietary Landrover diagnostics equipment. 

The factory ecu controls the injectors in 2 batches, one for each bank of 4 cylinders using a number of input sensors (which have a habit of failing) and separate narrow band O2 sensor in each manifold for feedback.

We are considering the idea of fitting an Atom to control idle speed and fuel only (with the potential to move from the distributor to wasted spark ignition in the future). A few queries:

  1. Can an Atom be customised to control the injectors in the factory manner? (ie batch fire on each bank rather than alternating cylinders like reccomended in the help file). 
  2. Each injector loom has a resistance of only 4.5 ohms, if we wire 2 inj drives to each bank will this draw too much current?
  3. Will the existing engine speed trigger from the dizzy be sufficient for the g4+ to do fuel only?

If anyone has encountered other potential difficulties with this installation, your comments would be appreciated.

More info about the existing landrover system can be found here: https://en.wikipedia.org/wiki/Lucas_14CUX

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1. Yes, in “multi group” injection mode the injector drives are fired odd/even, so just connect one bank to inj drive 1, and 2nd bank to inj 2.

2. The Atom inj drives can do about 5A each so just one drive per bank is needed.

3. I would guess the distributor just has an 8 tooth “chopper disc” inside?  If so this will be fine.  Even with the distributor you could still have the Atom control ignition advance which will often give you better idle control than air valve alone.  To do wasted spark you would need some different chopper wheel to get a “sync” reference.  You might just be able to cut one tooth off to make it 8-1.

You will probably want a MAP sensor and may need an ignitor if you want to control the coil (not sure if these engines already have an ignitor fitted).

 

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Thanks for the quick reply.

Checked the distributor and there is an 8 tooth chopper wheel in there which should be ideal for our purposes.  The current ignition coil only takes power and ground, there's no igniter just a set of points in the dizzy.   At this stage we would be just be looking at fuel/idle control as that is where the factory ecu really falls short, a decent trigger wheel and ignition control may come later. Will sufficient idle control be able to be achieved with just the fuel and idle valve being controlled? 

We'll fit a MAP sensor to and the current stepper idle control will have to be deleted. As this is on a budget, do you guys recommend any particular OEM produced MAP sensors or 2/3-wire IAC solenoids that we can find at the wreckers?

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43 minutes ago, mitch8198 said:

As this is on a budget, do you guys recommend any particular OEM produced MAP sensors or 2/3-wire IAC solenoids that we can find at the wreckers?

The Bosch idle valves found on BMW's and many other european cars are very convenient with simple hose type connections.  You can get 2 and 3 wire versions but 2 wire would be the preferable one since you dont have too many spare aux outputs on the Atom.  Expensive new but good value 2nd hand and rarely give any trouble.  For the MAP sensor I cant think of too many good examples off the top of my head.  Many 90's toyotas have them or the GM/delphi 1Bar might be options.

lg_1570a8c8-1308-4c42-97aa-982bcbd4caca.  

 

 

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Hi mitch8198 , i used to run RV8 in my off road comp truck , they are a good engine but if you are going anywhere near water you will need to ditch the dizzy , my truck used to run under water , we used a 36-1 on the crank and fired the injectors in 4 blocks of 2 . 

As Adam said the BMW 2 wire is a good and cheap option , as are the GM map sensors. It will be the best thing you can do to the motor for reliable off roading..

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Awesome info, thanks everyone. Update and another quick question:

We picked up an atom, have wired it up and it's talking to the PC. All sensors are reporting reasonable values. 

We're having trouble with triggering, there's 0 rpm reported in pc link while cranking so it's not firing the injectors.

Theres some sort of trigger wheel in the dizzy with a speed sensor. It's wired to trigger 1. I've set it up as a multi tooth, reluctor, with 8 teeth. Are there any other settings I'd need to change to get it to trigger? 

 

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Have done a bit more searching, I originally connected the trigger 1 input to the factory trigger wire which goes to the negative side of the coil. As I only need engine speed (as we're doing fuel only)  is this even possible to be used to trigger the link? 

The dizzy has a two wire reluctor type sensor which is used to somehow provide ground to the coil when it needs to fire. 

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Hi - When i originally set my Dodge V8 up i used the dizzy with group fire injection . The dizzy is a 2 wire magnetic reluctor type so sounds similar to your set up . I used the reluctor to trigger 1 and set it to - 1 tooth per TDC .The polarity of the wiring is important   . Unfortunately  the difference between our set ups is i used an MSD box to fire my coil and the timing was through the ECU . I dont know if you can piggy back your reluctor wiring to trigger 1 and your ignition ? Does the dizzy trigger a separate ignition box ?  

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That's interesting, yeah sounds similar but I'm pretty sure I can't piggy back the current reluctor as landrover have something called an "amplifier" inside the dizzy which acts as an ign box and switches GND to the coil. 

I've actually managed to get it running by setting the trigger type to optical/hall and turning on pull ups and setting trigger to falling edge. This means when the coil is pulled low by the amplifier I get a trigger pulse. 

It is really unstable and rpm fluctuates between ~700 and over 50k lol. 

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Is this what your distributor looks like?:

dizzy_new_01a.jpg

 

If so it will be a bit of a trick.  You really need to get at the raw signal from the pickup before it goes into that ignition amp.  I dont know what they look like inside so you may be able to intercept/splice into it inside?

I see you can get "ignition amp relocation kits" for these so that might be another option.  Or you could get rid of that amp altogether and get the ecu to drive the coil (will still need another amp).  

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yep thats the one, although the 3 pins only have 2 wires plugged in.

qwFOZFk.jpg

 

We've got it running quite well using optical/hall setting and triggering when the gnd side of the coil is pulled low by the amp (lots of filtering required). Took it for a drive up and down the road and managed to do a quick fuel tune (attached) to keep AFR between 12 and 15.  Improvements to the idle quality, power and economy are noticeable already.

However for the first minute of start up the rpm reported by the ecu is really unstable or '0'. I think the pull up on the atom isn't raising the signal fast enough to count as a negative edge so ill try fit a ~1k to the negative of the coil and see if that helps. What are your thoughts? Worst case scenario we retrofit a trigger wheel and a proper reluctance sensor (ie raid the wrx parts bin :D).

3.9 V8 Fuel G4+ Atom.pclr

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A pull up wont help, the coil itself is basically a very strong pull-up (like probably <1ohm) to 12V.  I suspect the problem will be the oscillation or "ringing" that you get in the primary waveform so the ecu will see multiple "teeth" for some spark events.  The 400 odd Volts will possibly damage the ECU also, so this is not a good idea.

Like I said earlier probably the easiest option is to remove the ignitor off the side of the distributor so you can get direct connection to the reluctor.

Another option maybe a coil/tacho interface device such as this:  https://wiki.autosportlabs.com/CoilX

 

waveform-ignition-2-638.jpg?cb=143133205

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wow don't know how we missed what sort of signal is actually from the coil, thankyou so much. Reluctant to rip into the dizzy so did some research on that CoilX device. Looks like a pretty decent chip, ordered one so we'll see how it goes.

 

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