Outer Limits 4x4 Board

Hey guys,

I just filled up the LPG tank (80 usable) in my 97 Disco V8 auto, and only got 250km which is 32L/100km......ouch! After doing a search on here I found that the previous owner had different plugs and gap which some of the other people on the forum recommand for LPG discos.

So I serviced the Disco yesterday, so hopefully this will make a difference. But I can't see how this will get the economy up to 350-400kms which some people are getting.

During my serach on the forum I read that the converters can get "waxed up" and that they eventaully run rich. I was wondering is it easy to fix this problem, because I don't won't to blow up or even worse wreck the engine. Or should I just leave this to the professionals.

Thanks

Andy

By 'converters' do you mean the vaporizer? Or are you running gas injectors?

The diaphram in the vaproizer does eventually become stiff and it becomes a right PITA to set up, let alone tune it.

Very often however, if there is not enough adjustment in the mixture screw, all you need to do is adjust the diaphram tension (usually a big plastic or metal hex plug wound in against a spring on the side of the vaporizer.

Somewhere I have the set up procedure for this, the mixture and powe-valve (screw adjustment inbetween the vaporizer and venturis/carbs, very often on the 'y' piece which splits the gas flow between the carbs).

All the adjustments have an effect on the settings of the others - this was just a sequence to go through which after a couple of rounds gives you something which will run good.

If it will not run good / the emissions are way off - then look at the diaphram.

Sequence below (I found it!). Might be useful to someone!

On my setup there are three controls.

1. The 'Power valve' which is a screw flow adjuster in the pipe from the vaporiser to the carbs.
2. The Diaphram Tension adjuster. This is a big plastic screw on the side of the vaporiser.
3. The Diaphram bypass (or idle) screw. This is a brass screw on top of the vapouriser next to the gas outlet.

Your setup may be different, but it will still have the three adjustments.

The power valve in part controls the mixture, but also the responsiveness of the throttle and the economy.

I set the power valve first.

Unscrew the valve completly (just before the screw drops out).
Rev the engine to about 3000 rpm
Screw in the power valve until the RPM drops a little
Unscrew the valve until the revs pick up and then unscrew another 1.5 turns.

Next the diaphram tension. You only need to do this if there is not enough adjustment in the brass screw to set a proper mixture. If it needs adjusting, with the brass screw all the way in, the mixture will be rich.

Unscrew the plastic screw in increments of one turn
If the revs start to die, screw in the brass screw on the top to keep the revs up.
Unscrewing the plastic screw is richening the mixture while screwing in the brass screw is weakening it.

Continue until the brass screw reaches it's end stop (fully screwed in).

Now screw in the plastic screw until the engine just dies then unscrew it a turn or so.

Now unscrew the brass screw 1.5 turns. This should allow the engine to re-start.
If not, unscrew the plastic screw a bit and try again.

Next set the emissions by screwing in (or out) the brass screw.

On mine, it needed about a 1/4 turn clockwise to set the CO2 emissions to about 2%.

The brass screw needs quite fine adjustment. As you screw it in, the mix gets weaker and the revs drop.

It is a case of choosing an rpm high enough not to stall but with acceptable emissions.

When the mixture is good, it is worth repeating the power valve adjustment.


If the power valve is screwed in too far, when you press the accelerator, there will be a delay before it does anything and the revs will only pick up slowly.

If it is too far out, you get lightning response - but it uses loads of fuel. The 3000 rpm guide seems a reasonable compromise, but you could adjust it a little either way for power or economy.

Good description, he has an efi disco so unless he has an impco system it will be the same - with impco there is basically only the power valve on the mixer to adjust, the other adjustment is inside the converter/ vapouriser.

Andy,

I was speaking to a LPG guy in brisbane who does tuning with a gas analyzer in Brisbane for around $80

I am about to let him have a look at mine so I can report back on any improvements if you like, I am getting my tank re-tested and I will have to refit this weekend.

Tom

Ragin Rover,

That would be very useful, keep me updated.

Thanks

Andy

RaginRover wrote:Andy,

I was speaking to a LPG guy in brisbane who does tuning with a gas analyzer in Brisbane for around $80

Tom

Hey Tom,

How'd the fella go with servicing your LPG?

What are his details?

Otherwise, can anyone recommend a centre to service a 3.5 carbie on LPG either close to the city (live at New Farm) or south-west (work at Wacol)

Cheers

Stu

Howdy there,

It was team green autogas in rocklea,

I have never used them - haven't got around to getting him to look at it
but give him a call.


Tom