Outer Limits 4x4 Board

Giday people...

I LOVE my PJ (96 JN 3500 Auto), and have had it for about two years now, but i am beginning to hate the fuel bill.
Has anyone Converted to gas to save on running costs? What about other mods to save on fuel? (a friend put in a different air filter, and one of those hurricain things on the air intake and said it helped)

If n e 1 has some more info, that would be great.

Cheers..

Kent

Hi,

it can take 5 - 10 years, maybe longer, to recover the initial cost of installing LPG, and can cost a lot more if the engine deteriorates because of the LPG (no upper cylinder lubrication in LPG)- and if they keep fiddling the tax law with respect to LPG, there may be less and less benefit in the future. Aftermarket air filters, inlet air cyclones etc make big claims but generally do not deliver much if anything. the best ways to improve your fuel economy is to revise your driving habits - keep the engine in its torque band - peak efficiency is near peak torque - keep your tyres pumped up, take off roof racks, don't carry unneccesary junk in the car, drive smoothly. at the end of the day you're driving a 2 ton truck with a big petrol engine and the aerodynamics of a brick - anything under about 17 litres/100km around town and maybe as good as 13 - 14 on the highway would be considered excellent. if you drive like a hooligan, always stomping the pedals hard, it will send your fuel bill up dramatically.

you MIGHT also benefit from exhaust modifications and computer re-tuning (unichip etc) but these are big dollar items more aimed at power production than efficiency.

the bottom line is, big, petrol powereed 4WD's use a lot of fuel - you either have to accept it or trade it in for a lancer.

what sort of fuel economy do you get? do you keep figures or is it just a general feeling that it's using too much? what sort of driving do you do - highway - traffic - off road?

cheers

Brian

Brian pretty well nailed it on the head cost wise..... so here's a tip that will save a heap of bucks if you decide to go the LPG way.....

BUY A 2nd hand unit !!!.... they are regularly advertised in all the usuall places and a complete setup can be snapped up for under $250 !!!!

They rarely have problems mechanicly speaking but the tanks do have a small problem of recertification dating..... again there IS a cheaper alternative ...... get a retested and certified unit.... they are about 1/2 the cost of a new tank !!!

All ya really need is.....
LPG tank ---- ( the best size to fit ya rig)
mounting brackets for the tank.
filler pipe and bowser conector.
long bit of either copper pipe or flexy hose ( pends on state regs )
LPG lockout valve
converter
hose from the converter to the mixer
mixer
mixer addaptor plate to suit the carby on ya motor
petrol lockout valve
about 3 metres of 5core trailer flex to wire it all

most of the stuff comes with 2nd hand kits so ya laughing !


A local car wrecker sells LPG kits for $100 provided you pull it out .... A hundred bucks and a w/end doing it all is a hell of a lot cheaper then a brand new system

Kingy

p/s....
try a place that crushes cars up ..... they are not allowed to crush em if a LPG tank is fitted ..... I picked up a 130 lit tank for free a few months back and it still has 9 years of usable date left

Being an EFI engine I imagine there would be a lot more involved than the above post due to the EFI computer most likely controlling the ignition timing etc.

Usually AFAIK some sort of interface computer is needed?

usually comes with a 2nd kit aswell !!!!!

must remember that alot of EFI motors are now at the wreckers too

even if it didn't, it wouldn't be too difficult to booty fab something to shut off the EFI - would just need a relay to lift the injector earth + shut off fuel pump when the engine is switched to LPG.

Its a good idea too leave the fuel pump operating when on LPG. This keeps the fuel rail and injectors cool and allows for easier change over from LPG to petrol on the move...
EFI\LPG systems also are required to use a feed back system for LPG mixture control. This uses a stepper motor to operate a valve in the vapor line and is controlled by the oxy sensor.
This needs to be done for certification.

V8Patrol wrote:usually comes with a 2nd kit aswell !!!!!

must remember that alot of EFI motors are now at the wreckers too

A 3.5 litre Pajero engine on gas at a wrecker with all the bits still intact for the gas system? Don't like your chances of finding that!

DAZZ wrote:Its a good idea too leave the fuel pump operating when on LPG. This keeps the fuel rail and injectors cool and allows for easier change over from LPG to petrol on the move...
EFI\LPG systems also are required to use a feed back system for LPG mixture control. This uses a stepper motor to operate a valve in the vapor line and is controlled by the oxy sensor.
This needs to be done for certification.

Except if you bleed the fuel dry and the pump runs without fuel in it and burns out due to lack of lubrication

Tom

Also the fuel cotinually being pumped arround has a tendancy to go flat
quicker then if it's just siting in the tank.
J Top

J Top wrote:Also the fuel cotinually being pumped arround has a tendancy to go flat
quicker then if it's just siting in the tank.
J Top

well normally it doesn't have anywhere to go because you usually but a fuel lock on the end of the fuel line in the engine bay

On an EFI vehicle the fuel is pumped back to the tank via the return line as is normal. It is also a requirment for certification that the fuel pump operates when on LPG. Look in most EFI\LPG vehicles and there will be a sticker stating that a 1\4 tank of petrol minimum be maintained at all times. All EFI\LPG vehicles also are required to be auto change over. Start on petrol and auto switch over to LPG.

Some people may not do this or agree with it but these are the Vic regulations for LPG conversions......

I agree dazz, when thinking about it this is the most logical method - makes the cutover very simple as all that is required is lifting the injector ground once the engine has started, keep fuel pressure up if there is a need to cut back to petrol running, prevents vapor locking the fuel rail. a trained monkey could wire it up.

anyway to point the whole thread back in the direction it came from, my personal opinion is that there's not much to be gained from installing LPG unless you're capable of finding a second handie, installing it yourself and getting it certified.

the best ways to improve fuel economy are:

drive smoothly and slowly
buy a diesel
buy a smaller car

dumbdunce wrote:
anyway to point the whole thread back in the direction it came from, my personal opinion is that there's not much to be gained from installing LPG unless you're capable of finding a second handie, installing it yourself and getting it certified.

the best ways to improve fuel economy are:

drive smoothly and slowly
buy a diesel
buy a smaller car

Very true,

one thing with the fuel, most installs I have seen have a fuel prime
setup where there is a momentary contact button that you can hold down to prime the fuel system before you switch over, however I didn't use that in my old carby setup, just cut over on a long down hill streach of road