Thread: What's the economy like on LPG?

Sounds about right,

I get between 350 400 K's for around 96 liters of LPG in a 4.2 EFI rangie

depends how heavy the right foot is.

Tony

Hi Tony,
I must admit that I was somewhat aprehensive when allowing this system to be fitted but I am now pleasantly surprised at the quality of the performance and at such a low cost for fitting.
It had a loss of 30 HP which was found on the Dyno when the wrong Air filter was changed, now it runs almost as good as when on petrol.
Hopefully it will improve in economy after the retune at 2000Kms as it was indicated that it could get 500 Kms to the tank on a trip when it settles in....
Should this happen I will be over the moon.
Still for now it's cheaper to run, smooth as silk, easier to start and has no backfires.
It seems like I got a really good job, so far anyhow....
Cheers,
Shirley....

Hi Shirley

What sort of system did you get put on, straight gas into the plenham or did you get a stepper valve system, I think 500k's is a bit optomistic, the most I have ever got is 450 for 96 liters and that was freeway driveing at 80k's

There should be no noticable power differance between the LPG & petrol and the switching on a EFI system should be smooth and instantainious

If you can put 2 maps into the computer it may be worth maping it for both fuels, thats gonna be my next step in the never ending search for more mpg

Tony

Hi Tony,
I am unfamilliar with these systems, both the Stepper or Direct Mixing in the Plenham but I feel that basic observation would indicate the latter.
The gas is sent through a regulator to a pre heated mixer in the Plenham and it has an adjustable valve on that input line.
The entire system was set up on a Dyno thus providing the highest performance and horsepower and is automatically controlled by a computer which provides petrol startup and auto change to gas once running and a push button to petrol when the gas tank is empty.
Four lights indicate the level of the fuel in the LPG tank and other LED's indicate which fuel is being used at any particular time. It all seems quite neat but the need for new plugs every 20,000 kms is recommended along with a test on the entire ignition system.
Exactly what plugs should be used is unclear although it is suggested that Fancy Gold Paladium or resistor plugs should NOT be used.
I guess I will leave that to the installation people when they do the servicing, assuming I can afford it, hey?
Cheers,
Shirley.....

Shirl, your economy figs are about average in my experience. I get 360kms out of 80 usable ('85 carby County V8), sometimes less depending on driving style.

I swear by iridium plugs - too expensive to change at 20,000kms (I go to 60,000) but good LPG running is very dependent on getting good ignition.

The fuel gauges can be a bit inconsistent in their readings; once you know the normal range of your tank, set your trip meter to zero every time you fill up and use it instead of the gauge. Much more reliable.

Chris

LPG can be tuned for either power or economy. If you want 20% better economy- you guessed it- expect 20-25% less power.
Sounds as though its tuned for the power. A lot of conversions are done this way as people tend to complain about the power loss if its done the other.
Cheers,
David

I get on average 390k from 78 useable but have achieved 430k at a constant speed and no load, car empty. I do have a smaller motor 3.5 but it has 361k on the clock now....um cant remember when I last changed the plugs 50k ago I think and I used the standard plugs. Yes I am down on power but also on petrol as well. Soon I will put in my nice new 3.9 I have sitting in the spare room at home....
Brad

shirl
do an lpg search there has been heaps of info on lpg systems on this site last month or so

cheers paul