Outer Limits 4x4 Board

a mate wants to know if anyone is running duek fuel or dedicated gas on a zook.
he has a N/T with a g16a carby motor that needs rebuilding and wants to know if it needs to be done differently to run dedicated gas. He cliams that when properly tuned it will develop more power than petrol plus no carby on angle problems.
thanks in advance
brett

Yes I think the the seals may have to be different. Also just to tidy the motor up he could use a injected manifold and block the injector holes. He won't need a computor to run it this way.

Don't know about more power but maybe the same amount.

It will only make more power if you up the compression. Gas handles higher comps quite well

Gas has higher effective octane than petrol, but if I'm correct, burns at a different rate/temperature. It will handle more compression, and maybe more timing.

However, I also believe that it is not quite as efficient. I was always told that you had either 20% worse perfomance and the same economy or the same performance and 20% worse economy. We ran a 91 rangie on gas for a while, with a high quality conversion and the latter was true for us.

However, most gas systems do not control their fuel as well as a petrol car - they are pretty crude. Additionally, they will vehave a little oddly inother areas off road - in areas like compression braking and key starting etc, gas seems to be inferior.

I have spent some time an a gas converted 4.5 petrol 80 series, and the owners ALWAYS ran them on petrol off road.

IMHO, the cost of doing a really high quality and nicely tuned gas conversion would be higher than fitting EFI to the existing G16A, and results would be inferior.

In addition, there is limited room for a tank in a SWB sierra anyway, so range qwould be pretty poor, and you can hardy carry a jerry of LPG.

Its been done before,if your rebuilding anyway bump up the compression & you need hardened valves & valve seats to run gas.They make odd shape tanks so maybe one made to fit in a spare wheel well would fit & sit higher than your zuk tank.

Hello to all & badooky

If your running an engine made after 1986
its already got hardend valves & hardend valve seats
so theres no need to replace them.

Cars made after 1986 use unleaderd fuel
hence hardend valve
(no lead in fuel to lube valve assemblys)
lpg gas has wax in its mix to help lube/cool the valves also

Timing STRAIGHT GAS ONLY

Your dizzy will need to be re-graphed to suit lpg fuel (not for dual fuel)
static timing set to 15d BTDC around 600rpm to 750rpm
vacumm advance hose disconnected
with a total (max) advance of 30d BTDC by 3000rpm

Gas runs the engine hotter than petrol
so you will need to fit colder plugs & close the plug cap up
spark plugs for lpg use (not dual)
close spark plug cap 0.2mm & lower heat range by 2
eg 0.8 to 0.9mm petrol specs for sierra
you would close to 0.6 to 0.7mm for straight gas

And also lower heat range by two
eg champion bosch etc RN9YX
you would fit RN7YX

But NGK use there heat range back to front
the higher the number the lower the heat range

From ur tank lpg is a liquad at 101psi its converterd to vapour
at your converter to 1.5psi

Liquad petrolium gas is alot thicker (dence) than petrol vapour
so it doesnt like to flow over 5500 rpm
in naturally aspiraterd engines

OHG & IMPCO would be the better systems to go for
they use a diaphram type mixer (carby)
around 25% to 30% more lpg used than petrol

Even better would be the gas research system
thay use a throttle body type mixer
with a tapperd needle & main jet type mixing system
eg like a needle & piston set up in motor bike carby
better throttle responce & around 15% to 20% more lpg used than petrol set up

But gas research dont make a carby to suit engine under 2.0litres
there smallest carby flows 320cfm
there biggest dual carbys flow 920cfm
cubic feet per minute


Some pic of the GRS systems

Hope that helps badooky

Keep in mind that a new lpg system will cost between
$1400 to $2400 depending on system used + size off tank
it will take around two years to get ur money back from using gas over petrol (half the cost to run around)

Hope that makes sense

daryl