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post #1 of 9 (permalink) Old 05-02-06, 05:26 AM Thread Starter
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gas questions

have been considering gas conversion for some time but for obvious reasons thinking about it more. any help appreciated
engine is only 8000 iles since rebuild,mild,street only use,650v/s holley,weiand,twin system,etc,standard stuff

a few questions

*how big is the power difference? i beleive you can up the compression on gas to overcome this,currently 2V o/c heads, could i just run c/c heads to up the comp? on a street engine would you notice the power drop?

*opinions on running both gas/fuel or gas only.

*if just gas only can a 'flat' tank be made to replace the fuel tank in the boot well

*how much gear is needed under the bonnet,any one got some pics of some neat installs. engine bay is currently very clean and neat and i dont really wanna clutter it up.

sorry know very little about it all and still trying to decide (then trying to find a shop without a massive waiting list i guess)

any info links?
any perth shop recommendations?
especially appreciate any pics of really neat gas engine bays



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post #2 of 9 (permalink) Old 05-02-06, 05:40 AM
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Re: gas questions

Gas tends to clutter the bay. Gas research does some relatively clean installs considering the extra hardware needed to be fitted.

Basically you'll need a mixer, meters of heater hose and a gas snorkel/aircleaner or carb.

XB Fairmont (street car) 11.07@123.02mph.
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post #3 of 9 (permalink) Old 05-02-06, 03:01 PM
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Re: gas questions


Power difference on lpg? For normally aspirated engines, there are various estimates, 10-20%? I think the difference with a stock-mild engine is negligible, whereas it is more noticeable with performance engines. LPG is good for torque in the low rpm range as it wants to be a gas. Petrol is a higher energy fuel, so it it's revs and hp you're chasing, it will have the edge (although forced lpg has been successful for some folk).

Most would strongly recommend running one or the other. The two fuel types require different engine setups, so duel fuel will always be a compromise one way or the other.

With straight lpg, the petrol tank can be removed and an lpg tank installed in the cavity. Tanks come in a feww different shapes and a wide range of sizes. Cylinders, toroidal (donut).
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post #4 of 9 (permalink) Old 05-02-06, 05:59 PM
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Re: gas questions

The link to gas research site is below:

These folk make lpg carburettors, range from 350 cfm to 510 cfm. The 510 will support upto 300hp. Above that, you'll need a twin set-up. They have pictures of both arrangements.

The other common option is to use either an Impco 425 or OHG 450 mixer. These mixers need to be mounted on throttle-body (botton part of holley or theroquad).

There are plenty of threads throughout this forum on both set ups.

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post #5 of 9 (permalink) Old 05-03-06, 01:58 AM Thread Starter
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Re: gas questions

thanks,so on my stockish street engine power drop should not be too much issue, chasing torque more than HP anyway. thanks will check out the gas research site now. would probably go straight gas as yes i assumed that duel fuel would cause you to tune half way between the two
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post #6 of 9 (permalink) Old 05-03-06, 02:35 AM
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Re: gas questions

Hi,has anyone looked into injected LPG in most cases it actually out performs fuel injected engines.A local bloke has done afew cars an xr6,a v6 with twin turbo,s and a gen 3 with an increase in performance and in dollar terms the equivalen t of 5.5 L per 100k,s.
I wish I could afford to purchase a injection manifold and match a set of alloy heads for my clevo, a good start for the conversion.Ford is quoting some promising performance and economy figures with the release of factory LPG injected cars later this year.
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post #7 of 9 (permalink) Old 05-03-06, 02:49 AM
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Re: gas questions

on your engine gas will run great, heaps of torque but not much hp up top if mine is anything to go by. Ive had mine on straight gas for 10 years and haven't had any dramas except fuel consumption is heavy but Im working on that. With the Impco mixers you can use a standard holley type air cleaner so it doesnt look dramatically different. The GRA is meant to be superior but so is the cost.

like WAX said there is heaps of info here for you.
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post #8 of 9 (permalink) Old 05-05-06, 09:13 AM
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Re: gas questions

Australians might want to check out Gas Injected Technologies (Smithfield, NSW):
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post #9 of 9 (permalink) Old 05-05-06, 06:49 PM
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Re: gas questions

Hey guys,
i draw your attention to the hi performance graph showed of the VY engine making more power on LPG that PULP. (

On the right vertical axis the scale is measured in "Ft Lbs Torque" and records both engines producing approx 1300+ Ft Lbs of torque

1300 Ft Lbs of torque is nearly 1760 Newton Metres and i can assure you there is not a VY Commodore in this country that would produce that much torque.
Most dynamometers measure tractive effort, not torque. Tractive effort is measured in Lbs or Newtons of Force, but not Ft Lbs or Newton Metres.
The scale they have used looks like tractive effort.

The conversion to Ft Lbs is not complex, so their "1300" is more like 540 Newton Metres or 400 Ft Lbs of torque.

I look forward to seeing the change on their website.....

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