which gas system right for me?

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14th September 2011, 06:24 PM
wozzlegummich

Quote:

Originally Posted by bee utey

I actually had a dual fuel Falcon XG 6cyl on petrol backfire while I was under the bonnet, (low fuel pressure problem). So while port injection definitely stops the kind of massive backfires that ruin air intakes, small ones are still possible.

Now that's interesting.

This system has a fuel filter between the converter and the injectors. I don't think it has been changed since the system was fitted in 2006 (previous owner) . I wonder if that is partially blocked and is unable to deliver fuel quickly enough on initial acceleration. I'll order a new element tonight and see how I go.
14th September 2011, 06:50 PM
bee utey

Quote:

Originally Posted by wozzlegummich

Now that's interesting.

This system has a fuel filter between the converter and the injectors. I don't think it has been changed since the system was fitted in 2006 (previous owner) . I wonder if that is partially blocked and is unable to deliver fuel quickly enough on initial acceleration. I'll order a new element tonight and see how I go.

Actually the Falcon backfired on petrol, however any lean mixture will raise the possibility of a backfire. On your gas system it depends on where the gas pressure sensor is. If it is after the filters it should self adjust. If before, yes there is a case for filter change. I believe that filter changes are recommended at around 40K anyway. Notwithstanding this, some of the systems I have fitted the vehicle ignition system cannot cope with full throttle off idle on gas only. I program in a dash of petrol that cures the stumble completely. (Toyota Prado in particular)

Another question is, if you are running the Thor system, are you using the coil packs? I found they perform best with smaller plug gaps, around 0.6mm/0.024".
15th September 2011, 06:14 AM
wozzlegummich

Quote:

Originally Posted by bee utey

Another question is, if you are running the Thor system, are you using the coil packs? I found they perform best with smaller plug gaps, around 0.6mm/0.024".

Interesting you ask. Yes it is running the coil packs (Is there an alternative?)

When I first got the vehicle all seemed OK and would only "pop" through the plenum on take off if I was lazy and took of without any throttle. (OK on petrol though). This gradually got worse to the point where unless I gave it a footfull it would pop on take off (it's a manual).

So I popped the plugs out, gave them a clean, dropped the gaps to .030". After refitting it had a massive flat spot when revved from idle (on gas - OK on petrol).

Again I regapped the plugs, this time back to where I thought I started at about .035". Still had a massive flat spot off idle when revved in neutral.

Jumped on the interweb and read in several places that platinum plugs shouldn't be cleaned. ****! So I jumped in the car to get some new plugs at the local Autobahn. It flat spotted once on take off then was OK. No sign's whatsoever of the flat spot or the backfire (pop) through the plenum. Hasn't missed a beat since. WTF??

All I can put it down to is the computer has "re-learnt" itself and adjusted the mixture according to plug voltages and/or O2 sensor readings. (I think this system uses the original computer in tandem with the gas computer) Maybe needed input from speed sensors to start that process??

Any thoughts?

(I will be dropping the plugs back down to .024" this weekend - be interesting to see if the flat spot returns until I drive it again).
15th September 2011, 07:26 AM
bee utey

Quote:

Originally Posted by wozzlegummich

Interesting you ask. Yes it is running the coil packs (Is there an alternative?)

Some people have used the Thor inlet manifold in conjunction with the distributor front cover. There are many aftermarket ECUs availabe to run anything you want.

Quote:

Originally Posted by wozzlegummich

All I can put it down to is the computer has "re-learnt" itself and adjusted the mixture according to plug voltages and/or O2 sensor readings. (I think this system uses the original computer in tandem with the gas computer) Maybe needed input from speed sensors to start that process??

Any thoughts?

(I will be dropping the plugs back down to .024" this weekend - be interesting to see if the flat spot returns until I drive it again).

All things are possible, the vehicle computer will self learn as it warms up. If the gas mixtures are originally off then running much on petrol may unlearn them. Only running the gas software can tell how much difference there is between petrol and gas settings. Software and adaptor available here:

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