zeus

Hi all,

I got my dual fuel EF about 6 months ago, and since having it,
its been missing on petrol at low revs and hesitating on LPG at higher revs.
After changing the air filter I noticed a hole had been drilled in the bottom
corner of the air box. The hole is roughly 7cm across. There is also
a slot cut at the lowest part of the snorkel that is approximately 4cm long
by 1.5cm wide. My guess on this is that it may have been to allow
water/condensation to drain away, but It would also have the side effect
of having warm/hot air from the engine bay drawn into the air intake.
Could this be the reason for the car missing/running rough?

At low revs and driving normally on LPG it runs normally. Fuel economy
is pretty reasonable on LPG. Its only at higher revs that it happens.
About 3000-4000rpm is where it starts to hesitate on LPG.

Anyone have any ideas or seen this before?

Thanks,
-Shaun

pedro

The hole in the airbox is for a hose which runs from the back of the gas converter. it runs from airbox across the radiator & to a fitting on back of converter,roughly 16mm dia. has to do with closed loop gas.some cars run better without air snorkel.

RaceCraft

they put the hole there as pedro states to mount the balance line.. the factory ones are 16mm but some of the aftermarket convertors use a brass elbow that would need about a 7mm hole.. Another thing to consider is that some gas mechs put a series of holes in the bottom of the airbox to stop the 'lpg backfire' from breaking the lid or popping off the inlet elbows.. As to the running rough at high revs.. is it factory gas?.. do you have mixture screws on the convertor?...do you have an electronic or a manual power valve?

zeus

There is also a brass elbow and a hose going back off to the converter...

Its after market gas fitted by 'The Gas Converters'

On the converter there is 2 knobs...

I took a couple of photos of the converter and the mixer.
From what I can gather, its a complex converter, and a simple mixer.
http://ctnet.dyndns.org:82/gallery/gas

The last place I took it to to have it 'tuned' said that the knobs on the
converter are for setting the idle speed. Is this right? or is their
information as good as their tuning ability (ie, non existant )

Whats the 'power valve'? I can probably take a photo of it if its not show in
the above shots.

Thanks for the info :)
-Shaun

RaceCraft

The convertor your using is made by OMVL...The small knob is the mixutre screw the second onne(bigger one) is the sensitivity..The idle speed screw is on the throttle body... although playing with the mixture screws can have an affect on the idle the place you go is not really giving you the correct info..... the power valve is on the main vapour line between the convertor and mixer.. i've found the $5 manual ones are more reliable than the electronic ones...
P.S> the manual ones have a large threaded screw that acts like a simple flow meter.. the electronic ones are a larger barrel with wires running out of them to a ECU

let me know?

zeus

Hi Tibbo,

Its an electronic power valve... I've added a couple more photos to
http://ctnet.dyndns.org:82/gallery/gas that show the power valve.

What does the sensitivity adjustment do?
Whats the job of the power valve?

I've tried searching google for info on gas converters and mixers
and information on how they actually work and there is basic info, but
nothing very specific :)

Thanks for your help,
-Shaun

RaceCraft

The sensitivity screw adjusts the mixture, same as the top one but only in smaller increments <--*spelling....You can lean the gas off using both..Because the car is running OK at most RPM's I'd give the sensitivity screw maybe 1/2 a turn out

The power valve restricts the maxium amount of gas that can flow into the throttle body.. The electronic ones meter the gas allowed to flow into the throttle body for performance and emissions using other vehicle electronic systems..So if the car is surging at 4000rpm it is not getting enough gas. The manual ones are adjustable with a screwdriver and once set are usually as good as gold

JackFC

Zeus! I take it that you run your car on both LPG and petrol. I have asked about 50 people what type of gas will get more horse power out of your engine, LPG or petrol. What have you found? I think that petrol has a big advantage over LPG when it comes to power. Do you agree?

zeus

Hi JackFC, Yes, both LPG and petrol, but I prefer LPG. Its cheaper
and the car runs alot better on it. So far every place I've taken
it to has not been able to fix the problem with it missing on
petrol, or hesitating on gas. I'm thinking of taking it to the local
Ford place to see if they can fix the petrol problem. IIRC, they
refuse to touch the gas. Dosn't matter too much as there is a
gas specialist around the corner from here.

Currently LPG seems to give me more, power, but I think this
is more due to the fact that it runs like a hairy goat on petrol.
Once its fixed I guess I'll see the results I should be seeing :)

-Shaun

JackFC

Could your problem be something to do with the timing? I was told that with a car that is running on both LPG and petrol that they with the petrol the timing is retarded and the LPG you advance the timing. In saying this they find a happy medium between the two. So have a look at that. In failing that I guess you could have a look at the carby. The petrol pump or the accelorator pump could be due for a replacement. I have to admit though. I am not all that mechanically minded however I am going by what I have been told by people that know what they are talking about.

In failing all of the above I wish good luck to you and hope that you find the problem.