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Is my lpg system crappy or my expectations? Please help 

 

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 Post subject: Is my lpg system crappy or my expectations? Please help
Posted: Sat Apr 19, 2008 2:24 pm 
Oompa Loompa
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Posts: 42

Joined: 19th Mar 2008

Location: Sydney
NSW, Australia

A86F / A86F5 = 85 ltr tank, with 68 usable.

Ford au series 3. Dedicated lpg

I get around 270km's before the dte beeps at having only 80km's till empty
I am very confused then as to weather my car is running crappy if it only has eighty kms left after 48ltrs used. Am I missing something or is the gas system faulty somewhere?

Tiffany
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Posted: Sat Apr 19, 2008 4:26 pm 
Oompa Loompa
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Posts: 42

Joined: 19th Mar 2008

Location: Sydney
NSW, Australia

Hi,

I recieved a pm from a member suggesting disconnecting the stepper motor wiring on my au. Does anyone have any pics on exactly what wiring this is?

Tiffany
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Posted: Sat Apr 19, 2008 4:28 pm 
Getting Side Ways
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Joined: 8th Jun 2006

Location: melbourne
VIC, Australia

From the info you have provided in this and your other post you are getting around 18lt/100km. This is about average for mixed (highway and city) driving and gives you over 100km left in your tank when your DTE beeps. DTE is not that accurate.
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Posted: Sat Apr 19, 2008 5:06 pm 
Getting Side Ways
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Age: 38

Posts: 520

Joined: 23rd Dec 2005

Ride: EF Futura Wagon

Location: Toowoomba
QLD, Australia

Disconnecting the stepper motor will either result in a very lean mixture as the stepper motor is closed when powered off (this is VERY bad for your engine - read BOOM) or a pot luck guess at where it is in it's stroke when you disconnect it.

Without any other tuning, removing the stepper motor will not improve your economy. The way it works when it is working properly is that a small micro-controller reads in various signals (O2 sensor, maybe rpm, tps, coolant, air temp, etc depending how complex it is). It then calculates whether you are likely to be too rich (too much LPG) or too lean (too little LPG). It will then open the stepper a certain amount based on all the other sensors if too lean or close the stepper a certain amount if too rich.

Now this is all based on what kind of tune your LPG vaporiser has. If your vaporiser is ok at idle but can't supply enough LPG when you use the throttle then there is nothing the stepper can do. It will open all the way to try and richen the mixture but everytime you come off throttle the stepper is way open so you have a period where you are wasting LPG. You will also have poor power resulting in you using more of the throttle to get to speed, etc. Conversely if the vaporiser is rich everywhere then the stepper has to close right down and everytime you use the throttle the stepper starts to open but floods the engine with excess LPG.

It all needs to be in balance.

But realistically if you are getting around 18l per 100k around town that is ok. You should be getting around 11l per 100k highway. This is what I am getting lately and I am still saving considerable dollars. On petrol you can realistically expect around 12-14l per 100k city and 8l per 100k highway. Some people have freaks of a car that get better than this but we are being realistic here.

So you can see you are only using about 4l more per 100k but are buying fuel at half the cost.

cheers
Scott

 

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If it doesn't fit, jam it. If that doesn't work use a hammer. - Engineers Motto

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Posted: Sat Apr 19, 2008 5:13 pm 
Oompa Loompa
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Joined: 19th Mar 2008

Location: Sydney
NSW, Australia

Hmm,

Put like that it doesn't seem that bad,

Cheers,

Tiff.
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