Bad fuel economy

[Philip Chidlow]

1 Imperial gallon = 4.54609188 litres

[saintjamesy89]

I round it down to 4.5 so I can do it in my head.

[kiwi]

Cool at least that part is done ok.

Somewhere in the darkest recess of this forums electronic memory is a chart of the official fuel consumption figures.

Something about the fuel figures I got on my own 19s compared to the official figures made me consider the enviroental factors in why they were not near those figures.
During the Brazilian F1 qualifying Martin Brundle mentioned about the altitude at the event reducing power by 10%, this made me start thing because that was just 800m above sea level and the majority of my driving is done between 400-900m even though open road speed (100kph) 62 mph the fuel efficany is way off but once I take 10% into account the figures becomes clearer.

Ok I bet no one in the UK can test that theory for me

[Kevin B]

LPG on a Carb engine is actually a lot easier than on an injection engine, and if set up properly is safer than petrol.

Yes it is easier to install on a carb engine, but your most likely to be using, an open loop system = crude system.

It works and is reliable, but is not without its problems:

Poor fuel economy compared to more advanced LPG systems.

Loss of power, due to the mixer ring orifice size always being a compromise between being small enough diameter on tickover to suck the required amount of LPG into the engine, and large enough diameter on full throttle openings to get sufficient air into the engine, consequently the engine can feel lumpy or even stall on tickover, and strangled at the top of the rev range due to this restriction.

The float chamber will have to empty before changing to LPG, and consequently refill before starting again on petrol (so expect some serious cranking over upon starting on Petrol a car with a mechanical fuel pump), hence the need for three position changeover switches on open loop systems.

When running on LPG or changing to it, the petrol supply is interupted by a 12V solenoid placed in the fuel line, which is not good for mechanical fuel pumps as it is then pumping against a 'dead head'

In my opinion if your going to LPG a carb engine consider using a BLOS mixer (variable oriface gas carburetor similar to SU carb in operation), and replace the mechanical lift pump with an electronic version that can easily be switched off via a relay.

Far better to convert an injection engine to LPG, be it closed loop Lambda system or a sequential LPG conversion, for better fuel economy, and driving experience.

The only disadvantage is a more complex system ie injector emulators required, a lambda sensor required (however this can easily be intalled in the down pipe just for the LPG system)

A good compromise would be a closed loop lambda system operating in conjunction with a BLOS mixer and petrol injector emulators, fitted onto an injected engine.

LPG is an excellent fuel for an internal combustion engine really. Burns lovely and cleanly, meaning you have very little engine damage, oil comes out clean.

Yes it is, but again not without problems:

As LPG has the lubricating properties of a dry fart, valve seat reccession can be a serious problem. Honda and some Ford engines are notoroius for it, and this can only be overcome by using flashlube which constantly measures a metered qty of upper cylinder lubricant into the inlet manifold.

[Defender110]

A classic mistake often made it seems more and more each day is the calculation to miles per gallon

You buy your fuel in Litres then convert it to gallons what figure you use can affect that number. How many litres do you think a Gallon is?

I use this very handy little calculator from another forum althought this states 4.561 ltrs per gallon. Perhaps we could have our own Citroen BX version?

http://www.mdocuk.co.uk/mpg_calculator.htm

[Defender110]

There is also this problem of US gallons and UK Imperial gallons getting mixed up.

1 US gallon = 0.83267384 Imperial gallons

[Defender110]

As LPG has the lubricating properties of a dry fart,

[kiwi]

There is also this problem of US gallons and UK Imperial gallons getting mixed up.

1 US gallon = 0.83267384 Imperial gallons

Thats the point I was raising but 4.5 ltrs per Gallon is perfectly acceptable until you get into really big litres like over 100.

[sdelasal]

i find myself working the old 9 x table and working iin multiples of 9litres (2 gallons) - so 33litres = 3 lots of 9 plus a bit leftover(6litres). so makes about 7 1/3 gallons. I've never considered it before, but Miles per litre might be interesting i.e. 45mpg = 10mpl I can't get used to litres per 100km.

[kiwi]

I've never considered it before, but Miles per litre might be interesting i.e. 45mpg = 10mpl I can't get used to litres per 100km.

Same here I used to do the Miles Per Litre in the UK could never be bothered to fluff around on converting to gallons or the other formula of litres per 100km

Even now I use Kms per litre and not the litres per 100kms. Such an easy calculation to just grab distance divided by quantity.