Have just bought Disco 2 4L V8 - to LPG or not to LPG??

Mudron said:

The difference between LPG mpg and petrol mpg is very small now compared to what it was, due to better control of the timing of the injection.
LPG does produce more heat in the combustion process than petrol and burns at a faster rate, its not a huge amount more heat, but it is enough to overwhelm an 'adequate' cooling system that has managed for years on petrol. For extra insurance, I have always made sure I fit a new lower opening thermostat, flush the cooling system and make sure the pump and rad are up to the job.

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We've still got the original radiator, but had a new thermostat and water pump at the time of the new short engine.

Using the correct coolant mix is very important, keeps heat transfer rate good internally.

Peter

we found that LPG is not good on shorter journeys, we were advised when it was fitted that that LPG doesn't heat up properly until after about 6 miles so still using petrol

mand85 said:

we found that LPG is not good on shorter journeys, we were advised when it was fitted that that LPG doesn't heat up properly until after about 6 miles so still using petrol

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TIP:

Most LPG fitters use a T-piece for the hot water take-off for the vapouriser, which means that the main flow goes past the T-off to the vapouriser and it takes a long while to get any heat through. This is not helped by the T-pieces being too small in bore diameter. Also, throw the plastic T's away, they collapse and leak eventually anyway.

Re-route the water flow so that the water goes:-

engine outlet > vapouriser > heater > engine return. Thus connecting the water circuits in series, not parallel.

That slows the heater up a little, but makes the vapouriser warm up much more quickly. We are normally on gas in a mile, even on cold mornings and sometimes before the engine is really warm enough to take it.

Peter

I start mine on gas every day,no problems apart from a little lumpy for a mile or so. dont use petrol at all apart from when I shut it down, I switch to petrol give it a couple of revs then switch it off. If I dont do this & start it back up on gas within 5 or 10 mins it may sometimes backfire either in inlet plenum & blow my MAF sensor or in the exhaust causing CAT damage. Mine is a single point Impco system though, just a simple no hassle setup fitted 13 years ago. I fitted new gas tanks last year as original ones were severely corroded.

Question for the OP, did you have a single or multi point system fitted ?

wilcosarge said:

OK so you think hang in there and I will see improvement?

My maths tell me on petrol, the 80 litre tank was giving me 313 miles so c 17 mpg.

The LPG is giving me 10 LPG. (55 litres, 133 miles).

I aint making much of a saving - cost per mile 33p vs 36p.

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Standard tank size is 95l, so your petrol consumption is possibly a bit higher. I get 17.9mpg out of mine, but that's almost exclusively motorway journeys of more than 200 miles. Shorter journeys are much thirstier.