SLROC Forum

Hello

Does anybody know what MPG to expect when I covert my 3.5 twin carb V8 to LPG. I had a Rang roev classic 3.9 that was doing 10 mpg on LPG so that was no use.

Matt

How were you working out that 10mpg,
If a gallon was only costing you ?2.60, was that not pretty good?

Depending on the set up you can probably expect a minimum of 2 miles per litre to a max of 3.5 miles per litre.
So if the LPG is 58 pence a litre thats 20 miles for ?5.80
 up to 35 miles for ?5.80
If you get more than 3.5 miles to the litre thats great.
I know thats not how many MPG,
 but it doesnt really work out as that.

An Asda credit card gets you 1 pence a litre off when paying at Asda with the card.

Remember that when petrol/diesel goes up by say 1 pence a litre in the budget,
you are using approx twice as many litres.
So the saving reduces.

george
PS  was the 3.9 tuned properly?
 you will need quality plugs & leads with the LPG conversion.
a 90 litre tank takes only 72 litres, so you can expect around 150 mile range at least with that.

I have this exact set up on my RR. Does 14-15mpg on a run, will do more if I sit less than 70/am not laden up with junk.

Depends on a couple of big variables:

1) The condition of the engine, non LR genuine ignition parts, worn cam, worn valvegear and leaky gaskets will put fuel consumption through the roof and lose loads of performance.
2) The system you fit, the normal single point mixing rings are to be honest, c@p. They do the job but are so restrictive you have to use the engine much harder to get going anywhere - rubbish economy.

I bought a BLOS lpg carb from a guy in Poland on ebay, best ?100 I have spent. Look up "LPG carburettor" on ebay. Am about to fit a second one to completely remove the restriction, if you want to use 1 BLOS then I could sell you the defender V8 intake pipe you need.

Where do you stay? Happy to show you my own car if it is helpful to you.

cheers

i used to have a duel fuel astra. i thought it was great, a full tank and i got change from ?15 (ok that was 4 years ago at 30p/40p a litre prices) i used to top up petrol maybe once every 6 months. maybe 25-30mpg on a 1.6 16v. thought i was doing great. then when i finaly ran a tank of petrol and was hitting 40+mpg......
 i was convinced by it, now im not so sure

i used to have a duel fuel astra. i thought it was great, a full tank and i got change from ?15 (ok that was 4 years ago at 30p/40p a litre prices) i used to top up petrol maybe once every 6 months. maybe 25-30mpg on a 1.6 16v. thought i was doing great. then when i finaly ran a tank of petrol and was hitting 40+mpg......
 i was convinced by it, now im not so sure

The way I work it out is what the comparison to a diesel LR would be. The benefit of LPG depends on what the price is against petrol/diesel.

Taking LPG at 70.9p per litre and diesel at 120.9, the cost equivelant of 14mpg on LPG is a 23.8mpg diesel. Now the point where you have to make up your mind, my RR will do 14mpg without particularly careful driving (the odd traffic light launch may occur occasionally ). A diesel driven to TRY and match the V8s performance will be doing 23mpg OR LESS. It depends what you want.
I prefer the hit driving around town of lower mpg, but I get to have a V8 that can be enjoyed more than a diesel the rest of the time.

So long as the gap doesen't close up too much between LPG and diesel it is fine by me! If it keeps narrowing there will be a point at which it would be more cost effective to run on petrol at 18mpg than gas.

Thanks so much for the advice. I already thought it was the setup. If set up right you should get around the same milage as on petrol only to a fraction of the cost Is it not? Still not sure what to do with mine. I just love the v8 sound and preformance but to enjoy my LR more I either have to earn more or pain less per mile. Converting it to diesel is also not very easy. You have to get the right gear box and an original defender 200tdi cost so much more. Diesel is however much more availabe in the rest of the world and less can go wrong with a simple diesel (they do like water compaired to a v8 that stops in the middle of a puddle) I sold the RR after it started to have problem after i went to a puddle of water near Milngavie so didnot get to the bottom of the problem. Do want to spent al that money on something that won't safe money.

I live near Stirling and would like to come and see the set up with the LPG carb where abouts do you stay?.

Matt 

lpg doesnt produce as much power as petrol so either you accept it and drive slower or if you push the performance you loose mpg. my astra was fine running about in around town or cruising but lacked oomph. when i towed a mate i used petrol instead. also used to switch to petrol before overtaking . have to admit i prefer driving diesel than petrol or lpg. better to drive.....

I am at Edinburgh for uni, though at Kinross for most weekends. Drop me a PM if you want to come over.

@ Jumbo, yes I like diesels too, low end grunt is great. Probably why I am not a fan of small petrols, they need more work to go the same. Performance is exciting on petrol with mine but such levels of enthusiasm cost money

I agree the low down grunt of a diesel makes a huge difference in the mud but I have been surprised by the disco mpi 2.l petrol sits at 80mph if you want and off road copes but you have to boot it,that said on Sunday we had a steep boulder (football  size) slope a 90 and 110 both stopped on before they made it the wee disco under full throtle  made it no bother,that said there is a price in low box working not sure but probably down to 10mpg or less going by amount of fuel used