Vehicle & Technical > Discovery

GAS IS IT WORTH IT?

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peasey:
What mpg would i get if i was to get my 3.9 discovery converted to gas?are there any hidden pitfalls and probs i should know about. could i install it myself? what would it cost me to get it installed by a pro?and is it all worth it?

Range Rover Blues:
My multipoint sytem was £1250 with an upright torriodal tank in place of the spare, it's the most expensive tank BTW.  I fitted it myself, the hardest parts being the tank/piping and removing the inlet manifold to fit the nozzles.  I get about 12mpg being careful now that I've binned the cats and fitted a sports pipe.  I get 9.5 towing about 2 tonnes of caravan.  My LSE has a 5.0 V8 BTW.

Blue has a crappy old draw throughg system and is currently doing about 240 miles to £32, havn't worked out any figures yet but that system is less powerfull than petrol though it's more economical.  the mixer reduces the engine's ability to breath so the car is less powerful on petrol too and the draw-through sytem runs a bit lean on LPG.

My advice would be Multipoint if the car is worth the money and a cheapish single point (with lambda feedback) if it isn't.  You can still buy draw-through systems (and fit an economiser to regulate the richness) but these rely on a restrcition in the airflow to work properly, sulk with a snorkel fitted and are harder to set up (single and multipoints are set up with a PC).

SteveGoodz:
My previous Discovery was a 3.9V8 and I had that converted to LPG ~ best thing I ever did. Cost was a straight £1000 for a single point system with Lambda feedback. You need to figure out how long it will take you to recover the initial outlay based on your mileage. Mine paid for itself very quickly, but I was doing almost 1000 miles per week!

I had the original petrol tank removed and two 40litre gas tanks fitted in the same space. Then we installed a small (20-odd litre) petrol tank in the back wing to give some patrol for starting/emergencies.

Once the system had been tuned properly the engine ran better (i.e. smoother) on LPG than petrol without a notable drop in mpg. 16 vs 18 mpg, if I remember correctly. The saving with LPG is not in improved mileage but reduced fuel costs.

You can certainly do it yourself but your insurance company may want you to get it checked over and certified by a registered installer.

Rossko:
For a loose rule-of-thumb, you won't save the installation cost of a good pro job until you've done 20-25,000 miles on LPG. After that comes the half-price costs.

That shocks a lot of folks  :)   Do the sums and see if it works for you. Roughly, LPG cost per mile 50-60% of petrol.  You can shorten the payback time by investing your own effort in a DIY job.

Tanks are always a compromise, you must choose whether you want to keep the loadspace, dicky seats, fullsize petrol tank, or ground clearance; there are choices for a Disco. However not all the options would be sensible for driveway mechanics. Expect around 200 miles range for most tank fittings.

If it runs rough'n'smokey on petrol it will NOT run better on gas. Which is a way of saying high mileage cars can be disappointing on LPG, but against that I've converted lots of 100,000+ cars with good results. And turned just a few sow's ears away. Sometimes the people seeking to reduce fuel costs are already scrimping on maintenance, which isn't a happy combination. LPG is more demanding of ignition systems and general engine condition.

Whether to use the simplistic, cheaper venturi systems on a 3.9 or the higher performance, higher cost injection systems is your choice. As with most things, you get what you pay for. The simpler system is more likely to have issues with pre-existing wear and tear on the car. We fitted lots in the past (a) they were all that were available once! (b) chances of success were better on low-miles engine. Many of those older systems soldier on quite happily. But now we'd only install injection on RR classic/Disco, simply because it won't come back on us.  If the customer wants a really cheap job we point them at eBay and wish them luck.

As an aside, it's a hiding to nothing attempting to fit a venturi system to later 4.0/4.6s, the only sensible way is with injection for those.

CAUTION blatent plug http://www.blazegas.com/kits.html

good luck, Ross K

Wireless:
Mine's a '96 3.9 injection, I had the older venturi system, a Landi system, fitted in March 1999, just had to replace the vapouriser for an OMV unit in July this year, so not bad service.

I average 17 mpg on LPG, and 18 mpg on petrol, although on a run to Scotland I had a 19 mpg average on LPG up the motorway.

I'd hope that power delivery must be higher for injected LPG systems when under heavy load or towing, since that is the only area on LPG where power delivery and fuel consumption suffers using a venturi system.

As a matter of interest, not that I'm desperate to change things after 8 years on an old car, but what would the cost be to upgrade to an injected system from the venturi system I'm on now?

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