ASTRA 1.6 LPD DUALFUEL - DOES LPG GIVES SAME POWER AS GAS - waz777

Hi

I am looking to buy a used lpg converted car. There are two option either buy a petrol or get a ready made factory fitted lpg cars.I think getting afactory fit lpg will be better than getting someone to convert a petrol car. PLease advise on this , which option is best?

The only used car fits my budget/requirement is Vauhall Astra 1.6lpg dual fuel.

I am concerned if you get the same power and mpg in gas/lpg as you get in petrol. I was told you loose power/mpg in lpg in comparison to petrol. Also I was told look for bigger engines like Vectora whick offers 1.8 litre engine. But that car will be too big for me and my requirement.

Please advise?

wAZ

Edited by Avant on 11/07/2012 at 19:49

ASTRA 1.6 LPD DUALFUEL - DOES LPF GIVES SAME POWER AS GAS - RT

LPG has a lower energy content than unleaded petrol - so power, torque, performance and fuel consumption are all down by about 5%

ASTRA 1.6 LPD DUALFUEL - DOES LPF GIVES SAME POWER AS GAS - unthrottled

The density of LPG is roughly 20% lower than that of petrol-so fuel economy is roughly 20% less. Torque will be about 5% less.

ASTRA 1.6 LPD DUALFUEL - DOES LPF GIVES SAME POWER AS GAS - Ethan Edwards

Unless you drive everywhere at 100mph in the REAL world your simply NOT going to notice any power loss at all. I have been using LPG for years. Unless your a pub F1 racing driver it's just not an issue at all.

Yes you get less power. Yes you get less mpg than petrol. BUT due to the tax it costs a heck of a LOT less than petrol. The calculation you should be doing is miles per pound.

Roughly speaking it's half price motoring.

The Astra is a cracking little car. I'm currently runninga Nissan Note 1.6 Automatic on LPG Dual fuel. So if your Astra is manual you'll get even better than my figures. I get the petrol equivalent of 60 mpg. That is unless your petrol car gives you excess of 60mpg then my LPG car is travelling cheaper than yours.

OK that said ask yourself a couple of important questions.

Do I do a lot of short trips? If so LPG is no good for you as it only cuts in when the engine is warmed up, and short trips yours won't be, so it'll be on petrol for nearly all the time - no saving there!

Do I have local sources to buy LPG? If not then it's not going to save you cash travelling 20 miles to fill up every other day is it.

Do I need to use the Eurotunnel? Utterly forbidden I believe. It's the old ferries for me!

Thats about all you need to know about LPG. Other than I wish more than only the 1200 or so garages int he UK sold it. You need to plan a bit more so that you find LPG garages especially on trips to unfamiliar areas. Sat Nav poi files and the interweb help there.

ASTRA 1.6 LPD DUALFUEL - DOES LPF GIVES SAME POWER AS GAS - unthrottled

I'd say that is a pretty fair assessment.

I'd quibble over half price motoring though.

Based on the average price of unleaded and LPG (131.66 and 72.05P respectively), there is a saving of 45% on a volume basis. But you you only go 80% as far on LPG, which erodes the total saving down to about 1/3.

As you noted that car starts on petrol (which is when it is at it's thirstiest anyway) so there's no saving there.

Add in the cost of conversion, loss of bootspace, frequency of fill-ups and the savings can end being marginal unless you keep the car for a long time. It's good for some users, but not for everyone!

ASTRA 1.6 LPD DUALFUEL - DOES LPF GIVES SAME POWER AS GAS - unthrottled

I did a slightly more detailed calculation on the relative costs of road fuels.

Density Calorific value (LHV) Cost/litre Cost/MJ Normalised cost

LPG 0.520kg/l 24MJ/l 72p 3.0p 0.75

Petrol 0.737kg/l 32.7MJ/l 132p 4.0p 1.0

Diesel 0.831kg/l 36MJ/l 137p 3.8p 0.95

So even if you ignore the price of the kit, your saving is 25%, not 50%. A saving of 25% of your fuel cost is not to be sniffed at-but it's not as large as the companies claim.

ASTRA 1.6 LPD DUALFUEL - DOES LPF GIVES SAME POWER AS GAS - Wulbert

Thought I'd add my tuppenceworth. My Saab 9000 2.3 turbo did an easy 32mpg on petrol and only 24mpg on LPG.

When I did my sums the cost of LPG was like getting 38mpg on petrol, not a huge margin. However maybe the turbo did not suit the LPG. I needed 2 regulators to supply enough gas to the turbo and my installer made it run on the rich side for safety. Think about fitting a "Flashlube" system if you are worried about valve wear (LPG runs hotter)

ASTRA 1.6 LPD DUALFUEL - DOES LPF GIVES SAME POWER AS GAS - unthrottled

my installer made it run on the rich side for safety. Think about fitting a "Flashlube" system if you are worried about valve wear (LPG runs hotter)

Your installer didn't understand what he was doing. Running rich only works for petrol because the evaporation of the excess fuel cools the intake charge and hence inhibits detonation. There is no evaporative cooling effect with gaseous fuels, so running rich simply wastes fuel and increases emissions-the very thing LPG is purported to reduce.

The notion that LPG burns hotter than petrol is also a myth-all hydrocarbons burn at a similar temperature, exhaust valves burn for a different reason.

The LPG industry is rather like the BPA-there are a lot of rogues squeezing out the honest operators.

ASTRA 1.6 LPD DUALFUEL - DOES LPF GIVES SAME POWER AS GAS - TeeCee

>> I needed 2 regulators to supply enough gas to the turbo and my installer made it run on the rich side for safety.

That's what you get for fitting a mixer system to a modern car. Very old hat and a competant installer would have insisted you went for a modern, but far more expensive, system with injectors in the manifold.

With regulators feeding mixture through a turbo you run the very real risk of detonation in the turbo and blowing the induction side of the engine to bits.

NB: Injected systems will run directly from cold as there's no mixer to ice up and are thus also more suitable for cars used for short journeys.

ASTRA 1.6 LPD DUALFUEL - DOES LPF GIVES SAME POWER AS GAS - gordonbennet

Indeed, my LPG'd car will change over to gas within about 30 seconds this weather, and in about a mile from cold start on a freezing day, or as is the usual case by the time i've put me work stuff in the boot and cleaned the windows of condensation or frost, whichever, changeover has occured.

As for OP question, yes there is very slightly less power on gas, so if the car you are contemplating is underpowered in its normal petrol form LPG won't help.

Having gone for LPG i wish i'd done so years ago, i have no regrets, it is now my fuel of choice with Toyota (only) hybrid coming in a close second, Diesel is off my future shopping list unless a rare unmissable bargain presents itself, too expensive to buy, fuel and maintain properly especially now with increasingly dubious complexity.

As for buying a dual fuel from new car, not too sure thats the best choice, some car makers as drivers of many makes are finding out are only interested in the car lasting til warranty runs out, a well chosen independent LPG converter wants repeat custom and needs a good reputation to stay in business.

German cars seem to do well generally with LPG conversions, valve seat recession isn't poking its ugly head up too often as it seems to with some others, though my indy LPGer assures me that Lexus models he has converted are showing no probelms after huge mileages, i see no reason for him to mislead me, it should all being well be many years before my old MB pegs out, but he always fits a Flashlube system for belt and braces support, a requirement of mine anyway.

Edited by gordonbennet on 12/07/2012 at 10:15

ASTRA 1.6 LPD DUALFUEL - DOES LPF GIVES SAME POWER AS GAS - GolfR_Caravelle_S-Max

I run three LPG cars and a Diesel.

The 110bhp LPG Suzuki Ignis Sport

The 220bhp LPG Ford S-Max 2.5t

The 245bhp LPG Subaru Legacy Spec-B

The 220Bhp BMW 530d (Not LPG!)

The Suzuki - I use most often - done 80,000 miles in last 4 years.

Daily on LPG - Fine. Twisty B-Roads when you need to overtake 2 cars and a tractor - Switch to petrol for 1 minute, overtake and switch back to LPG. Works for me.

For the Subaru and the S-Max, kepp them in LPG pretty much all the time apart from launch (warmup) 4 minutes.

Done 1,200,000 miles in last 23 years, and I love (IAM) "progressive driving" and economical motoring.. Now considering getting a 6.1L 425bhp petrol and converting to LPG to replace the Suzuki&BMW&Subaru...

ASTRA 1.6 LPD DUALFUEL - DOES LPF GIVES SAME POWER AS GAS - pd

I don't think it is the same with ther Astra factory LPG (which actually has a pretty poor reputation) but I do know on the Volvo factory LPG systems you did get the same power on petrol and LPG.

The engine had a slightly different map on LPG and the power came in about 300 rpm higher but the peak power and torque were exactly the same figures.