LPG: Help me do the sums

[bernmc]

I've been investigating LPG for the VR4, and have done some research and some sums. I'd like someone else to do the same sums and see if they agree with me - She Who Must Be Obeyed is a car sceptic, and bizarrely believes that me head is filled with crazy schemes atm :huh:. Well I never.

There is an LPG system that is suitable for the VR4 (anything up to 600bhp in fact!). The installer tells me that there will be no noticeable difference between LPG and Petrol. The system is fully automated - car will start on petrol. When the engine reaches 45 degrees C, the system automatically switches over to LPG. If the gas runs out, it switches back to petrol. The system can be overridden by the driver at any time.

LPG has a calorific value of about 20% less than petrol. ie if you need to firebomb your local MP, a litre of petrol will make a 20% bigger bang than a litre of LPG. In the early days of LPG, there was a noticeable drop in power when the car switched over to LPG because of this. It doesn't happen with modern systems, so I'm assuming that the system is simply injecting 20% more LPG for the petrol equivalent (all rough figures, but you get the idea).

The system costs £1950 + VAT = around £2300 :o, and takes 4 days to istall.

So, the sums: How long will it take to make the conversion worthwhile? Drove through my local shell service station on the way to work last night:



Petrol 89.9p/l
LPG 39.9p/l
=50p difference per litre (fairly consistent difference accross the country as far as I can make out).
However, you need 20% more LPG - ie if your car does 20mpg on petrol, it'll do 20 miles per 1.2 gallons of LPG. ie 16.67mpg LPG.

you might find it easier to convert to litres for the sums...

I will do 14000 miles this year, mostly sitting on the motorway. Not sure what will happen to me after that, but I've never done less than 10000m/annum. Bear in mind that the 14k will be at motorway mpg, and the 10k at mixed/urban mpg.

Do the math, and post your answers here - how much will LPG save per year, and consequently, how long would I have to keep the car to make the conversion worthwhile? I've tried to be pessimistic - always rounding off to favour petrol, and based my mpg figures on posts on the forum.

[paulmc]

I did the very same as you. I was going to buy a Jag XJR before I decided on the legnum. The kit I was after had sequential injection it all looked very good. But what happens when Gordon Brown reduces the relief on LPG and the price shoots up. Look what is going on with Diesel. I stopped the hunt for the Jag and bought a Legnum.

good idea though. 20% less calorific but 102 ron or maybe more cant remember now anyway very good for DET free motoring

[I-S]

The mileage works out around 5 miles per litre of lpg. So, 10p per mile saving.

Thus, for £2300, you need to drive 23000 miles to break even. Give a bit of wiggle room and say two years. After that you'll be into the profit zone.

[bernmc]

I did the very same as you. I was going to buy a Jag XJR before I decided on the legnum. The kit I was after had sequential injection it all looked very good. But what happens when Gordon Brown reduces the relief on LPG and the price shoots up. Look what is going on with Diesel.
Agreed, but if I remember correctly, the duty is fixed until 2007 ( I'll look this up when I have a mo), and from then on, the government is committed to informing and fixing the duty in three year chunks - so you'll know what you're paying over each three year period. There is also a subsidy/grant program for newer cars, which will stop once LPG is established. There are no signs that it's about to go yet, so I think we're in for a few more years of cheap fuel. Scrapping the discount now would destroy the market because of the high setup costs, so I can't see the bubble bursting just yet.

Isaac- that's around what I got --> 2 to 2.5 years to make it worthwhile (around £1000/year saving). Anyone disagree?

[Dream Weaver]

LPG is a "green" fuel with much less emissions than petrol and particularly diesel. Any tax loaded onto it is a disincentive for motorists (particularly fleet owners) to convert - so the scottish windbag would need to make a very, very strong case for a big rise in tax on LPG. That doesn't mean he won't do it though if he needs more money to waste in Africa.

As an aside I got nearly 100K miles out of my Range Rover after I had it converted.

One great advantage is that engine wear is considerably reduced with LPG. Also emissions tests at MOT time are easily passed.

One thing though, is that LPG tends to shorten the life of catalytic converters.

[Brunty]

Aside from the financial aspects, what is the space implication of having two fuel tanks in the car? Is there a considerable playoff between available space, finding more space (OK you're in a Legnum so you've got acres to play with) and tank range?

Also, I'm sure there are current H&S restrictions with taking your car on the channel tunnel and also probably the ferries.

Steve

[avander_be]

Hi guys,

Finally someone talking about LPG here!

I've equipped my 2000 GLS with an LPi Vialle ( Liquid Propane injection) kit, there are some pictures in my profile if you like...

I trawl along some french/dutch lpg forums, converting turbo cars to lpg is delicate matter, as far as i know only low pressure turbo's can be converted...
don't know if vr4's fit in this group...

What make is the kit your aiming at? i haven't tried to figure out your sums because i have to convert to much stuff to continental measures, i can give you my figures though:

I do about 15.000km per year

PETROL BUDGET
my GLS runs about 10l/100km, so i need 1500litres of petrol a year
at the moment petrol is about 1.2€/litre, so it'll cost me 1800€

LPG BUDGET
my GLS runs about 12l/100km, so i need 1800litres of lpg a year
at the moment lpg is about 0.4€/litre, so it'll cost me 720€

LPG save's me 1080€ a year, my kit cost me 2350€ all in, so i break even in 2.1 year, sooner if i drive around more... pretty close aren't we?

Feel free to ask if you have any questions!

[Dream Weaver]

If you bear in mind a 90 litre tank (liquid capacity) cannot take 90 litres of LPG. The tank is a bit of a bummer, I had one in the R-R (Classic) where the spare wheel was and also the petrol tank was replaced by another gas tank with a small (for a R-R !!!) petrol tank as you only need petrol for starting and a bit of reserve if you run out of gas.

I would imagine the only option with the legnum would be underside tanks as the internal tanks do take up space. And they are noisy ! When they get low on fuel, they gurgle, whistle rumble and bubble. Its totally safe but sometimes worries back seat passengers.

You are correct about the channel tunnel (don't know why) but I took my R-R to Ireland on the HSS fast ferry and there was no problem.

[ritch_w]

regardless of the sums and savings - there were some serious discussion on LPG & VR4s last year - with general consensus (from those that had looked into it) that LPG and turbo engines could have issues - needless to say those that were looking into it decided against taking the risk!!!!

I think there are a few LPG V6 and 2.0 non turbos out there with no issues.
The problem seems to nbe that nobody knows of a LPG converted turbo charged car (let alone one with 2 turbos) that has been done - and survived!!!



http://www.clubvr4.com/forum/showthread.php?t=5458&highlight=LPG
http://www.clubvr4.com/forum/showthread.php?t=5631&highlight=LPG
http://www.clubvr4.com/forum/showthread.php?t=2673&highlight=LPG

and the verdict:
http://www.clubvr4.com/forum/showthread.php?t=5562&highlight=LPG

I dare say if someone is brave enough to take the plunge or finds evidence of a reliable conversion on a twin turbo this may give confidence for more to follow???

[paulmc]

here is the set up i was going to use

http://www.fesautogas.co.uk/

[Nick Mann]

What ritch_w said!

I looked at it as a way of reducing running costs. I couldn't find anyone who had converted a VR4, or anyone who would talk sensibly about turbo'd cars.

What it came down to was a gamble. IF the ecu can cope, IF the turbo system copes. It is a long term gamble and I remain unconvinced, but the sums are about right. IF it works the system should be in profit after 20-30 thousand miles.

[paulmc]

.....or

Buy an e-manage lean it off during light throttle up to about 16:1 for cruising. I bet these things run really rich all the time to cope with the heat in Japan. After all it is only a 2.5 and the compression ratio is quite high for a turbo so there is no reason we can't get good mpg when driving normally. This is what I will be doing in the near future, Just need to get a wiring diagram for my e-manage :embarasse

Stew at motorsport developments in Blackpool is getting 36mpg out of a 400bhp cossie

[ritch_w]

.....or

Buy an e-manage lean it off during light throttle up to about 16:1 for cruising. I bet these things run really rich all the time to cope with the heat in Japan. After all it is only a 2.5 and the compression ratio is quite high for a turbo so there is no reason we can't get good mpg when driving normally. This is what I will be doing in the near future, Just need to get a wiring diagram for my e-manage :embarasse

Stew at motorsport developments in Blackpool is getting 36mpg out of a 400bhp cossie


now that sounds more interesting!!!

for my normal driving i only use a light throttle an doubt that im boosting the turbos, an improvement over mid teens mpg.

that could make the difference between selling the VR4 and keeping for a couple of years

[Kieran]

.....or

Buy an e-manage lean it off during light throttle up to about 16:1 for cruising. I bet these things run really rich all the time to cope with the heat in Japan...

I think you're probably right. There seem to be no fuelling issues in terms of capacity from wanging the boost from 0.65 right to 0.9 bar, and every time I've been in pursuit of a VR-4, they always STINK of petrol out of the exhaust.

[bernmc]

The system is suitable for turbo cars.
The company is LPGA approved. (I'll put his website up - just can't be bothered to go to the other PC atm!
System is warranteed for 2 years/60000miles.

He seemed fairly knowledgeable about turbos - He said: if you drive like a hooligan all the time, don't bother with LPG - it won;t save you anything. It's best suited for the long motorway haul. The efficiency falls off dramatically on boost. Switch over to petrol if you need to teach someone a lesson, then go back to LPG. etc.

I don;t think that gas is a panacea, but I'm inclined to have a go if it'll save me money! I'm waiting for another contact who apparently imports Jap cars and converts them, so I'll see if I can find out more...

[Brunty]

.....or

Buy an e-manage lean it off during light throttle up to about 16:1 for cruising. I bet these things run really rich all the time to cope with the heat in Japan.

Other than paulmc has anyone else tried this - or is anyone else in a position to try this?

Paul - keep us informed - anything to reduce the running costs is likely to be popular.

Cheers :thumbsup:

Steve

[Roadrunner]

anything to reduce the running costs is likely to be popular
You buy a twin-turbo 2.5-litre V6 with near 300bhp and then worry about the running costs??! :inquisiti :joker:

[Dream Weaver]

if you drive like a hooligan all the time

Not me, your honour.......

[Brunty]

You buy a twin-turbo 2.5-litre V6 with near 300bhp and then worry about the running costs??! :inquisiti :joker:

Nope. I was worrying about the running costs for months before I bought it!

[paulmc]

Not so much running costs but if it is running to rich we are losing power and wasting fuel into the bargin.

[Sulli]

I am having exactly the same thoughts Bern.
The only downside, and it's a big one, to owning a VR4, is fuel costs - OK, all that performance doesn't come for free, but this could help. Despite the fact I knew fuel would be an issue before I bought it, when it actually hits you in the pocket, and you have a family and house to spend on too, the reality does get a little scary.
I have been told by a couple of people that Gas Conversion is the way to go, and the prices you quote are too high - I think I could get it for way less than £1500.
Just spoke to Auto Gas Power in Telford, who told me he could do the VR4 no probs, and it'd be around £1400 - though scope for reduction via group buy.
A further benefit I can see is ability to go further per tank(s) - I hate being low, and desperately searching for Optimax, or some other SUL.
Speaking to the bloke at AutoGas he says there is little chance of power reduction, but if there is a slight decrease, then if you are booting it, you can click over to petrol temporarily.
He also says they have a special map, which links into the fuel control on the ECU, to ensure LPG goes through in the correct amounts.
It's something to consider.

[bernmc]

If you can get a decent system at that price, then it's definately worth it. I've discovered an LPG BP outlet just down the road from me :o -don't know how I missed it before.

Do you think you can get some details from autogas? I've spent £700 in fuel in two months, and will be visiting Xtreme in a week for my next service :o:o:o

Questions - is the system fully automated, or do you have to flick the switch yourself? Is it a sequential gas injection system (as opposed to the plain old digital gas injection system)? Is he LPGA approved (important for insurance), and what warranty does he offer?

If it's a sequential system, I'll be around there like a shot - does the price include VAT?

[nick-f1]

I had lpg fitted to a 5ltr chevy (volvo) v8 in a boat and what a disaster that was!. The calorific value maybe lower but the power losses were immense something in the region of 25% i estimated. Getting onto the plane or in a roughish sea was not good because of the power losses. Also lpg runs hotter so claims that engine wear is reduced are seriously debateable if not utter bo****ks imo. The tanks needed took up valuable space and added weight and plus the carb rubbers used to dry out and had to be replaced annually to prevent fuel leakage. i know this is not an issue with fuel injection but the hassle and hidden costs far outweighed any potential cost savings.

I realise a boat is different to a car scenario but the aims are the same ie: to cut running costs, but in my experience the drawbacks seriously eat into any savings making lpg a lot less cheaper than is claimed. Heavier fuel consumption, loss of space for tanks ( and you need at least 2 to get any sort of range) , the extra weight, and added servicing costs because most dealers wont touch them! All of this means more time /miles travelled to gain any savings certainly more than 2 years even with high mileage.

And at the end of the day we buy vr4`s for the performance so why would one want to compromise that for economy? If you do high mileage buy a diesel eurobox for this and keep the vr4 for what you bought it for in the first place. :rolleyes4

[Smokinmasta2]

Now, not having read ALL this thread............
Also check with your insurance company!!
My brother-in-law (works in insurance) says most charge a lot more unless
they are from the car maker (like Volvo Bi-fuel for example)............
Might be worth check this aspect also??


Smokin............