Monster MotorsportChris Nott
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  1. #1
    1st Gear

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    1.8T avant LPG conversion?

    Okay, i've come to a crossroads transport wise and I'm looking for some advice and feedback.

    I've recently accepted a new job offer which means that i'll be commuting some 120 miles per day. I currently drive the following:

    B5 a4 1.8t sport
    '97 AEB code engine
    145k miles
    Custom Code stage 1 ma[
    engine is in good order and returns nearly 40mpg on a run and uses minimal oil/water

    As i see it it have a number of options:

    1) Keep the car and run it into the ground on petrol (cost for the year 3,600 - 3,800 on petrol + maint).

    2) sell the car for about 1k and buy a small diesel for less than 2k, criteria to include A/C for the occasional sunny days we get here in scotland, be comfy enough for the daily commute, give 55mpg and not be too rubbish (i'm not wanting to spend more than this as i'm not the new car type and there seems to be little economic sense in spending money to save money).

    3) convert the car to LPG. I have found what i believe to be a knowledgeable installer near to me who specialises in high performance and turbo LPG conversions. A sequential ROMANO kit would be about 1,800 fully installed and certified. There is minimal insurance impact, and i'm assured minimal impact on economy and performance too. So on the surface for a 1 off hit of 1,800 i will have a payback period of just less than 1 year providing it doesn't go bang......


    I've spoken at some length with him about a number reservations I had regarding the LPG kit, including:

    exhaust issues
    petrol starting issues
    valve/seat wear
    mapping/running issues
    economy
    use of flashlube kits
    etc etc.

    All of which i've been re-assured about, as always though, I always take this with a healthy dose of "he's bound to say that".

    I'm also aware that the internet, whilst a great tool, is a place for moaners to voice their opinions rather that a place to sing a products praises. To that end, most of the threads/searches i've done online through up questions or gripes from 2 years plus ago (maybe kits have moved on in this time).

    So my question is, given the info above what would you do? I have done the sums and know what will save money given time, i have (i think) considered most angles of the conversion including the increase caps on LPG duty increases until 2014.

    I am also interested to hear any anecdotal stories, or indeed any 1st hand stories and feedback of LPG - especially on this engine and any other potential issues that i may have overlooked.

    Cheers
    Last edited by fARQUARE; 5th July 2010 at 21:39.

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  3. #2
    jcb
    6th Gear

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    I looked into LPG briefly.
    If you look at worst case scenarios you will get 10% worse mpg.
    It will cost you 65p/l rather than 1.30/l (worst case!) so half price
    your LPG tank won't hold its capacity only 70-80%
    you will lose your boot space.

    so rough maths on a 50 litre LPG tank
    it is going to cost you 26 to fill it with 40 litres (80% capacity due to expansion
    that wull get you 27-30mpg (assuming your 40mpg is an absolute best effort and 30-35mpg is more realistic on a drive)
    call it 30mpg which is 30 miles per 4.54 litres.
    your LPG tank will see you travel 260 miles approximately your daily journey give or take a trip to the chippy for lunch!

    if you run it on petrol only then 260 miles at 30-35mpg will cost you 49 (32mpg at 1.25 a litre)

    assuming you work 45 weeks of the year it will cost you 11000 (45weeks x 5 days x 49 per day)

    same year in LPG only is 6k (26 x 45 weeks x 5 days a week) even adding 2k for the conversion you are still 3k better off at the end

    obviously the less mileage you do the closer those two figures get to each other.
    no brainer IF it works as well on a chipped and turboed car. I suspect that the gaseous expansion factor leads to a cooler charge and better MPG in a turbo than an NA car. no evidence though.
    I aslo suspect that a mapped turboed car running a leaner charge and higher boost may be feeling a bit close to the edge on a lower octane fuel and same boost. depends entirely on the Map though I would imagine.

    I would be interested to see if a static car can be hooked up to a external LPG fuel system to run it and look at AFR and exhaust EGT's before you commit to plumbing it all in.

  4. #3
    "Stick a V8 in it!"

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    LPG has a much higher octane rating than petrol, something like 110 ron.

    It uses more (ie you get worse mpg) of it because it has a lower calorific value, meaning a litre of LPG has less energy than a litre of petrol (just like derv has a higher calorific value)

    So assuming its mapped properly, ie the LPG ECU is setup correctly, its very safe.

    Theres a guy over on SRS running LPG on his mapped RS6 thats making 500+ hp.

    I'm not sure jcb's maths is right.

    120miles a day is 600 a week, 45 weeks working gives 27000miles in a year.

    27000miles at 35mpg is 771 gallons of petrol, which is 3502litres. At 1.20 a litre thats 4202 in petrol

    Running on LPG:

    27000miles at 30mpg is 900 gallons of LPG, which is 4086 litres. At 60p a litre thats 2451 on Gas.

    So yes, the conversion will more or less pay for itself inside the first year, and will continue providing savings thereafter. The kit is also an investment. If in a year or two you decide to replace the car, the kit can be transferred over for not much at all.

    2000 A4 1.8T Sport Quattro Avant, Berry Pearl
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  5. #4
    jcb
    6th Gear

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    ah, thought it was 120 miles each way...

    either way it is worth it

 

 

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