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7 Responses to “Alternate Fuels: CNG vs LPG”

  1. Laersen says:

    Thanks for the information, I think a comparison of all say LPG, CNG, Diesel & Petrol on one particular car or more in terms of power, fuel efficiency, cost of running emission levels etc. would have put the consumers in better state of mind deciding on which mode of fuel to go for.

  2. Vishnu says:

    I used to drive an LPG car (2000 Sep model M-800 Carb Engine). It was converted to LPG at 80000 kms on the ODO. B4 conversion, the mileage was 18-24 kmpl of Petrol. The Conversion cost was Rs.20000 in the year 2007 (incl RC Book endorsement and all legal charges). The fuel efficiency was 11.2 kmpl of LPG. (i used only “autogas” as the mechanic said that the warranty of the LPG kit will void if LPG from household cylinder is used). Initially the car felt same like petrol, but as i bega to climb kilometers, it began to show its real charactoristics.

    1. Loss of power – the car just crawls…… it never ran after the LPG conversion.
    2. Oil consumption – 1 Ltr of oil for every 2000 kms. (When i drain oil for periodic oil change only 1 or 1.5 Ltr came out)
    3. High engine temperature
    4. Coolent consumption – It needed a lot of Coolent (2 Ltr for every 1500 Kms)

    Then i changed Std Wheel Discs with light weight alloys and filled N2 instead of AIR. There was a mileage hike (18 kmpl of LPG), but all the above said problems persisted. Still i was using the LPG because of it’s low price (only 28 Rs/Ltr). But once i analysed all the cost incurred (Oil, Coolent, and the lack of power), I was convinced that the total cost of running is more than an average petrol engine.

    I needed to visit the LPG mechanic almost every month (i drive a MAX of 2000 kms/month) to clean the white powder-like sediment accumulated around the spark plug. (Think about the harm this sediment can do for an MPFI engine’s sensors and tiny internal parts).

    So finally i sold the POOR M-800 after 125000 kms (80000 petrol+45000 LPG). It would have survived a 150000 kms if kept on using petrol.

    SO My humble requst is NEVER EVER GO FOR CNG or LPG. choose Between Petrol or Diesel. CNG or LPG is not meant for present day engines. Tomorrow some intelligent engineer may develop an engine which might run on LPG or CNG.

    Fitting LPG to a brand new MPFI engine is like asking a 4 year old child to drink smirnoff, smoke a cigar and run…………..

  3. Naresh says:

    I have used a Zavoli kit in my 2002 M-800 (Carb.) since 2007, and it has covered almost 95,000 km after that.
    No problem, even on long trips, the average has been 1 – 1.5 km. per litre less than petrol, but the fuel cost works out to be less than 2 rupees.
    Oil has not been a problem, about 1 litre added over the full level over the normal 6-7000 km interval when I change the oil, I use API SF or higher grade from Penzzoil or Bharat Petroleum. Plugs stay cleaner than petrol, points wear out more.
    Issues: most mechanics set the mixture lean for higher mileage, that causes the rings to wear out. The solution is to set the air idling at normal working temperature using a tachometer : set for highest idling speed, and adjust the gas volume slightly higher than needed. It is difficult for inexperienced mechanics to set by ear without a meter as gas does not knock as easily as petrol. Another thing is that as gas burns faster than petrol, the timing has to be advanced by about 3 degrees compared to petrol. If set properly, it is difficult to distinguish the performance between gas and petrol. Too much gas causes poor performance, as the mixture is too rich, and also causes high fuel consumption.
    Another thing is that the coolant lines to the vaporizer tend to clog, so periodic cleaning of the lines, the vaporiser itself and the gas filter are necessary, most people don’t do that and cry.
    The best kits in my opinion are BRC, with Landi Renzo, Zavoli, logas, lovato and other Italian makes more or less similar, mine cost 16,500 including RTO formalities, BRC was 20,000 or so.
    Please bear in mind that these kits are not car specific, the same kit is useful for a car engine displacement range of 600 cc to about 1600 cc, so you do have to set the flow rates.
    A simple guide: the exhaust should smell the same and drip water as on a properly set petrol engine, that means all is well regarding the settings.
    And no, I never use domestic LPG, as it has a different chemical composition compared to auto LPG, and leaves a smelly tar like deposit in the vaporiser.
    Practicality and economics: CNG kit in 2007 was 42 – 45000, with a 70 kg. empty weight tank (10 kilos gas capacity) good for 250 km, and then a 2 – 3 hour queue to fill up, in my use that is 3 days.
    LPG tank has empty weight of about 22 kilos, and full tank range is more than 600 km., and the line is at most 3 vehicles, so 10 minutes max.Add to that the lower conversion cost, and there you are…
    Now more CNG stations are coming, and the kits start at 24,000 here with RTO charges included, so for city or medium use everybody is going for CNG.
    For long range, from here in Baroda to Mumbai, I have gone non stop , CNG would have meant 2 stops, ie 4 -6 hours wasted, so it is not practical for long range in cars as the largest tanks are about 12 kilos capacity, or about 300 km in a medium size car.
    A good friend has a Wagon R Duo with the factory Impco kit, he gets 12.5 to 13 km. a litre on LPG, on petrol he has never checked his car’s consumption, it has done about 60,000 km with no serious problems, and no oil toppings beyond service time, and periodic spark plug replacement.
    So I feel our friend Vishnu was the victim of poor fitting by an inexperienced mechanic or cheated in some way by poor quality of kit or workmanship.
    Another practical tip : start the car on petrol in the morning and run it on that till the temperature gauge starts to rise, then switch to gas and stay on that all day long. Cold LPG on the vaporiser damages the rubber diaphragms inside, but as the coolant circulates the rubber warms up and the vaporiser works better to change the liquefied gas to vapour.
    In the Wagon R , the changeover is at about 2500 rpm, then it stays on gas after starting on petrol other cars may have the same system in place.

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