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-   -   CNG vs LPG Comparision (https://www.team-bhp.com/forum/technical-stuff/22225-cng-vs-lpg-comparision-15.html)

Is it possible to fit LPG for old cars. I have a Premier Padmini S1 car that I would like to install it on.

Also, which is the best place to fit it in Bangalore?(Specifically, where can I find a very good tuner in Bangalore)

Yes you can fit an LPG kit in your Fiat. It's no rocket science, infact its lot easy to convert Carburated cars.

But then the effect of these fuels is bad on engine, personally my recomendation is not to go for these fuels.

you better check with your local RTO first, because I think in Maharashtra there is some rule that the passenger vehicle must not be older than 13 years for fitting these kits

Hmmm. Interesting. I do not know of any thing of that sort in Bangalore. Logically, what would be the reason behind such a decision?

I had a ZEN 12 year old, had gas kit fitted and RTO endorsed on my RC book so should not be an issue


Now to my question: the ZEN gas job was done by a local mechanic, though no major problems with the kit - after sale service was a night mare.

So want to go with some professional for my Santro AT conversion now. I have been researching net & this fourm. and have narrowed down to two retro fitter EcoGas in Jayamahal Extension and Dars Auto on Queens road. (Bangalore)

any reviews of these place?
OR
any one recomend any one fitter in North Bangalore?

I own a Hyundai Accent which is 2 years old now and has done around 25k Kms. I am planning to install a CNG kit now. Which kit would you guys recommend and from where in Noida/Delhi can I get it installed. Any particular brand and what will be the costs involved?

I have a maruti zen 1998 model - got LPG installed a year back - the average i am getting on LPG is 8 km per litre - is this the average i am to expect from LPG in maruti zen (Carburetor) ? I visited garage of Shrimankar who adviced me to switch to CNG and guarantees average of 18 kmpl + - Would request your views please - regards Deepak

Deepak, I recently switched to a CNG kit for my Maruti Alto. Yes, the averages you should get on CNG shall be much higher than petrol or LPG. It can go as high as 50% over petrol for a well tuned system with lambda sensor & TAP.

I went for an installation without the lambda (open loop), but put the TAP since I require the additional power and cannot work with lower power on an Alto. For such a setup, you can expect around 35-40% over petrol. My current running cost is a shade over Rs. 1 per km on my Alto (I used to get around 17kmpl on Petrol and on my first refill I got around 23km/kg on CNG.

Again, my Alto's on MPFI, so your Zen would be a shade lower, but still you can expect over 30% increase in average over petrol for sure.

I really don't know how one can get more mileage with CNG than LPG, LPG has higher LHV (Lower Heat Value) than CNG and thus the Flow rate required is less for an LPG than CNG :). Les flow rate = less consumption?

Dear Manish Saraswat - 1 kg of CNG is equivalent to 1.5 litres of petrol / lpg - so i guess the claims of 35% to 50% more mileage should be correct - am requesting my mechanic to see if i can get mileage of 12 kmpl in city in zen - if yes then i would like to drive on petrol regards Deepak

Well, CNG is sold per kg and not per kilo. it's not an apples to apples comparison when you compare lpg to cng. their composition is different, storage methods is different (CNG is stored at very high pressures of nearly 200 bar). Flow rate and heat value is not pertinent here since the bases are different. One is sold as volume, other is weight.

I just checked my averages over the last couple fillings of CNG. On Petrol, my Alto used to give me 17kmpl. Now with CNG, I'm getting around 24-25km per kg. So yes, you should get a 40% increase in average with CNG. Plus the fact that that it costs less than half the price of Petrol means that your running cost should be just 35% of petrol.

Again, i'm running an open loop system. If you run a closed loop system with LCS, you should see marginally better numbers than mine on an MPFI system.

Lower heat value of the fuel is the one criteria that relates to the fuel effieincy. Higher the LHV lesser is the consumption for the same amount of power developed. Propeane has an LHV of 92.78 MJ/Nm3, Butane 122.70 MJ/Nm3 and Methane has 35.87 MJ/Nm3.

So any given day LPG (propne & Butane) has Higher LHV than CNG (primiraly methane).

I have seen practically that as the the LHV increases the flow rate (i.e consumption) goes down. Though the fuel is more unstable, prone to knock.

Hi Manish,

Agreed about the output per unit. CNG has a lower heat value. Highest is Petrol though for a given unit. The reason why we all don't bother about this is due to the substantial advantages of cng over other fuels:
1. Running Costs: CNG is the lowest. Followed by diesel, then LPG, while petrol is the most expensive.
2. Safety: IMHO, diesel is the safest, but I'm no expert on this. When converting to CNG, I did look at safety and CNG is definitely safer than LPG. It's also safer than petrol as per online publications, but then again, only experience shall tell.
3. CNG is the greenest of all fuels. Period. Amongst these options, it's the lowest (significantly lower CO as compared to petrol engines) and approx 30% lower CO2 gases. It's got the lowest greenhouse gases (non-methane), but some of this advantage is lost to methane which itself is a greenhouse gas (probably a little methane released due to unburnt fuel at starts / stops and while filling up, etc.)
4. Online publications also say that CNG has the lower maintenance due to lower spark plug fouling and lower engine oil contamination. Again only time will tell, but I feel it would be the same or marginally higher than petrol because the engine runs hotter than petrol and also since most of us in India install open loop systems, we need to ensure very clean air filters to ensure good mileage and performance. I'm sticking to a routine of cleaning the air filters every 1000km or so. Also I'm going to upgrade to a higher grade oil 20w50 magnatec / gtx from my current 20w40
5. On performance, nothing can beat modern diesels due to their huge torque advantage. In my personal experience, low end torque drops significantly on CNG inspite of putting a timing advancer on my alto, although it's good at the top end. Probably that's because I'm running an open loop kit. People say that if you need performance and aren't worried about the cost, then a sequential kit is the best, although it's north of Rs. 60k.

These were a few of the criteria I researched while converting to CNG. Personally I'm extremely happy with moving onto CNG. Zero regrets and I really don't bother switching on the AC or even taking out my car for drives anymore. Only now can I truly say "Let's go" on my Alto :uncontrol . There are definitely tradeoffs, but overall it's been a happy experience and I'm completely sold on it

Hi Sas,

1.) Yes CNG is cheapest as it is Locally Produced, every thing else is imported.

2.) you are right, diesel is least volatile. CNG is safer than LPG cause its lighter then air and so in event of leaks it escapes out of the scene, where as LPG stays there being heavier than air. The flammability limits of CNG is 5 to 15%, that gives even less chance for fire.

3.) yes CNG is Greenest fuel.

4.) Spark plug fouling much depends on the Air/ Fuel ratio, but as a rule of thumb gaseous are said to be better. As for the wear on engine all gaseous fuel are the same. There are special oils meant to be use on CNG Vehicles, we should use them. However I do not see people using that, for the Generator / power generation definitely they use special CNG Oils. They give better life. A 20w50 oil will help cause the engine is running hotter than before.

5.) Petrol has an Octane rating of 80 –95, LPG 100-105 and CNG 120, thus CNG has good antiknock quality, but then it’s the slowest burning fuel giving sluggish performance. An increase in compression ration, timing advance and properly designed venturi (Gas Carburetor) CNG vehicles do give better performance.

6.) Could you elaborate by Open loop kit, the close loop as far as I know is linked with oxygen sensor in the exhaust to better control emission and air fuel ratio and do not necessarily warrant an increase in pickup. If you have an stepper motor type Gas valve between the Vaporizer and the Engine gas inlet line, then because of electronics you have better response compared to mechanical system working on the vacuum created by the engine.

Essentially an open loop system is manually adjusted (2 adjustments are available, 1 each for mid-rpm and idle). It's more like a carburetor. You're right, in a closed loop, the AFR is adjusted by the sensor, the lambda control unit. The closed loop system is far better, especially for emissions and mileage, but it's difficult to diagnose when something goes wrong, hence I decided to give it the skip. I can always go for it later on. Entry level LCS systems start from Rs. 2000.