sgiitk

LPG & CNG?

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The issue of LPG and CNG is finding mention in many posts. I thought I might as well start this thread to cater to this fraternity! Please feel free about discussing conversions as well as CNG & LPG cars per se. I for one will not go for either!

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Hey sgiitk,

A good topic, this one! First of all, for every one's benefit around here, lets tackle the basic questions:-

1) Difference b/ween LPG and CNG

2) Which is the safer of the two?

3) Availability, commercially.

4) As to why some manufacturers opt for CNG { cedia } and some LPG{ WAGONR, Santro}

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1.

 LPG - Liquefied Petroleum Gas - what you get in the cylinders of cooking gas. Comprises primarily of Butane & Propane.

CNG - Compressed natural Gas which is piped around. Has a lower molecular weight, less calorific value, contains Hydrogen.

2. Safety: CNG should be safer since it is lighter than air and so diffuses away.

3. Commercial Availability: Variable. Most mid/large towns have LPG filling stations. Many towns may have CNG as well.

4. Matter of choice and perception of market demand.

CNG has a lower calorific value and hence a larger power drop than LPG - typically 30% for CNG, half that for LPG. CNG works out cheaper than LPG to run vehicles.

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Well Cedia is LPG dude and doesn't make economical sense as the economy of LPG will over run the petrol one .CNG is better option one-third price and Lpg performance with good availability .......

Actually CNG are better for diesel engines and LPG for petrol.

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Well Cedia is LPG dude and doesn't make economical sense as the economy of LPG will over run the petrol one .CNG is better option one-third price and Lpg performance with good availability .......

Actually CNG are better for diesel engines and LPG for petrol.

 

but the initial cost of lpg is less than that of cng
ankit.jhamb2008-01-31 16:00:05

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A brief on CNG v LPG.

 

There are a variety of kits available for CNG as well as LPG and it pays to be well informed. Lets go over a few basics.

 

Kits

There are basically two kinds of kits available - closed loop kits and open loop kits. Closed loop kits are more sophisticated as they employ a number of sensors in real time to give the best performance/efficiency all the time. Needless to say, these cost a bit more than the regular as well.

 

The open loop kits are basic kits. These need checks from time to time to keep them in a proper state of tune. When buying a kit, ensure you buy from an RTO approved installer and keep brands like Landi-Renso, Lovato, OMVL, Tartarini, BRC and Bedini in mind.

 

Safety

Modern day kits are quite safe and approved for automobile use from authorities like ARAI. But it is essential that you install the kit from RTO approved installers only. The tanks are built to stringent quality standards, but note that CNG is stored at a much higher pressure than LPG which is why the tanks are much heavier. A safety valve called the multifunction valve releases the extra pressure in case of an accident through the filler valve, which is why it is important to have the filler valve located outside the vehicle.

 

Briefly put, LPG/CNG cars if taken care of are as safe as their petrol/diesel counterparts.

 

Performance

When running on LPG or CNG, engines experience a power loss. The power loss is greater in the case of CNG powered vehicles when compared to LPG. Also when running on CNG, you will get better FE than running on petrol. But in the case of LPG, you will get slightly less FE than on petrol. If you have nothing but money savings on mind, CNG makes good sense, but if you want savings but don't want to compromise too much on performance then LPG is for you.

 

Maintenence

It is observed that CNG powered vehicles need a little more attention. Due to characteristics of CNG, engines tend to heat up more than usual which affects the life of the spark plugs and also the cooling system. The extra heat also changes the engine oil viscosity which means oil change intervals are more frequent. Heavier tank also tends to wear the suspension components.

 

LPG engines tend to run cooler which doesn't put any undue stress on the engine. But common to both the fuels, the electrical system of the car needs to be in top condition and therefore needs timely checks to replace worn-out components.

 

For more information, refer to the article LPG v CNG in WhatCar Oct-Nov 2006 issue.

 

FRG
FuelRunGod2008-09-16 07:47:17

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FRG: Excellent as usual.

Let me add a couple of points. The gas cylinders require periodic testing - once is 20 years or so for LPG, once in 5(?) years or so for CNG. This will be an issue. Also, I guess the distance per tankful will be higher in LPG.

The power drop is due to the calorific content. The Fuel-air mixture has to have a higher fraction of fuel than petrol in the cylinder in order to burn. The same is incidentally true for Hydrogen (even worse) and hence the use of Direct Injection.

It thus leaves less room for the air and hence a lower output. As CNG occupies even more fraction of the cylinder in order to burn, you end up with  an even lower output.

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Also' date=' I guess the distance per tankful will be higher in LPG.[/quote']

 

LPG is measured in litres while CNG is measured in Kg.

 

FRG

Has to be, since a gas cannot be measured (and dispensed) by volume. Incidentally Aircraft are fuelled in weight of fuel, and not volume since the volume of ATF (or for than matter petrol) changes with temperature. This is more precise.smiley1.gif

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Actually there is no use of LPG I asked a tourist guy he said with WagonR

1.Insurance high

2.Petrol kind FE

3.Low power

4.Space constraints

5.Fear of bursting (I told him not to fear)

 

 

HE said he could have bought a VXi ABS with it or saved 80k. Phew!! one last thing he rarely gets to tank up LPG

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My brother-in-law bought a LPG Omni (from Maruti). He has been most unhappy with it.

Repeated loss of gas - never really traced down. Seems to be cured.

Running cost comparable to Diesel or higher.

After only 1-1/2 years he wants to get rid of it.

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FRG: Excellent as usual.

Let me add a couple of points. The gas cylinders require periodic testing - once is 20 years or so for LPG' date=' once in 5(?) years or so for CNG. This will be an issue. Also, I guess the distance per tankful will be higher in LPG.

The power drop is due to the calorific content. The Fuel-air mixture has to have a higher fraction of fuel than petrol in the cylinder in order to burn. The same is incidentally true for Hydrogen (even worse) and hence the use of Direct Injection.

It thus leaves less room for the air and hence a lower output. As CNG occupies even more fraction of the cylinder in order to burn, you end up with  an even lower output.

[/quote']

After the Maruti Van tragedy in Mumbai (28/01/08), wherein 4 school kids were killed and some more injured the Maharashtra Govt is cracking on the CNG/LPG fitted vehicles. How far they will taste success is not known. after market fitting of LPG/CNG is not permitted (in Maharashtra) for any car or motorised vehicle that is more than 5 years old. The van which csught fire was a 1991 model and had fitted this kit recently. Though the van burnt due to electrical short circuit, the LPG in it was illegal.

Hydro-testing of LPG/CNG cylinders is compulsory in Maharashtra every 5 years. The dealer  takes out the cylinder and puts it in a pit of water, subjecting it to two times the normal pressure. Its then certified as fit for use for 5 more years. The cylinder's life is 15 years. a cylinder bursts when the temperature exceeds 400 degrees C.

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Some more  facts::::

 -The mileage  given by  one litre of  LPG/CNG will be cut by 10 to 20% vis a vis petrol. So if a car runs 10 kms /litre it will run 8 to 9 kms on a litre of gas.

-CNG costs 40% less than petrol.

-LPG conversion costs Rs 22-27K, while CNG costs Rs 33-37K.

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Dude the Van tragdy in Mumbai was due to the petrol bottle below the seat where the battery was kept .The LPG cylinder was empty and the guy had connected it directly to the carburrator .

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rssh: Diesel engines cannot be retrofitted with either of the Gas Kits, as the diesel engines do nat have Spark Plugs.

 

anjan: In Delhi running a car on CNG costs  Rs 0.9- 1.0/km and i tell you this after seeing it myself on a friends Honda City-II 1.3, which gives an Average of 20-22 kms per Kilo of CNG which is Rs. 19.20 per kg, and the average is for both A/c and Non A/c.

 

Yes, running a car on LPG does cost more than on CNG it costs around Rs. 2.5 - 3.0 per km. as LPG is around 30-35 per litre and the car gives an almost equal FE as on petrol.

 

 

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Some more  facts::::

 So if a car runs 10 kms /litre it will run 8 to 9 kms on a litre of gas.

How do you measure a litre of CNG?

Sorry,LPG/CNG are sold by weight viz. Kilograms-- please read Kgs for litre in my post

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Some more  facts::::
 So if a car runs 10 kms /litre it will run 8 to 9 kms on a litre of gas.

How do you measure a litre of CNG?

 

CNG is measured in Kilograms whereas LPG sold at Car filling stations is measured in Litres and by weight 1 litre of LPG is approximately 600 gms.

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Remember you are down by about 30% in power with CNG (half that with LPG). I have ridden a few CNG Esteems and the power drop shows. The driver seems to be stirring the gearbox all the time. Probably this will be less of a problem in the long stroke engines (Accent, City!).

So cost savings must be balanced against poor driveability, and somewhat questionable reliability of the gas conversions. LPG has a lower power loss but then also has a higher running cost (comparable to diesel according to one person who is now planning to get rid of his dual fuel Mmni)

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i have 3 questions.

Q1. What is lambda and its function? how does it differ from advancer?

Q2. Are CNG kits interchangable between cars? e.g can a CNG kit in Santro can be removed and fitted in to Esteem?

Q3. Which sedans are most suited for CNG conversion?

 

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CNG over LPG due to availability and better value for money spent on fuel as over LPG, and if one one isn'nt bothered about the economy part might as well stick to diesel or petrol.

The air in Delhi people say has improved after corporation buses switched to CNG. CNG driven engine emissions have a lesser toll on the enviornment as compared to other fossil fuels.

 

 

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