CNG engine

[chmabdullah]

I wanna know whether the factory fitted cng cars have the same engine (with addition of cng kit of course) or is there any modification bcose engine tends to heat up more on cng compared to petrol.

[nossee]

Same engine.

[chmabdullah]

but then additional heat may wear the engine more.

this is the only negative impact of cng on engine life i persume

[spectra]

i cannot think of a reason why engine heats up more on CNG. Can u please explain?

[chmabdullah]

when petrol is sprayed in the cylinders just before compression stroke the sprayed fluid causes cooling effect and secondly petrol also has lubricting effect on pistons rubbing against cylinder walls.

[spectra]

dont u think that cooling effect is negigible

[chmabdullah]

It is proposed on basis of laws of physics. There is no measurement done yet. but i ve heard from mechanic ppl that the rings may get extra heated up. but also never heard of a CNG engine needing remake before any petrol ones.

P.S i m in favor of cng

[autophile]

@chmabdullah. Petrol is anti-lubricant bhai.

[testdriver]

@chm

Look what research says about CNG:
"The life of an engine increases by using CNG. Lubricating oil life is extended considerably because CNG does not contaminate and dilute the crankcase oil. Due to the absence of any lead content lead fouling of plugs is completely eliminated and plug life is greatly extended. Another aspect, which increases engine life, is that CNG enters the engine in the form of a gas whereas petrol or diesel enters in the form of spray or mist. This spray/mist washes down the lubricating oil from the piston ring area thereby increases the rate of depreciation of the engine. Since this is not the case when using CNG, the life of the engine increased. On the whole, the maintenance costs are reduced and engine life is increased. Some 13,000 CNG users in Pakistan would confirm that.

CNG provides easy starting, reliable idling and smooth acceleration. When your vehicle is running on CNG, you may notice its acceleration to be a bit slower which is due to a power loss of typically 5-15 per cent, which can be minimized by proper tuning on the CNG kit (e.g. advancing the spark timing) to take advantage of the high octane rating of the fuel. CNG has a Research Octane Number (RON) of 130. The power loss on CNG is generally not noticeable in ordinary city driving.CNG has a good mixture distribution quality. When the correct proportions are brought together they mix thoroughly and rapidly, which improves the combustion efficiency of the engine. The Research Octane Number of CNG is 130 as compared to 87 of premium motor gasoline. When gas fuel is used, no carbon is formed during combustion and engine stays very clean internally.

CNG has four big safety features that make it an inherently safer fuel than petrol, diesel, or LPG. Firstly, CNG has a specific gravity of 0.587. This means that it is lighter than air so if it leaks, it just rises up and dissipates into the atmosphere. On the ground other fuels will form a hazardous puddle on should a leak occur. Secondly, it has a self-ignition temperature of 700 degree centigrade as opposed to 455 degree centigrade of petrol. Thirdly, CNG has to mix air within small range of 4 to 14 percent by volume for combustion to occur. This is a far narrower range than for petrol. Fourthly, CNG cylinders are designed and built with special materials to the highest safety specifications, which make storage far safer than petrol tanks."

[Beamers]

@ All....... On Cng the burning temp point is much higher as compared to petrol. thus the engine faces more heat then that of petrol where the buring point is less. The rings, valves and valve seats are the most effected parts when running on cng.

[chmabdullah]

if this is so then these parts may need an early replacement.
Do the new factory fitted cng cars have modified rings ,valves etc??

[robin]

engine dissipates heat through plugs and to heat exchanger (radiator), if they r fine, everything goes fine then. behaviour of egine oil changes when heated, so use good oil also. i see no issue at all except engine's out put.
btw, now i am quite used to baba-style driving, with no offence to babas.

[kkoool]

no they dont have modified rings/valves etc.......engine has a wide range to accept heat as u are mwntioning in case of CNG(which actually is negligible)..........

[spectra]

extra heat is produced in a CNG engine, how?
Its same petrol engine with at best narrowed plug gaps. Do u think it will create that big a spark to produce so much excessive heat to damage valve seats, rings etc.
I dont think so.

CNG has higher RON that does not mean it produces more heat that means it gives a bigger flame with bigger spart and inc ase of petrol engine running on CNG spark is the same.

So i dont agree to this statement that CNG produces more heat in combustion.
My car is 65000Km driven and i replace oil at 5000
and it comes out yellow. Conventional local service station people advise me not to change when they see the oil coming out. Where is the heat effect in that oil. It should be blackish, but its not

[Beamers]

The buring point of cng is much higher as compared to petrol. This has been discussed a lot on the forum.
Then why does engines that run regularly on cng wearsout earlier to that of pertol.
I remember at a post someone mentioned that cng engine would run till 150k whereas petrol engine would go over 200k.
There must be some reasons behind the difference.

[spectra]

there is no substantial evidence to 2nd the claim of reduced engine life on CNG coz maintenance blunders in any case play a large part

[SpeedDemon]

I would like to see a certified technician verify any claims about any fuel.

Better yet, someone with a CNG engine can get their engines opened and inspected for damage!

It seems there are a lot of rumours here that are being portrayed as facts about CNG and stuff.

Anyone here who is going to try and get a 1000km from a tank of CNG by leaning out the mixture is going to end up with an overheated engine!

Remember that a gas at cold temperature being injected in a cylinder and expanding at the same time will have a cooling effect. Ever felt the air coming out of a balloon is colder due to sudden expansion?

Cheers.

[mscsyed]

Auto-Ignition & Peak Flame tempearture (°F)
Natural gas=842, 3423
Petrol=572, 3591
Diesel =446, 3729

There is a home NG home appliance coming soon through which you can compress NG at home and refill your car.

[spectra]

whats the conclusion from these numbers syed sahab ??

[mscsyed]

Well, I have added some content to the ongoing disucssion, where it had not been clear that what are the heat values NG vs Petrol? From these figures it appears that NG wont be producing drastically more heat during combustion as compared to the petrol.