Cons of CNG?

[Icy2fire]

Below is an extract from the NGV community in Malaysia by drander. Just wanna bring this article up for discussion as it shows some cons of converting to cng.

 

Comments pls:

 

Since CNG octane rating is at 130, it burns very efficiently. In technical terms, it burns almost perfectly and emit a large volume of heat. While petrol octane rating at 97, it burns less hot.

 

When you are operating at CNG-mode, you are burning very efficiently (eventhough you do not have a timing advance processor to ignite earlier which is only to counter the slow flaming rate on CNG). For NGV Users, you can by now notice that your car is extremely hot (pretty unbearable to place your hand for a couple of minutes).

 

For simple arithmatic, the entire cooling system in your vehicle operate 7 times more than when you are using petrol-only.

 

In percentage, the increase in heat is about 113% more, and not 15%, 20%. If you do hear taxi driver complaining about overheating, this is the one of the reasons. Here are some signs of extreme heat with CNG-mode driving:

 

(a) Please keep track of your spare radiator water level (in plastic bottle). It should be dropping a couple centimeter everyweek.

 

(b) Please keep an eye on your temperature indicator at your speedometer. It should be slightly higher than 80-85 degree C.

 

© Please keep track of your battery acid liquid level. It should be drying up pretty rapidly as well.

 

(d) For vehicle older than 5 years, please keep an eye on your radiator fan as it can be overworked and spolit.

 

(e) Based on our experience, we have found that car battery can only last up to 2 years most. For taxi, you can sometime see them place a styrofoam to block the heat from the battery plastic wall. Since they wait in line for gas refill, the battery plastic get too hot and it cracks. And once it cracks, it leaks and damages.

 

 

Heat is the biggest enemy to any vehicle. It reduces the engine efficiency to produce power. It can lead to mechnical damage, valve train, timing belt reduced-life span. In older vehicle, the power-loss can be also contributed to heat, and not just 'very dirty' engine.

 

Heat can cause wiring damage, particularly when NGV Installer are not properly encapsulating NGV wiring with PVC tubes. The humidity and heat will build high resistance ® in copper wires; thus, it makes the gas soleniod semi-open due to low voltage. Some car has lower performance power during hot day is perhaps a heating problem.

 

Heat can cause valve & valve seat damage due to dry fuel. The heat in the engine makes your standard engine oil 15W 40 to lose its viscosity (lubrication) and melted down to become watery. Once it become watery, it become dried easily by the dry CNG fuel at the valve and seatings. In petrol, a chemical called benzene is added to provide extra lubricant for valve. This is why we need to adjust our Valve Tappet every 10,000-15,000km. The tappet is knocking on the valve head, while the valve shaft is moving without lubrication. After a thousand of kilometers, it becomes misaligned and need a readjustment. For hydraulic valve, when its valve head get over knocked, it thins out. By then, you need change the entire top side.

 

A NGV Member, CLKONG' has been championing this issue overa a couple of weeks now. He is strugglingly looking for a good solution to this problem. Thank you, CLKONG. He found one, but he can't seems to get his hands on the solution.

 

Why then this heat problem can happen to our vehicles. Petrol engines were designed to tolerate petrol heat-emission (at max), and the cooling system engineered to disperse the generated heat. BUT these engines were NOT make to run on CNG fuel. It is we who converted the engine and subjected it to CNG-heating. It is our fault, and not the Manufacturer.

 

For me, I have been using an improved engine oil, specially formulated for LPG & Diesel engines. It is the LPG side that is most applicable to CNG-mode. It is a dry fuel & has extreme heat too. My valve does not misalign so easily. The engine runs cooler, and easier to start. For coolant water, i use Lubeguard formula that is designed to reduce heat faster. For those who have driven my car, now you will understand why it have better power than usual. This is why we have always been asking NGV Users to think of safety. Overheating can cause fire (short circuit wiring, burning rubber hose, etc) and the refilling NOZZLE is in the engine compartment as well.

 

So, please keep an eye on the heat, and kindly be COOL about this issue!

[Tmtan]

But have LTA approve to this conversion yet? I think i read somewhere that some private car owners r already converting as it is already LTA compliant ....can any1 advice on this?

[Ronnie]

my main concern is that it voids manufacturer's warrenty.... as mine is a relatively new car... and conversion to cng is a different ball game altogether.

[Icy2fire]

i believe that lta has already approved it

cost around $2000

www.cng.com.sg

heard that there will be a booth at the motor show

 

previously there were a lot of pros for converting and the cons are the space, weight and 10% drop in power only

those above i can live with, esp if jb cng is at 0.68rm only

 

however i am worried about the heat part and whether the lifespan of the parts are affected

[Icy2fire]

yes it voids the warranty except for one (can't rem, anyone can help?)

[Kelpie]

A Korean car, ssangyong, something like that. The car manufacturer that use dated Mercz engines.

 

Regards,

Edited October 24, 2006 by Kelpie

[Try_conti]

Isn't this always the case ? The converter will only tell you the pros of converting. Even if they knew the possible problems that may arise, they wouldn't be telling you, won't they ? To do that, they might as well close shop & go home !

 

In the event of problems occuring with the engine due to overheating, the blame game starts. Converter says its not their product problem as everything is working as designed & you can't claim warranty for your car as car disti said you modified the car.

 

Meantime, LTA say not their problem. They certified that the product is safe to be installed in cars & it worked as designed. And if you try to modifiy the cooling system of your car, LTA say another thing ..... must get approval for this & that & you pay & pay.

 

So whose problem then ? Ultimately, its ours, car owners. If the car is not designed for it, something else will give way sooner than you expect. There's no free lunch. If its too good to be true, it probably is.

[Icy2fire]

guess u r right to a certain extent

with proper installation and proper care, it should be fine

this was what i found in the malaysia ngv community

kl cabs all use cng with no prob

many jb cars also

 

instead of waiting for pple to install and tell us the cons in sg

i went to find out more in the malaysia community

it seems that the installer is very impt too

as some encounter problems due to installation although the price for conversion there is much cheaper than sg

 

i will prob try the conversion since my car got no more warranty

if something cocks up, i can just change to a new car

afterall, many remaining depreciation per yr is around 4k per remaining yr (regardless of when i change)

the pros of being able to endure not changing to a rex

 

the purpose of this thread is to inform all on the unknown cons

cheers!

[Genie47]

Number one. You can deal with the heat with cooler spark plugs. Cooler spark plugs transfer more heat out of the engine block into the coolant. Coolant systems are over-engineered. They can take more heat. The reason why the engine is hotter is because the coolant system did not absorb the heat from the block efficiently.

 

Second, you need better sparks. Lower plug gap by 0.1 or 0.2mm for better and cooler sparking.

[Falc]

Dun understand this part, care to explain... how does lowering gap result in "cooler sparking" ?

[Genie47]

The converter didn't tell you because this is quite common knowledge to me at least. There are huge resources on the net and there are also solutions to the problems in the net most of which are European using LPG.

 

Valve seats and valve stems for example are hardened because we use unleaded petrol. So with gaseous fuel it is a non-issue. Hondas might have some problems because they use very thin valve stems.

 

Can't expect everything to be spoon-fed to you. A huge amount of research is done prior to even buying a car. Likewise, a huge amount of research effort goes on prior to any modifications. Makes me wonder if anyone actually spends time on such things before they stuff in that new spangled "lightning discharge sized spark booster".

[Genie47]

Sorry it is not cooler sparking. It is more efficient spark ignition. Gas requires 12-16kV to ignite compared to the 7-12kV for petrol. By lowering the plug gap, you lower the required spark voltage.

[Try_conti]

Have not thought of going that route yet. Its just that I was wondering how many would go research such issues other than just accepting what was dished out by the relevant parties.

 

Even if they dig around a bit more, how many would be technically savvy enough to understand the technical issues involved. I know I do struggle a bit to try to figure out the terminologies involved.

 

Apart from supposedly environmentally friendlier & maybe cost savings in terms of cheaper CNG compared to petrol, how many of those interested would actually go in-depth to figure out the technical issues involved or if their ride is able to take it.

[Genie47]

Well, those who actually bought a car they like went through a lot of research already. If they want to do something risky on it, they will go through the research again. Otherwise, forget it. Swimming is enjoyable as much as it is dangerous. That is why people learn to swim or cycle.

 

Planning reduces heartaches and headaches.