New fort Bus running on CNG

[bmacavanza]

To convert to LPG, the engine must be a gasoline fed engine.

[uls]

Kakatuwa nga ung CNG vs. LPG thing...ung CNG, government na ang nagback, pumalpak; on the other hand a couple of relatively small companies started putting up small LPG conversion and fueling stations -- uncoordinated at that -- yun pa ang nagclick.

private enterprise > govt planning

market forces > govt planning

[niky]

As far as I remember, CNG is cheaper, but LPG gives more power and doesn't require extremely thick-walled tanks.

CNG is hard to implement on small cars... but a bus doesn't care as much that its fuel tank is suddenly heavier than a Charade...

[ghosthunter]

question lang: why can't we use LPG for buses? Kulang sa power factor or something?

it is the difference between diesel and gasoline engines.

diesel engine = ignition by air/fuel compression

gasoline engine = spark ignition

To get a diesel engine to run on LPG only, you need to retrofit a sparkplug in each cylinder and retrofit a throttle-valve on the engine among other stuff.

CNG runs nearly like diesel.

LPG runs nearly like gasoline.

BTW, you can use LPG in a diesel engine in a diesel/lpg mix. But the system tends to be expensive and savings not as big.

[reym]

taken from http://www.afsglobal.com/faq/diesel-...onversion.html

Diesel to Natural Gas Conversion

Many cities and countries today have programs to convert older, polluting diesel transit buses and trucks to run on clean, economical natural gas. Properly implemented, this is an excellent way to quickly reduce fuel costs, clean up the air and reduce noise with minimum capital costs. A poorly executed conversion program, however, can lead to higher exhaust emissions, much higher fuel consumption, unacceptable power losses, poor durability and high maintenance costs.

Diesel to natural gas conversion requires careful engineering on the base engine modifications as well as the control system. The investment required means that these projects only make sense for larger volume fleets. Following is a very basic overview of modifications required for a successful conversion:

Compression Ratio: A typical diesel engine has a compression ratio of between 16 and 18 to 1. CNG usually works best between 10 and 12; so new or modified pistons are required, with an appropriately shaped combustion chamber to allow proper air-fuel mixing.

Spark Plugs: Diesels don’t have spark plugs; instead they have diesel fuel injectors. A diesel conversion replaces the injector with a spark plug and may also require an insert to go through the valve cover – depending on the engine. Spark plug wear is a common problem, and the high compression ratio and use of gaseous fuel requires higher spark voltage than a petrol car.

Valves: Natural Gas is a dry fuel so valve seats in a converted engine need to be hardened to prevent abnormal wear. Older engines need valve guide seals to prevent engine vacuum from drawing oil into the combustion chamber.

Thermal Issues: Spark ignited engines run hotter than diesels. Such engines may require upgraded thermal management components, including larger oil coolers, larger radiators, and heat shields around exhaust components.

Catalytic Converter: A catalyst will generally be required to meet emission regulations. The exception is lean-burn engines, which, if carefully engineered, can meet certain emissions targets without a converter.

Engine Management System: Your choice will depend on the exhaust emissions requirements, efficiency targets, durability expectations, technology level of the vehicle and peripheral device control requirements such as cruise control, power take-off, automatic transmissions etc. AFS produces a range of products or can custom design for these varying requirements.

[ghosthunter]

AFAIK Buses franchise are good only for a few years, then you have to replace your unit.

Even if standard diesel fed bus franchise last for a few years, replacing the unit with another diesel fed unit makes better sense than going for a unit that uses cheaper fuel (CNG) but no where in the city to get that fuel.

You can get diesel from any petrol station.

Can you name a place in the city you can regularly refuel a bus running on CNG?

Even after years of the government pushing for the adoption of CNG for bus use, we have yet to see it happen beyond the testing phase.

[mark_t]

Are we not producing CNG at Malampaya, Palawan?

[ghosthunter]

Are we not producing CNG at Malampaya, Palawan?

yes but most of the production is being used to fuel a natural gas power plant. A small amount was used to supply the pilot CNG refueling station project along SLEX.

http://www.doe.gov.ph/ER/Natgas.htm

[uls]

having a source of NG is one thing

storage, transport, distribution is another thing

where is the infrastructure?

[uls]

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