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City Engines In 30% HCNG Transit Bus Project

The 11-liter City Engine for HCNG

City Engines is undertaking an 18-month low-emissions bus program to be funded jointly by the Los Angeles County Metropolitan Transit Authority (LACMTA) and California’s South Coast Air Quality Management District (SCAQMD). The LACMTA is the largest single operator of natural gas fueled transit buses in the United States.

The program will include the re-powering and evaluation of four transit buses, two running on Compressed Natural Gas (CNG) and two running on a 30% Hydrogen, 70% Natural Gas (HCNG) blend. All four engines will employ the very low emissions lean burn HCNG and CNG technologies developed and patented by Collier Technologies Inc. over the past 13 years. City Engines is the exclusive licensee of those Collier technologies.

Hydrogen-CNG volumetric mixtures of 20% or less hydrogen are called Hythane; mixtures above 21% are patented and held by Collier Technologies, which has licensed it to City Engines. With a properly tuned and configured engine, vehicles can increase thermal efficiency while achieving extremely low emissions.

NOx vs torque for a 30% HCNG City Engine compared to an 8.1-liter John Deere engine.

The hydrogen in HCNG is a flame enhancer that promotes combustion with a large amount of charge dilution (lean burn or EGR). HCNG engines operate in lower-combustion temperature regimes that produce very low NOx.

The new 30% HCNG 11-liter City Engine to be employed is based on a proven Doosan Infracore (Korea) short block engine design, with newly redesigned Collier/City Engines cylinder heads that support quiescent combustion and increased air flow. (Earlier post.)

The new engine configuration was demonstrated on a dynamometer in 2005, and proved its ability to more than meet the upcoming 2007 California CARB/EPA heavy-duty emissions standard. The direct drive engine produced NOx emissions of 0.1 g/hp-hr across the engine’s entire operating range. The upcoming 2007 Standard calls for 0.2 g/hp-hr of NOx. The emissions results were obtained at the exhaust, without the use or need of a three-way exhaust catalyst.

Part of the project will be certification of the engines to both existing and upcoming CARB/EPA emissions standards.

Subcontractors to City Engines will be Trillium USA, LLC, who will provide the HCNG fueling infrastructure for the demonstration; and Valley Power Systems Inc., who will provide installation and testing support, as well as future regional distribution services.

City Engines is also developing 8-liter and 5.9-liter HCNG engines.



Rafael Seidl

City buses are a niche where HCNG may be an excellent solution. There is enough space on top of the roof for the voluminous fuel tank and fleet operators can afford to maintain their own filling stations. Also, public transport is usually subsidized so cost is usually not as great an obstacle to adoption as for say, the haulage industry.

Of course, there is no fundamental reason why a CNG or HCNG bus engine could not be downsized and paired with a parallel hydraulic or electric hybrid system in the future. Such systems, based on diesel engines, are in operation today.

Of course, you could argue that a larger fleet of sharecab vans wiht 10-12 seats each would reduce fuel consumption and pollution even further. Customers would call the fleet operator, asking for pickup from and travel to a particular destination for a certain number of passengers. A large bank of computers at fleet HQ would approximately solve the associated traveling salesman problem for each candidate vehicle in the fleet and, determine which one is best placed to perform the pickup. Done right, this computation takes just a fraction of a second. The customer is immediately quoted an estimated time of pickup, estimated travel time and a price. The route change is applied once the customer confirms the order and has pre-paid the fare (via the phone bill).

Of course, you'd have to employ more drivers but with the right incentives, it might be possible to persuade consumers to actually use such a service instead of purchasing an additional car or truck. For LA, that remains a pious hope but it might work in e.g. NY, London or Paris.


While I like Rafael's idea of a dynamically-routed share-cab, it seems that there is an even simpler use for small vans or buses -- use them to supplement frequency and off-peak service on established urban bus or trolley lines.

To offer an example to show why this is a good idea: I know that one major drawback to using public transportation to go cross-town in Boston, especially during off-peak hours, is the infrequency of bus service. My previous home was astride a major bus line that went to stops that were almost directly adjacent to the homes of my friends whom I wanted to visit. Knowing that there could be a 20-30 minute wait between each bus during the evening hours, though, encouraged me to use my car. While the bus ride itself, without traffic, was only about 15 minutes long (and the drive clocked in at 10, since I could take a shortcut over a cars-only parkway), the real turnoff was the prospect of spending a cumulative total of 30-45 minutes waiting for buses if I missed a departure that I had planned on taking. If the intervals between buses were reduced to 10 minutes, I would have been far more inclined to leave the car behind. It would save me gas, avert parking headaches, and allow me to drink more wine with my meals, seeing as I would not have to worry about the drive back home. But, since service was so infrequent, I felt it necessary to use my car.

This proposal is hardly a novel use for small vans or buses. Jitney services -- small vans "poaching" riders off of establish trolley lines -- were popular in American cities when my long-deceased grandparents were youngsters. Such services are still widespread in Eastern Europe and the Middle East, and were wildly popular in Kishinev (of all places) last time I was there. They ran very frequently until really late hours.

There are many reasons we don't have jitneys in America anymore, and none of them are good. Historical jitney services were put out of business by regulations widely adopted in many cities, in the 1920s and 1930s, at the behest of major transit operators. Today, the Federal government, when disbursing transit subsidies meant for purchasing capital equipment, requires that all buses have an expected service life of 12.5 years. Jitney vans would not qualify for this money. Other reasons might include (and I'm speculating here a bit) opposition from mass transit worker unions, the high cost of unionized drivers, opposition from local taxi drivers (who positively dominate the post 1:00 AM Boston streetscape), and the relative unsuitability of newer, low density, dispersed suburban developments to any kind of transit at all.

Most of these factors stem from bad policies, and not the inherent limitations of technology or economics. Residents of older, bigger, denser cities would be well served by bringing back some form of jitney service, and it is fairly ridiculous that this nifty, convenient and highly uncomplicated transit option is not available.


Thinking about Rafael's comment on LA a little more, it is my feeling that LA is probably a good candidate for his dynamically-routed van concept, while a not very suitable candidate for jitney services. Population density in the LA basin is actually very high at this point, recently reaching 3000 persons per square mile, if I recall correctly. While many people live in truly non-dense suburbs even further afield, there is probably high enough density to support this sort of service in LA, in theory.

One of the big transportation challenges in the LA basin is that while the overall density approaches that of traditional cities, the spatial relations of the various neighborhoods and land uses do not. LA is very polycentric, with major employment centers in: (1) Downtown (2) Century City (3) Long Beach (4) Pasadena (5) LAX Corridor and (6) Wilshire Corridor from Downton to Santa Monica, among others. This makes it very difficult to successfully serve the population using traditional fixed-route mass transit solutions. Yet, with such density, it is virtually certain than multiple people want to go from any reasonable half-square mile patch to another half square mile patch at roughly the same time. Dynamically routes vans could act like car-pools on steriods, and really take advantage of that demand.


The rationale for dynamically routed vans makes great sense until you factor in the cost of the driver (with benefits).

Similar advantages could be obtained through the use of PRT systems, which would have the added potential benefit of avoiding the frequent stops busses make on crowded streets which further slow traffic. The obvious limitation to PRT is the capital required. However, I think as EV's become lighter, electronic controls become more sophistochated, and petroleum more expensive (along with asphalt and concrete), the capital issues will fade. In fact, with smaller, lighter EV's, dual mode systems may become practical.


JMartin -- What is a PRT system ???

Joe Adiletta

Rather than a dynamically routed bus, why not a dynamically generated carpool system?

I log on in the am, and say I'll be (or I'm at) corner X. At that point, the central server is pinged for anyone that has previously mentioned they frequently drove that route, between times A and B.

Ping is sent out to the cell phone (text format) of drivers, who then might respond yes/no to the request for pickup based on the pickup/destination match.

Being a consumer of public transportation, for a time the bus, specifically, I can sympathize with the "cross town" problem. While waiting at the stop, every day I would see literally hundreds of cars pass by, figuring someone must be going near to where I'm headed.

Security issues could be addressed with some form of heightened requirement for drivers/passengers, and a "fare" might be levied per transaction, thus turning your morning drive downtown into a revenue generating one!

allen zheng

PRT system:

In NYC, they ar called "Dollar Vans", since they used to cost a dollaar to get from pt. a to b. Increases in transit fares have led to higher fares from the vans too; $1.5, $1.75, $2, ... they are really hurting right now due to high gas prices.
___As to higher bus service, the idea looks good for increased subway service too. Many TA trains can be decoupled/split/shortened. They used to do this during specific times to respond to ridership levels during the day. However, the mechanical/electrical/air hose failures in the couples made this a hassle. Then you had hazard and union reasons. Keeping track of decoupled segments of trains was bothersome too. Today, computers, radios, and possibly manned automated trains would make this possible. Better couple designs may be incorporated in existing rolling stock and for new ones too. Conductors could be retrained to be Motormen (nod to union), and specially trained transit police aboard would allay security concerns. The bottom line would be:
1) To have double the service during non-peak hours, without increased wear and tear/manning issues.
2) At night, 2-5 car trains every 10 min, instead of 4-11 car trains every 20 min.
3) Possible super-express trains that follow the first half 3-10 min after the first half left from terminal. They would quick recouple at a station further down the line. Excellent and redundant command/control/communication and specialized equiptment/signals would be necessary for this to function safely, and efficiently.
___Commuter rail could follow this model (or a modified one) to various degrees. More frequent service would be welcomed for some communities that only get one or two train per hour during peak.


Private jitneys, like the dollar-vans cited in New York, are not a bad idea. At minimum, out-moded protectionist regulations meant to put them out of business should be repealed.

Under the current circumstances, however, simply re-opening the market to private cash-fare jitneys may not be an ideal solution. It is hard to compete on a price basis when public buses charge extra-low fares and are being run at a dead loss. It is hard to attract customers when their pre-paid unlimited-use public bus passes are not valid on your jitney, or when their stored-value farecard is not valid on your jitney.

Reasonable people can differ as to the best solution to these problems. Having public transit companies own and operate jitney-class vehicles in addition to their full size buses is one. Making pre-paid farecard readers available to private jitney operators is another, as is cutting them a share of all unlimited-ride passes sold, in proportion to their contribution to ridership or capacity. Privatizing municipal mass transit systems is another option, or simply having public operations charge fares that are at least remotely related to operating costs (I'll grant them the right to use public money for capital improvements for argument's sake).

tom deplume

As a 24 year transit system veteran I can tell you that it certainly wasn't union opposition the prevents jitney service. It is simply that no one could make a living doing it unless an area has very high parking costs. The abundance of free parking outside of city centers means that driving your own car to and from work doesn't cost much even a $3/gal for gas.
There is also a commercial driver's lisence law in the US that requires random drug tests physicals every 2 years. If someone didn't have a CDL and a serious accident happened the insurance company is off the hook.

allen zheng

Getting back to engines, what is the issue with the Bourke engine?

John Baldwin

CNG will win if there is a proper well to wheels analysis...makes no sense to burn a bit more gas to make electricity to then make hydrogen!! Completely barking mad, huge extra amount of natural gas used....most new buses ordered in France, Germany, Italy, Spain are now powered by CNG.....its obviously the cleanest fuel and has an advantage of running quiet which makes customers love CNG buses.

Dave Zeller

I would like to know what the gas consumption is for these HCNG City Engines. Does anyone know what it is? Also, what are the fuel costs per mile? I will do some research on this question myself. Considering that these are spark ignition engines, I am not especially optimistic.

I have another question. Where is this natural gas going to come from? North American gas production has sadly peaked out already, and Canada is having problems trying to keep up the slack:

With the advent of this technology we may not need to worry about emissions, as without a reliable supply of cheap fuel, these buses may wind up spending a lot of time sitting idle!

Mel Finstein

Question: Does City Engines (or equivalent) use HCNG or (and I don't quite know how to phrase this) HCOCNG? In other words, is the H2 produced through step 1 of SMR:
1.CH4 + H2O --> 3H2 + CO, and burned in the engine,

or is the water shift used:

2. CO + H2O --> H2 + CO2

and the CO2 removed prior to burning?

If the question is naive - chalk it up to the questioner being a simple-minded microbiologist.

Thanks much,


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