Got a Strange Question CNG engines?

[Hartley]

Only a Bus Guy would ask these questions...

I am surmising here because I haven't gone down that road of checking into this.

On buses that have the CNG engines. Does anyone know first hand what configuration the engine is in to run CNG ?

Do they take a diesel bottom end and change to a spark-plug style head and fuel system or are the engines a modified Gasoline style engine?

There is some rational to this question, It seems I heard that they use the same heavy duty Allison and other transmissions with these due to the weight of these buses.??

Are they operating in the same RPM range as the diesel counterparts or is that different?

I see occasionally CNG buses appear at auctions and they all go really cheap, But since you can't just fill your tank just anywhere is there a possibility to do a little extra fuel conversions without breaking the bank.

Dave.. Always Thinking....

[makemineatwostroke]

Dave, I can answer your question about the series 50 DD all you can use to convert that engine back to a diesel is the block and crank even the front cover has to be changed most of the CNG equipment on it was John Deere design including the head and cam that they manufactured and they run on about the same RPM with no power.The John Deere 9L used in buses are just as expensive to change back as the 50 series.Maybe someone will give some info on the Cat and Cummins engines, but to me it would not be worth the money to try and convert one back to another type of fuel but you could always change to propane for a few thousand dollars       have a good day

[TomC]

Cummins is making the ISL gas plus that is a 8.9 liter.  Again about the only same thing as the Diesel is the block and crank.  Everything else is different.  Because of the lower btu's in natural gas, it has a upper rating of 330hp and 1000lb/ft of torque, compared to the motorhome Diesel version of the ISL that puts out 425hp and 1200lb/ft torque.
Personally do not like natural gas. It emits Flourine, alot of carbon monoxide, and other chemicals that are not even regulated.  If you use compressed natural gas, the tanks cost around $50,000 (3500lb/sq in).  If you run liquified natural gas, you have to be equipped to handle the severe cold (like -150) and protect against it when filling the tank.  I think all this natural gas stuff will be a moot point in 2010 when Diesels are extremely clean.  But-we do have alot of natural gas in the ground and the Earth is constantly creating more-unlike petroleum that once used up it is gone.  Good Luck, TomC

[Charles Seaton]

TomC,

You are absolutely correct.  The timeline was written for CNG a few years ago when municpal busfleets started turning to diesel hybrids in large numbers.  CNG engines do not have the longevity of diesels, converting infrastucture to support it is expensive and if it is not handled properly it is extremely dangerous. The fact that CNG burns without a vsible flame has also been an issue of concern.


-- Seaton

[belfert]

The local fairgrounds here converted some trams to CNG.  They were gas engines originally.  Fuel mileage sucked and all the CNG tanks made the vehicles really heavy.  They traveled at low speeds, but they only got at most 100 miles to a tank.  They had to be filled halfway through the day and again at night.  Power was way down on CNG.  The only reason the conversion was done was because the local gas utility paid for it and promoted it with signs on the vehicles.

I do remember looking at some buses being sold by a transit agency that originally had been Cummins 8.3 CNG powered.  The engines had worn out in less than 80,000 miles and the replacement engine was a diesel Cummins 8.3.  They gave up on CNG due to the engine wear.

[TomC]

Converting a gasoline engine with around 8.5 to one compression ratio to natural gas doesn't take full advantage of natural gas.  On the Diesel conversions, (if I remember right) the compression ratio is around 12 to one and they also use turbocharging with air to air intercooling with lean burn technology.  Granted it isn't a Diesel, and just a couple of days ago heard a bus go buy running on 5 cylinders (anytime you have a dead spark plug it creates a tremendous amount of additional air pollutants-far outreaching what a normal Diesel would do).  What has been used is dual fuel-the engine runs on 100% Diesel at idle and then it is accelerated on natural gas (using Diesel as a spark plug).  But the EPA and CARB (California Air Resource Board) is afraid of people running the engine out of natural gas and running it on straight Diesel.  Once again- nimmnals that are ignorant in government agencies trying to tell us what works.  Good Luck, TomC

[buswarrior]

Up here in Toronto, the Orion V CNG had Cummins L10 blocks, originally coupled to ZF tranny, converted to Allison B400 because of durability issues.

They burned up exhaust valves like mad, swallowing the valve and beating the crap out of the piston/cylinder.

Hot rodder problem, lean burn for fuel efficiency, massive heat. Cummins tried a lot of things...I'm told they even put their marine racing guys on the case...

All sold off, giant compressors sold off, good riddance.

A natural gas bus would be a good parts bus for the stuff other than the engine. 24 volt goodies, lighting, one or two vanner battery equalizers, transmission, alternator, tilt wheel, driver's seat, etc???

happy coaching!
buswarrior

[Hartley]

Up here in Toronto, the Orion V CNG had Cummins L10 blocks, originally coupled to ZF tranny, converted to Allison B400 because of durability issues.

They burned up exhaust valves like mad, swallowing the valve and beating the crap out of the piston/cylinder.

Hot rodder problem, lean burn for fuel efficiency, massive heat. Cummins tried a lot of things...I'm told they even put their marine racing guys on the case...

All sold off, giant compressors sold off, good riddance.

A natural gas bus would be a good parts bus for the stuff other than the engine. 24 volt goodies, lighting, one or two vanner battery equalizers, transmission, alternator, tilt wheel, driver's seat, etc???

happy coaching!
buswarrior

Now you have an indication of where I am going with this.. The Old Spare parts thing..

Next is to find some really cheap spare parts buses...

Dave....

[TomCat]

Dave,

If in your searching you manage to find an Eaton 22123 rear axle in 4:11 ratio, with a 12v Telma focal mount retarder installed, that is attached to some other stuff you need, I'll kick in with you.

Jay
87 SaftLiner