O/T LPG/CNG powered vehicles

[radkins]

I see that GM is about to produce duel-fuel pickup trucks that will run on either CNG or gasoline at the push of a button and this has me thinking about something I have wondered about for a while. It would seem, to me anyway, that an internal combustion engine can not be designed simply to run efficiently on both types of fuel and that such engines would from a practical standpoint have to be compromised in efficiency for either or both types of fuel. I may be wrong but wouldn't an engine designed to run specifically on Natural gas or Propane need different internal engine specs to operate at maximum efficiency? What I am thinking is that compression ratios, cam timing/lobe design and ignition timing might need to be quite a bit different for maximum efficiency when switching between these two fuels. While changing the ignition timing and curve would be very simple things like compression ratio and cam specs would not so that the compromise becomes necessary. The current thinking is that CNG costs are about $2 equivalent to a gallon of gasoline which at today's prices would be around half the price of driving on gasoline but could a CNG or LPG specific engine get even better economy? Just thinking here and I may be off the mark with my understanding but I would like some other opinions on this.

[Thruthefence]

Real time ignition & limited cam timing are pretty much commonplace these days, commanded by ecu mapping.

[radkins]

Well I already pointed out that ignition timing is easily changed and so could cam timing but that does nothing for the compression ratio (although it could affect cylinder pressure) or even cam lobe profiles both of which I would think could have a lot of effect on efficiency between CNG vs gasoline.

[Dr Stan]

I converted my 1972 Ford F series to dual fuel (propane & gasoline) about 30 years ago. This of course had a carburetor, so it required a throttle body that sat on top of the carb. Ran quite well and was much cheaper than gasoline. Many of the utility company trucks & vans in Florida ran on propane at the time, so filling up was easy. The fuel cost was lower and the life span of the drive train was considerably longer.

I also remember from my under physics class that a gasoline internal combustion engine converted to hydrogen would produce about 80% of the power when compared to gasoline.

[aboard_epsilon]

LPG is over 100 octane ..so you can move the ignition timing ..it also has something like 20 percent less calorific content.

Another problem with it ..is that it is an insulator ..so needs good ignition to make the spark jump the gap....HT leads ..and other ignition componants give up the ghost a long time before they would on petrol.

it is also very dry ..so there is less lube for the upper cylinder components.

Some cars have to use something called flash-lube..basically a bottle of special lubricant is attatched to a tube that leads into the manifold

Modern LPG systems are designed to compensate for the loss of calories by shoving more of the stuff in .....this also keeps the o2 sensor happy and the cat happy.

My last car..before the present one ...i had it set up with adjustable ignition timing..on the fly .......it had open loop...no cat ..no o2 probe ...you could mess a lot more with it ...........it was slower in top speed and had less acceleration ..but it did the same MPG on LPG as petrol...sometimes more.

My present car ..has sequential injection .......it has to keep the o2 sensor happy and the cat .........it performs as on petrol .......but it does 25 percent less to the gallon ..

I miss the first car .....mpg meant more to me than performance.

oh yeah ..the oil stays clear for a long long time.

I believe cng is at very high pressure ...........so no DIY job

all the best..markj

[Willy]

You are right, a bi-fuel gasoline/cng-lng engine is going to be inherently a compromise design due to the vastly different combustion characteristics of the two fuels. Propane/gasoline conversions equally so.

The compression ratio required to take advantage of the 130 octane rating of natural gas is not available on engines that can operate on gasoline. So we end up with an engine that while cleaner emission wise while operating on NG, is still compromised in regards to power output due to the lack of technology required for variable compression.

Engine management of timing, fuel injection, and even valve opening and closing events have already been addressed. Engine component selection can also be optimized for NG operation, but the key hurdle for NG fuel optimization is a reliable means of varying the compression ratio to take advantage of NG's 130 octane rating.

Diesel/cng-lng engines can be more optimally designed to take advantage of NG's high octane rating due to those engines already having a high enough compression ratio.

At this time Cummins/Westport is marketing a very successful cng/lng series of engines to the medium and heavy duty engine market that is serving markets that either require a very low emission profile, or markets that want take advantage of lower fuel costs.

Large truck fleets are currently switching to NG engines in order to save on fuel costs. Federal, provincial, and state financial incentives are in place to help fleets during the conversion process, not only for the vehicles themselves, but also the infrastructure required to fuel these vehicles due to the 'green' connotation associated with NG as a vehicle fuel.

But don't forget the motto..."if it sounds too good to be true, it probably is".
As even now in NG's early stage of acceptance as a motor fuel, the same various federal, provincial, and state bodies that are giving financial incentives are already in the disscussion stage of legislating taxes on natural gas when used in a motor vehicle.:rolleyes:

[davidwdyer]

I run my little station wagon here on Natural Gas about 90 percent of the time. The fuel savings is tremendous! Plus, they say that it is about 80% less polluting.

I do have to deal with a slight power drop, but I'm not in any races.

The only ongoing problem is that the fuel injectors tend to carbon up with disuse. I've been running it for about 6 years now.

[Black_Moons]

One intresting thing to note, is you can effectively change compression by mucking with the valve timing. All you need to do is leave the intake open after bottom center, Or close it before the cylinder is at bottom center. Less intake volume = Less peak pressure = Less effective compression ratio.

Also, Its rather easy to alter the valve timing if you only have 2 'sets' of timing you wish to use, You just have 2 sets of cams on your camshaft and move the whole camshaft in/out an inch to switch between them.

[aboard_epsilon]

One intresting thing to note, is you can effectively change compression by mucking with the valve timing. All you need to do is leave the intake open after bottom center, Or close it before the cylinder is at bottom center. Less intake volume = Less peak pressure = Less effective compression ratio.

Also, Its rather easy to alter the valve timing if you only have 2 'sets' of timing you wish to use, You just have 2 sets of cams on your camshaft and move the whole camshaft in/out an inch to switch between them.

which isnt any good if you want to run on petrol

sometimes i run out because there isnt an lpg station near by.
or the stuff at that nearest station is too expensive ...ive seen a 25 percent difference in prices between stations ....petrol is always less than 10 percent.

it's half price in the uk for lpg overall........if a satation is selling it at 25 percent more ...then you add your 25 percent to the 25 {worst case} percent loss in economy ..and there isnt anything to be gained from running on lpg

all the best.markj

[justanengineer]

The compression ratio required to take advantage of the 130 octane rating of natural gas is not available on engines that can operate on gasoline. So we end up with an engine that while cleaner emission wise while operating on NG, is still compromised in regards to power output due to the lack of technology required for variable compression.

Diesel/cng-lng engines can be more optimally designed to take advantage of NG's high octane rating due to those engines already having a high enough compression ratio.

At this time Cummins/Westport is marketing a very successful cng/lng series of engines to the medium and heavy duty engine market that is serving markets that either require a very low emission profile, or markets that want take advantage of lower fuel costs.

But don't forget the motto..."if it sounds too good to be true, it probably is".
As even now in NG's early stage of acceptance as a motor fuel, the same various federal, provincial, and state bodies that are giving financial incentives are already in the disscussion stage of legislating taxes on natural gas when used in a motor vehicle.:rolleyes:

To correct a few points, no offense intended in the least...

NG engines that are running on 100% gas are low compression, usually 8-12:1 as they are spark ignited, not compression ignition. The reason many of the heavy duty manufacturers build them based upon diesel platforms is that traditionally gas engines have gone into stationary platforms for electric power generation or petroleum pumping. In both applications these engines may run 24/7/365 for years on end (some of ours go 40k+ hrs), and thus it makes sense to build them as heavy/overbuilt as possible. These are not high compression however.

The Cummins/Westport high pressure direct injection (hpdi) 8.9L "ISX" engine is IMHO a POS novelty. Others have done similar systems better. The nation's largest fleet of them is based ~30 miles north of here, and being that I work in engine development I have made it my business to become rather "close" with quite a few of the mechanics, drivers, and owners. Very few of the individuals I have spoken with, to include some of my contacts inside of Westport, will give it a good review. Personally, I think their "technology" is anything but, but that is personal opinion.

NG already has a road tax applied to it, just not in all areas.

Personally I wouldnt see a gasoline/NG hybrid whether its a dual-fuel setup or straight either/or fueling setup as much of a problem. Considering the possible technologies such as fuel/timing/ignition/detonation/etc mapping available along with variable cam timing, the possibilities for some engines are basically unlimited. Even the aforementioned compression ratio is often adjusted "on the fly" in modern vehicles (you just dont know it). There are going to be compromises, but the engineering ones will be small. I cannot comment on the compromises made by the "business" folks however.

[Black_Moons]

which isnt any good if you want to run on petrol


... Uh, Why not? you have one set of cam timing deticated to petrol and another deticated to NG.

Some engines actualy already do have 'shorter intake*' strokes then exhaust, by using valve timing, because its more efficent as you don't need a full intake stroke worth of fuel/air to produce a full stroke of hot, expanded exhaust.

*Effectively shorter because of valve timing. Slightly reduces pumping losses.

[aboard_epsilon]

... Uh, Why not? you have one set of cam timing dedicated to petrol and another dedicated to NG.

Some engines actual already do have 'shorter intake*' strokes then exhaust, by using valve timing, because its more efficient as you don't need a full intake stroke worth of fuel/air to produce a full stroke of hot, expanded exhaust.

*Effectively shorter because of valve timing. Slightly reduces pumping losses.

sorry never read the second line of your post

sounds expensive ..like in the thousands 4 figures expensive ...the payback time will lengthen a lot

standard LPG conversion here takes some 25,000 miles to pay for its self, if not done by yourself.

the LPG used to be 1/3rd of the price of petrol ..now its more than half.

and government pulled out of subsidising conversions over 5 years ago.

over 60 percent of the price of petrol here is now tax

all the best...markj

[Willy]

To correct a few points, no offense intended in the least...

NG engines that are running on 100% gas are low compression, usually 8-12:1 as they are spark ignited, not compression ignition. The reason many of the heavy duty manufacturers build them based upon diesel platforms is that traditionally gas engines have gone into stationary platforms for electric power generation or petroleum pumping. In both applications these engines may run 24/7/365 for years on end (some of ours go 40k+ hrs), and thus it makes sense to build them as heavy/overbuilt as possible. These are not high compression however.

The Cummins/Westport high pressure direct injection (hpdi) 8.9L "ISX" engine is IMHO a POS novelty. Others have done similar systems better. The nation's largest fleet of them is based ~30 miles north of here, and being that I work in engine development I have made it my business to become rather "close" with quite a few of the mechanics, drivers, and owners. Very few of the individuals I have spoken with, to include some of my contacts inside of Westport, will give it a good review. Personally, I think their "technology" is anything but, but that is personal opinion.

NG already has a road tax applied to it, just not in all areas.

Personally I wouldnt see a gasoline/NG hybrid whether its a dual-fuel setup or straight either/or fueling setup as much of a problem. Considering the possible technologies such as fuel/timing/ignition/detonation/etc mapping available along with variable cam timing, the possibilities for some engines are basically unlimited. Even the aforementioned compression ratio is often adjusted "on the fly" in modern vehicles (you just dont know it). There are going to be compromises, but the engineering ones will be small. I cannot comment on the compromises made by the "business" folks however.

As an engineer for the competition I can certainly appreciate you being in the loop so to speak more than I, and understandably perhaps also a little biased toward the significant inroads that Cummins/Westport has made into the heavy duty engine market.

I also realize that the company you work for, although very active in the heavy duty engine market, and also a dominant force there, does no longer directly produce engines for the on-highway market so it is understandable that Cummins Westport is the dominant player in that segment with Kenworth/Peterbuilt both offering the Cummins Westport gaseous fueled engines.

I also should have qualified some of my statements by stating that for the most part I was referring to the 15L HD 400/450/475 series (http://www.westport-hd.com/products/specifications)of compression ignition engines. These of course rely on a 5% diesel pilot injection, 95% NG. Using high pressure LNG in this application allows a significant range vs. CNG. Some very large fleets are currently in the process of utilizing this powerplant for 'B' train applications in Canada and probably the US market as well.

But more to the point these engines are not bi-fuel engines. I personally do not under estimate the ability of the industry to overcome the technological hurdle of variable compression if that is the direction it wants to direct it's focus on. All one has to do is look back just two decades to see how far we've come in terms of meterials, lubricants, machining precision, and engine management.

The spark ignited B/C/G series of engines are I agree, lower compression versions of their diesel fueled brothers.

The price advantage for NG will in my opinion be lost when government officials realize that there is a large enough presence of NG fueled vehicles to institute tax increases. Never under estimate the length of the governments arms when it sees a potential source of revenue.

It will be a cold day in hell when you see a politician with his hands in his own pockets instead of yours.:D

[justanengineer]

Thanks for remaining a gentleman Willy. I didnt intend that to be insulting in the least, and on second glance my earlier comment was rather harsh.

I understood the engine you meant, I simply mistook the displacement between what is known here as the "ISL-G" and the "ISX." Ive actually attended a few Paccar/Westport training sessions on the west coast on both, but simply believe that the dual injector "technology" is more of the "next step" in a natural progression and not really a "leap." I give Westport credit for producing them, but believe that a true "dual fuel" that reverts back to full diesel mode has more practical advantages, and as I said earlier the local fleet doesnt seem to like them. Granted, Im wearing the wrong color, so maybe they are simply "playing up" to me. Personally, I like the other Westport gas engines, and honestly think they saved Cummins' NG engine line, but that other one simply doesnt appeal to me.

You are definitely correct about the politicians' hands. This time of year especially, I get rather disappointed as I dont even get a reach around.

Slightly OT, but had to post after seeing this on PM.

http://www.youtube.com/watch?v=7qGI6Ogiasg&feature=related

[h12721]

Run a Truck like that in 1948.
Wood Gas or Propane.
If you don't know what wood gas is, you have 5-6 bags of wood cubes in the back witch gets burned up in some big round 6ft tall 2 ft OD kettle, (burner).
H12721

[Willy]

Thanks for remaining a gentleman Willy. I didnt intend that to be insulting in the least, and on second glance my earlier comment was rather harsh.
..............
.........

Hey most of that stuff usually goes over my head, but I certainly did not take your remarks to be the least bit insulting.
Besides you've already covered your ass with the disclaimer in your sig. line.:D

I as well did not mean to imply that Cummins Westport was the be-all and end-all in the heavy duty engine market insofar as gaseous fueled engines is concerned. I only chose them based on their public presence due to there on-highway applications.

The technological prowess displayed by your 'color' has certainly impressed me over the years. I have personally experienced countless hours of admirable service from both camps during my career and am not at all discounting the engineering capabilities of either one. Or any other major players for that matter that choose to direct their engineering talent in this direction.

[Optics Curmudgeon]

My last work truck (before the one I have now) was a 2008 Silverado that was CNG/gasoline. We didn't have a CNG station at the time (you might ask why we got the truck with dual fuel, we use GSA motor pool vehicles and don't get a choice) so the load of CNG it came with was all it ever got. The truck changed from CNG to gasoline while I was driving it and I didn't even notice. My only gripe was that the CNG tank was in the bed, and took up 30% of it.

[RWO]

I read somewhere that NG and propane converted diesels have to have about 10% diesel fuel injected into the cylinders in the conventional manner as an ignition source. This is needed because the fuels' auto ignition temp is higher than than that reached by the air in the cylinder head at full compression in a conventional diesel.

RWO

[rancherbill]

There were a number of propane powered vehicles around here - they were very popular on 1/2 tons to 3 tons carbureted engines. Propane conversions werre not done when all those models started fuel injection.

Everybody I talked to love the propane and especially loved the lower price. The only 'negative' is they are hard to start in the cold (-30c , -22f). Everybody started with gasoline, warned the engine, then flipped over to propane.

[justanengineer]

Willy - If youre ever in the midwest, the first beverage is on me.


I read somewhere that NG and propane converted diesels have to have about 10% diesel fuel injected into the cylinders in the conventional manner as an ignition source. This is needed because the fuels' auto ignition temp is higher than than that reached by the air in the cylinder head at full compression in a conventional diesel.

RWO

It depends on the hardware used in your "conversion." If your conversion is purely adding a gas "train" (regulators, shutoffs, mixers etc), then yes you would need a diesel pilot for ignition. If youre willing to/can swap pistons to lower the compression ratio, and can bore the heads for spark plugs in addition to the aforementioned gas train, then you can run 100% gas. The latter is the method of choice for the majority of the heavy duty "factory" conversions/builds by the various companies.

[davidwdyer]

I would like to see the US Government invest in expanding the Natural Gas infrastructure to have it available in gas stations everywhere.

Then, everyone could save on fuel. We would use our own energy instead of importing it. It would reduce pollution. It seems like an interesting way for the gov. to spend money on something which might really work.

Or, they could invest it some really new and exciting "green" companies for the benefit of the, the,...the...who?

[radkins]

This has been interesting and I have learned a few things about these conversions but to refine the original question, would there be any major gains in performance and economy by building an engine optimized to run on only on CNG/LPG vs an engine that is compromised in design in order to operate on these fuels or gasoline?

[danlb]

I would like to see the US Government invest in expanding the Natural Gas infrastructure to have it available in gas stations everywhere.

Then, everyone could save on fuel.

I'm not sure we would be saving on fuel. Cars still use fossil fuel, just a different one. CNG is cheaper now because there is a surplus. Once you add a few million or CNG cars or trucks to the demand it will go up in price too.

My dad had a dual mode gas/propane (butane???) Chevy Impala in the 60's. The tank took up most of the huge trunk. I recall that it ran well enough and had no problem with his daily 60 mile commute. I recall that there was no propane gage on the dash. When the tank ran dry it would run rough and he'd switch it over to gas again.

My mom hated it. The wasted trunk and the scary and smelly refills turned her off. The uncertainty of the propane level unnerved her.

Dan

[Black_Moons]

My mom hated it. The wasted trunk and the scary and smelly refills turned her off. The uncertainty of the propane level unnerved her.
Dan

Heh, My dad had a propane van at one point.. It had 6 leds for a fuel gage.. The first 3 would go out within 15 minutes of filling, And the next would take 15 minutes or so. 2nd to last I think was good for half an hour...
the last one would run for a good hour after that before going out. No idea how much range you would have after the last one went out.. He never ran it dry.

[davidwdyer]

I'm not sure we would be saving on fuel. Cars still use fossil fuel, just a different one. CNG is cheaper now because there is a surplus. Once you add a few million or CNG cars or trucks to the demand it will go up in price too.

My dad had a dual mode gas/propane (butane???) Chevy Impala in the 60's. The tank took up most of the huge trunk. I recall that it ran well enough and had no problem with his daily 60 mile commute. I recall that there was no propane gage on the dash. When the tank ran dry it would run rough and he'd switch it over to gas again.

My mom hated it. The wasted trunk and the scary and smelly refills turned her off. The uncertainty of the propane level unnerved her.

Dan

I'm certainly not an expert, but I have heard that not only is there a surplus, there's a HUGE surplus.

The price is very low because of this. What I heard was that there is enough Natural Gas in the US to supply all the energy needs of the country, including converting coal fired plants to gas and powering all cars for 100 years. While this may not be completely true (I have not studied the exact statistics) there certainly is a lot at a cheap price.

One of the financial burdens which may "blue collar" Americans are bearing is the cost of fuel today. It takes a big bite of of many wallets. If the gov. wishes to do something to change this situation in a real way and stimulate the economy, this is one.

However, there seems to be a policy to try to eliminate fossil fuels by letting people feel the pinch so badly that they try something else, even though this "something else" is not yet very workable.

[danlb]

I'm certainly not an expert, but I have heard that not only is there a surplus, there's a HUGE surplus.

The price is very low because of this. What I heard was that there is enough Natural Gas in the US to supply all the energy needs of the country, including converting coal fired plants to gas and powering all cars for 100 years. While this may not be completely true (I have not studied the exact statistics) there certainly is a lot at a cheap price.



I've heard similar claims, but find them hard to believe. Most of the areas I live in already have natural gas piped to every single house and business. My heater, clothes dryer and water heater all run on it. It costs me $100 a month for that 'cheap, surplus fuel'.

The energy crisis of 2000? It was caused by the energy traders (Enron being one) reserving natural gas pipeline capacity that they were not really using. That effectively blocked the sale of NG from competitors. There was plenty of NG available, it just could not be transported to the Electric generators that needed it.

If it were really economical to build a NG infrastructure for cars, the companies that own the NG supplies would be funding it. Instead, they are pushing for the government to create the demand for them.


Dan

[Chester]

Around here, CNG is not practical. The short range tanks, the weight of them and the cost of the installation and the cost of the CNG all say no to that idea.

Had two Caravans that I bought, already converted, otherwise I would have kept on walking. Would take forever to recoup your investment. Most of the re-fuelling stations (Shell) are long gone and about the only user left is the gas company themselves.

Propane started with a big bang here in the early eighties then trickled off to nearly nothing lately. Most of those re-fuelling stations are long gone also.

There were big users like Canada Post, Fed Ex, UPS...........about the only ones left are taxi's and a few odd balls like me. My old Dodges do just fine on propane and I got my investment back in under two years.

Locally it is priced about half that of gas. But that advantage disappears once away from the metro area. On trips to E. Canada and So. U.S. propane costs more than gas in many places. Dual fuel capability is a must!

Chrysler made propane fuelled cars around '86/87 ........Diplomats and Caravelles. Stopped after that.

Have a look here if you want more discussion..

http://fuelsforum.rasoenterprises.com/

[davidwdyer]

I really know very little about politics or baseball, but I am thankful that the Brazilian government made it available every time I go down the gas station and fill up my little car with NG.

On an average week I spend $20 US on driving around the city. On gasoline here I would spend at least $50 for the same amount of driving. At about $30 per week, that comes to about $1,560 per year.

The cost of a conversion kit is with installation is about $2,000. As usual, the US gov. has a lot of regulations etc. which probably inhibit people converting. Also, the prices I have heard for kits there is absurd.

[Charles P]

I had a bifuel Volvo V70 that ran on petrol/CNG. Fine car, indistinguisable from the petrol one except each tank had a range of 180 miles (PITA). The real killer was a lack of CNG stations to fill up in. However I saved a fortune on the London Congestion Charge of £8 per day

Charles

[knedvecki]

As for the LPG conversion, a Vacuum fuel lock-off is about $60, an Impco Cobra regulater about $120, and a Mixer in the $200-300 range plus a tank for the conversion. I work on forklifts which have hour-meters instead of odometers. A common engine used in this application is the GM 4.3L Vortec V-6. I figure that if you drive a car for 100 hours at 30 m.p.h., then you have gone 3000 miles. I have a lot of forklifts with well over 20,000 hours of run time on the motors, which would equate to 600,000 miles not accounting for idling time, without ever being taken apart for repairs. Seems pretty Good to me. Just my 2 cents.

[justanengineer]

I've heard similar claims, but find them hard to believe. Most of the areas I live in already have natural gas piped to every single house and business. My heater, clothes dryer and water heater all run on it. It costs me $100 a month for that 'cheap, surplus fuel'.

If it were really economical to build a NG infrastructure for cars, the companies that own the NG supplies would be funding it. Instead, they are pushing for the government to create the demand for them.


Not to start an argument Dan, but for comparison my home (with heat sucking NG fireplace) has NG hot water, heat, and dryer. <2 hours to Chicago, and my bill reaches $100 maybe one month of the year despite keeping the house at 80F and regular use of the gas fireplace (her). The average bill in winter is ~$70, in summer its $30.

As to the second part...which came first, the chicken or the egg?

The necessary infrastructure is fueling stations. Fueling stations are typically franchises in most of this country, or otherwise privately owned. If a company owns a pipeline, why would they want to be involved in owning a fueling station? They dont know/understand/profit from that business directly. Yes its a byproduct, but not within the business model and involves a huge amount of risk and outside knowledge. The government provides incentives for private individuals/companies to open these stations bc without a CNG/LNG vehicle population to feed off of (as is the case in much of rural US), risking/spending millions of dollars on a station doesnt make sense. If you build it, they may come. But without the "it," no one will.

Is it right for the government to spend everyone's money on these projects? Thats another subject, and I am torn on it. I was just explaining the logic behind it.

[rancherbill]

I would like to see the US Government invest in expanding the Natural Gas infrastructure to have it available in gas stations everywhere.

That is not the job of government.

Natural Gas is CHEAPER than gasoline. We proved here and had many happy users. It was fuel injection that stopped it's popularity. Now that manufacturers are making dual fuel vehicles, the market will demand filling stations.

I am thinking I might buy a 'new' truck for the first time in 30 years. It is that much of a motivator!

[danlb]

Not to start an argument Dan, but for comparison my home (with heat sucking NG fireplace) has NG hot water, heat, and dryer. <2 hours to Chicago, and my bill reaches $100 maybe one month of the year despite keeping the house at 80F and regular use of the gas fireplace (her). The average bill in winter is ~$70, in summer its $30.


No argument here. :) The point is exactly illustrated by the price differential. It's supply and demand.

Right now there is more supply than needed. At some point the prices will rise quickly as enough demand is created one way or another.

I wonder why I have a hard time finding residential NG compressors that will fill your car's tank from the same pipe that services your furnace. The few that I found run on electricity, not on NG.

I would think that the compressor would use a NG fired engine to compress the gas instead of using electricity.

Dan

[Black_Moons]

I would think that the compressor would use a NG fired engine to compress the gas instead of using electricity.

Dan

If you are REALLY smart, You get a cogeneration motor and heat your house while you refill your car! Now you might actualy get some savings... :)

[fixerdave]

I have one of those someday-projects to convert a van (RV) to propane. The research I did a few years back (more than I care to think about actually), said that the optimal compression ratio for propane was 14:1. I was thinking of building up a 12:1 Chevy V8 - figured that's would be a sweet spot for parts availability as it seems to be a target for the racing crowd. Any more would get stupid-expensive.

Recently, I've read the big thing is to supplement diesel engines with propane. All the usual claims about huge performance/mileage benefits, lower maintenance, etc.. Some of it is likely true as there's at least a wee bit of logic to it. The propane is suppose to keep the diesel burning longer, and thus more completely. Never did figure out the logic behind those magnets on the fuel line :rolleyes:

As for the price. It spiked, then they started fracking. That worked very, very well and the price crashed. At least the wholesale price. I don't expect any consumers noticed that part though. They're getting big-time into fracking oil now. Some say North America could be self-sufficient in oil fairly soon. That would be interesting if it every happened.

David...

[davidwdyer]

As for the LPG conversion, a Vacuum fuel lock-off is about $60, an Impco Cobra regulater about $120, and a Mixer in the $200-300 range plus a tank for the conversion. I work on forklifts which have hour-meters instead of odometers. A common engine used in this application is the GM 4.3L Vortec V-6. I figure that if you drive a car for 100 hours at 30 m.p.h., then you have gone 3000 miles. I have a lot of forklifts with well over 20,000 hours of run time on the motors, which would equate to 600,000 miles not accounting for idling time, without ever being taken apart for repairs. Seems pretty Good to me. Just my 2 cents.

Here the tanks have some kind of lead casing to protect them in case of a crash. Hence they are VERY heavy. You have to reinforce the rear springs of the car. They also must be fastened directly to the car frame. Every year a car which runs on NG must pass an inspection.

The result of all this is that, with the millions of cars running on NG, I have never heard of an accident in which the tank exploded or the gas figured significantly in the damage. That's really saying something, since I have never seen such spectacular accidents as here in Brazil.

[AD5MB]

I see that GM is about to produce duel-fuel pickup trucks that will run on either CNG or gasoline at the push of a button and this has me thinking about something I have wondered about for a while. It would seem, to me anyway, that an internal combustion engine can not be designed simply to run efficiently on both types of fuel and that such engines would from a practical standpoint have to be compromised in efficiency for either or both types of fuel.

exactly right.

Propane is 105 octane, LNG 135. both burn 99% pure. if things were as they should be you should be able to build a 10.5 or 13.5:1 compression ratio engine with a shaggy camshaft.

if things were as they should be... but state legislators are involved. The pharmacist from Podunk who got elected to the state legislature insists that the smog controls and the 8:1 compression remain, because them engineers in Detroit must know what they're doing, eh? so you have to keep the heat riser under the manifold which helps vaporise liquid gasoline in a vehicle that runs off a gas vapor. completely counterproductive in a liquified gas powered vehicle.

the tanks must have hemispherical ends, and can have a round middle. so you can't whip up a big flat rectangle to fit into the available under vehicle space.

I knew a gent in the Mojave desert who had 200 gallon propane tanks under his bus. It cost him less to drive it to Tijuana and fill it up than it cost him to drive a block to the local propane seller. $.38 a gallon there VS $1.38 a block away, and you got a Mexican vacation ( back when you could survive one ) too.