Forum Opinion: CNG Conversion
 

My read of the energy tea leaves is that natural gas will continue to be a bargain for at least the next 5-7 years.

One can again get a PHILL home gas compressor for about $4,700. For me, installation won't be too bad. I have a 240V circuit and a gas line handy in my garage. With projected residential gas and electric rate over the next 5-7 years, I could pump CNG for about $1.00/gge (gallon gasoline equivalent) which is less than a third of the price of RUG here.

I drive a good deal more than the average Joe - about 30,000 miles a year. I split between my F350 and my 96 Impala SS. the truck is mostly my cold weather vehicle. The Impala is a lousy snow vehicle and not Ziebarted so its afraid of the Midwest snow and gets parked in the garage mid-December to mid-March.

I like the Impala but simply cannot hypermile the darned thing. About 20 MPG is about all I can do with it. A full-on aero project might gain me a couple MPG and a stick might get me some more. But it already has reasonable 3.08 gears and I really don't see more than 25 MPG without converting it to a diesel.

I'm gonna do something with it anyway. The mid-90s electronics are buggy although the LT1 engine is OK. The 4E60E tranny is too frail. A very doable swap is a L92 (iron LS3) engine and a 6L80E transmission. Common truck/SUV drivetrain. The iron LS engine weighs about the same as my LT1 so it won't throw the weight distribution out of limits. The L92 has displacement on demand and variable cam timing. Six speeds gotta help MPG some. So this should get me at least 2 MPG improvement by itself. By doing this swap and a few other things, I've modernized the car for a fraction of what a new car costs.

BTW, a small car is simply out of the question. Aerohead (Phil) can confirm: I earn my moniker and prefer a big car or truck for very real reasons.

But why stop at a simple engine swap. I can get the LS engine converted to CNG for about $9,000 installed. At the rate I drive, it pays for itself in three years, including the PHILL.

CNG is much cleaner burning so maintenance is greatly reduced.

At this stage I'm thinking a bi-fuel conversion. If CNG gets more commonly available (for trips) I'll go fully CNG.

By getting a 10% increase in MPG and cutting fuel price by two-thirds I'll be driving for a little over a quarter of the per-mile fuel costs I have today.

Equipment is old tech and commercially available and not overly outrageously expensive. Project looks doable.

Forum opinions?

Your best bet is if you have a local fill station that you can drive to, it fills quicker at a higher price but you never need to rebuild or buy or jump through hoops to get a pump in your house.

This is of coarse unless you can locate an adsorbed CNG tank that also tollerates high pressure fills. Only foreign companies make them but then you can buy an antique cheap 500psi rated industrial unit for home use and when you need to drive further go to the high pressure fill at a gas station.

Most smaller cars and trucks have a fairly lengthy repayment period (aka 140,000 miles +)

Cheers
Ryan

I know tech has advanced a lot since 1992, but if my old Tempo was any indication your transmission will last a LOT longer behind a CNG powered engine because there's a lot less power available. I got very nearly the same MPG/MPGGE on CNG vs. gasoline in the Tempo, but horsepower was down by probably a third or half. It was still driveable barely in Phoenix, but wouldn't make it up any hills in a town with elevation changes - that was a 4cyl car in good mechanical shape.

There are plenty of vehicles that even a very large person can utilize that get much better than either of your vehicles and can be had for under $9K. I'd sell the Impala and get a more fuel efficient sedan. An Accord with manual trans comes to mind. Hypermiling it should get you in the 40s I'd imagine. They're also pretty good in the snow.

Random thoughts:

• Considering your mileage, I'd expect you'd find repair costs significant also, I'm really curious how CNG compares vs Gas in per mile maintenance, and I think that should weigh on your decision. (I find for my ooold Corolla at 45 MPG that gas and repairs cost almost the same, each in the $0.1 per mile range, although I expect my repair costs to come down since I'm doing more things myself now, and I think that Honda's and Toyota's are mostly in the $0.05 per mile range for most of their life (prior to 200k)).
• (I'm just guessing, if you did a CNG conversion on the Impala that the Impala would end up with lower throttle loss and higher efficiency, corresponding to the reduced HP, so your overall savings with CNG may be noticeably higher than you'd predict just comparing cost per unit energy. If this is true, it would also open you up to more significant benefits available from aero mods.)
• Can't seem to find front-seat specs, but if you want to look at replacing the Impala in search of better gasoline MPG, I believe that Ford Escort's are noticeably more roomy than Honda Accord's or Toyota Camry's, but are comparable in other ways. That being said, my personal belief is that Ford's cost more to maintain per mile, particularly in comparison with the Honda.
• Also if you go in search of a different car, if you can put up with 2 doors, my impression is that coupe's usually have more aerodynamic rear windshield areas, so (short of a boattail), you can probably get more from hypermiling and modest aero mods in a coupe vs sedan or hatchback, especially if it's a manual.
• EDIT: Even if you find that you can tolerate a mid-size car, considering your mileage it may still be favorable to do a CNG conversion. (I'll leave you to do the math though. :))

I think its a winner. If your going to do the LS swap and run it on dedicated cng. kick the cr. ratio up at least one point. The motor octane rating of cng is something like 114

If you have read any of my postings, I do not favor CNG as a fuel for environmental and corporate welfare reasons. I don't think a cheaper cost per mile driving justifies the damage unregulated fracking is doing to our fresh water and air quality

CNG is widely used here in Brazil. Altough I'd be more favorable to a Diesel swap, if you would rather get a CNG conversion for the Impala I wouldn't try to discourage you.

"...the damage unregulated fracking is doing to our fresh water and air quality"

Big Dave says:
I thought we agreed to keep the discussion on the cars.



"...I'd be more favorable to a Diesel swap..."

Big Dave says:
Normally, I would be as well, but diesel is disproprotionately taxed, and EPA meddling has made suitable diesels a scarce commodity in the US.

No CNG stations anywhere near you ?
$ 4700 would buy a lot of gas.

That's what makes it viable.

That's steep.
A 4 in line conversion will run about 3000 - 3500 EUR locally.
(USD and EUR are worth about as much )
More cylinders means more injectors though, and you'll also need bigger tanks, but still ...

Power is often down by about 10% as well, unless it's restored by tuning the mixture, and power delivery is more gradual - hence CNG vehicles will feel more sluggish - so the tranny might cope better with the lower power ;)

Less power means you're further up the load curve, which should be OK for MPG with steady driving - but not in the conditions where you need lots of power.

The normal practice with conversions is that the regular fuel tank stays in place, so you always have an expensive back-up.

OEM car conversions usually sacrifice most of the regular fuel tank to mount the tanks - which also changes their official status to CNG car in the EU ;) - on a light truck you'll probably have plenty of space to put the tanks.

Even if an engine such as the Cummins 4BT is technically-viable to be swapped in, the bureaucracy ruins it.

Is that just the engine conversion, or does that include the tanks? You might be able to find a CNG/bi-fuel GM van to swap from for less.

My dad has looked into converting one of their vehicles to CNG over the last few years. Unfortunately, the EPA certified conversion kits are very expensive. There are many cheaper kits that are certified by international agencies, but they're technically illegal to use in a road vehicle in the US (offroad or racing are fine).

As long as those non-certified cheaper kits retain a good safety level, you could manage the legal issues submitting the vehicle to a smog referee after the conversion.

There are a couple of CNG stations in the Naptown area...about 25 miles from where I live.

I've been driving on biodiesel for 8 years on 3 separate vehicles, and I think I am fairly informed. You asked for opinions. I gave you mine.

So, are you still considering the CNG conversion?

Someone mentioned it up top...about using an existing fueling station if its available rather than using a PHIL home station. they are expensive and slow. I would wait for the technology to catch up or someone to engineer a newer/better system because I believe the demand and opportunity is out there. In regards to the CNG retrofit there assuming you do have the fuel supply available there are some great kits out there now. Especially the newer injection kits. i have retrofitted several vehicles both using the venturi systems and have recently done a couple injected systems that were slick. They took a little longer for the install time but overall where possible i will use the injected systems from now on. They were worth the price and the extra install time. So if you are in the market and the vehicle you are wanting to convert is accessible for the injection systems, spend the extra money and you will absolutely be grateful you did.
Best of luck on your endeavor.

For what its worth...they aren't fracking for the natural gas. They are fracking for the crude. Natural gas is simply present in the wells they dig and they typically vent it or burn it off because they don't think its valuable enough to capture and transport it.....Sorry for the rant.
Other than that CNG is nearly 88% times cleaner than gasoline that regular vehicles are burning and it costs a fraction of what gasoline costs. Unfortunately the USA hasn't caught the picture like the rest of the world including the middle east in developing an ifrastructure to use it for vehicles. It is nearly as efficient if your vehicle is tuned for it and for the price a little less performance won't hurt me.
As far as mileage and maintenance goes on CNG because it is a cleaner fuel it causes less carbon build up for cleaner cylinders which results in a longer lasting higher engine performance for again less emissions. If you have a good cng kit installed it will run well and not have any major maintenance required. I have run CNG on both of my vehicles for the last 4.5 years and only had to replace a simple stepper motor on one system. (it had been on the vehicle since it was brand new. Over 10 yrs old) Also because it is cleaner you can run longer between oil changes. Typically you would need to perform the 3k-4k miles oil change and now my oil is still a light maple color at that point so i extended it to 5.5k miles and it still looks good.
If you are new to the CNG market and you are looking for a good and reliable vehicle. Look for a newer cavalier. They give you the benefit of a bifuel so you aren't left stranded if there isn't CNG available. If you want to go for an aftermarket CNK kit there are dozens of reputable kits available. I've installed several and they run great along with the benefit of running on both CNG and regular gas if needed. I believe the only draw back it the space the tank requires. It consumes your truck in a car and about the size of a truck tool box in a truck. Its worth it to me. hope this helped and good luck.
CNG Conversion Kits Info

Yeah. I'm still considering the conversion.

Buying a Phill is very salty. It might be more practical to install 20 gge CNG tanks (and lose all my trunk) to make the 50 mile round trip for CNG practical. 20 gallons would get me through a week of commuting. Maybe a lot of tankage will hold me until somebody builds CNG filling station close by. I see that GE/Chesapeake Energy are no offering a package CNG compressor fill setup for public commercial use.

Going that far would get me moving on installing a six-speed (gaining 1-3 MPG). This may be my first move under any circumstance.

The performance loss is overcome with bigger CNG injectors. Lingenfelter (the hot rod engine builders) have messed with CNG LS7s. Lingenfelter would not put their name on a dog.

I have to talk to an installer. It may be the EPA restrictions have relaxed on my thirteen year-old-car.

If I had a source of grease, I would be using biodiesel. It is an outstanding idea. There is a guy about a hundred miles away that refines ASTM-quality B100 and will do business on a "sharecropper" basis. (I bring him 100 gal of cooking grease, he gives me 25 gal of high-quality B100) To operate my truck 24 weeks a year i need about 500 gallons of B100 so I'd need 2,000 gallons of grease. I just don't have that much of a source of restaurant grease.

Apologies for perpetuating this OT, but you must not be in Colorado - they are fracking FOR natural gas, there is a huge gas boom going on right now and TBoone is proud.

Have you tried setting up with the local restaurants for their grease? If you had 5+ restaurants you might be able to supple enough of the grease for your biodiesel.

I'm not in Colorado. Im in Utah and have a few friends in the oil fields right now for the oil. They are working for different companies one in ND and another in WY, TX. All three of them perform different duties but say after the well is drilled they either vent or burn off the natural gas then frack for the oil. I didn't know they were fracking for the nat gas.

CNG Conversion Kits Info

Hello,

this is quite the conundrum:)

I currently have a BMW 328 with LPG setup (basically the same kit as CNG) and a Diesel VW Golf that I run on a mix of veg/diesel (a poor man's bio, if you will)

For work my commute is circa 17000 miles p/a, and then I do 10-15k on top running about, so similar overall mileage to you- here's what I think:

LPG/CNG

1. My 328 gets circa 26 imp mpg using an old style single point set up- its not the best for economy, or power, but it gets the job done, and car is fast and smooth

2. In terms of servicing costs, mine needed a new vapourisor in Nov last year, was £75 (less than a new petrol pump for in the tank). Filters are peanuts (£5 ish max). The gas means less bore wash of the oil by petrol, which means the oil lasts longer, and comes out golden.

3. Range- with a 60L tank holding 50L (can only fill to 80%) I get circa 270-300 miles depending on what I'm doing. this makes the PEMPG (Petrol Equiv MPG) circa 45-50 imp mpg. On straight unleaded the best I've managed over a tank is 37mpg, so it does offer a saving. My car had the kit already fitted, but if I installed it today (£900) the payback is approx 12 months. Between the Petrol and LPG, I'm close on 800 miles range:)

4. Availability- Having moved house, I no longer have an LPG station near my home, but I still have 3 within 5 miles of work. If I need to fill up at home, I combine it with a trip to see my parents (earn some "good son" points!). I also have an App on my phone that has maps of all the LPG stations in the UK, and has prices updated by users daily.

5. Cost- Our Chancellor (head of the treasury) announced on Wednesday that the LPG taxation was being held at current levels for the next couple of years- so its approx 1/2 the cost of Petrol here


Diesel/Bio Diesel

1. No noticable difference in MPG between running pump diesel vs 30% veg oil. It has to be noted though, the car is nowhere near as engaging or entertaining to drive as the 328i- but runs ok on veg (unless its too cold, then its stuttery and wont hold an idle!)

2. I reckon I need a new fuel filter, due to the gunk cleaned out my lines (£12) and the glowplugs are having a hard shift in the cold mornings- but blending the fuel seems to help. Regular bio diesel wont have this problem as it wont be as thick as Veg

3. Being Diesel, range is not an issue 650 miles is not uncommon- veg/no veg appears to have no real impact on range. this is a big thing for me, means less than a tank a week- rather than 2 fills of LPG

4.Availability- Pump diesel available everywhere, Veg oil available from all supermarkets ( I use a couple of sites to compare prices- aiming for £1 a litre of veg). Regarding Bio- Diesel, I reckon discussions with local take aways etc could be fruitful- but I dont know how happy the girlfriend would be with me refining bio at the house

5. Still using pump diesel (£1.459/L) and paying £1/L for veg. Assuming I can get to using more veg- say 50% in summer, my costs per mile should go down.

I use the golf for commuting, my Mrs uses the 328 for her work (she gets 15 days commuting to a tank of LPG)

Both cars have their place, but at the moment, diesel wins for my purposes (low cost commuting on boring roads!)

In short- in your position, I'd be asking myself " do I need my truck as it is?"

If you need load hauling capacity- then probably yes,

but if you just need 4wd, then something like a Subaru with CNG would be a better bet.

or do you have any smaller 4wd pickups with diesel- like the Ford Ranger etc?

responses:

Somebody beat me to all the local restauranteurs. I'm not willing to bid up the price of inedible grease for biofuel feedstock.

No way I'm gonna have a unibody car. Low top sills (for torsional stiffness) defeat me. I'm a body-on-frame kinda guy. Hence the F350 and Imp.

My truck is not 4x4, which makes it unusual. I rely on good tires and good driving (just like the state police) to get around in the winter. I like it because it is roomy, solidly made, reliable, a diesel and a manual transmission. Phil Knox (aerohead) drove it and found the combination of gearing and engine torque to be satisfactory.

Do I ever think of getting a smaller vehicle to replace the F-350? Yeah. Every time I park it. It's like parking the USS Nimitz. I muse about a Ranger with a Benz OM 606. The trick is mating up the DIN engine with a SAE bellhousing and transmission. Can be done, but will take some custom machining. As with many denizens of this site, I find an automatic to be unacceptable.

Fair play- just thinking out loud:)

I'd love to be able to afford to run an e30 with a 3.5 in it for a daily, without LPG..however, I'd need to be making 3x my salary to do that

a good compromise leaves everyone thoroughly frustrated:rolleyes:

CNG fuel systems are more overbuilt than LPG ones, since their working pressures are also higher. I'm aware of some accidents due to the refuelling of LPG-converted vehicles with CNG...

LPG kits might be easier to get in America, most notably EPA-certified ones, than an EPA-certified CNG kit. It's also worth to note that some Chinese-made non-EPA-certified kits have a lower safety standard, so it wouldn't worth the risk to use them in America due to the CNG pressure back there. In China there are still some CNG refuelling stations which have pressures around 1800psi...

As long as you stick with the DOT approved cylinders (not chinese) and have legitimate high pressure tubing rated up 5000psi, the cng kits are safe. Also make sure you have a shutoff valve in a location between the tank and regulator in the event it is ever needed.

This is as far as I got with using CNG.
Any one using this type of CNG tank set up? - Diesel Place : Chevrolet and GMC Diesel Truck Forums

Operating costs are dirt cheap, start up costs are sky high.

CNG has lost some of its appeal among the general public in Brazil recently, but remains strong in Argentina
https://4.bp.blogspot.com/-yab7F2kR_...ro-direito.jpg
https://3.bp.blogspot.com/-d3byLffnW...2Btraseiro.jpg

I have been pomdering about lpg and cng for a long time now. My desire is not to use it as a primary fuel but to have it as a supplemental fuel for diesel.

I recently did a calculation with my local prices vs energy content.

Diesel 6.04 MJ/TL
LPG 7.06 MJ/TL
NG 122.3 MJ/TL
Where TL is Turkish liras.
Natural gas is way cheaper than the rest. But it is atmpspheric (at my home) and does not include compression costs.


A conversion is not really feasible (for me) unless it is diy.

With a small econobox which consumes 4-5 l/100 km and my daily commute of about 50km that would equate to about 2-2.5 liters of diesel per day.

Current diesel supplementation systems can go up to 70 percent cng and 30 percent diesel. (I have heard of 90-10 aswell).

Although i have all the equipment for scooba diving, for cng i would not want to mess with the high pressure gasses. Especially with cobbled up diy equipment. Examining my daily needs i would be consuming about 2-3 m^3 of NG worth of energy daily.

A fridge compressor that can go up to 20 bars and a scooba tank of 30L will give me 600 liters or 0.6 m^3 of NG. It could also be stored in an air mattress. Which are in the ballpark of diesel substitution territory.

Will the hassle be worth it to save a liter of diesel every day be worth the hassle is the point i am considering.

Every lng/cng conversion ends up being a system to deliver X volume GAS. The compression/storage issue is to provide a small system to deliver that gas. If you could develop a low pressure system to store all the fuel required that would fit in your available space, them imho you are ahead of the issue and it is worth converting.

People have been doing this since 1975, some successful, some not.

Indeed, that was my reasonning.

One should already be using as little as possible (for personal transport)

And small quantities are easier to transport.

Ideally methane from biodigestion at a later stage.

Hello teoman,

To get high volume of CNG at low pressure, look into Adsorbed Natural Gas. No, not "absorbed", specifically "adsorbed". Different phenomenon.

https://cenergysolutions.com/ has a fair bit on the tech.

Here's a commercial source of similar tech tanks, albeit not rated for road use (though they do state safe/rated to take around in a truck to get to a place to use them.) cylinders

It would be crazy to do some makeshift with scuba-diving equipment in order to repurpose it as a CNG tank. I'd rather try a wood gas generator instead...

What is crazy about it?

A tank is a tank, a leak is a leak and a half ass job is a half ass job in both cases.

The tanks have dot rating. And a burt pressure of 200 bars. It is the compressor side that i am worried about.

The system is an order of magnitude more complicated than a liquid fuel tank.

PS: i do not recommended it to anyone who does not understand what they are doing.

CNG tanks usually can stand to a 900-bar pressure, even though nobody would really want to try it... But anyway, considering that I'm aware of LPG bottles being used as a makeshift cylinder for scuba diving, and since LPG tanks are rated to a much lower pressure than CNG tanks, I wouldn't trust a scuba diving cylinder as a CNG tank.

I have seen my fair share of ignorant people using cylinders way beyond their rated pressures.

A friend fills 300 bar scooba tanks (test pressure of 450 bar) for PCP (airrifle) use.

Once while I was at his house this guy came with an aluminium tank rated for 200 bars filled all the way to 300 bars. The real horror was the standard plumbing parts rated for 10 bars that he had concocted to transfer the gas!

Lpg tanks are usually rated to 20 bars with a much higher burat pressure.

All this is rather extraneous if you cant aquire the compressor / system to actually do this.

Have we determined how much mass is required, and secondly, how big a space this storage has to be in? A 100 gallon tank is way different than a 5 gallon tank.

Around here I see stoopid people doing very stupid things all the time, causing me to doubt Darwin's theory of evolution.

https://1.bp.blogspot.com/-vpfXQL6Zy...ro-direito.jpg
CNG might not be so cheaper than gasoline as it used to be, but it's still what prevents some old American imports from heading to the scrapyard in Brazil... Notice the underbody CNG tanks on this Explorer.
https://1.bp.blogspot.com/-sa04fsomI...0%2Bmostra.jpg

Actually, the tanks are rated to similar pressures (250-300 bar)

And scuba compressors are actually used -in adapted form- in commercial at-home CNG-filling stations