With the price of gas going up and no hope in sight that E85 ethanol will be available in my area OR will be any better in price with gasoline even if it was, I'm looking at possibly a Propane or NatGas conversion. There's a few kits on the Internet and CNG seems to be the most attractive purely because I can buy a CNG compressor which connects right to my house's NatGas line and will compress NatGas right into a CNG tank. That's tax-free fuel there and with NatGas being at all time lows for price, that makes CNG an interesting option. Add to that, CNG is a high octane fuel so you could run a high compression with it and get both good power and fuel economy with it. Although there are even fewer public CNG refueling stations than E85 stations around Atlanta. AFAICT, there's only 1 public CNG station in Atlanta and only 1 more somewhere else in Ga.

Now LPG (Propane) has more locations to fill up. And LPG is under much lower pressure but also isn't nearly as attractive in price and I can't buy a home unit to refuel. And I have no clue what the "mood" of the Propane suppliers would be with me driving a vehicle in there to fill up when they aren't really setup to tax their fuel for road use. I'm not even sure Ga attempts to tax alternative fuels like LPG and CNG since there's so few of them on the roads. I do know you can get emissions exemption for complete conversions. However if the vehicle is capable of still burning gasoline, it still must be tested. What I doubt though is the emissions guys would know the difference if the vehicle was being tested while burning NatGas or not.

When I 1st started thinking about this, I was thinking maybe I could rig something up so I just flip a switch and sometimes the fuel injectors would be supplying whatever's in the fuel tank (gasoline, E10, E85, etc) OR supplying CNG (uncompressed) so the EEC would still control fueling...but with a different tune to compensate for differences in AFR, injector performance, and spark. However there are other issues. I doubt injector slopes would work quite the same for NatGas which uncompressed would be partly liquid and partly gas. Depending on the under-hood temps, you have an undefined difference in very cold liquid and gas in the fuel rail, so how would you compensate for injectors closest to the inlet getting more liquid and the injectors furthest from the inlet getting more gas and that ratio changing as throttle (fuel consumption) and temperature changes? And would I need to insulate the lines to keep them cold (NatGas is a refrigerant when compressed)? Finally, then there's the issue of how you prevent the NatGas from dumping into the gas tank through the FPR? I started realizing that trying to reuse the gasoline injectors was problematic and a piggyback system was going to be a much cleaner solution. So I started looking on the Interwebs for CNG conversion kits.

The CNG kits I found are all add-ons to an existing gas-burning engine. The info I've found so far is vague at best but it does seem they piggyback on top of your existing carb/EFI system. They supply a computer, their own injector, and somehow disable your stock computer's ability to supply fuel (most likely they just kill the fuel pump). So the stock computer continues believing it is controlling and delivering fuel when in fact the only thing it is doing is controlling the EGR and spark control. But the CNG computer is actually handling fueling. Since we do have control over the tunes of our EECs, it would make sense to have separate tunes for gasoline and CNG in the EEC so we could change things like the Spark advance, EGR contributions, and force the EEC into an Open Loop mode so it wouldn't attempt Closed Loop/Adaptive Learning when it isn't really in control of fueling. What I don't have any info on is how the CNG computer knows things like airflow and WOT AFR control. For simplicity, I'm betting its Speed Density based and simply taps into the engine's vacuum to infer engine load. It might also have a PIP connection so it knows RPMs. But does it run Closed Loop using its own O2 sensors or again for simplicity does it just force Open Loop and avoid the need for separate HEGOs? I haven't found any info that answers these technical questions yet but there does seem to be some tuning of the CNG computer required (not surprising).

Since I'm still in the "how does it all work" phase, I thought I'd ask others here that might have dealt with CNG/LPG systems in the past and knew how they work in conjunction with EFI systems like ours.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

thats a pretty cool idea chris, LMK if you go with it as i would def be interested in the outcome

I got more info on the CNG kits. It's my hope to make this thread an FAQ for others looking for information about CNG Conversions, Conversion Kits, Refueling Stations (aka CNG Compressors), and CNG tanks. This has been a learning process and I'm hoping to collect as much information about the pitfalls and whats to be expected from the choice to do a CNG conversion into a single location. It'd also be nice if it was a high hit on Google for common CNG searches.

The cheaper kits are well, you get what you pay for. They sell for about $600 or so. For specifics about the kits and some interesting FAQ reading, click around all the pages here:
Energy & Water Solutions>CNG Conversions

The bottom line is they are rudimentary CNG conversions away from gasoline, but the installation of the conversion kit reduces your performance substantially. This is because the mixer you have to install into your intake track is an orifice device that is quite smaller than even the 55mm stock GT MAFs. The mixer creates a venturi effect to pull the CNG into the air much like a carburetor does. There are various size mixers, but ALL of the engine air has to flow through the center of this device for proper CNG metering:


As you can see, even the largest one still only has an opening of maybe 30-35mm if that. This gets installed right in front of your throttle body and they give rubber stuffing to go around the mixer so air doesn't flow around it. Using these kits can cut airflow by as much as 60-70% over stock which is a substantial performance reducer. Although the conversion to CNG, even if it isn't going through a reducer tends to reduce performance since NatGas has an octane rating of about 120 (cited from Wikipedia) and most gas-engines just don't have the compression to make good use of that high of an octane rated fuel. Even high compression engines (DCR in the mid 8s) are still not really taking advantage of the fuel's performance potential. My estimate is that you need an engine with a Dynamic Compression Ratio up in the 9s to run optimally with NatGas. This would explain why NatGas conversions of Diesels are much more popular. Although even on Diesel conversion, you still need a small amount of diesel always being injected just to lite-off the NatGas. But diesel consumption with NatGas conversions is still substantially reduced.

There is a computer that "influences" the NatGas flow via a stepper motor. At 1st, I thought the stepper motor was like an injector, but it isn't. In concept, you can think of it more like metering rods in a carburetor. When opened wider, it simply lets more NatGas flow into the air that is passing through the venturid mixing device. This computer taps directly into the TPS and a single HEGO's sensor lines. While at "closed loop" TPS positions, the computer modulates the stepper to maintain the mix near stoic via the HEGO feedback. With wider TPS positions, the stepper is opened up to give an enriched mix. No details are given as to how far it is opened or what the target lambda AFR is at high load/WOT. But based on the simplicity of this system, my guess is the stepper is just set wide open and whatever AFR you get is what you get. With the engine having a vast majority of its airflow potential restricted, it's not like running lean at WOT is going to hurt the engine.

There's also a device that goes between your EEC and injectors called an Injector Emulator. In reality it's nothing but a commanded series of switches...for the electricians out there, think of this device as a 4-pole, single-throw relay. So for a 6/8 cyl, you need 2 of these devices. When in CNG mode, these devices simply cut the connection between the EEC and injectors. If you manually flip back to gasoline mode or you run out of CNG, then the CNG computer reactivates the gasoline injectors. It's as simple as that. The stock computer continues believing it is in control so it'll maintain spark, EGR, Canister Purge, Smog Pump, transmission, and whatever else the EEC might normally do. The catch is there's nothing to keep the CNG system in sync with the EEC's attempts to control AFRs. So it is possible that the EEC LAMBSEs, while in Closed Loop, could hit adjustable limits and eventually activate Check Engine codes. In older EECs as long as the EEC see's some HEGO switching going on, that's not likely to happen, but in newer EECs, you may hit a limit that triggers a code that the EEC has adjusted too far rich or lean which could result in Check Engine lights and codes. Regardless of the era EEC, having the LAMBSEs at or near their limits is likely to make returning to gasoline harsh upon reactivation. Once control is given back to the EEC, Closed Loop action will adjust the LAMBSEs back to where they need to be for running gasoline. But that could take 10-30 seconds to completely correct for depending on your HEGO bias settings. EECs setup for forced Open Loop will have a flawless return to gasoline since the EEC was never aware it wasn't in control the whole time.


There are higher performance CNG conversion kits and as you would expect, they are more expensive. These kits are in the $1500 range. These include solenoids that get mounted in the intake near the ports like injectors. This of course, requires that if you are maintaining your existing gasoline tank and gasoline fuel system, that you drill your lower intake for these CNG solenoids. For these kits, you can think of the CNG solenoids as injectors. I haven't seen them, but I wouldn't be surprised if they literally were injectors. The solenoids get fired by a Sequential Fire Computer which is more complex than the CNG computer in the above kit, but still not nearly as complex as Ford EEC. I believe these CNG computers are Speed-Density based. They evidently do have a fuel rail and a regulator that monitors vacuum just like gasoline FPRs do. But I haven't gotten nearly as much info about them yet...still inquiring. My question to the guy that sells these is can I buy just the CNG solenoids, fuel rail, and other supporting hardware without the computer. I'd use those "Injector Emulators" and flip between CNG and gasoline tunes while also flipping between CNG and gasoline injectors but control it all from my Ford EEC. The catch is these solenoids are 3 ohm impedance. So just like running low impedance injectors, you'd need low impedance injector drivers to control the CNG solenoids. The upside to these kits is you don't have the vast restriction of air and you have true port injection of CNG. On a moderately high compression engine or blown engine, I expect you could get substantially higher performance and fuel economy than you could with gasoline since you could run a 120 octane rated fuel right on up as high as you could boost. The limits would be your booster/turbo/block, not the fuel's ability to resist detonation. If I were to do a CNG conversion, it would be with one of these kits. Although for a stock beater car, the above kits might still be compelling particularly if you've already invested in a home refueling station.


Keep in mind, these are just the kits. These are not the CNG cylinders (fuel tank) nor the home refueling stations. CNG cylinders will run anywhere from $400 to $1500 shipped depending on new or used, how large, and how close to their expiration date they are if used. CNG cylinders are often sized in Gasoline Gallon Equivalent (GGE) values. The larger cylinders I've found are capable of holding 10GGEs@3000PSI and are upwards of 150lbs. They do have smaller "trunk size" tanks, but they have much lower GGE ratings...some as low as 2-3GGEs. If you have tanks and CNG conversion kits that can handle pressures up to 3600PSI, then that GGE value increases by 10-12%. You can combine cylinders together to get longer driving distances.

Home refueling stations are nothing but multi-stage high PSI compressors. They take in NatGas from your house's gas supply, and compress it up to 3000/3600PSI depending on your setup. They wire up to 240v service and cost around $4500 shipped. I can't remember exact values, but I believe a 10GGE tank takes about 6-7hrs for a home refueling station to refill. If you have public CNG refueling where the CNG is already compressed, refueling can be done in about the same time it takes to fill up a normal gasoline tank.

Now for the real numbers.

$700-1500 Kit (depends on supplier, hardware supplied, and how extravagant the kit is)
$200 extra crap to get it installed and getting lower intake drilled/machined
$1500 used 10GGE@3000PSI tank
$4500 Home Refueling station & shipping
$100 for parts and wire to get it installed in your house yourself

$7800 total. That sounds like a lot and to be honest, it is. But lets see how long it'd take to pay off.


With gasoline at $3.50/gal, getting 22.7MPG, and driving 150 miles/week, lets see how many weeks or years it'll take to pay off...and this assumes NatGas doesn't get more expensive and gasoline doesn't get cheaper.

22.7 Miles/Gal
------------------- = 6.48 Miles/$
$3.50/Gal


150 Miles/Week
----------------------- = $23.15/week in gasoline I spend
6.48 Miles/$


If NatGas is something like $1.80/gal equivalent cost to gasoline when you consider its cost, the electricity for running the compressor, and the difference in fuel economy for running CNG vs gasoline. I haven't seen a number on the Internet this high for a $/gal gas equivalent so I believe it is actually a lot lower than this, but I'm going conservative here to get a worst case payback time.

22.7 Miles/gal
---------------------- = 12.61 miles/$
$1.80/gal


150 Miles/Week
---------------------- = $11.9/week in CNG
12.61 miles/$


How long before I "save" enough in CNG to pay for the $7800 investment:

$7800
------------------- = 693 weeks or 13.3 years
(23.15-11.9)


That's a long time for the gas and NatGas prices to stay stable AND for my vehicle to stay running. Doing a CNG conversion for the fuel economy alone just doesn't make sense. You have to really WANT to do the conversion or have a delivery job that causes you to drive a lot of miles a day. And in those cases, your payoff time would be a lot sooner. Lets say I drove 150 miles/day, not 150 miles/week, that would have the CNG system paid off in less than 2 years. Now that might be worth it.

Now, what if your state has an alternatives conversion incentive or tax rebate. If you can deduct these costs off on taxes OR get an out-right subsidy reimbursement for the conversion, then obviously this payoff time comes down. But often these deals from the gov't are only on EPA-approved conversion kits. And none of the kits I looked at are EPA-approved. Those kits are WAY more expensive and targeted for fleet vehicles and diesel vehicles.

For an easier formula to plug into to see what your CNG payoff time would be with your estimate of CNG installation cost and tax/state savings, use this formula:

MPG = Your vehicle's gasoline fuel economy
Update the $1.8 if you find the CNG gas equivalent cost has changed (CNG cost goes up substantially)
Update the $3.50 for going rate for a gallon of the grade gasoline you use.

Solve for X where X will be total number of miles you'd have to drive to pay for the investment. Divide X by the number of miles you drive in a day/week/year to determine how much time it'll take to pay off.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

It could also be worthwhile if, say, you lived in an area that had filling stations. I know the post office uses CNG, but think they have private filling stations. Still an interesting concept, would be cool if a company worked on getting pricing down for all components involved

_________________
1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm

If there were gas stations around that sold CNG, then that could easily affect the economical viability of the conversion particularly given the biggest component of the investment is the home refueling compressor. If you didn't have to buy that, that's at least $4800 off the initial cost. But currently, there just aren't that many public CNG refueling centers.

I updated the post above with a simpler formula for figuring out how many miles it'll take to pay off a CNG conversion and thus how long it'd take to pay off. Hopefully that simpler formula will make it easier to calculate the CNG benefit.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

Might as well make it $4xMPG ><

_________________
1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm

I was about to do that, but there's no guarantee the prices will stay high for years to come nor that NatGas will stay low. And since I knew that my payback time would be in years, I didn't want to under-inflate the payback time period. I wanted to err on the side of worst-case, not best case.

It's the same dilemma when people buy hybrids. They get sold on them because the sales guy claims they'll pay for themselves after like 8 years assuming existing gas prices hold stead AND the sales guy probably also assumes a price increase average every year just to make the numbers look even better. But for all the people that bought hybrids in and before 2007, that got shot when the price of gas went from $4/gal to ~$1.50/gal. So in case that's about to happen or happens in the next year or so, I decided to keep the numbers conservative.

However if you want to make optimistic predictions, enter $4/gal and lower the CNG equivalent price to about $1.50-1.60/gal which I think is about where it is right now.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

lol I was just givin you a hard time, no need to explain

_________________
1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm

you can disabled the injectors by setting the numego scalar to 0

else you can just demand a 0 lambse, better option than hacking up the wiring with relays to disconnect them

i would opt to let the ford ecu control the fueling, i don't see why it couldn't if you think outside the box

It depends on what you are doing. If you go purely by the kit instructions using their CNG computer, then using those injector cutouts is what they suggest. But since we have tuning ability, we have those options to disable the injectors in a number of different ways. However this now requires coordination of flipping ON the CNG computer and activating your EEC's CNG tune that disables the injectors. If you are really crafty, you can wire in the CNG-active line to the QH to flip to the CNG tune automatically kinda like wiring to the QH for nitrous.

But I agree, I'd prefer the Ford EEC would control everything especially with the Sequential Injection CNG kit. Ditch the CNG computer, and flip between gas injectors or CNG injectors. But if the same injector outputs are going to control the CNG injectors as gas, then you still need those Injector cutouts to disable the gasoline injectors while in CNG mode. And when in gasoline mode, you can probably disable the CNG injectors by simply not powering the low-impedance drivers. And again, use a single switch on the dash to control the Injector cutouts, CNG injector drivers, and gas/CNG QH tune selection.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

tin fo

thats what i would do, now if you could pipe the cng into the fuel rail you'd be working with something

I still have some outstanding questions. But I've gotten more answers that are worth putting here.

First off is how to deal with the CNG low impedance injectors using a stock EEC. Evidently it's the same as dealing with any other low impedance injector. You can either spring for Peak-n-Hold low-Z drivers or you can put current-limiting resistors inline with the injectors so the injectors don't burn out the EEC. Here's the thread with more details I found on this issue:
Using low impedance injectors on stock EECs

Next, I wanted to get a better comparison of price. The above values were "worst case" and in worst case, it really makes CNG not attractive at all. So I'd like to update with a little more realistic values for CNG. First off, I needed to calculate how much it'll cost to fill up a 10GGE tank with NatGas. The tank is rated in GGE sizing. However my NatGas supplier doesn't bill me in terms of GGE. They bill me in terms of $/therm. So here's how I figured the cost.

1 therm = 100,000BTU

1 GGE = 114,000 BTU since 1 gallon of 100% gasoline typically has that much BTU. However as we all know, few people can actually get 100% gasoline unless you live in the midwest. What passes as regular gasoline at most American pumps is actually E10. And reformulated E10 for distribution is typically 111,836BTU/gal, not 114,000 BTU/gal. So I'd rather use that value when comparing CNG to the gasoline I have to compare against.

So to determine $/GGE, here's the formula:
$/therm x 1 therm/100,000BTU x 111,000BTU/GGE

Simplified down, look on your NatGas bill for your $/therm value and enter it for X below:

1.11836X = $/GGE (assuming E10)

Looking at my bill, I pay $.979/therm so that's $1.095/GGE. What this doesn't include is the electricity it takes to run the CNG compressor for 3-5hrs per 10/GGE. A 5Nm3/hr compressor has a 5HP motor in it which is about like running your house air conditioner for the same amount of time. Just to be reasonable, I'd say that's probably ~$3.00 per 10/GGE fillup or an additional ~$.30/GGE. This gives a much more realistic $1.40/GGE for CNG, not $1.80/GGE I used in my example above.


Right now, I get 22.7MPG on 87 octane E10 running in my stock 302. However I have no clue what the fuel economy will be in the 331 I'm building. Also consider that the 331 will be high compression and will NOT be able to run 87, and instead will have to burn premium 92/93 octane. And I have no clue how much better/worse the fuel economy will be with CNG. Yeah the CNG is rated in GGE, but that's only from a BTU standpoint. The difference in octane rating could change the way the fuel burns in a way that changes the fuel economy between E10 and CNG. But without more info, I'm forced to assume that BOTH will be what my fuel economy is today. So until I do get more info, I'll continue to assume it's 22.7MPG for both.

With more "realistic" numbers, I'm calculating anywhere between 4.5-7 years of return on investment assuming NatGas prices stay the same and gasoline prices either stay where they are or go higher.

Finally, the low impedance injectors are on a header together. Check it out:


From the header, there's a flexible pipe that goes from the header to the intake manifold. In the manifold, you drill-n-tap to install a fitting that the hose connects to. Since CNG is always gas (and in fact is not a refrigerant the way LPG is), there's no liquid going in or coming out. The injectors are literally metering the flow of gas hence why CNG injectors are generally VERY high flow (160-240lb/hr). The good news is this means I don't actually need room under the plenum for the injectors to fit. All I need is enough room to get the taps installed and the hoses in place.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

interrresting... so you'd actually have 2 injector headers on each side, with hoses for each cylinder to the intake (to each runner)? Very cool stuff.

Now, where you could potentially really get your money's worth, is if you put this setup on multiple vehicles in your household, not just 1. Therefore cutting down on your payback because your filling unit would be utilized more.

How does that pay off look without the home compressor?

_________________
1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm

Agreed. If I could setup my wife's car to run CNG (not happenin' BTW), then yeah the CNG would really pay for itself faster.

As for without the home refueling station, that all depends on the availability of CNG in your area and the price. There are only 2 in Atlanta and that's IN Atlanta. I don't actually live IN Atlanta and it wouldn't be feasible at all for me to drive to either of those stations for a fill up. I'd waste 1/3rd of my fill up just getting there and back. So for me, it's a no-go without the home refueling station.

Although if you do have a public CNG station that is relatively convenient to get to, it depends on the cost. Some areas are selling CNG for $2.20/GGE. Others, like one in Alabama are selling for $1.39/GGE (not much higher than what I could fill up for using a home unit).

I have not priced out how much Propane would be. Since CNG is stored at significantly higher pressure than LPG, all the CNG hardware should be quite capable of dispensing LPG as well. They are both high octane rated fuels so they are compatible in that way as well. But that's where their similarity ends. Here are the known differences:

• CNG is 17.2 stoic AFR vs Propane at 15.5 AFR (minor tune difference).
• I believe the connection to dispense CNG and LPG are different so you'd need to swap fittings or somehow fit both to your tank if you swap between the two.
• Propane is quite readily available. Most U-Haul rentals have an LPG filling tank as do many camp grounds and some privately owned hardware stores (not Lowes or Home Depot). Or just fillup at the local Propane Company's tank.
• Unfortunately, Propane isn't nearly as well priced as CNG when compressed at home but is still better than gasoline right now.
• I think Propane, in the form of LPG, has a better energy density since it compresses into a liquid which would be a plus. But that could also create a different problem if the NatGas regulator isn't warm (as is the case on cold-crank). Both Propane and NatGas regulators have fittings to circulate engine coolant through them so they don't freeze up. But in the case of Propane, the coolant must be hot enough to boil off any liquified Propane before it is injected into the engine. Otherwise you'd get random rich spikes as droplets of liquid Propane was sprayed.
• NatGas is lighter than air so it dissipates into the atmosphere easier. However Propane is heavier than air and actually is more dangerous in the event of a leak. I've heard of people in the country that have Propane furnaces in their basement that get a leak. The basement fills with Propane and as they step into the basement, if they don't smell the gas in time and know to get out of there while they can, they faint, falling to the floor where the concentration of Propane is even thicker and die due to lack of oxygen. Far more people have died from Propane leaks due to this than from explosion.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

Yes, if I could get multiple vehicles using the same compressor, that would increase the payout time. And another thing that none of my cost values include is tax credits/writeoffs/subsidies/etc from federal and state. Although I'm not counting on them since those generally require that you have it done by an EPA certified CNG installer using an EPA certified kit which runs the numbers up higher than the subsidies are worth. Although if I find a way to "slip" the receipts in as approved, then I will. Or if I could just get a break on the refueling station, and not on the tank-n-kit, that would be worth it.

But to answer your question, yes there would be two of those 4-injector rails, two regulators, and both regulating injector line pressure just like your gasoline FPR does. The only difference is they are much larger and require the circulation of coolant through them to keep them from freezing up. I've about decided I am going forward with this and I think I've found the kit I'm going with. Here's a pic of it:


Of the things in this kit, all I need is the hardware. I don't need the computer or a lot of the wiring. In fact the only parts of the wiring I do need are the connectors to the injectors. That's it. I'm hoping I can find somebody that recognizes those injector connectors and can tell me what mfg used those connectors so I can go to a junkyard and clip the connectors off a junker and splice them into my injector harness.

I talked with another CNG conversion provider (provider of the kit shown above), and interestingly his kit is better and cheaper than others I've found. He sells his SEFI CNG kit for around $670 including CNG computer and his kit uses dual regulators to get better HP flow potential. He's working me up a cheaper price for a kit, less the computer. He did confirm that these kits have been installed on high performance vehicles making upward of 400hp. So my ~300hp 331 should have no problems with lean-out due to lack of gas-flow. Unfortunately due to the devaluation of the dollar, the CNG Refueling compressors just went up in price by $250 about a week ago.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

awesome! (other than compressor price, lol). Let me know how this works out. I don't think it's something I could do in the short term, but I'm very interested in doing it down the road. I might actually have to replace my cavalier and get myself a ford DD to put this on...

_________________
1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm

Another thought (and I may be way off), have you checked with any of the gas/welding supply companies to see if they do tank fills, to where you could get a couple tanks and do a tank exchange? It wouldn't be a regular filling station per say, but still might work out for your needs and save you the money of the compressor. Even if they don't do it, if they see a potential market it's something they might invest in...

Edit: nm, I see with the size of the tank exchanging would not be an option. Still even then, it's something that a place like that might consider setting up a filling station.

_________________
1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm

What doesn't make sense is why more gas station owners don't invest in CNG infrastructure. I didn't realize how much subsidy and support gas station owners get from gov't to install that infrastructure. Here's an interesting article on CNG:
Technology allows CNG users to fuel at home

But yeah the tanks are pretty big and not something that can be easily swapped out. Empty, they are around 120-140lbs and have to be strapped down pretty tightly. Add to that, they are only 10-12gallon equiv. so it'd have to be swapped once or so a week. That's way too frequent to be worth it for me. And unfortunately, the refill time isn't quick, so it's not like I could talk neighbors into a CNG conversion and charge them for fillups.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

is the fillup quicker at commercial stations? I'm guessing that home delivery is low pressure and that is the cause of the long fillups?

_________________
1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm

The home fillup is the same pressure as what you would get at a CNG filling station. The reason home units are slow (3-6hrs depending on compressor and tank) is that it is taking NatGas from at or less than 1PSI to 3600PSI. That's a HUGE increase in pressure and takes a decent CID compressor to do. Even the commercial units that have 4-20x the CID as home units, still have a slow charge time relatively speaking and if that's all they had, would probably take 15-20 minutes to fill your tank. So to combat that, what they install is a huge CNG storage tank. The compressor keeps the storage tank full. Then when someone drives up to refill their vehicle's CNG tank, the station's storage tank (probably held at higher than 3600PSI) easily transfers pre-compressed NatGas with no waiting in about the same time it would take to fill up with gasoline.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

gotcha, that's what i thought, thanks.

_________________
1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm

This is kind of related and may be of interest to you.

Back in the Mid 90s there was a company over here (Liquphase I think they were) that set up a Ford Falcon 4.0 Inline Six to run factory EEC4 and Liquid LPG injection not vapour.
It was a dual fuel set up.

They did this using the factory Injectors (EV1 style) and cutting slots in the body for the liquid LPG to enter, and making an auxillary fuel rail for the gas, to feed into these slots.
The factory fuel rail was retained as is to allow for running on petrol (gasoline).
The LPG tank had a high pressure fuel pump (from a Mitsubishi Magna/Diamante to you guys)installed inside it, this fed the auxillary fuel rail, and then LPG was returned to the tank, just like a petrol setup.
They claimed that the performance was equal to the petrol version.

Ford Australia was said to be looking to introduce it in the next model Falcon (1994 EF) as a factory fitment, instead they stayed with a vapour system.
17 years later and the next model Falcon (FG series 2, may be the last as well) may actually get some sort of liquid system.

I have the article in my colection of magazines I will see if I can find it.

_________________
Ford Falcon 4.1/250 EFI Xflow, Eaton M90, Water/Air intercooler,
C0S/GURE ECU, 42# Injectors, 70mm MAF, AEM wideband, QH, BE/EA.

Well, I got some confirmation from the guy that the rail-mounted injectors as seen above are 4Ω so adding an 8Ω wire-wound ceramic resistor in-line with these will put me well within the range of a Ford EEC to handle.

I also found a great price for 8Ω 20watt ceramic injectors from Amazon. I can get 16 of them for $20 shipped. I only need 8 of them, but I was thinking with these being 10%, I might want to pick-n-choose among a selection to get a "matching" set. And with them only being $1 each and $5 to ship them, buying an extra 8 isn't a big deal.

The resistors are actually from Parts Express, just being sold on Amazon. So I decided to go to the Parts Express website and they have the individual resistors for about $.75 each, but, their shipping is much worse...like around $11. So it's a much better deal to buy them through Amazon for the quantities I'm looking at.

Another suggestion that was made by the hardware guys at work is that I add a diode across each injector to shunt their dropping-field voltage to further protect the EEC. This is probably not necessary, just something they do for the coil-side of relays to protect components driving relays on our hardware and saw that as an obvious place to put a diode.

If I really wanted to get elaborate, they drew me up a schematic of how I could drive the injectors with full line voltage using a MOS FET, NOT, a pullup resistor, and one or two other components. The problem is their circuit is a PEAK-only circuit. From what I can tell, low impedance aren't designed to receive constant 12v. They use Peak-n-Hold circuits which means full 12v line voltage is sent to the injector, then .1ms or so later (after the injector has fully opened), the current is reduced since it takes far less current to hold the injector open after it's been opened. I could probably expand on their Peak-only circuit by adding a parallel 1000μF capacitor & 8Ω 20w resistor in series with the injector. The capacitor would allow a quick-jolt of "peak" current, but once the cap is charged, the current would transition over to the resistor for the "hold" current. But that was getting so elaborate I would need a circuitboard made to stuff the components onto since it'd be all those components x8 for all 8 injectors. So I decided I'd start off simple and go that route if I found that the resistor-only technique just wasn't consistent enough at low PWs to work well.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

still watching, keep updating with progress

_________________
1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm

The only new news I have is that the tank supplier just got in some Type4 2012 expiring tanks for $500. The shipping is still $250 shipping and $150 for mounting brackets.

They also have a new tank mounting system:


I think I could go to Lowes or Home Depot and get all these same components and probably for cheaper than what he's charging.

What I don't know is if this kit will support suspending a tank under the frame rails or if this kit assumes that the tank will be mounted in a bed or in a trunk, and all the strap will have to do is keep the tank from sliding around as seen installed here:
7.4 GGE Type2 16"x39" 175lbs

BTW, for some perspective, here's some pics of the Type4 10GGE and 12GGE tanks:
10GGE tanks are 16"x50" 120lbs
12GGE tanks are 18"x50" 140lbs

Here are some smaller DOT approved CNG dual-tanks that together are 7&9 GGE which include mounting brackets:
7 GGE 19"x42"x10" Weight 200 lb
9 GGE 20"x42"x12" Weight 220 lb

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

are you planning on mounting to the framerail under the bed? obviously if it can fit that would be ideal.

I personally would prefer the metal bolt down straps over the ratchet straps. Ratchet strap would work for just a tie down, but for suspended i'd be worried. I have seen them snap before. I *think* they'd hold up, at least to normal use, but I wouldn't risk it in case of accident with a suspended tank. also keep in mind, that your biggest risk is going to be a forward collision (head on). if you mount the tank inline with the frame rail, you have a greater risk of the tank "sliding out" of whatever mounting system you have. may want to look into creating some sort of stop for it, to make sure worst case it can't slide in either direction.

_________________
1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm

If I were replacing the gas tank, then yes, it would be mounted parallel with the frame. But since I do plan to maintain gasoline capability, the CNG tank will either need to go into the bed lengthwise against the back wall or just in front of the rear bumper where the spare tire is right now and in that case, it would also be mounted perpendicular to the frame rails.

If mounted in the bed, a strap would be just fine since a head-on would have the whole length of the tank pushing into the bed back wall of which it would already be tightly strapped against. The downside is a portion of the bed would be used limiting the truck's utility capacity.

If mounted in front of the bumper, there would only be the mounting bracket holding the tank. The mounting bracket would bolt to the portion of the frame that a towing package would normally bolt to. Since I don't tow, I wouldn't be loosing anything in that aspect. And it wouldn't be in the bed so the bed wouldn't be used. The only downsides to this configuration are I'd have to find a way to mount the spare in the bed somewhere and the additional weight of the tank at the very back of the truck would increase the chance of over-steer which could be problematic when taking tight turns in the rain like the kinds of turns you make getting on or off of tight-turn interstate exits.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

I'd think center mounted would be better than rear mounted, far more pro's to that setup.

_________________
1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm

I called the guys up that sell the used CNG tanks and they got a new shipment of $500 12 GGE tanks in. I'm glad I did call them. He said he expected all of them to be gone by Friday. So...I bought one.

He did confirm that the straps are NOT intended for a hanging configuration, only for a tank mounted on a surface. Although the Type4 mounting bracket is designed for a hanging configuration and in most cases, that's the way the tanks were installed new.

Next is the CNG kit.

And finally the BIG purchase, the CNG compressor. So I guess the project is officially a GO.

_________________
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

Member V8-Ranger.com

awesome man, best of luck!

_________________
1978 Mustang II King Cobra
89 5.0HO, Stock Short Block, Edelbrock 4bbl aluminum intake, Holley 650 double pumper, MSD 6AL, Ford F303 cam, 1.7:1 Crane Roller Rockers, Pocket Ported stock heads, Hedman Long Tube Headers
5 spd Manual
Full roll cage, 9" full floater w/Currie trac lock/373 gears, RCI Fuel Cell
Project Page: http://www.brandttuning.com/projects.htm