CNG, is it the Answer for the Fuel Crisis? (Part 2 of 3)

October 9, 2008 07:00 PM

CNG, which is 80 to 95 percent methane gas, "Natural" gas is the key word here, same methane you smell driving by a feedlot or dairy. Waste Management harvests methane natural gas from it's landfills to run their garbage trucks. Methane gas is renewable. Natural gas has a simple chemical make-up: one molecule of carbon and four molecules of hydrogen (CH4). That's what makes it burn so cleanly. Oil and coal are more chemically complex. They contain higher proportions of carbon, sulphur and nitrogen. Maybe CNG is a better solution to cleaning up diesel emissions for the next emissions law hurdle in 2010. Might be an alternative to urea which the 2010 diesel trucks will use to produce clean diesel. CNG is a safe fuel as it's lighter than air and dissipates when released into the atmosphere while propane is heavier than air, congregates at ground level. CNG tanks are certified and have stamped on them a date from 10 to 20 years to be recertifed.

Compressed Natural Gas, comes back in fashion when fuel prices soar. It's an old solution not promoted as well as ethanol and hybrids until now with T. Boone Pickens on TV everyday. During the last fuel crisis, there were more CNG fuel stations and dual fuel conversion companies, cheap gas came back and many CNG guys went bust. The infrastructure of CNG filling stations will need to increase to allow expanded use and competition. Right now your choice of new vehicles is limited to one: The Honda Civic GX. Toyota will introduce a natural gas Camary at the Los Angles Auto Show in November. GM and Ford during the last CNG surge, made several models of natural gas cars and trucks. CNG has the ability to improve Cost Per Mile 23 to 48% from my test. Yes big numbers, some improvement in (MPG) Miles Per Gallon, but real costs for us on the road, the same way the IRS gives you a a business deduction as cents per mile.

$1500 to $1800 for a CNG diesel/conversion system, another $3800 for a new 30 gallon carbon fiber tank and it isn't cheap. My tanks were used, similar to what you find on EBay. But if you put miles on your truck like I do (30k/year), it can still pay for itself in a year depending on which state you get most of the CNG from. Those of use towing trailers across the country can benefit the most, because we spend the most on fuel. We haven't dyno'd the test truck yet. I'm hearing from folks using CNG and propane boost that they get from 60 to 100 hp increase. It's easy to see the power boost, flipping the switch with the cruise control on. Nice on the Interstate on-ramp with a trailer, the extra power helps. I'm sure the 130 octane from CNG, and cooler condensed air caused by the pressure drop from 3600 psi in the tank to 200 psi in the regulator, all contribute. We ran hoses from the trucks recirculation reservoir to the regulators to keep them from freezing.

Having the correct spring setting in the regulator, controls how much CNG goes in the engine and at what RPM, the engine sucks in the gas mixture. The unit has adjustments for pressure and volume. You use less throttle for the same RPM, reducing diesel consumption. Fine tuning the volume control determines how much flutter you have when you let off the throttle or drop below the RPM that gas is drawn in. That was around 1600 rpm on my test truck. Torque peak on a 6.0L Power Stroke is 1800 rpm, so I gained some bottom end power.

In Detroit I drove Louie Fecteau's 2001 GMC Sierra 2500HD Duramax/Alison with the Deluca CNG dual fuel conversion. He had similar fuel economy improvements and said turbo lag was eliminated. Louie installed a new Lincoln Composites CNG 21 GGE Tank, carbon fiber composite 30 gallon tank, 200 lbs verses my 400 lb tanks. Louie's truck stutters at 1500 rpm when CNG shuts off. Louie changed to a lighter spring in the regulator for his first generation Duramax with less vacuum for better CNG fumigation draw. Louie put his regulators in front of rear wheel on the drivers side. Marc Deluca installed his regulators in the engine compartment of his GM Duramax. My unit is installed in the bed next to the tanks along with pressure gauge and fill nipple.

Found my trucks sweet spot for fuel savings and drivability. Changed volume setting 5 times, highest setting had 3 CNG to 1 diesel. But it was surging at highway speeds as anytime the cruise control adjusted itself on hill or wind, the reaction was a surge or pulse at set speed. Adjusted volume down, took the surge out, drivability is now same with or without gas. So I can have it on all the time.

Results; Towing a trailer had a 23% reduction ($.10) in cost per mile, from $.43 to .33. MPG improved 12% from 9.08 to 10.3 miles per gallon combined both fuels. 22.2 mpg CNG, 19.18 mpg diesel. This fueling at less than one to one, .75 CNG to 1 part diesel.

Empty truck had a 27% improvement of cost per mile, from $.26 to .19. MPG improved 8% from 15.36 to 16.48 combined fuels. 26.92 mpg CNG, 42.53 mpg diesel at 2 CNG to 1 part diesel.

This is with diesel at $3.94 and CNG at $2.74 in Colorado. CNG is sold as Gasoline Gallon Equivalent equal to gas in BTU units at 114,100 blended by Xcel Energy to achieve said BTU.

Using my gallons used for CNG and diesel, I converted to Utah prices for CNG and diesel. Average diesel price in Utah was $3.59 the same week I paid $3.94 in Colorado, CNG in Utah averaged $.88 with Colorado as one of the highest states for CNG prices at $2.74.

Towing a trailer on Utah fuel could have a 45% reduction in cost per mile from $.40 to $.22. Empty truck could have a 48% reduction in cost per mile from $.23 to $.12. Can you imagine driving for $.12 a mile? It would be equivalent to driving a car that got 30 mpg on $3.50 gas. Tempted to move to Utah or Oklahoma.

Turbo boost dropped in half using CNG. I think with a boost regulator, increasing boost would allow using more CNG or an injection system. Other diesel engines may have the ability to use CNG more efficiently, that will be another review, maybe a Cummins or Cat. This is the largest increase of fuel savings we experienced on our test truck 2006 Ford F250 Power Stroke diesel.

One of the benefits of natural gas as fuel, is they burn cleaner, releasing smaller amounts of by-products of combustion (carbon particulates and acids) into the motor oil. Because the oil stays cleaner longer, it's possible to expect longer intervals between oil changes.

At the CNG pump in Colorado is a $.06 a gallon Federal Excise Tax. This may be deductable with the IRS. There are incentives, grants and rebates associated with alternative fuels like CNG. In an effort to reduce America's dependence on foreign oil, reduce emissions and greenhouse gases, the US federal and state governments have incentives to encourage the purchase and use of natural gas vehicles (NGVs).

Part 3 will have our CNG install and more details. Next project maybe I'll get a windmill for my trailer and more solar panels.

Author H. Kent Sundling writes for via a special agreement with  

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