Back in the early 90s ONG (Oklahoma Natural Gas) put on a big pitch to my city to convert the fleet to use their product. They supplied us with a entire kit to convert one of our Patrol Cars over and the mechanic to do it. Stock 350 Chevy Police Package with about 20000 miles. I was tasked with doing the testing since I was the Departments driving instructor. There was a toggle switch mounted on the radio stack that allowed me to switch back and forth between natural gas and gasoline. I took baseline readings on gasoline from dead stop to 80mph at full throttle letting the transmission shift on its own. Then switched to natural gas and duplicated the test. The difference was dramatic. Natural gas was like driving a 60s VW while gasoline was as it always had been. I also tested starting out from 0 and accelerating to 60 on natural gas then flipping the switch to gasoline while holding the accelerator to the floor. It was like hitting passing gear. I wrote up my findings and presented them to the Chief. The next day the system was removed from the patrol car and ONG was sent packing. I believe the system was used on a few of the public works trucks but never mentioned again for police cars.
Martin, very good summary of CNG vehicles with 8:1 or 8.5:1 engines.
Back in the '90s I was one of 3 folks on our company's (Arkla Gas at the time) task force for CNG. With both state and Federal tax incentives the cost of CNG conversions wasn't bad. Gasoline was around $1.25 gallon and NG was in the $4 to $5 per MCF range. The GGE (gasoline gallon equivalent) is 7.8 gallons gas per MCF of NG. So, the CNG equivalency cost was about $0.60 per gallon.
With fuel cost halved, the payback on the conversion cost was fairly quick for most. Oil changes could be extended (many times) and emissions were improved.
CNG has a octane rating of 130. You really need a compression ratio of around 12:1 for best performance. My company car was a Chrysler Concorde with the optional 10.5 compression 3.5 engine. It was pretty happy with CNG. As you mentioned, most vehicles with the standard 8.5 cr engines of the day were not so happy.
Fleet owners were pleased with the reduced fuel cost and didn't have any problem with extended oil changes and reduced damage from kid drivers abusing equipment. If they invested in a yard slow fill system, the drivers saved time on fueling. Just get in their truck/van and go.
One of the best things about my CNG car was I had a home fuel station, meaning I'd plug it in at night and next morning it was full of fuel. I'd go for many weeks and never need to take time to stop at a gas station. Then it'd only be when on the road and no public fast fill CNG stations were available. If no CNG, then just flip a switch for gasoline.
My observations were if a fleet driver didn't like the idea of change and CNG, he wasn't going to be happy. If he couldn't find a problem he'd cause one. Many folks liked it, some didn't.
RonR
