I've heard of ricers doing it, but have actually seen one car set up like that. It's still pretty Greek to me...and I'm Greek. When I looked his car over, it was interesting to say the least. His propane was in an actual dive tank. I'm a diver...so I could understand why he would keep it in a steel cylinder.
It was bolted down in the trunk. Keep in mind that dive tanks like his (OMS steel tank) have a burst disk, so if the pressure went over board, he wouldn't become an organ donor. The burst disk would rupture, and he could hit the trunk release lever and air that puppy out...no problem. He also told me that during the summer, he had an ice chest that the cylinder would remain in. He said he noticed no true gains by keeping iced down...it was just a safety precaution since this was his daily driver. And in Houston on a mid August day, it gets HOT, so I could feel his concern.
His little Honda was fuel injected, so he used a modified NOS setup, complete with fogger nozzles and a computerized fuel monitoring system (have no idea what the brand name was).
But he told me that the biggest difference in being able to run it in his car was the 12:1 ratio he was running. Seemed like a suicide mission on wheels, but it worked!!! This guy had some pretty impressive timeslips and video footage too. One time slip had an E.T. of 10.91 and another was 11.03. Not bad considering that he had only been dialing this setup for just six months. And one other thing...it's turbo charged!!!
Sneaky little ba$tard. His IC was a front mount painted black and had a black screen to hide it. The turbo was located at the bottom of the engine on the passenger side. At a quick glance when the hood went up you noticed NOTHING, but the VTEC logo on the engine which he told me had been set to turn on at 4000 RPM. A true sleeper...it had no decals, no rice lights. It had been lowered, and had light weight racing rims, and of course, the ever so popular fart can.
But it does make you wonder.
HTH
Erik