Azmio,
Do you mean DI - Direct Injection, or PFI - Port Fuel Injection. The injectors I mentioned in my previous post are all Port injectors. With the exception of other products that might be in development somewhere and not publically announced, I am only aware of one DI CNG injector; Westport Innovations.
Diesel Injectors won't work, as they are designed for much higher pressures, of a much more dense liquid fuel, and have very small annular flow passageways through the injectors. Plus, they rely on the diesel fuel to lubricate their innards. CNG requires a design specifically for CNG. The only CNG injector manufacturers I'm aware of are:
Westport - DI
Quantum - Port
Keihin - Port
Bosch - Port. Not really a CNG injector. Bosch actually sells a Methanol Racing Injector (i.e. Indy Cars and such, based on the original EV1 outline), that several companies have attempted to use as a CNG injector. It has almost as much flow capacity as the Quantum. I know of two very large Detroit based OEM's who have lost 7 figures warranty dollars replacing those things becuase they gum up rather quickly in service. CNG has a lot of "crap" that comes along with it in actual use (compressor oils, water, rust, etc . . ..)
Siemens - Port. On again, off again in development. The last I heard was it was working, but the durability was not anywhere near what it needed to be. Small package size, but about 2/3 the flow capacity of the Quantum, based on numbers given to me by my former customers who were also evaluating them. Availabilty unknown.
Teleflex GFI - Purchased the AutoGas group in Belgium. They supposedly manufacture an injector in partnership with what used to SAGEM Automotive. I believe it's been folded into VALEO now. It's a side feed design with a barb fitting on a plastic housing. It looks more like an EGR valve in cross section than an injector. It seems to work, but no OEM's will go near it as it could easily crack in an accident, which could lead to a thermal event.
Zenith Fuel Systems - Industial Market. They sell an "injector" which is really a throttle body with some metering solenoids. OK for a forklift truck (low power) but not going to work for a higher power engine.
Clean Air Power - They sell some stuff for heavy duty trucks, but their injectors (the ones I've tested) don't have sufficient flow capacity at 50 psi delta to fuel an engine. They work fiarly well from 125 psi on up. However, most OEM's I've dealt with didn't like the fact that they could not drain their compressed storage tanks down nearly as far with the CAP system, effectively cutting vehicle range. If that isn't a limitation for you, then their system might be worth investigation. I have no idea if they have durability issues.
I've heard of a couple of other Mom and Pops, but have never seen any actual hardware that worked. I've never heard of Delphi, Marelli, Denso, or Aisan having anything for the CNG sector, but it's possible that something is just coming to market.
If you find something new, please post it here. Up until very recently, I worked at ground zero of that industry. I like to stay current.
-Tony Staples