Natural Gas instead of petrol

[Seth]

On Thu, 3 Jul 1997, Mark a Reed wrote:

> Hi all, 
> 
> Could a EFI system be converted easily to Natural Gas by connecting 
> the fuel rail to a gas bottle with the appropriate pressure 
> regulator?
 Strictly speaking, no.  But with an appropriate fuel rail, and 
appropriately sized natural gas injectors, and some dynamic modification 
of acceleration enrichment, it works very well.

We have an injected natural gas Dodge Neon here at the VRI.  It passed 
the ULEV emissions standard, which I don't think any production gasoline 
engnie car has done yet.  Once the correctly sized injectors were 
sources, the adaptive ecu worked with the CNG quite well.  And the rail 
presure is set at about 150 psig.  The CNG is never a liquid in pur 
tanks, even at 3600 psig.  Liquid NG requires lower temperatures, and 
that means a vacuum flask.  We used carbon fiber and polyethylene tanks.  
I think Literider is the brand.  The car runs great with the o2 sensor 
adjustment that I posted to the group about a month ago, and a circuit to 
reduce the apparent throttle position input acceleration in order to 
reduce acceleration enrichment.  Without this, it will go too rich on 
acceleration and will even quit.

One other thing, the ignition timing is considerably advanced.  If NOX 
emissions are not a problem, then a higher compression ratio works well.  
We used 14:1 without a problem, with ignition timing near  stock.  
Without this CR increase, the advance (static) was in excess of 30 
degrees, if I remember correctly.  

 > 
> If the regulation pressure was set correctly then the fuel/air 
> mixture could be set to allow the use of existing mixture maps in the 
> EFI system.
> 
> Is this feasible or a wild dream ?
> 
> Mark Reed 
> Farnborough UK
> 
> mareed at dra.hmg.gb  
> 


Good luck,

Seth Allen