off topic but interesting

[john carroll]

The discussion of propane and cng fueled engines 
reminds me of a fleet of Peterbuilt log haulers 
that use propane introduced into the induction 
system to replace some of the diesel.  The concept 
could be useful to others. 

The system works as follows.  Advancing the pedal 
first causes propane vapor to be introduced to the 
air stream, increasing power.  The diesel injectors 
introduce fuel at a low level and provide ignition 
source and timing.  As the pedal is advanced, more 
and more propane is added.  At the point where the 
fuel vapor displaces so much air as to destroy the 
economic and mechanical efficiency of the hybrid, 
the call for additional power increases diesel and 
reduces propane until, at maximum power, the engine 
runs entirely on diesel.  It may be that transition 
takes place at a point where the propane/air 
mixture is still sufficiently lean that dentonation 
is not a problem,

They claim that over all and particularly at 
mid-power operation, there is a net benefit.

The value of the system is certainly a function of 
the relative cost of diesel and propane.  Does any 
one think the propane was taxed?  I believe they 
run a kiln on propane as well.  I am certain the 
systems are commercial, but I have no idea of the 
source.

The most exciting corollary of this system that I 
have observed was when a diesel powered drill rig 
hit a natural gas tranmission line at about six 
feet.  Every one abandoned ship without hitting the 
fuel cut off and the engine ran away as the engine 
began inducing gas along with air. A brave soul 
(the owner) went back and shut the fuel off before 
the engine came apart or a fire started.

-----------------------------------------------
jac at wave.sheridan.wy.us
john carroll