CRD Joe wrote:
Propane is not more expensive than diesel here in the Seattle area. As I understand it propane acts as a catalyst and increases the amount of diesel fuel burnt. It in effect gives more BTU's than does standard diesel. Therefore more power.
The defnition of a catalyst is: a species that lowers the activation energy of a reaction while not being consumed itself. The net effect observed is an increase in the kinetic rate of a reaction. Because it is consumed during combustion, propane is a reagent, not a catalyst.
If it has fewer BTUs than diesel, it has fewer BTUs than diesel. No sort of alchemy takes place to increase the energy content.
Depending on how it's introduced to the cylinder, there are likely only two main effects it could have.... If introduced with the air charge, it is going to really cool that down due to heat of expansion and allow for a denser air charge to be fed into the cylinder...in a way, this would be like getting additional boost from the turbo. If introduced with the fuel through the injectors, it would probably help with atomization. Packing more air into the cylinder is probalby the bigger bang for your buck though.