Running LPG injection on a diesel

Question:

Hi Andrew, someone asked you a couple of issues back about running LPG injection on a diesel. 
I have started doing a bit more reading on the subject but I can only ever find the positives about it, not what to look out for or any negatives. I like the idea of running LPG for the fuel economy and power benefits, but I believe in the saying ‘no such thing as a free lunch’. 
No doubt you’ve seen a few of these systems come through your work, so does anything typically go wrong with such a setup? 

Brendan Lyons,
Albion Park Rail, NSW

Answer:

Hi Brendan,
I’m still waiting to see a system that excites me pass my dyno test but so far what I have seen on our dyno when I start putting layers of test gear and exhaust gas testers on is ‘no free lunch’. Meaning power is gained but the emissions are richer. Turn it off- power drops and emissions lean off (which is normal for a Diesel). It’s probably not the area to begin the debate here in a ‘tech help’ page but I am waiting to see a system that, let’s say, generates more power with no AFR (Air Fuel Ratio) change. You must remember that the advertising says that it burns the Diesel more complete generating basically free power. 
Unfortunately I have seen no better than what you could gain by adjusting the existing fuel loadings for a similar AFR change to Power gained ratio. Sure there are a few systems out there but without knowledge as to how the power was gained it appears to be ok up front. As far as reliability of these setups I would have to say they appear reliable if a little complex though and remember you end up with a issue of where do I put the LPG tank’ safely for off-road clearance.