John,
I installed one diode and found the smoke output to be much improved. Would I be correct in saying the the voltage dropped from 18 volts to 9 volts with the single diode? I assume with each additional diode it would drop an additional .7 volts. I found the output to be good on my test track with an LW transformer. When I switched to the layout, where I use ZW-L transformers, I found the smoke output to be a little more than on the LW at the test bench. Is the ZW-L that much more powerful that I would notice stronger smoke output? What is the optimal voltage for the MTH smoke unit? I may add another diode.