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Temperature needed for smoke oil??

gossend

Well Known Member
I've got an Aeromomentum AM15 HP on my RV-12 and want to add smoke just for fun. How far down the exhaust path can I go before the exhaust is too cool? I have a four-into-one tuned exhaust followed by a small glass-pac muffler - then an 18" tailpipe. I can't put the nozzle in any of the tuned pipes because there's an O2 sensor after the 4>1. If I put it after that, but before the muffler, I'll gunk up the glass-pac. So am I ok after the muffler?? That would leave only the 18" tailpipe to develop the smoke.
At what temp does the smoke oil smoke, anyway??
Help ;)
 
I removed and sold my smoke system but will comment on my experience.

Most smoke system sellers will tell you to put the injection pretty close to the exhaust port on the engine or where two or more runs from the exhaust valve comes together.

I originally installed one injection nozzle after the intersection of the #2 and #4 exhaust pipes coming together.

One injection nozzle on a 4 cylinder engine with only two cylinder exhaust created puffs. Not a big deal 75 or 100' behind the airplane but one could tell at less than 50'.

I added a 2nd injector BUT because I had a heat muff on that side, I added the inject port AFT of the heat muff or less than a foot from the end of the exhaust pipe. No difference in smoke.

When I replaced cylinders at 2,200 hours, I also installed a new exhaust system. I put both smoke injectors less than one foot from the end of the exhaust pipes. No difference in smoke output than there was before the change. Both injector ports were a few inches forward of the firewall in the top of the two exhaust pipes.

In other words, the difference in exhaust gas temperature for smoke oil vaporization is not much difference between the engine exhaust port and the end of the normal Vetterman crossover exhaust system.

Now it would be nice to instrument an exhaust system every one inch or so to get real data to actually find out how much exhaust heat is lost from the exhaust port to the exhaust pipe end. Would even be great to just use a 2nd EGT probe in the same run near the end of the exhaust pipe.

Typically the EPA recommends vaporization as the way to dispose of the smoke oil we use. Injecting it into the exhaust does the vaporization. The temperature that the oil requires to vaporize is lower than the exhaust gas temperature. Complete combustion of the air / fuel change leaves little oxygen to start a fire in the exhaust from the oil injected.
 
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