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  #1  
Old 05-31-2020, 04:22 PM
gossend gossend is offline
 
Join Date: Dec 2011
Location: Georgetown, Texas
Posts: 175
Question Temperature needed for smoke oil??

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
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Flying: EAB RV-12 with Aeromomentum AM15-HP engine
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  #2  
Old 05-31-2020, 04:57 PM
RV6_flyer's Avatar
RV6_flyer RV6_flyer is offline
 
Join Date: Jan 2005
Location: NC25
Posts: 3,430
Default

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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Gary A. Sobek
NC25 RV-6
Flying
3,400+ hours
Where is N157GS
Building RV-8 S/N: 80012

To most people, the sky is the limit.
To those who love aviation, the sky is home.

Last edited by RV6_flyer : 05-31-2020 at 08:15 PM. Reason: spelling
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  #3  
Old 05-31-2020, 05:00 PM
gossend gossend is offline
 
Join Date: Dec 2011
Location: Georgetown, Texas
Posts: 175
Default ....do you be an engineer??

great response - thanks!
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Dick Gossen
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Flying: EAB RV-12 with Aeromomentum AM15-HP engine
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  #4  
Old 05-31-2020, 08:14 PM
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RV6_flyer RV6_flyer is offline
 
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Location: NC25
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Quote:
Originally Posted by gossend View Post
great response - thanks!
I am a RETIRED engineer.
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Gary A. Sobek
NC25 RV-6
Flying
3,400+ hours
Where is N157GS
Building RV-8 S/N: 80012

To most people, the sky is the limit.
To those who love aviation, the sky is home.
Reply With Quote
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