Frequently asked questions

Q-    My muffler is already tapped for smoke can I use the existing port?

A-    Many mufflers come pre tapped with smoke ports from the factory. Typical smoke nipples inject a stream of oil straight through the fitting. BDS atomizing nozzles spray at roughly a 45° angle to the centerline of the nozzle. For best smoke performance, a new tapped hole positioned to direct the spray of smoke fluid across the exhaust port window opening. Pay careful attention to not spray up and into the engine cylinder or onto the piston face.  This will produce the best results for your smoke system. 

** Be mindful of internal muffler baffles or muffler bolt guide tubes that could be obstructing the spray path.  

Q-    Do I really need a check valve?

A-     A check valve will prevent siphoning of smoke fluid through your pump which can lead to smoke run-on when the smoke pump is switched OFF.  A delay or lag time of a few seconds can then be experienced when switching the smoke ON again as your re-priming the line.  Positioning a check valve just before the smoke nozzle will eliminate the lag time and provide more positive smoke switching at precise timing during your routine.

Q-     I’m setting up a twin cylinder setup and plumbing diagram shows multiple check valves. Why?

A-     A single check valve before a tee fitting or no check valve at all will allow venting through the straight portion of the tee fitting leading to each nozzle. Uneven exhaust back pressure or compression pressure between cylinders can cause a pressure differential or a venting action to force smoke fluid to the weaker cylinder. This can result in smoke run-on from one muffler or a loss of smoke line prime meaning slow smoke ON switching.  Some smoke pumps advertise no check valve required-  This is true for keeping the pump head primed, but this does not account for the inherent venting action of multiple nozzles when fed from a single supply line and tee fitting from the pump output.  

** Equal lengths of smoke tubing after the tee fitting & through the check valves,  continuing to  the smoke nozzles is also very important in maintaining equal back pressure.

Q-     How much and what type of tubing do I need?

A-     The last 6"-8" of tubing leading  up to the muffler should be F-5500 High Temp tubing.  This will give the best protection from intense muffler heat. Check valves are unaffected by heat and can be installed as close to the nozzle as possible. This is more important when multiple nozzles are being used.  The check valve can be installed upstream 6"-8" on a single cylinder application and creates the transition for F-4040 tubing to F-5500 tubing.

F-5500 is also excellent for use inside fuel and smoke oil tanks and will not harden or get brittle even after several flying seasons.   It is always a good practice to inspect the entire fuel & smoke plumbing systems at the end of the flying season.

The balance of the plumbing and vent  system can be standard F-4040 tubing.

Q-     Do nozzles require cleaning?  

A-      If running a rich fuel  premix ratio nozzles can occasionally carbon up.  This can be more common on 4 stroke engines.  Most nozzles can run for years without issues. A good practice is to remove and inspect smoke nozzles at the end of a flying season just as you would inspect or exchange fuel lines. If nozzles should require cleaning a simple soak in a carb dip such as barrymans carb dip and a scrub with a fine wire stainless steel or brass brush works well. A pipe cleaner and acetone can be used to clean the nozzle interior followed by a careful backflush of compressed air.  More aggressive cleaning risks damaging the nozzle and spray pattern. Please never pick or poke anything into the tip of your nozzle.  The tip can be damaged and spray pattern compromised. 

Q-     How do I choose the right nozzle material?

A-     All nozzles preform the same regardless of nozzle material.  Choose the features that best suit your application.

Stainless Steel features

  • High corrosion resistance
  • Proprietary surface & heat treating process

Titanium features

  • Lighter weight than SST
  • Grade 2 Titanium alloy (for bragging rights)

Aluminum features

  • Lightest weight nozzle
  • Matched thermal expansion rate as stock Al mufflers

Brass nozzle features

  • Extended depth adjustment
  • Remote connection for hard to access setups
  • Ability to incorporate copper tubing as an integrated preheater coil