I am building a Midwest Citabria and have begun the powerplant phase. I intend to use a Saito .91 and I would like to use a TME Simple Smoke II with it. I am also looking into getting a new radio too because my older radios I don't trust as much as I used to. So I have the following questions.

1. With a Saito .91 can anyone recommend a smoke muffler that will produce the best heat?

2. How do you mix the TME Simple Smoke II with the throttle (smoke off < 1/2 throttle)? And if the module can't do it, which radios can? (I would like to stick with JR or Airtronics 5 channels)

3. What size hopper tank would be necassary for 5-10 minutes of smoke?

Thanks for your help guys.

Brandon

The stock muffler will produce good smoke if you wrap the header with a few turns of copper tube.

The "metering valve" in the TME kit is junk. it just squeezes the oil line to restrict flow. You are better off putting a remote needle in the line. A needle will allow you to make more accurate adjustments to the flow at the low volumn needed for the .91. (the pump system is able to feed enough oil for a 2 ci gasoline engine with ease.)

My best results came when I mounted a needle valve from a CL airplane engine into a tuned pipe near the header. The needle injecting the oil in the middle of the exhaust stream at the high velocity section is ideal. For the stock muyffler you would put a second pressure tap as close tot he header pipe as possible. (with the heavy guage header that ships with the O.S. .91 FS you can tap the header and inject there.)


You size the smoke oil tank to match the size of your fuel tank and you'll have smoke for about 1/3 of your flight. If using the stock muffler, you set the smoke oil flow for maximum smoke at 1/2 throttle If you set the oil flow higher the increased backpressure can be a BIG problem. Start from needle closed an open until you don't get increased smoke at 1/2 throttle then close 1/8 turn.

Smoke being n below 1/2 throttle is not a serious problem especially with a 4-stroke. the oil won't back up int the cylinder when the engine has low backpressure. You just end up dribbling the un-vaporized oil out the exhaust.

I didn't mix the smoke to the throttle. I used the channel 5 gear switch to turn the pump on and off. (no retracts on the airplane.) I'm not sure how the TME pump controller would react to just Y connecting to the throttle... but that MIGHT do what you want.

You will probably want to run a 5 cell battery to power the pump. At high throttle the pump can have problems ovrecoming muffler pressure using a 4 cell pack.

You will be adding close to 1 lb (maybe more with a large smoke oil tank..) to the aircraft's takeoff weight by adding the smoke system.

"If using the stock muffler, you set the smoke oil flow for maximum smoke at 1/2 throttle If you set the oil flow higher the increased backpressure can be a BIG problem. Start from needle closed an open until you don't get increased smoke at 1/2 throttle then close 1/8 turn. " - FHHuber

Can you explain this in a little more detail? I assume what you're saying is run it up to 1/2 throttle and then increase the oil flow until you don't notice an increase in smoke and then back it off 1/8 of a turn. I guess what I'm not following is why wouldn't you do this at full throttle? And second, I'm not sure I followed the line about the increased back pressure. Can you explain? Thanks.

Maximum smoke at full thrttle can create enough backpressure to reduce power by over 30%. The oil expanding presurizes the muffler more than the exhaust gases leaving the combustion chamber.

Even the setting for max moke at 50% throttle will give a noticeable power loss. Its tollerable at that level. If you are used to being able to do torque rolls and set for max smoke at full throttle... you will not be able to torque roll at full throttle.

What about preheating? I've heard that preheating is where it's at when it comes to successful smoke. How is preheating done? Should the smoke oil be routed through the copper tubing wrapped around the header on the muffler?

Try it without preheating first. If you don't need it, why do it?

But if you find it's helpful, I recommend wrapping the copper tubing around the engine's cylinder, as opposed to the header or muffler, after all, you NEED the heat there, so why rob your muffler of the heat it needs by taking some of that heat away? (Remember, by heating the oil by wrapping the line around the muffler, as the muffler heats the oil, the oil cools the muffler. So you are effectively robbing Peter to pay Paul).