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Smoke System Effects On Engine

Old 03-06-2007, 01:58 AM
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Rod Bender
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Default Smoke System Effects On Engine

Hey Guys,

I am wanting to put a smoke system on one of my new 1/4 scales, but had some input from a club member that a smoke system raises the engines temp? Stated, he said by running a smoke system on an engine reduces the heat of the muffler from the oil, therefore the engine temps rise because the muffler cannot transfer the heat from it, or not as much. Anyone know\have the scoop on this? I'd hate to damage my new engines just for some smoke trails ................. Thanks, Greg
Old 03-06-2007, 07:21 AM
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MILDBILL-RCU
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Default RE: Smoke System Effects On Engine

Smoke systems will NOT hurt or damage your engine. the cooling effect to the muffler from oil being heated up will not have any effect to the burning of fuel inside the engine, which is what dictate's the running temp of the engine. Run it lean, & she'll be hot. Run it rich, & she'll be cooler. SMOKE-UM IF YOU GOT-UM. & enjoy.
Old 03-06-2007, 07:25 AM
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MinnFlyer
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Default RE: Smoke System Effects On Engine

Ditto
Old 03-06-2007, 11:41 AM
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KC36330
 
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Default RE: Smoke System Effects On Engine

i loose about 100 RPM when i hit full smoke on my 50cc engines but the temp doent change enough to notice.

kc
Old 03-06-2007, 04:33 PM
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khodges
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Default RE: Smoke System Effects On Engine

But you CAN run the smoke oil so rich it will cool the muffler below the temperature required to ignite the smoke oil. The engine however is still producing heat from its combustion so it isn't going to cool the cylinder/head.
Old 03-06-2007, 05:14 PM
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Geistware
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Default RE: Smoke System Effects On Engine

Rod,
I don't have smoke on my planes.
I do understand the properties of thermal conductivity of metals.
If you cool the muffler, this reduced temperature will reduce the temperature of any hotter metals touching the muffler.
Now what also will happen, the oil will reduce the volume available for expansion in the muffler.
This will not increase the engine temperature, but it should reduce the RPM of the motor a small amount.

Now if you could force enough oil into the muffler to restrict the exhaust flow, then the engine will run bad.
It may also draw smoke oil into the combustion chamber following the exhaust pulse.
I would not consider the above as pertinent to your concern.
Just a theoretical possibility

ORIGINAL: Rod Bender

Hey Guys,

I am wanting to put a smoke system on one of my new 1/4 scales, but had some input from a club member that a smoke system raises the engines temp? Stated, he said by running a smoke system on an engine reduces the heat of the muffler from the oil, therefore the engine temps rise because the muffler cannot transfer the heat from it, or not as much. Anyone know\have the scoop on this? I'd hate to damage my new engines just for some smoke trails ................. Thanks, Greg
Old 03-06-2007, 09:23 PM
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Default RE: Smoke System Effects On Engine

Yes, the muffler giving off some heat, to heat the oil will cool itself to a point, & that heat transfer from the hotter engine will travel to the now cooler muffler through it contact with the muffler, but the airflow over the engine will pull more heat out of the engine than the cooler muffler will. As far as KC's loss of rpm's, it is due to the mufflers size in relation to the engines size. The oil is being heated & expanding, adding to the total volume of air, (exhaust & smoke) that has to be expelled out the exit. A increase of the exit size of the muffler will help get some of the rpm's back,
Old 03-06-2007, 09:34 PM
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Default RE: Smoke System Effects On Engine

the only way to prevent the minimal loss of RPM when you are injecting smoke oil is to inject it outside the exhaust system (like in a turbine) increasing the exhaust exit size will increase RPM, but it increases it also prior to oil injection and when the smoke is turned on, the RPM drop will still be present, no way to avoid that, the oil injection is changing the back pressure on the engine and reducing chamber volume in the exhaust.

kc
Old 03-06-2007, 09:40 PM
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thewrap
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Default RE: Smoke System Effects On Engine

Well then how do we set up a smoke system. Do we have to run it through the engine or can it just go through a pump and turn into smoke.
I want to put one in corsair and one in my 50CC but have no idea where to start.
Old 03-06-2007, 09:49 PM
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Default RE: Smoke System Effects On Engine

you inject the oil into the exhaust system as close to the exhaust port from the engine as you can. you'll loose a little RPM but it's minimal and you'll never notice it in flight.

kc

EDIT: i reread your post and NO you can't just pump smoke, you pump oil, the oil is heated and vaporized by the heat in the exhaust system, that is what produces the smoke.
Old 03-06-2007, 10:09 PM
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Rod Bender
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Default RE: Smoke System Effects On Engine

Thanks for the comebacks guys,

I'm going to be running a Moki 2.1 with a bisson muffler. Can I use the pressure port on the muffler for my oil injection point, or does it need to be even closer to the engines exhaust port? Just trying to make what I have work ..... Greg
Old 03-06-2007, 10:30 PM
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Default RE: Smoke System Effects On Engine

you can always try it and if it doesn't smoke as much as you'd like you can add an external pre heater by wrapping soft bend brass tubing around the head or exhaust.

kc
Old 03-06-2007, 10:53 PM
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lcyrace
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Default RE: Smoke System Effects On Engine

Glad to see this thread. I just set up a smoke system on my 25% Edge. Using the Sullivan Skywriter pump mixed with the throttle on my DX7. A very wise hobby store owner gave me a few tips...

The smoke is not made by the hot exhaust buring the oil. It is made when the parafin in the smoke oil boils and vaporizes inside the muffler. If you inject the oil too close to the exhaust outlet it will simply blow the unvaporized oil out the muffler. You actually want to inject the oil in a place where it will pool in the muffler and boil away. His theory, not mine but it sounded good and seemed to work for me and makes goobs of smoke.

I do have a problem though. This is on a ST2300 with Bisson pitts muffler. If I am smoking in a hover (1/2 throttle) then go to idle it will deadstick every time. I have my mix setup so it shuts off the oil at about 40% throttle or less. Am I injecting too much oil? I have it set to the lowest possible pump rate at midstick. Should I restrict the flow even more?
Old 03-06-2007, 11:23 PM
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Default RE: Smoke System Effects On Engine

ORIGINAL: lcyrace

If you inject the oil too close to the exhaust outlet it will simply blow the unvaporized oil out the muffler. You actually want to inject the oil in a place where it will pool in the muffler and boil away.
i hate to contradict a LHS owner, God only knows how much great information they give out but...........i inject my smoke oil directly into the muffler where the engine exhaust port enters the muffler and it defiantly doesn't puddle up anywhere in the muffler yet it does a fair job of smoking IMO.

kc

EDIT: my best guess would be your dead sticking is caused by the puddle of smoke oil you have in the muffler


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Old 03-07-2007, 01:02 AM
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Default RE: Smoke System Effects On Engine

You should put the wings on if your going to run the motor.

The wings act as a dampener and smooth out the engine vibrations. It softens the stress on the entire airframe.

Running it like that at higher throttle settings (ANY throttle setting) is hard on the airframe without the wings on there to counteract the engine pulses.
Old 03-07-2007, 01:51 AM
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Rod Bender
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Default RE: Smoke System Effects On Engine

ORIGINAL: lcyrace

I do have a problem though. This is on a ST2300 with Bisson pitts muffler. If I am smoking in a hover (1/2 throttle) then go to idle it will deadstick every time.
The ST2300 is a whole new bag of tricks, having one myself, I know the inherant problems with its carburation issues. Buy a OS 7D carb and be done with it.

KC What kind of smoke you puffin? I like the cloud........................Greg
Old 03-07-2007, 09:01 AM
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Default RE: Smoke System Effects On Engine

For those of you who have not read it, I suggest reading my article on Smoke Systems. It will answer a lot of questions about where to put what:

[link=http://www.rcuniverse.com/magazine/article_display.cfm?article_id=455]Got Smoke?[/link]
Old 03-07-2007, 09:32 AM
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Default RE: Smoke System Effects On Engine

Once again Minn. thanks for the article. I am going to be building a world models super chip with retracts and i think that i will hook up the smoke pump to my retracts. When the retracts are up the smoke is on once you put them down it is off. Just use a Y harness on the retract servo so i can activate it and off we go. I am using a OS Surpass 92 so that should work great.

Flyboy76
Old 03-07-2007, 11:01 AM
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Default RE: Smoke System Effects On Engine

ORIGINAL: Rcpilet

You should put the wings on if your going to run the motor.
it's soft mounted and is only ran minimally with wings/canopy off, no need to drag them out just for the shot of the smoke which is what it was ran for that day.

ORIGINAL: Rod Bender

KC What kind of smoke you puffin? I like the cloud........................Greg
MDW Aviation Smoke Oil


@ Flyboy76

i don't think you'll like the smoke being on the retracts myself. 16oz of smoke oil last about 4-5 min at WOT on my 50cc, flight time is about 15-25 min and i use smoke only to accent maneuvers, if it was on all the time I'd have gear up it would long be dry and pumping air or I'd be doing allot of flying with gear down.

kc
Old 07-06-2007, 11:17 AM
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Default RE: Smoke System Effects On Engine

I know this is an old thread....

Miniflyer, have you ever considered putting some sort of screen material inside the muffler itself.

This would increase the area available for the smoke fluid to boil off while not restricting air flow.

I was thinking about trying this.

Old 07-06-2007, 01:39 PM
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Default RE: Smoke System Effects On Engine

Great minds think alike

I have often though about doing that, or in the case of large mufflers, maybe a piece of steel wool, but no, I haven't tried it.

But like I have said before, ANYTHING might work, so everything is worth trying.
Old 07-06-2007, 11:19 PM
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Default RE: Smoke System Effects On Engine


Ok I ran some tests today...

- Steel wool combusts so it is not suitable.
- Aluminum mesh oxidizes in the exhaust stream which could lead to particles re-entering the engine. Not suitable.
- Steel mesh works better, but quickly becomes brittle and breaks, leading to particles that could foul the engine. Not viable.


Since the idea is to have something within the muffler that absorbs and retains the exhaust heat, but at the same time provides additional surface area for the smoke oil to heat up...

I took a slightly larger volume muffler... I created a spring of tubing coil out of thin copper thermocouple tubing.

I coiled it around a screwdriver and inserted it within the muffler. Once in the muffler I "unwound" the coil to get it to expand.

My thought is that this would be directly in the exhaust stream and would remain quite hot...

I also took 1/4" copper tubing and coiled it around the outside of the muffler, flattening it a bit as I went, then pinched off the ends.


To check this concoction I put the flame from a propane torch into the intake side of the muffler.


The muffler now retains heat for quite a LONG time, far longer than I had expected.


I'm going to try this out on Sunday.




I also found that Bisson now sells small smoke oil injector fittings for about $5.00/ea.

These would work well with the above to create a finer "spray" of smoke oil inside the muffler.


I'll let you know how it works out.

Old 07-07-2007, 07:47 AM
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Default RE: Smoke System Effects On Engine

Cool! Thanks for the results
Old 07-09-2007, 05:41 AM
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Rod Bender
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Default RE: Smoke System Effects On Engine

Great effort and thoughts................. Sounds like you were\are in the R & D area of product design?

Keep us posted

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