I have new G38 that I want to make smoke. I'm currently using the tap in the crankcase for pressure and a Dubro pinch valve. I have the feed to the muffler going in both sides from a tee. The trouble is with the smoke on you can't tell it is doing much. But when you squeeze the tank and for more oil in it starts to smoke a little, but not like I want. I have made a set of injectors out of brass tubing that I have not tried yet, on a tip from another pilot. I'm wondering if I should can the current set up and go for a pump?

You will need a pump.

I used the Perry Smoke pump on a Q42 and it worked ok. The perry kit came with a needle valve to adjust the flow. I found I needed to just remove the valve as flow was maxed out.

It might work with a check valve on the lines. You might need one on each line to the tank. But I would not want to bleed off any flow from the crankcase as it may effect the idle mixture.

The check valve on the exhaust side will pevent it from blowing the oil back into the tank.

The check valve on the crank pressure line will change the pressure/vacuum pulses into a one way flow.

On my new GP Extra/ZDZ-40, I did not want to drill a hole in the case of my new ZDZ. I opted for a windshield washer pump and a electronic speed control. It still needed to have a check valve to prevent the exhaust pressure from blowing out the pump prime while the smoke was off.

How far from the exhaust did you put the check valve?

I had about 2" of neoprane tubing to the valve. Then rest was Tygon.

TME smoke system, Slimline smoke muffler.

Thats what I'm aiming for!!! Guess I'll check on buying a system then. What size tank are you using for the smoke oil?

That particular one had a 20oz. tank. I usually landed with smoke left. One of the secrets of good smoke is using just enough fluid to produce good smoke without pumping unburnt smoke fluid down the bottom of your plane. Too much actually cools the muffler which lessens the smoke. It's kind of a trial and error process to get it right. There should be very little residue on the bottom.

Aaron,
I ran the pinch valve system for years on the Big Hots and made great smoke with it. You said you got smoke when you squeezed the tank? That leads me to think that you don't have enough tank pressure. Do you have a check valve between your crankcase line and your tank? I know it sounds like a dumb question but we have to cover the basics,right? This system will make a lot of pressure so make sure your hoses are properly secured so you don't end up with a plane full of smoke fluid. You may also find it helpful to install a needle valve on the pressure line to the muffler to make sure you don't "flood" the muffler and cool it too much. I would be glad to help you sort this out if you need me to.
Rusty

I tried the valve on the pressure tap side and it didn't seem to make a lot of difference. I don't guess the engine being pretty new has anything to do with it. Seems like if the rings weren't seated yet I'd have more pressure. I was going to rig up a windshield washer motor to try see if it would help the supply.

better be careful with those windshield washer motors. They aren't made for RC and can cause radio interference!

Okay, I reinstalled the one-way valve in the pressure tap, replaced the supply line with the largest size lines I could get, and added nozzles to the muffler. Made the nozzles from 1/16 brass tubing and silver soldered them in the nipples. I drilled 4 .055" in the tube and soldered the ends shut. Here is what she'll do now.