found this on google-- hope it helps

So, a small thread going here previously about whether or not you can get
smoke out of a tuned pipe. Despite the naysayers - YOU CAN! Here's my
setup:

A Supertiger .61 with ST Tuned pipe, 12x6 prop (this is not a long stroke
engine!), 10% fuel. Pressure tap on the crankcase, with a check valve,
going to the smoke tank. Du-Bro shutoff valve. 18" of brass tubing
wrapped around the cylinder head (not obstructing any cooling fins), and
then another 36" of tubing wrapped around the exhaust header, as close to
the exhaust port as possible. The header tubing has been wrapped with
flame resistant cloth, which is originally from a pad sold in hardware
stores to protect areas from torch burns while soldering water pipe. The
insulation is used to keep heat in, and wind chill off. The smoke tap is
about 1" from the exhaust port. My ST header had cooling fins on it, which
I ground off to make room for the tubing. Smoke trail is not as fantastic
as that previously produced using my YS 120, but is still very acceptable.
Clearly visible, good hang time, produces enough that I can pull VERY large
loops and complete the smoke circle. Residual heat is good for smoke
throughout a stall turn, if I keep the power off for a minimum of time. No
flameouts at idle. I do loose a few hundred rpm with smoke on. Unsure
whether this is due to the change in crankcase pressure, or blow back of
fluid into the cylinder. 1 gal. of Bennet's Best smoke oil use, no sign of
problems when I pulled the head to check. No, I wouldn't use this system
on a YS or any engine with silicon parts, but I have no reason to believe
it wouldn't work on most other 61 piped installations. Consumption is 16
oz. in about 10 min.
--
Ted Sander
University of Minn.
**[email protected]**