ORIGINAL: retransit

To further clarify the slobber line from the crankcase. If you connect your pressure tap from the muffler to the slobber line you will be pressurizing it. The purpose of the slobber line is to release blow-by gasses from the crankcase, created when the piston allows pressure to get by it during the power cycle. Any presurization of this line defeats its purpose. That tap and line gives the unburned lube oil a place to go since our 4-stroke Saitos (and a lot of others) do not have a dedicated sump as in automobile engines. As a matter of fact, auto engines have a form of slobber line and it is called a positive crankcase ventilation line. The EPA has not allowed this to vent to atmosphere since the 60's and hence is returned to the induction system to be re-burned. Remember the old crankcase vents? Nothing but a hogs hair cap on the crankcase vent line.

If you place a crimp on a straight exhaust pipe, this is a form of back pressure. This helps with pressurizing the tap for the fuel tank. On your car you may have a restrictive exhaust system which will also create back pressure. Did you ever hear 'glass pack mufflers on a by-gone hot rod? You can hear the result of back pressure when the individual takes his foot off the accelerator. The exhaust note pops as it decelerates.

The pressure tap on the muffler is just that, a pressure line. It allows you to plumb a line to the fuel tank to keep a slight pressure on the fluid in the tank for even-running with a set high speed needle. With a pressure line to the tank, I find very little reason to fiddle with the high speed needle here in Florida. I see some guys in my club forever toying with needle settings on their aircraft. They are the ones with the most engine problems and I just shake my head.

Bob