Tracy's EFI system uses manifold pressure as a key
 sensor when setting the mixture. The trouble is:
 manifold pressure where? There is no standardization
 on the best place for intake manifolds to date. All sorts
 of different home made intake manifolds have been built
 to date.

 The second problem is no two people put the manifold
 pressure tap in the same place.

 The third problem is (I think) because as far as I know
 Tracy has not told us **** WHEN **** he samples the manifold
 pressure. The sensor only responds in one one thousands
 of a second. AKA 1 millisecond. It could be at any e-shaft
 angle. What goes on in an intake manifold is like a cross
 between a hurricane and a tornado. Air is bouncing around
 in there like bowling balls in a cement mixture.

 My theory is if the pressure is always measured
 in the same common place it is possible to compare
 mixture maps from different rotary engines to make it a lot
 easier to tune your engine. Some people have
 spent months fooling around trying to get
 the Mazda rotary engine tuned using Tracy's EFI system.

 IMHO the best place to measure the manifold
 pressure is just inside the intake section
 of the engine. That is the apex seal oil metering
 holes which almost nobody uses for oiling
 the apex seals. The vast majority of people
 mix the oil with the fuel. The bottom line is:
 how much air is actually getting in there?

 If somebody is using the apex seal oil metering holes
 to measure the manifold pressure please send me your
 mixture map. Hopefully we can use that as a starting
 point for other people using the apex seal oil
 metering holes.

 Mark Suspinski reported amazing results using
 these pressure tap locations. Tee both of them
 together.

 Paul Lamar




Tracy's EFI like any good aircraft fuel system has a lean-rich knob.
MAP isn't a "how much air is going in there" it's more of a "how much
load are we under"
A temperature corrected MAF is a "how much air is going in there" sensor.
imo, MAP/MAF neither eliminates lean-rich knob unless you have an O2
sensor and don't run AvGas ( but maybe soon... Unleaded AvGas) If you
didn't know, leaded gas will foul an O2 sensor.

BrianG
Iowa

Since the manifold pressure is measured downstream of the throttle
it is all about how much air is getting in there. No O2 sensor.
No mass airflow sensor. Throttle opening with a prop is proportional
to load.

Paul Lamar