Scott:

Reducing MP 1" from WOT will not give proper FF change readings as the fuel enrichment feature causes a larger drop in FF than MP as the throttle is first retarded. This results in a a leaning effect and the mixture is not staying the same. The drop in FF as RPM is retarded is a much more accurate measure as the the change in the engine driven fuel pump allows the mixture to remain fairly constant.

Walter


On Dec 27, 2004, at 5:39 PM, Sky2high@aol.com wrote:


Matt,
 
Thanks for the data.
 
1. What was the MAP and Baro readings taken before engine start? 
 
2.  How do you explain the magic of TAS in trial 3?
 
Interestingly enough, 4 people have used this to recognize problems with the "snubber valve" on the engine side of the firewall for VM systems.  Trial 1 and 2 are consistent with respect to all variables, change in MAP, fuel flow and airspeed.  A good way to test this particular instrumentation is, at a reasonable cruise altitude and WOT, reduce the MAP by 1" and record the change in fuel flow and speed - after returning to WOT, reduce the RPM by 100 and record the change in fuel flow and airspeed.  These numbers should be within 5-10% of each other.  If not, something is wrong.
 
Scott Krueger AKA Grayhawk
N92EX IO320 Aurora, IL (KARR)