Sorry Dan, Just like I can't argue with the results we got at Barrett on my engine (Skewed, not skewed, who knows, we introduced a questionable variable that we'll never know for sure), Also can't argue with the results that came directly From Titan's Dyno... (And since I don't work for any of these companies I can post 'em
I mis-place the fuel burn chart...
Since you brought it up.....
Robert's "explanation" was included as a
courtesy. He proposed it the morning after the tests, without the benefit of the complete dyno record.
Both you and I have a copy of that record. It is available to anyone, a matter of good journalism.
As stated in the article, the theory is, fundamentally, fuel supplied to the injectors with a high vapor content. However, there doesn't seem to be any evidence in the dyno record, notably exhaust gas temperatures.
As most are aware, EGT indicates what fuel-air ratio was actually delivered to the cylinder. From the record, here are the individual cylinder EGTs for the maximum power runs with the two delivery systems:
The power curve response to mixture variation is quite flat in the best power region; regular readers have seen it on a number of Lycoming charts presented in other threads. EGT deltas this small would not indicate a significant mixture variation, nor result in the 4% horsepower reduction (276 HP vs 265 HP, corrected) seen here.
Here's an example (Lycoming dyno, WOT/2700, angle valve 360). The EGT range for best power extends about 90F, and as much as 200 with small loss:
Keep in mind that the bubble argument is based on the engine being fed vapor rather than liquid fuel during the finite injector open time. If the system was regulating that open time based only on the base speed-density calculation, then the system would supply a lean mixture. The EGTs say that didn't happen. Even if it was happening, it wouldn't have mattered; both the Bendix and EFii runs were made
with operator control of mixture. Mr. Barrett held RPM with with the water brake, advanced to WOT, then dialed the mixture to find max torque.
There are other good arguments, but let's get to the point. Any given day and any given engine might net slightly different results. The key word (and bottom line here) is
slightly. So far, the range of published max HP deltas between conventional and EFii is (a) down 4%, (b) up 1% (the 360 posted above), and (c) up 2% (R409). Prior to your 540, Robert had never made a dyno run with the system installed on a Lycoming.