HAPPY Instrumentation on Jabiru 3300 (so far)


Subject:    HAPPY Instrumentation on Jabiru 3300 (so far)
From:    Fiveonepw@aol.com
Date:    Mon Oct 06 - 9:34 PM
-ain't breakin' out the Champagne yet, but here is current synopsis:

Further analysis determines that due to FWF packaging considerations  the VDO 
fuel pressure sender provided by GRT with the EIS package is located  about 
1" from the right magneto harness and about 3" from the automotive-style  
distributor.  Suspicion is that arcing between the rotor and distributor  cap is

impressing emf pulses on the sender somehow.  Removing the  2 wires to the 
sender result in zero spikes on the EGT/CHT traces and any  other phantom alarms.

Hmmm...  Victim identified?  Fuel hoses to  sender are lengthened and an 
extension for the electrical connections is  fabricated from 22AWG wire using 
faston connectors- this "pigtail" is about 12"  in length with the wires tightly

twisted.  Idea is to experiment with  sender location by manually moving it 
around in the engine compartment with  engine running and review effects on EGT

trace spikes.  

On initial engine start, trace spikes are completely gone, regardless of  
sender positioning or orientation between the engine and firewall.   Locating 
sender in close proximity to either distributor or magneto results  in clean 
spike-free EGT traces.  Sender is re-mounted to engine mount  about 2" farther

away from previous location to magneto harness with pigtail  still installed. 

EIS is fat, dumb & happy with no phantom alarms, no  spikes present on EGT or 
CHT traces.

Ya think I'd be shickled titless by this, but I can't explain WHY,  dammit...

Measured resistance using a Fluke multimeter indicates .2 ohms on each lead  
of extension.  Here's the question:  Is it the additional resistance  in the 
connections to the sender (length of extension), or the fact that they  are 
tightly twisted (about 10 turns per inch) that resolved (band-aided?) this  issue?

"Problem" "appears" to be solved, but without knowing why.   Serendipity?  I 
don't buy it.  Awaiting knowledgeable insights or  explanations...

A big THANKS! for all of those who have chimed in with their thoughts and  
suggestions...

Mark


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