From: <daveleonard@cox.net>
To: flyrotary@lancaironline.net
CC: Engine Surging Problems@cox.net
Subject: 
Date: Wed, 5 May 2004 14:51:02 -0400
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Hi all,  I spent a couple of hours the other day gathering clues to my ro=
ugh running problems.  First the facts, then my theories.  I=92m looking =
for any input.

Description of the problem:  The problem is really more of a surging rath=
er than rough running.  At less than about 2200 RPM the engine will begin=
 to surge.   It gets worse the more I lower the RPM.  Each time I make a =
change to the throttle setting I adjust the manual mixture knob to find t=
he leanest point where the engine does not surge.  I have Tracy=92s stand=
ard mixture monitor.

Each cycle of the surging takes a little over 1 sec.  RPM surges buy 300-=
400 RPM.  Manifold pressure fluctuates by 2-3 inches, and the mixture mon=
itor fluctuates the full range of its scale.

At this point I can manually increase the mixture up to the first red bar=
=2E  This is over rich and the engine runs a little rough and the RPM dro=
ps a couple of hundred.  It will smoke a little more, but at least the su=
rging stops.  If I lean down into the amber area the surging starts again=
=2E  The surging gets very bad if I lean down into the middle of the scal=
e.  This is what happens around 2000 RPM and 15in MAP.

If I further close the throttle, the surging is similar but to a great sc=
ale.  In order to stop the surging I have to increase the mixture beyond =
the top of the scale.  Here it will be running rough from an overly rich =
condition but still surging a little too.   Down around 1000 RPM it is st=
ill surging but so rich it will barely run.  Beyond that point, either th=
e richness kills the engine, or the surging kills the engine.

Assorted clues:  Several additional clues may shed some light on the situ=
ation.  Mostly centering around the Fuel Pump.  I have noticed that if th=
e engine is running rough from being too rich (wont run leaner because of=
 the surging) and I turn the engine off (by shutting off the fuel pump) t=
he will run perfectly smoothly for several seconds before it stops.  In o=
ther words, as the fuel pressure drops below 10 psi the mixture is lean e=
nough for the engine to run well and it purrs for a couple of seconds wit=
hout surging until the fuel pressure reaches zero.

In an attempt to track this down more I ran a couple of experiments.  I n=
ormally run 45 psi of fuel pressure.  I have the TWM adjustable with mani=
fold compensation.  First I turned down the fuel pressure to 40 ( as low =
as mine goes) and possibly saw a slight improvement.  Then I turned up th=
e fuel pressure to 55psi and the surging definitely got worse.  The cycle=
 time was faster, it was harder to get it to go away by enriching and the=
 problem continued up to about 2800 RPM. =


So it wants a lower fuel pressure.  But why?  More experiments:
1.	Did my best to match the mixture between the two rotors, but with the =
turbo I only have a single common EGT.  I noticed a slight improvement.
2.	Unplugged the turbo air inlet (engine now running n.a.) =96 no change.=

3.	Disconnected the MAP line from the fuel pressure regulator =96 no chan=
ge.
4.	Had my EGR passages welded closed (in case they were leaking) =96 no c=
hange.
5.	Tried assorted arrangements of where to sample MAP  -  no change.
6.	Run engine on either the primary injectors (stock turbo in the engine =
block) or the 52 lb secondaries in the Throttle body =96 no change.
7.	Run on leading or trailing coils. =96 no change.
8.	adjust timing with light =96 no change.

Other findings.  I had previously that turning off my alternator caused m=
y engine to stop.  I turns out that turning off the alternator just makes=
 the mixture leaner.  The effect is smaller if running on only one set of=
 coils, and exaggerated if there is a high amp load.  But this situation =
is always fixed simply by enriching the mixture (about 110 deg turn of th=
e knob).  The buss voltage =


Summary:  So it seems that installation is particularly sensitive to chan=
ges in fuel pressure.  My next  step will probably be to buy a lower pres=
sure fuel regulator.  The thought is that maybe running 35 PSI will stabi=
lize everything (i.e. maybe with only having to hold 35 psi the pump will=
 no be as affected by changes in fuel flow or system voltage.  I will hav=
e my injectors checked and cleaned although I don=92t imagine that will h=
elp.

Any other thoughts?  =


Thanks ahead of time for any input I may get.

Dave Leonard