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Well, I'm pretty sure it's not a burnt valve.
:-)
In the early tuning stages I was all over the
engine with starting fluid, soapy water, you name it, looking for vacuum leaks.
Never found a thing. Timing is set per Tracy's manual.
Odd thing is the lack of consistency. Most of the
time it runs great. I think if there was a vacuum leak it would be more
consistent.
Acts to me like there is something just a little
off in the tuning. Get everything in just the right (wrong) condition and
it sets up a resonance. Most of the time this doesnt happen. Changing
mixture kills the resonance and its fine after that.
Mike Wills
RV-4 N144MW
----- Original Message -----
Sent: Friday, June 20, 2008 8:56 PM
Subject: [FlyRotary] Re: The SAGA
continues; More checking basics and development progress
I hate to say it Mike, but in a recip, that's a sure
sign of a burnt valve or a major vacuum leak. Maybe in this case,
there's a leak in your intake? A bad gasket or loose bolt could do
it. Timing is a possibility for sure.
Greg Ward
Lancair 20B N178RG in Progress
----- Original Message -----
Sent: Friday, June 20, 2008 8:33
PM
Subject: [FlyRotary] Re: The SAGA
continues; More checking basics and development progress
I too still have intermittent surging issues
that havent been fully conquered. Doesnt happen all the time. Always in the
2000 - 3000 RPM range. Usually happens when I'm taxiing and back off the
throttle. In my case the A/F reading is useless. The engine surges
rhythmically at about a 1Hz rate with RPMs varying several hundred, MAP
varying from high to low (hard to pin down exact numbers - its moving around
too much), and the A/F bouncing back and forth from the rich stop to the
lean stop. Fiddling with mixture always stops it, but its a little
disconcerting (and embarassing) when it happens (usually as I'm taxiing away
from the crowd at the local EAA chapter while everyone is watching). For a
while I thought adding some capacity to the MAP sensing line (Dave Leonard's
suggestion) had cured it, but not entirely. I'll need to get this
figured out before it flies. Could be a real problem if it happens on short
final.
I occasionally have a pretty good backfire at
the secondary staging point. The operational solution seems to be to not
linger in the area - just advance the throttle or retard it right on through
and it seems to be OK. Advancing the throttle too slowly almost
guarantees a big pop! I'm told it's particularly impressive after
dark!
I havent worked on the tuning in months while
I've been tweaking other little issues in prep for my DAR inspection. Just
about ready to get back to it. I'm sure i'll get it more or less figured out
eventually.
Mike Wills
RV-4 N144MW
----- Original Message -----
Sent: Friday, June 20, 2008 7:06
PM
Subject: [FlyRotary] Re: The SAGA
continues; More checking basics and development progress
Chris,
As you've probably read from the archives
surging is usually caused by an overly lean air-fuel ratio. What is
your A/F reading during the surging?
Mark S.
On Fri, Jun 20, 2008 at 8:41 PM, Christopher Barber
< CBarber@texasattorney.net>
wrote:
Well, to continue the saga, I have not run
the new 13b much since I got it running a few weeks ago due to the EM2
not showing oil pressure as it should. It was giving me erratic
readings like -1, -3 etc. I hand propped the engine before I ran
it and oil pumped through the system fine....much onto the hangar
floor...alas, the sacrifices for certainty ;-). Also, during my
short runs everything heated up in the oil system evenly and the oil
temp stayed pretty much in line with coolant temp. BUT, since I
was not sure if this was a gage/sender issue or an actual oil system
problem I was very cautious about my few short engine runs.
Well, today while dreading the idea of
dropping my pan, I happened across an extra oil pressure sender (still
in the package) I happened to have. I had seen it laying around
for a while, but didn't give it much thought until I was thinking about
dropping the pan. Low and behold, The problem was the sender. I am
getting good pressure reading now, along with coolant and oil temp.
Yeah. I am surprised at the temps as they seem to be staying in
check considering the 95 + degree Houston weather.
I am able to start the engine, shut it down
and restart it (something I was not able to do with the old
engine). It is somewhat difficult, but seems to be getting easier
as I continue to tweak things (ie timing). I am trying to do the
various tuning via Tracy's manual. To be honest a lot of the
information in the manual is seemingly abstract until I actually get to
the step and/or problem. So, tonight, I got it to run, and it
seems to run better, but......
I am having a surging problem. It
seems intermittent, but it just may be I have not been setting the
throttle quite the same way as I get use to it all. Also, I have
had the coil C/B pop on me several times now....it seems as if this is
when the engine is near or at idle. I have not had a chance to
look into this as of yet. Also, I have gotten a number of
horrendously loud/powerful backfires. Not sure what changes as the
engine may have run fine. It backfires when attempting to
start. I wait a few minutes and it may then start. Gee,
isn't inconsistent crap fun <g>
I just did a search of the archives on the
surging issue, but have just started reading the 105 post on the
topic. Seems our own Mr. Slade had the same problem back in the
day <g>.
Well, it is the middle of my work week and
I gotta turn in soon, but I wanted to share that it seems as if actual
progress is being made (hmmmm, wonder what will screw this positive
statement up<g>) as the Saga continues.
All the best,
Chris
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