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01-06-2014, 09:04 AM
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Join Date: Nov 2013
Location: Prescott, AZ
Posts: 1,614
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Light Speed ignition behavior
Still learning here... 40 years on mags and now in the 9 with an electronic ignition on one set of plugs. After about 20 minutes of flight (8500 ft) I hear a subtle change in the engine sound. Is the timing changing or maybe something else going on? It is barely noticeable, but I do pay close attention... 
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"Kindness is never a bad plan."
exemption option waived. Donation appropriate.
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01-06-2014, 09:22 AM
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Join Date: Jan 2007
Location: Ontario Canada
Posts: 1,452
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More info and tests?
I am running one mag one lightspeed. 400 hrs without an issue other than one small adjustment to mag.
I am no expert hopefully they chime in.....but you talk of a change in sound? Like what would you say it does?
Is there an RPM fluctuation, fuel flow change, temp change. Do you have a efis....if so download it and run it through something like savvy.
If you run in steady cruise and shut down the mag, still hear it. Turn mag back on and shut off lightspeed. Give some more stuff and the smart dudes will give you some good ideas.
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Rick Woodall C-GSTT "ghost"
9a -TMX io-320, catto three blade, dual dynon hdx with a/p. 900+ hrs in 8 yrs flying.
Flew to Osh 11,12,15,17,19. SNF 2013. West to Cali /Washington/Vancouver/crossed the Rockies north to Red Deer east to Moosonee and over to maritimes. South to Jekyll Isl, cedar key, and Key West etc. 6 trips and 17 islands of the Bahamas. Flown turtles and dogs for Pilots n Paws too. Love our Rv's
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01-06-2014, 09:27 AM
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Join Date: Dec 2004
Location: Gold Hill, NC25
Posts: 2,400
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Quote:
Originally Posted by flightlogic
Still learning here... 40 years on mags and now in the 9 with an electronic ignition on one set of plugs. After about 20 minutes of flight (8500 ft) I hear a subtle change in the engine sound. Is the timing changing or maybe something else going on? It is barely noticeable, but I do pay close attention... 
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You should not hear any change in engine noise from your lightspeed ignition under any circumstances. The adjustments its making are far faster than your ear and brain can process as you are moving the black or blue knobs.
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Kahuna
6A, S8 ,
Gold Hill, NC25
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01-06-2014, 12:24 PM
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Join Date: May 2012
Location: Bowdoinham
Posts: 180
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1000+ hours on dual Lightspeeds with flywheel pickups.
The -only- problem I ever had was when I developed an intermittent leak in the plumbing leading to the manifold pressure transducer. The ignition would try and adjust the spark timing based on the inaccurate readings it was getting.
Fixing the leak fixed the problem.
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Nick "Hairball" Knobil
RV8 N80549 (First Flight 2003)
Aerosport O-360A1A, Dual LS CDIs, WW200C
Bowdoinham, Maine
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01-06-2014, 05:18 PM
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Join Date: Nov 2013
Location: Prescott, AZ
Posts: 1,614
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As usual... quick replies and very useful. Thanks !
Will check the plumbing to be sure that is not causing some timing change.
My original post said subtle changes. I really mean subtle. No change on EFIS, rpm or any other data I can see. But I can hear it. Guess it comes from three forced landings. I listen REALLY carefully to my engines.
__________________
"Kindness is never a bad plan."
exemption option waived. Donation appropriate.
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01-07-2014, 12:33 AM
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Join Date: Dec 2007
Location: Breda, The Netherlands
Posts: 42
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Do an inflight magcheck
I also experienced a noticeble change in sound. Seemed some sort of a pulsing change in power. Had it for a few months, but there was nothing visible on the Efis or in the logfiles. On the ground the runup checks gave no indictions of any problem. But an inflight magcheck revealled that the electronic ignition wasn't firing properly. Changing the automotive plugs solved the problem.
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01-07-2014, 07:08 AM
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Join Date: Jan 2005
Location: Round Rock, TX
Posts: 3,778
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+ 1 with Victor... try a new set of Spark Plugs. 
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Reiley
Retired N622DR - Serial #V7A1467
VAF# 671
Repeat Offender / Race 007
Friend of the RV-1
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01-07-2014, 09:25 AM
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Join Date: Mar 2005
Location: Molalla, Oregon (KOL05)
Posts: 529
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Normally you cannot hear any change in engine performance if everything is operating normally with a Mag/LSI combination.
Are you sure that this is even engine related? You or your Pax just picking your heels up off of the floor will produce a change in sound or tone that could be construed as an 'engine noise' chance. The first time it happened in my -6 I immediately started looking at the engine monitor. I have chased more than a few noises down in RV's that were just caused by vibrational characteristics related to feet movement...
If you hear the 'change' and notice that your EGT's are spiking, then the LSI system has gone offline for some reason. (Breaker tripped, cable became disconnected, etc).
Dump your EFIS data and look at the time period that you described for any anomalies. That will tell you more than anything about the health of your engine.
Unfortunately unless you have the LSI Plasma III system you can't immediately observed the timing curve.
__________________
Joe Blank
RV-6
IO-320-D1A
Advanced Flight Systems
Van's Aircraft Inc. Technical Support-Retired
EAA Tech Counselor & Flight Advisor
www.westcoastravens.com
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01-28-2014, 09:16 PM
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Join Date: Nov 2013
Location: Prescott, AZ
Posts: 1,614
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Joe,
Thanks for the detailed reply. Checked all the plugs but one. A misplaced egt probe is causing trouble in removing that one. Did check the vacuum plumbing and found a pinched line under a tie wrap. After re-routing the line I checked for rpm drop by pulling it off the vacuum source. Seemed to behave as it should.
The sound is subtle and not coming from the floor. Will investigate further and report back. On another thread, they are talking about carb heat. Do you know what kind of drop is expected in run up with a stock muff and electronic ignition?
Thanks for any advice.
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"Kindness is never a bad plan."
exemption option waived. Donation appropriate.
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01-29-2014, 04:05 AM
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Join Date: Oct 2005
Location: Melbourne, Australia
Posts: 1,868
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Quote:
Originally Posted by Joe Blank
Unfortunately unless you have the LSI Plasma III system you can't immediately observed the timing curve.
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The LightSpeed manual states that both the LSI Plasma 11+ and the Plasma 111 will output the timing advance.
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You’re only as good as your last landing 
Bob Barrow
RV7A
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