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01-16-2018, 11:33 AM
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Join Date: Apr 2013
Location: Evanston, IL
Posts: 124
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4th flight engine issue
Hi All!
Just completed the 4th flight in my RV-7 on Sunday and experienced some variation in engine power that I hadn't before. It was very subtle actually, but I could sense by the sound of the engine and just feeling the acceleration / deceleration that the engine power was surging at times. Hard to detect in terms of engine RPM change, maybe around 50 RPM. After feeling it a few times I decided to head back to the airport to be safe.
I downloaded the engine data (below) and I noticed that on previous flights the EGTs for all cylinders were all very consistent (within maybe 30 deg of each other and tracking nicely). On this last flight cyl 1 and 2 were much higher than 3&4 for most of the flight. Occasionally they would come down to match the others for a brief period and then diverge again. First thing that comes to mind is an ignition issue. Perhaps one of set of plugs on cyl 1 and 2 weren't firing all the time, because that would cause an increase in EGT. Other thoughts?? Thanks in advance.
New Superior IO-360
1 LightSpeed II+ ignition
1 Slick Mag
Catto FP Prop
Flight 3 (no issue detected)
Flight 4

__________________
Matt K.
RV-7 Tip-up - Flying!
XP Superior IO-360 w/cold air sump, Catto 3 blade prop
Garmin G3X
CFI, CFII, MEI
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01-16-2018, 11:54 AM
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Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,597
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After you eliminate any spark plug issues (just replace them to be sure), I would next look at:
- Intake air leak on #1 and #2 cylinders
- Injector clog
- Spider issue (do the simple shot glass fuel flow test)
After that, and assuming the mag/EI checks on runup are correct, then I?d look at the LightSpeed.
Carl
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01-16-2018, 12:05 PM
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Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,147
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1 and 2 are opposed cylinders, and share a single ignition coil for the lightspeed, that would be my #1 suspect. I doubt the induction leak or injection flow rates would change as cleanly and uniformly as they did, this looks like ignition.
__________________
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2020 dues paid 
N16GN flying 700 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, 430W
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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01-16-2018, 02:15 PM
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Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,687
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Quote:
Originally Posted by airguy
1 and 2 are opposed cylinders, and share a single ignition coil for the lightspeed, that would be my #1 suspect. I doubt the induction leak or injection flow rates would change as cleanly and uniformly as they did, this looks like ignition.
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I think Greg nailed it.
__________________
Walt Aronow, DFW, TX (52F)
EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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01-16-2018, 07:40 PM
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Join Date: Mar 2013
Location: Flathead Lake Montana - 8S1
Posts: 334
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Carefully inspect the spade connectors on the coil, and the integrity of the BNC on the other end of the RG400 cable. If all seems okay, re-read the troubleshooting section of the LSE manual and then - and only then - call Klaus 
__________________
'83 LongEZ - N888EZ 3,671 hours
'89 LimoEZ - N26EZ 686 hours (sold)
A couple of Glasairs and a Lancair 320...
Next: a RV14 need something to build
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01-16-2018, 08:27 PM
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Join Date: Apr 2013
Location: Evanston, IL
Posts: 124
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Thanks All! That reinforces what I was thinking. I'll run through the LSE troubleshooting and see what I come up with.
__________________
Matt K.
RV-7 Tip-up - Flying!
XP Superior IO-360 w/cold air sump, Catto 3 blade prop
Garmin G3X
CFI, CFII, MEI
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01-16-2018, 08:35 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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I'm confused, are all your numbers EGT's? What is going on with your CHT's?
If you have a bad coil pack, then both the CHT's and EGT's should be going down, not up.
If the LS is firing one coil pack out of time (is this even possible?), then you could see a rise in CHT and a drop in EGT or a drop in CHT and a rise in EGT.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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01-17-2018, 08:41 AM
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Join Date: Sep 2010
Location: Charlotte NC
Posts: 1,168
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Be aware that a the coil light speed uses can work normally at sea level but fail at altitude. This caused us a long trouble shooting process.
G
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01-17-2018, 10:54 AM
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Join Date: Aug 2009
Location: Southern California
Posts: 881
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Dead Plug/ignition
Quote:
Originally Posted by N941WR
If you have a bad coil pack, then both the CHT's and EGT's should be going down, not up.
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Usually when one of the 2 plugs on a cylinder stops firing the EGT rises due to the slower mixture burn, and the CHT will drop.
Skylor
RV-8
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01-17-2018, 11:32 AM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,298
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Quote:
Originally Posted by skylor
Usually when one of the 2 plugs on a cylinder stops firing the EGT rises due to the slower mixture burn, and the CHT will drop.
Skylor
RV-8
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+1
Losing one of two plugs in a cylinder will cause the "effective timing" to retard for that cylinder. This causes an increased EGT and decreased CHT. I also would be looking at the coil pack if it is shared by the two problem cylinders.
Larry
__________________
N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
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