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4th flight engine issue

MK77

Well Known Member
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)
Y2CIHlVPS1gIR0IhWDIsjbDrG9xx4D7mruA9gRSUWWgsi5dj59PdYp3BWNF0_hRZCmJw2jYAjcYFYOCgI_Ww-irS9MHgJGlx-PiQMhRB-es_a2kyqINNrV1OUUJJmSqK1FbmK_qXIvmO7gZfz6f1rU2DVjBUtTjaD95uRaCdrb6mTO17OybSc11OmWFd30dydPyc9r8U5OHeDRauolvIqUM1GtgGbx8h78dv_qRlLGlr2ydb-a5nCgJabJaClc6kiEouWp1zSu--XbShVPIS7J0M9ozvU5SIRDJoMUOE4J9NtGjelIBiT0delBqWMB4rIGy3uTBzqyOaf7WRGqP7cSPS0qSGn2a3vIzxZMojL8qzP4labfJW6IvqOoyi3HUyKGGoiUWaU_zDzU3VoG4rTW24Ra8_8hQBSghu3cplCwaPwp3L6l-L77jkS86DKJzMAhiMy--yO3WXjZi21CNQFOd6vsaJ-kJBfyAfo3j8aMlE1zwNPFflCaTIzwYxqmKtXEr7C4T_7fOAvEWAvREoHCUwl_K537k-ibEwQ_YhPs13RXiCNFgBJiLub8vGdNO4EgvFNhLK3VD8foJjIRNTjQ2kQsfj3bF2mHsN8Uyh=w864-h513-no



Flight 4

Ix62-CRSgaqjwqpUunS2sH5BFrDSreFqW6aXxD3TQ1cab2gLykXohGPCgRB6jl9N4ItarHMGRf6rkZkkfzUtuxqscDYjRH7-vU1yzoCVkZdtxCFyUuGchTxrwUTPn0biCcGqk2W3SIFVz0Xi_GQm2_iYw_Arz_2sWVqRUmZlWrxnBqGDaKCaUsC6Q3MzmmYo66d6rb8he9mb77bDa_B81-e3KUbsrOaDkh6nacvfLezQKkCDTWY0GDCjeeazXUCw8wlHX7JPHQ7jPEzoULLwXjZOOTyBs-c5Y7ad7XhwANcisKVk3XL4R8Lkgc4-x0WFHIPamlZwhsXdj7W3alMgzgeSTHM-8aNj37bmfKfJ58BsiqwNqi1arn7nEsseOS-2m3qbXllUfogeOCVT2Rb58C1kzoebsdhpD7DFwFtQqdAnzG16MZXQ-AhdggMhhhAKD0IOPCJbX_K1qLXOzI8FYpbqDW618bqyAVb4DDq0_2CYNAWfw4ITTqvinPuuFkjy7QUanjDbR84zVTzNDnL6GCG2TasLG8-IgriAcrcqU_CFt0mRozDG83iPBFiU-Or7zEDJQcfXMiMDuzYuI7SAVKkaziG7jnyXptH0i0YU=w864-h516-no
 
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
 
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.
 
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.

I think Greg nailed it.
 
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 :D
 
Thanks All! That reinforces what I was thinking. I'll run through the LSE troubleshooting and see what I come up with.
 
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.
 
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
 
Dead Plug/ignition

If you have a bad coil pack, then both the CHT's and EGT's should be going down, not up.

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
 
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

+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
 
+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

Yes, both #1 and #2 cylinders are fired from the same coil pack so it certainly is pointing in that direction.
 
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

Yes, I wasn't sure if he was talking CHT or EGT's and I had thought, maybe, just maybe he had tried running it one just one ignition. That will tell you pretty quickly where the problem lies.
 
I have about 6,600+ hours with LSE equipped planes. 1 coil intermittent coil failure above FL200, one bad coil spade connector/spade interface, and one intermittent RG58 (prior to Klaus being urged to supply RG400) failure due to long term thermal degradation with migration of center conductor towards the ground foil/braid.

I'd check the RG 400 lead and the male/female spades *very* carefully with a DVOM, actively wiggling the lead.
 
I've only got a couple hundred hours with LSE but I've had one user-caused installation error related to the coax, and one bad spade connector on a coil causing the coil to drop out. No problems with the coils themselves, as long as the connections to it were good.
 
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