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03-02-2021, 01:36 PM
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Join Date: Apr 2012
Location: Kingsville, Ontario, Canada
Posts: 318
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Air Filter Damage
I had a dirty injector, cleaned it and did another GAMI Lean test using Savvy's procedure. The lean test came out good with .4 GPH spread. However at the end of the 3rd run I also did an in-flight mag check. I was aggressively leaned at this point and heard what I thought was a cylinder missing on both the Left & Right mags (a little worse on the Right).
On my walk around today I saw this on my intake filter.
It looks more like a backfire than a cylinder miss. Is it possible to get a backfire in a situation like this?
I'll be ordering a new filter K&N 33-2060.
__________________
Dennis Enns
Bellanca Champ 7ACA since 1986, restored 1990.
RV-8 IO375, Hartzell CS, dual PMags, OW Award Oshkosh 2017
2021 Donation In 
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03-02-2021, 02:34 PM
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Join Date: Oct 2007
Location: Sacramento, CA
Posts: 3,515
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Quote:
Originally Posted by Champ
I had a dirty injector, cleaned it and did another GAMI Lean test using Savvy's procedure. The lean test came out good with .4 GPH spread. However at the end of the 3rd run I also did an in-flight mag check. I was aggressively leaned at this point and heard what I thought was a cylinder missing on both the Left & Right mags (a little worse on the Right).
On my walk around today I saw this on my intake filter.
Attachment 8967
It looks more like a backfire than a cylinder miss. Is it possible to get a backfire in a situation like this?
I'll be ordering a new filter K&N 33-2060. |
Is it electronic Mag or slick? I am not sure if .4 GPH spread is all that good. The aim is for .2G or less. but to I think it is possible to have back fire in those condition depending on power setting, advance timing.
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Mehrdad
N825SM RV7A - IO360M1B - SOLD
N825MS RV14A - IO390 - Flying
Dues paid
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03-02-2021, 06:53 PM
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Join Date: Jan 2005
Location: KMCE
Posts: 328
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Quote:
Originally Posted by Champ
It looks more like a backfire than a cylinder miss. Is it possible to get a backfire in a situation like this?
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Yes. It can happen easily on a kickback as in my case about 10 years ago. It only happened once, and I promised not to let it happen again. Keep that starter engaged until you have a clean start. My guess that your filter suffered a backfire during one of your startups, but you didn't notice the filter until after the GAMI test.
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Scott Chastain
RV-8 N898W Descending Dove
Last edited by Scott Chastain : 03-02-2021 at 07:00 PM.
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03-02-2021, 07:27 PM
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Join Date: Feb 2013
Location: Idaho
Posts: 204
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Ive had a couple hot start backfires that did that. Now I never have the throttle full open on a hot start. I hot start with throttle closed and butterfly in servo keeps it from backfiring in the airbox blowing out the filter. Haven't had to replace one since. Basically my hot start is throttle closed and mixture idle cutoff and then slowly add mixture as it catches.
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03-02-2021, 07:53 PM
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Join Date: Apr 2012
Location: Kingsville, Ontario, Canada
Posts: 318
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A start up backfire makes sense. It could have happened on a less careful recent start where I let off cranking before I got a clean start. I start with the throttle cracked and mixture at ICO and advance on firing. I'll have to try a throttle closed start and make sure I keep the starter engaged.
Bavafa - I have had .2 GPH spread on previous GAMI tests. I have dual P-Mags.
Thanks everyone.
__________________
Dennis Enns
Bellanca Champ 7ACA since 1986, restored 1990.
RV-8 IO375, Hartzell CS, dual PMags, OW Award Oshkosh 2017
2021 Donation In
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03-02-2021, 08:04 PM
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Join Date: Oct 2019
Location: SoCal
Posts: 476
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I thought K&N filters were free-flow........
Shouldn't a blast just flow right thru it ?
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Ed
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03-03-2021, 12:08 AM
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Join Date: Feb 2005
Location: LSGY
Posts: 3,647
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Quote:
Originally Posted by emsvitil
I thought K&N filters were free-flow........
Shouldn't a blast just flow right thru it ?
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Ed, not sure if you are kidding or not, but even a bug screen would be deformed during a backfire. |
03-03-2021, 12:20 AM
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Join Date: Oct 2019
Location: SoCal
Posts: 476
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Forgot this:
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Ed
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03-03-2021, 12:43 AM
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Join Date: Feb 2005
Location: LSGY
Posts: 3,647
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Quote:
Originally Posted by emsvitil
Forgot this:
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 got it! |
03-03-2021, 03:12 AM
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Join Date: Feb 2005
Location: Central Alabama
Posts: 319
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Just a thought...
You may want to take a look at your snorkel and assess it's condition. I had a startup fart once (which at the tome didn't think it was too bad) but later found the snorkel had about an 8" split from the back pressure.
No big deal to fix it but you gotta find it first!
__________________
Hwood 
N469SH / "Crazy Woman" (sold)
Working on Another -8
Exempt but paid
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