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Date: Tue, 15 Oct 2013 09:21:03 -0400
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From: vtailjeff@aol.com
Subject: Re: [LML] LOP ops on O-360 A1A

Have you checked your baffling?

Sent from my iPad

On Oct 15, 2013, at 7:53 AM, Keith Smith <keith.smith@gmail.com> wrote:

> Hey all,
>=20
> I'm waiting for winter to come around but it seems like my O-360 A1A has b=
een running warmer than usual, requiring me to power back very shortly after=
 takeoff to avoid an excursion north of 425 degree CHT's.
>=20
> In any case, I know that LOP ops are hard to come by with an O-360 due to p=
oor fuel distribution. Indeed, my #4 cylinder peaks well before the others, m=
aking it tricky to get them LOP.
>=20
> I've been running in two modes...one is around 20 LOP to cool it down to a=
round 385 CHT while the others run just slightly rich of peak. I can do this=
 without much effort, and under a wide range of throttle positions, and dens=
ity altitudes.
>=20
> On a recent flight, though, I found #1 and #3 settling on temps that were j=
ust too high to be happy with. I would go well ROP to get them cooled, but b=
urned a lot of fuel in the process and still had a warm 4th cylinder due to t=
he fact that it runs quite a bit leaner. This was all done at 75% power or l=
ess, btw, density altitude was well above 11k (I was at 11k and it was +10C)=

>=20
> Eventually, I tried something somewhat dramatic. I was determined to get A=
LL the cylinders LOP. I leaned relatively rapidly and ignored the disconcert=
ing knocking/shuddering associated with the uneven amounts of power being pr=
oduced between the 4th cylinder and all the rest.
>=20
> It all happened a bit quickly, but with cylinder 1-3 roughly 20-40 LOP and=
 #4 70-90 LOP, the CHTs dropped like a stone, seemingly in seconds, down to 3=
80-385 across the board for #1-3 with #4 now in the 350-360 range. With care=
ful fiddling of the mixture, and countless experiments with throttle positio=
n, I got the vibration down to the point where it was barely noticeable. Eve=
ntually it just felt smooth...but I can't tell if I got used to it, or thing=
s just settled down, although I wouldn't think it was possible.
>=20
> Final fuel flow was around 8.8-9.0 gph.
>=20
> Finally, living the LOP dream with my O-360 :)
>=20
> I tried repeating this later on, down low and wasn't able to repeat it (ie=
, never got it smooth).
>=20
> So, it's elusive, but possibly doable under just the right circumstances. S=
ince I do long trips on a regular basis, I'm definitely interested in making=
 this work.
>=20
> Separately, I'll try to find out why it's running warmer in general. I did=
 have a mag replaced, the other rebuilt, and 4 new plugs installed in the la=
st year.
>=20
> Honestly, I'm going to try to save some clams and get this converted to an=
 IO-360 (didn't realize it was relatively inexpensive until my mechanic sugg=
ested it), get balanced injectors and run LOP as SOP. The difference in cool=
ing really is staggering. I know I'm probably preaching to the choir, but I t=
hought that O-360 owners might find it eye opening. Get up high and give it a=
 try if you have a 4 point engine monitor. You'll know it's working when you=
r leaning results in EGT and CHT's coming down :)
>=20
> The trip, btw, was N07-KFTW-KSAV-N07, around 2600nm.
>=20
> Keith