Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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 Posted: Sun Aug 06, 2006 7:28 pm Post subject: LOP?ROP |
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Close, but a few incorrect items. Sodium filled valve stems transfer
heat to the valve guides, not the valve seat. That is why Lycomings tend
to have more valve guide problems. Lycoming's stated red lines are 425
for cruise and 475 absolute, while recommending 400 or less for
longevity. LOP is actually easier to fly than ROP, because you don't
have to worry about adjusting mixture in the descent. Danger zone is
really dependent on power setting. At 75% it really is about 25 LOP to
80 ROP, with max CHT at 40-50 ROP. You really want to either be LOP or
100 ROP in cruise, and about 200 ROP in climb.
For more detail and demonstration of actual values, the Advanced Pilots
Seminar in Ada or on-line is highly recommended, open to all, and only
loosely affiliated with GAMI.
John W. Cox wrote:
[quote] As you increase the mixture control from Idle Cutoff off to greater
richness, the EGT indicates the increase in exhaust gas temperature as
the ratio of fuel to air increase. Hence, ROP is on the rich of Peak
side once the temperature MAXs and you continue the control of fuel to
air, you go over to LEAN of PEAK, hence LOP. The danger zone for
detonation and internal damage is within 50 degrees ROP to 50 degrees
LOP where cylinder pressures are their greatest. At 75% Lean of Peak
the CHT and EGT comes down and you fly a more frugal fuel:air mixture.
It is not for the faint of heart, it is not for climb configuration
(need for maximum power) it is not for aircraft without EGT probes on
each of your cylinders.
With the reduction in EGT usually comes reduction in CHT and extended
component life for pistons, cam lobes, exhaust valves and seats and
other oil cooled components which begin to COKE up with higher
temperatures. The Lycoming features sodium filled valves which do a
better job of heat transfer to the valve seat than a Continental.
Control of spark intensity and timing event all come together to
increase temperature of the fuel:air mixture which can lead to
Detonation. We each have individual opinions on LOP/ROP and timing
devices. Detonation always wins the discussion. Aluminum does not do
well in the 400 degree range so LOP fans are growing in popularity.
GAMI gives classes to ole mechanics and FAA types who misunderstand the
black magic.
FADEC (Full Authority Digital Engine Control) takes all of this away and
hides that and the mixture lever beyond the reach of pilots. Or KISS –
Keep it Simple Stupid pilot control.
John Cox
N49CX – 40600
Do not Archive
------------------------------------------------------------------------
*From:* owner-rv10-list-server(at)matronics.com
[mailto:owner-rv10-list-server(at)matronics.com] *On Behalf Of *DAVE LEIKAM
*Sent:* Sunday, August 06, 2006 4:15 PM
*To:* rv10-list(at)matronics.com
*Subject:* Re: Kitplanes article on the Lyc 390X and BPE
I've seen the term "LOP" operation used. Can you explain?
Dave Leikam
RV-10 N89DA
#40496 - elevators
do not archive
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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD |
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