Rich of Peak vs. Lean of Peak

[CaptainBen]

Hello Ovation folks! I have recently learned that leaning to 50 ROP, as prescribed by the Ovation POH is actually a "red box" that I should not be operating in. So, my understanding is I should be leaning to 80-100 ROP or 20-30 LOP. Is that correct?

I tried leaning to ~30 LOP, and the engine seemed smooth enough and CHTs were OK, but EGT was pegged right at max (almost 1,650). This was at a lower altitude (4,000 ft) at about 23" MP. Getting ready to do a trip to Texas from California this week, so curious about best practices and the implications of the EGT temp issue.

Thank you!

[NickG]

Ben

Here is a link to articles by John Deakin https://www.avweb.com/features/avweb-classics/pelicans-perch/pelicans-perch-index/. Numbers 8, 15, 16, 18, 19, 43, 63-66, 77 & 78 deal with enginemanagement and running LOP.

These will be extremely helpful for you.

[Rick Junkin]

1 hour ago, CaptainBen said:

EGT was pegged right at max (almost 1,650)

Staying below 1600º is generally regarded as a best practice, but the values you are seeing vary from airplane to airplane due to differences in where the EGT probes are installed relative to the exhaust port and the flow inside the exhaust manifold. Can you go leaner without the engine stumbling or power dropping drastically? General guidance for how far lean of peak you need to be is based on power output, with 65% being ok to run at peak and increasing more or less linearly to 60º LOP at 80%, as long as your EGTs and CHTs stay reasonable.

As for ROP ops, the latest from the Cirrus and Bonanza camps is advocating for 180-200º ROP at 75% power IIRC to preserve cylinder longevity.

Do you subscribe to Savvy's engine analysis service? They produce a report that shows you where your engine is performing in relation to others across all the major parameters of temps and pressures.

[Max Clark]

@CaptainBen welcome to the Ovation family! I do KRBD <> KWHP a couple times each year. Let me know when you're planning on being in Texas (and where) - if it schedules work we could link up.

Nick's links to Pelican's perch are great. Also reading Mike's books are great. I give you the TLDR; for the Ovation and IO-550 - run it WOT and LOP.

I don't understand 1600 EGT. Looking through my logs 1505 is the highest I have recorded. What were your CHTs doing?

What equipment do you have in the plane? Specifically:

1. Do you have GAMI injectors? Do you know what the spread is?
2. What engine monitor do you have - you have CHT and EGT for each cylinder individually?
3. What are you doing to lean?

I had a JPI EDM 730 when I bought the plane. Lean find on that box was unbelievably easy and nailed it every time. I switched to a Garmin G3x and integrated EIS. Personal opinion - lean assist on the G3x blows. I've gotten comfortable leaning with the big pull (at least I think I am lol).

In my POH (and original gauge) there's a note on leaning for altitude and takeoff for best power (1400-1450 EGT). I found from experimenting with the lean assist this range is the target for both ROP and LOP for me. So on takeoff and initial climb I'm leaning to ROP just with EGT (and typically land at 1420/1430), once I'm at cruise I'll reduce RPM to 2400 and pull mixture until I have a heart attack and enrichen back to smooth running. Depending on altitude and MP I'm usually between 10.6 and 11.0 GPH.

Photo from a flight today, and Savvy from a flight a month ago.

[Bolter]

9 hours ago, CaptainBen said:

I tried leaning to ~30 LOP, and the engine seemed smooth enough and CHTs were OK, but EGT was pegged right at max (almost 1,650). This was at a lower altitude (4,000 ft) at about 23" MP. Getting ready to do a trip to Texas from California this week, so curious about best practices and the implications of the EGT temp issue.

If your are at 30 LOP then your EGT is NOT at peak (or max).  By definition.  EGT can vary from plane to plane based on the installation, take the absolute values with a grain of salt.  But peak is peak.  As a reference, my EGT's at LOP are in the 1450-1550 range, depending on which cylinder.  Your EGT's seem high compared to mine and mine seem a little high compared to what @Max Clark just shared.  

LOP at lower altitudes can be more difficult as your overall power is much higher.  I can run LOP at 4k, but usually drop the manifold a little bit to get overall power lower, then big pull to 13-13.5 GPH.  Your 23" seems low enough.  RPM will vary, but between 2400 and 2500 depending on my mood.  I am typically not cruising as low as 4k, I am either climbing or descending.  At 7k and up, getting a good LOP setting is easy.  If you are experimenting with LOP ops, go higher so there is an inherent safety buffer.

On hot days, I find that keeping the OVation CHT's cool enough can be difficult.  I have often gone extra LOP to keep temps down through the power reduction.  In cool Seattle weather, this is not a common issue.  When I am enroute to NorCal in warmer months, I can tell at altitude I am much warmer than std atmosphere through my CHT's creeping up.  

One thing I think that is an important takeaway is what you emphasized to start .... avoid the 50F ROP operating point of the POH, and be richer or get to LOP.

[NickG]

Ususally I cruise between 1440-1485 EGT. Keeps me lean, good power and generally nets an airspeed around 172-175KTAS (prop 2400 until higher atlitudes, then 2450-2500. There also a school of thought with the STC to cruise at 2550 RPM at altitude... EGT Temps will differ based on probe placement etc etc, but the ranges should not be that far off.

[LANCECASPER]

On 4/5/2026 at 2:21 PM, CaptainBen said:

Hello Ovation folks! I have recently learned that leaning to 50 ROP, as prescribed by the Ovation POH is actually a "red box" that I should not be operating in. So, my understanding is I should be leaning to 80-100 ROP or 20-30 LOP. Is that correct?

I tried leaning to ~30 LOP, and the engine seemed smooth enough and CHTs were OK, but EGT was pegged right at max (almost 1,650). This was at a lower altitude (4,000 ft) at about 23" MP. Getting ready to do a trip to Texas from California this week, so curious about best practices and the implications of the EGT temp issue.

Thank you!

On a turbocharged engine 1600 is the highest I'll go on the Turbine Inlet Temperature.

On the airplanes I've owned with normally aspirated engines, like your Ovation, I have never had an EGT close to 1600  . .  ever. 1650 is way too hot. Get some specific training on that airplane from a Mooney specific instructor before making that long of a trip. That's a very expensive engine to cook.

[GeeBee]

I run my Ovation at 65% power all the time, 50 LOP, 12.3 gph no problems. I have GAMI injectors and worked with GAMI to get all cylinders to peak within 0.1 gph of each other. I get a TAS of 168 knots with TKS panels. I have 1300 hours still on original cylinders. I boroscoped  all cylinders every oil change and did so last week. Compressions between 63 and 71 cold. My CHTs run between 290 and 330 in cruise/summer 30 degrees less winter. The IO-550 wants to run WOT so get it up at 10,000 density altitude, lean her out to 12.3 with balance injectors and watch the dollars roll in.

Yeah you can run 75% and get another 10 knots. What does that get you? On a 3 hour flight you save......10 minutes. 

The added benefit of LOP operation is low lead accumulation. Here is my latest report. Calcium and Phosphorus are higher due to Camguard.

[Ed de C.]

I get about what BeeGee gets for operating numbers on my O3.  

My suggestion to CaptainBen is to go to the Savvy website and explore inflight LOP tests.  But, a simple test he can do right now is settle into cruise and then pull the mixture back as far as he dares go.  He'll stop either because the engine runs rough or the engine sags.  If the engine runs rough, he probably would benefit from a set of GAMI injectors or an update on those.  (It runs rough because 1 or more cylinders is leaning out much faster than the others.)  That's what I did when I acquired my Ovation.  After that, he'll find that roughness is gone when aggressively leaning, and the limit is found when the engine noticeably sags.  

Mike Busch suggests simply leaning until roughness (or sag) and enriching slightly.  Then forget about it (don't worry about EGTs).  Keep in mind he's running turbo charged engines in his personal plane.  You'll pretty soon get a sense of what fuel flows occur at that point. I do that many times, but on a long cross country, I'll use the lean-find feature on the G1000 to help me fine-tune to somewhere between 0 and 50 degrees LOP depending on altitude and speed desire.  My current GAMI setup will run more than 100 degrees LOP, much more than I really want since speed drops off noticeably.

The only time I run my Ovation ROP is on takeoff and climb out.  Sometimes I'll do an intermediate climb LOP (after ATC levels my at 5k and I lean at that point, so I climb LOP from there).  If I'm climbing high, above 10k, I'll look for max power ROP crossing 10k when I'm low enough on power not to worry about the red box.  I'm looking for best rate of climb in this case.  Key is to watch CHTs throughout.  My CHTs are better on an LOP climb than a ROP climb.  

Best, 

Ed

[dkkim73]

On 4/16/2026 at 1:23 PM, Ed de C. said:

I get about what BeeGee gets for operating numbers on my O3.  

 

Now you can't unsee it. 

One minor addition to the good comments and techniques above was pointed out to me by a mechanic recently. The temp sensors (I use TIT given the turbo and occasionally cross-check with what looks to be the leanest or richest cylinder's EGT) do wear and change their absolute indications over time, so beware getting to used to seeing specific temp #s. Cross-check with smoothness of running and FF helps. Of course I "knew" this but would subsciously be looking for specific #s.