Here is an excellent article written by a Canadian test pilot and RV-8 builder. He’s also included a lot of great links to other resources.
A very good article indeed @eurogaguest1980 
Finding or setting a % power with the iPad:
It’s already been mentioned somewhere above before, but for those not having a direct % power readout display, nor wanting to pencil line power charts, Jim Petty has created a fantastic and free app called AircraftPower available on the App Store. This app has been kept to date over the years, and covers probably most Lycoming and Continental models (just click on the brand title to have it change to the other).
PS
Jim also created some other free aviation apps such as TruAirspeed, Falco W&B, etc.
Nice article, yes on typical 7.5-8.5 compression ratio, the placard fuel flow on 300ROP takeoff should be about 9% x max HP (18gph on 200hp), for best power 100ROP, one gets about 12hp for 1gph, at 60% power of 200hp is 120hp which is 10gph, the peak and lean setting are -1gph, -2gph bellow those of best power
There is NFW one can “red-box” 200hp with 8.5gph (max rated HP/24), irrespective of MP/RPM as long as engine is running smooth
About 80% of the cylinders that I see rejected at maintenance checks are for exhaust valve or cylinder cracking issues, both are caused by heat issues, while some may choose to reject EGT as a mixture setting reference to start ignoring it and things will not end well.
The key to good engine management is the big picture of CHT, EGT & fuel flow, not over focus on one indication.
I would say cracks are caused by
Flying at peak EGT is not only authorised by Lyco (and has been since for ever AFAIK, at 75% of max rated power or less) but is evidently fine for the engine. What peak EGT (or anywhere near peak EGT, including 50 ROP or 50 LOP) is not so good for is exhaust life which will be shorter at say 1550F (typical low level bimbling at peak EGT, 65% power) than at 1300F (typical full-rich mixture flying school type of flying). Hence, they say, the exhaust is shagged at TBO. But even at Socata exhaust prices – each pipe section @2.5k so probably 20k for an exhaust – best-economy is a lot cheaper than full-rich. Especially as the biggest bit – the muffler – runs quite cool.
I’ve just bought a used 1987 TB20 exhaust which the owner said had 6k hrs airborne time on it. Never had EGT probes (no holes drilled) and once cleaned up a bit, looks like new. Even allowing for the last owner having had it only since 2019, and IMHO dodgy maint logs before that (a “club” in a very wealthy country so probably full-rich all the way) it looks great.
In practice, engine management is very simple. Climb full-rich (or constant-EGT method if going above about 5000ft) then level off and set the rough fuel flow. Then tweak fuel flow for peak EGT or LOP. Simple.
I think not having engine instrumentation exposes you to problems. For example, on a PFL (PPL revalidation) you want to be < 300F CHT before doing it. It can take many minutes…
I use full throttle and max RPM for climb. I used to bring the power back to 25 square, but I have owned my Bonanza for going on 44 years and as it got updated with engine monitoring equipment and digital fuel flow, it became apparent that bringing the throttle back to 25 inches increased the EGT and CHT during the climb. At full throttle, the fuel flow is extra rich and the initial throttle reduction does not change the MP indication, but primarily reduces fuel flow, so you are leaning the engine by bringing the throttle back to 25 inches. On my Bonanza with an IO520BA engine, the initial reduction of the throttle makes no indication of MP reduction and you have to make a substantial reduction before anything shows up on the MP. Only belatedly, the MP indication starts to come down and eventually starts to follow the throttle reduction. So leaving full throttle keeps the engine cooler. I am in no hurry to reduce the RPM, but usually do it after 1000+ AGL. By the time I reach 4000 or so a little over 3 minutes, the full throttle is down to 25 inches anyway, so I view making regular changes to keep the MP at 25 inches a waste of effort and IMHO is harder on the engine. To lean the engine, I just set the fuel flow. 12.5 GPH gives me close to 65% which is what I use for cruise. I have found that the digital fuel flow is very accurate but the indication lags behind, so I use the analog fuel flow (fuel pressure calibrated in fuel flow) is less accurate but very repeatable and near instant indication, so I just pull the mixture until the analog gage reads 12 GPH (the big pull) and the digital settles out at 12.5 GPH. The Bonanza of my vintage has a combine MP/FF indication on the same instrument, which during climb, I set the fuel flow by sight where the MP indicator on the LH side forms a straight line with the FF indication on the RH side. I lean to 12.5 GPH for cruise at any altitude up to about 8000 MSL. Above that altitude I will lean more.
To lean the engine, I just set the fuel flow
That is what the “constant EGT climb” is. All the way from sea level to the operating ceiling, only the mixture is touched.
That is also fine for climbs to low level, say 5000ft, except that
So I set 23"/2400rpm then. Others set 23"/2300rpm, etc. But the fuel flow for low level is 11.7 USG/hr and that is the “immediate target” at top of climb.
Dan wrote:
Jim Petty has created a fantastic and free app called AircraftPower available on the App Store.
I can’t find this on the iOS App Store (I’m in the UK). Maybe it’s locked down to certain countries? Has anyone in the UK managed to find/download it?
Does this work: https://apps.apple.com/gb/app/aircraftpower/id718023187
Yes, thanks. There’s no iPhone version, iPad only. That explains why I couldn’t find it when searching from my phone.
