Turbo leaning via EGT

[daytonabch04]

On 12/17/2023 at 8:26 AM, ChrisH said:

Has anyone installed the scimitar on a Bravo? 

https://hartzellprop.com/stc-approved-for-hartzell-propeller-3-blade-mooney-bravo-prop/ 

My Bravo was used by Hartzell for the test bed for the M20M TopProp STC approval.  I can definitely say the propeller is more smooth in flight and have seen an increase in climb performance and in cruise flight.  I'd say the gain is somewhere in the realm of 3-6 kts. but is much smoother in performance than I have anticipated. 

[hazek]

On 12/8/2023 at 1:56 AM, Rick Junkin said:

Ok, please bear with me for a question with a practical example. Here's how I normally cruise:

30"/2200 RPM
13.2 GPH
TIT at 1615 (40dF LOP)

Now the question -  I increase the MP to 32" and adjust the mixture to maintain 13.2 GPH. What happens to my airspeed? 

Thanks for your patience.

Cheers,
Rick

The answer is your speed will reduce. By pushing in the throttle and increasing the MAP, you're putting more air AND fuel into the engine, if you now reduce the fuel via the mixture, the air-fuel ratio becomes leaner. SFC is not linear since the power curve is not linear. This means that the leaner LOP you are the more fuel you need for the same power. So for every MAP/RPM setting there's a sweet spot for FF LOP and both leaner and richer of it, you'll need more fuel for the same power e.g. IAS.

 

[Pinecone]

On 12/14/2023 at 5:22 PM, kortopates said:

So they've been saying for quite ahile now.

So I have the MT-composite prop.

True.  And when I get to the point of doing the prop swap, I will be OK with an MT unless Hartzell gets off their rear and gets the prop out.

[Pinecone]

On 12/11/2024 at 1:17 PM, hazek said:

The answer is your speed will reduce. By pushing in the throttle and increasing the MAP, you're putting more air AND fuel into the engine, if you now reduce the fuel via the mixture, the air-fuel ratio becomes leaner. SFC is not linear since the power curve is not linear. This means that the leaner LOP you are the more fuel you need for the same power. So for every MAP/RPM setting there's a sweet spot for FF LOP and both leaner and richer of it, you'll need more fuel for the same power e.g. IAS.

 

No.  LOP you will make the same power with the same fuel flow.  No matter what the RPM and manifold pressure.

For my turbo engine, 13.7 HP per GPH.

ROP does not work that way.

[jetdriven]

7 hours ago, Pinecone said:

No.  LOP you will make the same power with the same fuel flow.  No matter what the RPM and manifold pressure.

For my turbo engine, 13.7 HP per GPH.

ROP does not work that way.

Not necessarily, in the same spot on the curve, that’s true, but the leaner you get from peak, the slower the flame front and eventually power output will decline.  Put into practice, 27 inches of manifold pressure at 8 gallons an hour is a certain percentage of power at 30 lean of peak, but if you shove more manifold pressure through it and then lean it back to the same fuel flow,  it is now 100 lean of peak, and that won’t be the same horsepower at the crankshaft. You can see this with your airspeed. It’s because the efficiency is less because it’s actually too far down the backside of the peak.  The peak power pulse of combustion occurs further down the cylinder because it’s burning slower.

[Will.iam]

12 hours ago, jetdriven said:

Not necessarily, in the same spot on the curve, that’s true, but the leaner you get from peak, the slower the flame front and eventually power output will decline.  Put into practice, 27 inches of manifold pressure at 8 gallons an hour is a certain percentage of power at 30 lean of peak, but if you shove more manifold pressure through it and then lean it back to the same fuel flow,  it is now 100 lean of peak, and that won’t be the same horsepower at the crankshaft. You can see this with your airspeed. It’s because the efficiency is less because it’s actually too far down the backside of the peak.  The peak power pulse of combustion occurs further down the cylinder because it’s burning slower.

Yes true statement and verified myself. You can slow the RPM’s to capture more of that peak pressure closer to the optimal 18 degrees past TDC but the slower prop RPM’s, although more efficient, does not offset the less power pulses per minute and thus a slower over all speed. My chart’s interesting enough do not show a 78% power setting for 2200 rpm. Only 2300 to 2700.  So when I’m pushing high power LOP (equal or greater than 78%) i do not go lower than 2300. When I’m just putting around or going for a hamburger run, I’ll be somewhere below 65% and use 2200 for maximize fuel economy over speed.