Man.pressure Vs RPM

[splischke]

While perusing the Revmaster web site, I found the following chart for their R-2200 which has a 78mm stroke and 94mm bore:

I know this chart is for the R-2200 but what stands out is how an increase in RPM above 3400 yields less bang for the buck in HP and torque.

I just thought I throw this out for discussion.

-Scott

 

[Gaston]

Looks very strange that the torque figure is that constant between
2800 and 3400...

I probably miss something,
but I don't take it for cash...

Gaston

 

[phzabriskie]

The "favorite" prop will be different from plane to plane. Static RPMs might be the same between planes, but it flight its hard to compare.

I have been reading about Sonex airplanes that can only get 3050rpms wide open in flight. Aircraft propped like this are giving up both climb and cruise performance. At that rpm, its probably only making 50 hp.

Like Gaston said, the vw does not mind the rpms. It needs them to make decent power.

I have a 49.5x50 Sterba if anyone wants to try it in the air on a SII. Pay shipping both ways and let me know what it does.

Really great thread guys....Jeff I would not be able to get the prop in the air but could I borrow it for a couple weeks to put my engine on the mounts and see if I can get it to kick over. I never have run it and really want to know if it will.
-Pete

 

[phzabriskie]

As a side-note a Manifold Pressure Gauge is sort of a pricey instrument. The best I could find was UMA for $123, MGL did not have it as part of their E-1 Engine Management 3 1/8". So, surprise, we are back to Grand Rapids EIS which includes MP in all their offers.
-Pete

 

[Schmleff]

Pete,

Not sure that it will fit on your engine. You have an SAE-1 hub right?

And about MAP gauges. Be careful when buying. Make sure you get a read dual diaphragm gauge. Mine was billed as a MAP gauge, but its really a vac gauge labeled in reverse. I have to subtract 1" per 1k feet to get a proper reading.

 

[Schmleff]

About fuel burn being a true indicator of power. I agree totally. However, its only a true indicator if you are not cooling your engine with fuel. You have to be leaning properly to make it work out. If your peak egt is 150 degrees above where you run to keep things cool, your numbers are not going to be correct. You are using lots of fuel for cooling, not making BSFC. Lean it out to 50 degrees before peek and use those numbers in the formula.

 

[phzabriskie]

Pete,

Not sure that it will fit on your engine. You have an SAE-1 hub right?

And about MAP gauges. Be careful when buying. Make sure you get a read dual diaphragm gauge. Mine was billed as a MAP gauge, but its really a vac gauge labeled in reverse. I have to subtract 1" per 1k feet to get a proper reading.

Jeff can you tell me what I have from this pix? What about the Grand Rapids MAP? They only describe two sensors: 0-31 Hg/ 0-51 Hg- $60.

 

[JuergenA]

Hi Pete,
I have the UMA Manifold Pressure:

http://www.aircraftspruce.com/catalog/inpages/manifoldgauges4.php
it work very well, but don't forget the fuel trap.
with best regards
Juergen

 

[Kmccune]

Very interesting thread guys. This has answered a couple of things stated on websites that didn't add up. I am only thinking of building a Sonerai right now, the IIL version. First I have to finish my CH701. It will have a GPA 2276 and a VE redrive. Steve hints on the website about the over proping, MP and running a flatter pitch and more RPM, but then like stated above, says 3200 RPM +/-200 for cruise. I'll have to test all this out when I get it finished, I can't see why this would not apply to the redrive variant as well.

Thanks for the good info.


Kevin