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EMS setting for D180 fixed Sensenich 2600 rpm (Read 428 times)
Apr 30th, 2018 at 5:48pm

rjcthree   Offline
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A/C is an RV-9A with a O-320,  Sensenich fixed prop limited to 2600 RPM and a D180. For best % power accuracy, what should the recommended green to yellow and yellow to red setting for tach be? This is not equipped fuel flow, so it sees MAP, altitude and altimeter, and Tach.

Forgraphical reasons, I would like the yellow to red to be 2600, but I’m not sure if that will skew the results.

I’m not sure I believe what I have now, in that  2300rpm, 20.6 in MAP, 5460 p alt/5240 d alt, 6c OAT was showing 64% on the display.  I believe that to be closer to 50%-55% from the Lyc charts.  I was showing 132kt indicated,  142kt TAS at the time.

Thanks, Rick
« Last Edit: Apr 30th, 2018 at 5:49pm by rjcthree »  
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Reply #1 - May 1st, 2018 at 5:21pm

Dynon Avionics   Offline
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There are two things you can tweak to affect the percent power calculation. One is the yellow/red setting (redline), although that should really be set to the manufacturer's recommendation. The other is the horsepower rating in setup. We should have named this "adjustment factor" or something along those lines, because sometimes people don't like putting a number in that field that feels "wrong", even if then they have a percent power that isn't matching expectations against the chart. But basically, it affects the virtualized the table that produces the % number. It's admittedly the easiest to tune when you have a fuel flow sender, because you can use the LOP/ROP detection, along with that number, two ensure that the LOP/ROP changes over at your peak EGT values. When that's right, the % power also ends up being right too. Note that without a fuel flow sensor, you won't ever get accurate % power on the LOP side.
 

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Reply #2 - May 1st, 2018 at 5:28pm

rjcthree   Offline
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Thank you for the reply.  Setting yellow/red is what I had read earlier as a key element.  Since what I think is happening is the % power is reading higher than actual by 10%-15%, what is your best guess about how far and in what direction to move the adjustment factor?  I’m really not worried about LOP without fuel flow sensor.  Thanks.
« Last Edit: May 1st, 2018 at 6:30pm by rjcthree »  
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Reply #3 - May 7th, 2018 at 5:02pm

Dynon Avionics   Offline
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So just an update here - the horsepower number really only affects the way that the ROP/LOP detection works. Because you don't have fuel flow, that number doesn't affect anything. The redline does affect horsepower, but everything should line up if you follow the manufacturer's red line. Incidentally, we ran your numbers through a power calculator manually, and it lined up perfectly. So we think you're getting the power calculation we'd expect.
 

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Reply #4 - May 24th, 2018 at 9:49am

rjcthree   Offline
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Thank you for making the effort to clarify this.  I'm still struggling a little to understand.  I was able to do some 8000' DA flying yesterday.  After weeks of bad waether here, it was good to get off the planet.

Anyway, with the redline set for 2600 in compliance with the sensenich operating limitation, I ran the following:
2600 RPM
23.0 in MP WOT
7100 PA
8000 DA
11C OAT
Alitimeter 30.18
148 Kt IAS/167 Kt TAS - just like Vans said it would  Smiley
Percent power shown onteh D-180:  83%

When I go to the Lycoming power chart, I was making ~110HP at 2600/23.0.  110hp/160hp = 69% power  For grins, 110/150 = 73% power (engine is rated at 150hp at 2600 on the data plate, although the power chart suggest 155 hp is more accurate).

My conclusion is the D-180 is showing me 10% higher power than the Lycoming chart shows. 

Your previous post suggests (maybe) that the calcualtor is giving you what you would expect, but I'm not sure you're suggesting that or if there is any way to line that up with the Lycoming power estimates. 

I'm going out today or tomorrow, I may try the same run again with the redline at 2700 rpm, just to see what numbers the D-180 generates.  Any other advice would be fine (other than adding fuel flow - I'm not adding features to this plane other than AD-SB at this time).

Thanks again, Rick
« Last Edit: May 24th, 2018 at 9:50am by rjcthree »  
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Reply #5 - May 24th, 2018 at 10:08am

RayInGA   Offline
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Richmond Hill, GA

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It is my opinion that the rated HP in an engine on a RV is likely higher than the Lycoming stated rating due to several factors:

1 Straight exhaust
2 Higher MAP due to ram air effect
3 Higher speeds that help with 2
4 Electronic ignition and timing advance
5 Fuel injection and balanced injectors
6 Cold air sump (more air/fuel)

A friend with a Titan O360 rated at 180 HP had to send his Prince prop back 3 times to have the pitch increased (new prop) due to the increased HP he was making - estimated by the prop shop to be closer to 195 - and had all the above options.
 

Ray Eaker
RV-7A flying since 27 Jan 2017
Dual Skyview 1000T with all available Dynon VFR goodies
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