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Changing an EDM700 from 2 to 3 inch / data compression / TB20 performance settings

I think there are strobe applications for mobile phones that can do it.

Yes, though with a CS prop the prop RPM does not have a first order effect on the power absorbed by the prop (and thus the thrust produced). If the RPM is down say 2% then the blade pitch will auto adjust to be a bit coarser.

With a fixed pitch prop the difference is massive - a third power of the RPM - and a very small RPM indicator error will produce a large performance difference.

I have a Nokia app which gives you the RPM from the sound

Administrator
Shoreham EGKA, United Kingdom

A very easy way to measure power would be to tie the aircraft to a scale and measure the newtons at full takeoff power. Do that with two TB20s and you can see if power given by the engine is different.

I challenge you to find a suitable attachment point for the rope

Administrator
Shoreham EGKA, United Kingdom

I'll collect more data during following days and try to draw some conclusions.

LDZA LDVA, Croatia

FL110, OAT -1
- 2400/19, peak EGT, IAS 116, TAS 137, 38 lph
- 2400/19, ROP, IAS 121, TAS 143, 42 lph

FL110, OAT +5
- 2400/19, ROP, IAS 118, TAS 142, 43 lph

FL100. OAT +5
- 2400/20, ROP, IAS 120, TAS 141, 46 lph

It was full throttle in all cases. Tomorrow I'll fly at lower altitude and I'll post results.

LDZA LDVA, Croatia

6500 ft, OAT +15

  • 2300/21.5, peak EGT, IAS 124, TAS 138, 38 lph

  • 2300/22.5, ROP, IAS 130, TAS, 146, 50 lph

  • 2400/22, peak EGT, IAS 125, TAS 140, 41 lph

[edited for formatting; use 2 spaces after last word of a line to force a line break]

LDZA LDVA, Croatia

What do you get at 2400/23", say at 2000-3000ft, peak EGT?

Peak EGT should be about 11.5 USG/hr (43.5 litres/hr).

Your

2400/22, peak EGT, IAS 125, TAS 140, 41 lph

seems closest to that, and it does seem slow.

Administrator
Shoreham EGKA, United Kingdom

2000 ft, OAT +23

  • 2400/23, IAS 130, 47 LPH, peak EGT
  • 2300/22, IAS 125, 40 LPH, peak EGT

6500 ft, OAT +15 (density altitude 7600 ft)

  • 2400/23 (full throttle), IAS 130, TAS 145, 44 LPH, peak EGT
  • 2300/22, IAS 123, TAS 138, 39 LPH, peak EGT
LDZA LDVA, Croatia

2400/23, IAS 130, 47 LPH, peak EGT

130 IAS is definitely way too slow.

Even for ISA+12.

Also 47LPH is not peak EGT. It is well ROP so you should be going even faster.

Something does not add up. At 2400/23", low level, your EGTs should peak at a common flow rate of about 43.5LPH. I would bet that whatever is responsible for this much richer "peak" is also responsible for the low engine power output.

Have you done the GAMI test i.e. checked that all cylinders reach peak EGT at roughly the same time as you lean?

Administrator
Shoreham EGKA, United Kingdom
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