Upgrading DA42 with CD-155 engines

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TimS
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Re: Upgrading DA42 with CD-155 engines

Post by TimS »

At the same fuel flows there is a fairly consistent 3 knot improvement.
I can foresee five possible reasons for this:
1. The engine efficiency increased a touch
2. New props are more efficient
3. Reduced drag, likely from radiator changes
4. Inaccurate fuel flows
5. Inaccurate readings, caused by pressure changes to the pitot/static system

I do not see 1,4, or 5 as likely. But more data could help eliminate 4 & 5.
I wonder if there is an affordable way to determine if 2 and/or 3 made the speed change?

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Re: Upgrading DA42 with CD-155 engines

Post by ememic99 »

I agree about 1, 4 and 5 and definitely more data will help on clarifying 4 and 5. Regarding 3, the cowling modification is minor and I don’t think it has some influence. That leaves 2 as most probable reason. I remember that the tests Mr. Crosby did during certification showed some 3 kts IAS difference between original and scimitar props.
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Re: Upgrading DA42 with CD-155 engines

Post by ememic99 »

Here are some new cruise data for CD-155 - IAS, TAS.

FL 160:
- load 85% 137 kts, 178 kts, 2250 RPM, 7.1 g/h per engine
- load 80% 135 kts, 176 kts, 2200 RPM, 6.9 g/h per engine

FL 140:
- load 89% 142 kts, 180 kts, 2300 RPM, 7.6 g/h per engine
- load 85% 141 kts, 178 kts, 2230 RPM, 7.4 g/h per engine
- load 80% 138 kts, 175 kts, 2120 RPM, 7.0 g/h per engine
- load 75% 135 kts, 171 kts, 2040 RPM, 6.4 g/h per engine
- load 70% 132 kts, 167 kts, 1990 RPM, 6.0 g/h per engine
- load 65% 126 kts, 158 kts, 1950 RPM, 5.2 g/h per engine

FL110:
- load 90% 146 kts, 175 kts, 2180 RPM, 7.8 g/h per engine
- load 85% 144 kts, 173 kts, 2150 RPM, 7.5 g/h per engine
- load 80% 141 kts, 170 kts, 2100 RPM, 7.0 g/h per engine
- load 75% 136 kts, 164 kts, 2030 RPM, 6.4 g/h per engine
- load 70% 133 kts, 160 kts, 1990 RPM, 5.9 g/h per engine
- load 65% 128 kts, 154 kts, 1950 RPM, 5.2 g/h per engine
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Re: Upgrading DA42 with CD-155 engines

Post by dgger »

Curiosity got me going here and I took the liberty to plot your values against those take from my G1000 logs. While I would not give much about absolute performance (given that plenty of variables such as mass, CG. etc. are not controlled for), I like to see a tendency of the CD-155 to loose power at altitude faster than the E4.

Image

Image
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Re: Upgrading DA42 with CD-155 engines

Post by ememic99 »

dgger wrote:I like to see a tendency of the CD-155 to loose power at altitude faster than the E4.
Which is to be expected due to fact that CD-155 has critical altitude of 8000 ft while E4 has 11000 AFAIK.

Can you add FF data for specified load on diagrams?
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Re: Upgrading DA42 with CD-155 engines

Post by dgger »

ememic99 wrote:Can you add FF data for specified load on diagrams?
Certainly can. Tell you what. Would you be ok to provide the raw G1000 log files? I could then do a speed vs. FF plot and would correct for OAT and whatnot. That might yield a better comparison as at least the methodology to process data from both engine would be identical. It would be later next week, though, as I get to fly a bit in the course of the next days.

EDIT: Fixed false attribution of quote
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Re: Upgrading DA42 with CD-155 engines

Post by ememic99 »

Unfortunately I can’t provide logs since that feature doesn’t exist in old(er) G1000 software. However, your data gives great insight to AE performance.
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Re: Upgrading DA42 with CD-155 engines

Post by dgger »

ememic99 wrote:Unfortunately I can’t provide logs since that feature doesn’t exist in old(er) G1000 software. However, your data gives great insight to AE performance.
I wasn't aware of that. Not a problem. I will adjust the plots for FF using the values you had already posted, then.
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Re: Upgrading DA42 with CD-155 engines

Post by ememic99 »

Some new values are here.

FL120:
- load 92% 145 kts, 177 kts, 2300 RPM, 8.0 g/h per engine
- load 90% 144 kts, 176 kts, 2270 RPM, 7.9 g/h per engine
- load 85% 143 kts, 175 kts, 2150 RPM, 7.5 g/h per engine
- load 80% 140 kts, 170 kts, 2100 RPM, 7.0 g/h per engine
- load 75% 136 kts, 166 kts, 2030 RPM, 6.4 g/h per engine
- load 70% 132 kts, 162 kts, 1990 RPM, 5.9 g/h per engine
- load 65% 126 kts, 153 kts, 1950 RPM, 5.2 g/h per engine
- load 60% 121 kts, 147 kts, 1930 RPM, 4.8 g/h per engine
- load 55% 117 kts, 142 kts, 1915 RPM, 4.5 g/h per engine
- load 50% 112 kts, 137 kts, 1900 RPM, 4.2 g/h per engine
- load 45% 106 kts, 130 kts, 1890 RPM, 3.8 g/h per engine
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Re: Upgrading DA42 with CD-155 engines

Post by Antoine »

Emir congratulations on the great upgrade. I am delighted that DAI increased prices so that John Crosby's solution makes financial sense.
Peter: just to make sure I understand what you are comparing with:
Is your DA42 NG stock or an upgraded TDI ?
Do you have the conventional "chopstick" prop or the scimitar blade upgrade?

It seems that the "Crosby" DA42 with scimitar blades is generally faster than the NG, but the prop may be the primary reason assuming the NG has no scimitar blades.

Keeping in mind that the NG has a total of 26 additional HP, we can safely conclude that the Corsby solution has aerodynamics and weight playing in its favor - substantially.

Thank you for sharing the data. Very professional.

My dream DA42 would be a GFC700 equipped "Crosby" with as many as possible of the -VI mods implemented... Best bang for the buck and probably most fun and safest to fly due to lowest weight.
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