LOP - What kind of Fuel Flows do you see?
Moderators: Rick, Lance Murray
- Steve
- 5 Diamonds Member
- Posts: 1973
- Joined: Thu Aug 12, 2010 1:23 am
- First Name: Steve
- Aircraft Type: DA40
- Aircraft Registration: N432SC
- Airports: 1T7
- Has thanked: 85 times
- Been thanked: 503 times
LOP - What kind of Fuel Flows do you see?
So, as I have noted in the past, I could never run my old engine LOP (and never did the GAMI process). I rationalized that avgas was the cheapest component of my flying costs. About 5 months ago I replaced my engine with a Lycoming factory-rebuilt engine. Aside from the fact that it has roller lifters and is zero-timed, the other big difference I have noted is that I am able to run it LOP.
Today, I flew it at 6500' and 5500', both at Best Economy (BE) settings (8.2 GPH) and at 25-50 LOP. 2200 RPM. Adjusting for LOP is somewhat difficult in my airplane for a couple of reasons:
1) The non-vernier mixture control is difficult to make small changes with, and
2) The VMS Microsystems engine monitor only samples CHT and (more importantly) EGT about once a second, so you have to be very slow in your adjustments around Peak EGT to get an accurate peak value. I don't like to have the engine running at Peak any longer than necessary...
Other than a small difference in MP at the two test altitudes, engine parameters were similar. EGT was 1450, CHT was 356, and FF was 6.3 GPH. I was a few KTs slower LOP. At BE EGT was 1400, CHT was 368, and FF was 8.2 GPH.
Saving nearly 2 GPH would be a significant operational factor in my trips to the FL panhandle, allowing non-stop flights vs my routine one stop for fuel. I also sampled some vibration data under the two conditions. The engine felt just a slight bit rougher LOP, but you likely wouldn't notice it unless you were looking for it. The recorded vibration data differed slightly in the X- and Z-axes only. X- was 0.162 g(rms) LOP and 0.138 g(rms) BE, Z- was 0.098 g(rms) LOP and 0.082 g (rms) BE. Both testing conditions had a Y- component of 0.096 g(rms). I have not (yet) dynamically balanced the new prop.
So, a bit surprised at the FF I'm able to get LOP. Is this near what others are able to get? Obviously, I only tested at a couple of (close) altitudes at one RPM setting. In the future I plan to "expand the envelope" of LOP operations.
Steve
Today, I flew it at 6500' and 5500', both at Best Economy (BE) settings (8.2 GPH) and at 25-50 LOP. 2200 RPM. Adjusting for LOP is somewhat difficult in my airplane for a couple of reasons:
1) The non-vernier mixture control is difficult to make small changes with, and
2) The VMS Microsystems engine monitor only samples CHT and (more importantly) EGT about once a second, so you have to be very slow in your adjustments around Peak EGT to get an accurate peak value. I don't like to have the engine running at Peak any longer than necessary...
Other than a small difference in MP at the two test altitudes, engine parameters were similar. EGT was 1450, CHT was 356, and FF was 6.3 GPH. I was a few KTs slower LOP. At BE EGT was 1400, CHT was 368, and FF was 8.2 GPH.
Saving nearly 2 GPH would be a significant operational factor in my trips to the FL panhandle, allowing non-stop flights vs my routine one stop for fuel. I also sampled some vibration data under the two conditions. The engine felt just a slight bit rougher LOP, but you likely wouldn't notice it unless you were looking for it. The recorded vibration data differed slightly in the X- and Z-axes only. X- was 0.162 g(rms) LOP and 0.138 g(rms) BE, Z- was 0.098 g(rms) LOP and 0.082 g (rms) BE. Both testing conditions had a Y- component of 0.096 g(rms). I have not (yet) dynamically balanced the new prop.
So, a bit surprised at the FF I'm able to get LOP. Is this near what others are able to get? Obviously, I only tested at a couple of (close) altitudes at one RPM setting. In the future I plan to "expand the envelope" of LOP operations.
Steve
- Rich
- 5 Diamonds Member
- Posts: 4607
- Joined: Mon Aug 30, 2010 12:40 pm
- First Name: Rich
- Aircraft Type: DA40
- Aircraft Registration: N40XE
- Airports: S39 Prineville OR
- Has thanked: 145 times
- Been thanked: 1186 times
Re: LOP - What kind of Fuel Flows do you see?
I didn't keep really hard data, but the one trip I used this technique to speed up by slowing down was a leg KPAE -> KBYI a number of years ago, en route to KFNL. This mad the trip one fuel stop instead of two.
The actual route covered on this leg, due to ATC vectoring, was about 525 nm. The IFR/VMC flight included a climb from takeoff at 500' MSL to 11,000'. Being it was summer, DA at cruise was likely about 12,500. The hard data I have is that this leg was 4 hours in the air and the plane took exactly 30 gallons at KBYI. So 7.5 GPH average and average TAS 131. I was only able to get about 20 deg LOP but CHTs plummeted to something like 320. I now know this low for CHTs isn't a great idea. As I recall I was using 2200 RPM.
Steve, I didn't know the -M1A was available with roller cam lifters. Did you use another variant?
The actual route covered on this leg, due to ATC vectoring, was about 525 nm. The IFR/VMC flight included a climb from takeoff at 500' MSL to 11,000'. Being it was summer, DA at cruise was likely about 12,500. The hard data I have is that this leg was 4 hours in the air and the plane took exactly 30 gallons at KBYI. So 7.5 GPH average and average TAS 131. I was only able to get about 20 deg LOP but CHTs plummeted to something like 320. I now know this low for CHTs isn't a great idea. As I recall I was using 2200 RPM.
Steve, I didn't know the -M1A was available with roller cam lifters. Did you use another variant?
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
- Steve
- 5 Diamonds Member
- Posts: 1973
- Joined: Thu Aug 12, 2010 1:23 am
- First Name: Steve
- Aircraft Type: DA40
- Aircraft Registration: N432SC
- Airports: 1T7
- Has thanked: 85 times
- Been thanked: 503 times
Re: LOP - What kind of Fuel Flows do you see?
Rich:
The Lycoming factory rebuilt M1As (and most of their other rebuilds) all come with roller cams. Apparently, the case has to be machined for this modification. Roller cam engines will have an "E" as the last letter of the SN, as mine does.
As for the FF on mine, I actually had a hard time believing it was accurate, since most of the numbers I had seen were similar to yours, around 7.5 GPH. I was limited in my ability to confirm the FF number by fuel usage on the short flight, but I started with 20.8 gallons and finished with 10.3 (filled the tanks). So I used 10.5 gallons for the 1.5 hours (average of 7 GPH for the whole flight including taxi, takeoff, climb, and 2 short runs of 8.2 GPH, plus the descent, landing and short taxi to the fuel pump). My fuel gauges are very accurate.
The Lycoming factory rebuilt M1As (and most of their other rebuilds) all come with roller cams. Apparently, the case has to be machined for this modification. Roller cam engines will have an "E" as the last letter of the SN, as mine does.
As for the FF on mine, I actually had a hard time believing it was accurate, since most of the numbers I had seen were similar to yours, around 7.5 GPH. I was limited in my ability to confirm the FF number by fuel usage on the short flight, but I started with 20.8 gallons and finished with 10.3 (filled the tanks). So I used 10.5 gallons for the 1.5 hours (average of 7 GPH for the whole flight including taxi, takeoff, climb, and 2 short runs of 8.2 GPH, plus the descent, landing and short taxi to the fuel pump). My fuel gauges are very accurate.
- blsewardjr
- 4 Diamonds Member
- Posts: 485
- Joined: Tue Jul 26, 2011 11:19 pm
- First Name: Bernie
- Aircraft Type: DA40
- Aircraft Registration: N377DS
- Airports: KCHO
- Has thanked: 120 times
- Been thanked: 146 times
Re: LOP - What kind of Fuel Flows do you see?
My last cylinder to peak (#4) usually peaks around 7.8 gph so when I run LOP I'm usually at 7.5-7.6 gph. Bernie
Bernie Seward, IR, AGI
2003 DA40 N377DS
KCHO Charlottesville, VA
2003 DA40 N377DS
KCHO Charlottesville, VA
- MarkA
- 3 Diamonds Member
- Posts: 169
- Joined: Mon Aug 23, 2010 4:58 am
- First Name: Mark
- Aircraft Type: DA40
- Aircraft Registration: N123MZ
- Airports: KHIO
- Has thanked: 115 times
- Been thanked: 135 times
Re: LOP - What kind of Fuel Flows do you see?
I’m sure there will be lots of opinions on how to best set up the IO360 for lean of peak operation at > 5000 ft but here is what I do:
.
- Climb wide open throttle, full rich, 2700 RPM, booster pump on, takeoff flaps
- At 400 ft AGL, reduce to 2400 RPM, turn off booster pump, raise flaps and continue the climb
- At the target altitude, continue wide open throttle and set the desired cruise RPM – I typically use 2400 or 2200 RPM
- Lookup the resulting manifold pressure and RPM on the engine performance table from the POH (attached)
- Lean to slightly less (~.2 gph) than best economy for lean of peak or slightly more than best power for rich of peak operation
- This keeps the engine outside the “red fin” area as defined in the Mike Bush’s articles
- Confirm the expected fuel flow, RPM, manifold pressure, altitude, and OAT all make sense
- Monitor the cylinder head temperatures to make sure they don’t exceed 380 in cruise
- If the CHTs are getting close to that threshold, either lean more aggressively (if LOP) or enrichen (if ROP) to reduce the CHTs
.
- Attachments
-
- Kneeboard POH engine setting by RPM and MP.pdf
- (432.91 KiB) Downloaded 117 times
2010 DA40 XLS, N123MZ, KHIO
https://youtu.be/LuQr6mGxffg
https://youtu.be/LuQr6mGxffg
- perossichi
- 3 Diamonds Member
- Posts: 188
- Joined: Tue Sep 18, 2018 4:05 am
- First Name: Peter
- Aircraft Type: DA40
- Aircraft Registration: N925RH
- Airports: KVNY
- Has thanked: 31 times
- Been thanked: 75 times
Re: LOP - What kind of Fuel Flows do you see?
My experiences are as follows
8-10k: 8.2 GPH, 138 TAS ( this is about 50 degrees LOP)
12-14k: 7.2 GPH, 133 TAS ( this is about 70 degrees LOP)
At 2300 RPM, WOT.
Of course at the higher altitudes, you don’t get as high MP.
Max CHT is 370 at 8-10k and somewhat lower at 12-14k.
I’d love a vernier mixture control and a turbocharger.
8-10k: 8.2 GPH, 138 TAS ( this is about 50 degrees LOP)
12-14k: 7.2 GPH, 133 TAS ( this is about 70 degrees LOP)
At 2300 RPM, WOT.
Of course at the higher altitudes, you don’t get as high MP.
Max CHT is 370 at 8-10k and somewhat lower at 12-14k.
I’d love a vernier mixture control and a turbocharger.
Sold 2002. Powerflo, Hartzell composite two blade, 530W/430, 345 transponder.
- Lou
- 4 Diamonds Member
- Posts: 370
- Joined: Sat Nov 21, 2015 1:39 pm
- First Name: Louis
- Aircraft Type: DA40
- Aircraft Registration: CGXLO
- Airports: CZVL
- Has thanked: 118 times
- Been thanked: 115 times
Re: LOP - What kind of Fuel Flows do you see?
Since installing Tempest fine wire plugs last year, I fly LOP nearly always. Cylinder 1 is the last to peak for my aircraft and as soon as it has and is running a few degrees LOP I stop. If I go further it gets just a teensy rough and I prefer not to do that. No GAMI.
Sample data from today:
6500’, 10C OAT, 29.78”
24.0” Manifold
2500 RPM
9.0 GPH
142-144 kts
If I dial it back to 2200 I see low 7’s fuel flows and mid 130’s. But if I can cruise at 140+ at 9 gph, life’s great.
Sample data from today:
6500’, 10C OAT, 29.78”
24.0” Manifold
2500 RPM
9.0 GPH
142-144 kts
If I dial it back to 2200 I see low 7’s fuel flows and mid 130’s. But if I can cruise at 140+ at 9 gph, life’s great.
- danno2000
- 3 Diamonds Member
- Posts: 88
- Joined: Thu Apr 06, 2017 4:26 pm
- First Name: Dan
- Aircraft Type: DA40
- Aircraft Registration: N270DS
- Airports: KAQW
- Has thanked: 55 times
- Been thanked: 75 times
Re: LOP - What kind of Fuel Flows do you see?
Running LOP in my steam-gauge 2003 is a must for CHT management, but I can't get more than 0.5 to 0.8 gph lower than best economy before I get more engine roughness than I'm comfortable with. So high-7s or low-8s is much more common for me at my typical 2200-2400 RPM range.
best,
dan
- Charles
- 5 Diamonds Member
- Posts: 644
- Joined: Thu Aug 26, 2010 5:36 pm
- First Name: Charles
- Aircraft Type: DA40
- Aircraft Registration: C-FLEV
- Airports: CYHU
- Has thanked: 28 times
- Been thanked: 102 times
Re: LOP - What kind of Fuel Flows do you see?
Dan, I experienced the same CHT issue and needed to run LOP or reduce power on hot days on my 2002 DA40 until I had the Arizona baffle installed, which resolved everything. Although my engine runs fine LOP, I always run at peak EGT now. Engine has 1940 SNEW and is still running strong.
- Derek
- 3 Diamonds Member
- Posts: 117
- Joined: Fri Apr 06, 2012 7:07 am
- First Name: Derek
- Aircraft Type: DA40
- Aircraft Registration: CGPDN
- Airports: CYTZ
- Has thanked: 18 times
- Been thanked: 19 times
Re: LOP - What kind of Fuel Flows do you see?
I was somewhat surprised to see this as well on a new to me 2002 DA40. It runs 7gall/hr around 128knots, or I can use 25% more fuel to go 7% faster!! Sweet spot is definitely cruising at 7gall/hr or so. I guess I’m slower than most because I have the two blade metal hartzel and no power flow. Engine runs perfect though.Lou wrote: ↑Sun Sep 26, 2021 3:28 am Since installing Tempest fine wire plugs last year, I fly LOP nearly always. Cylinder 1 is the last to peak for my aircraft and as soon as it has and is running a few degrees LOP I stop. If I go further it gets just a teensy rough and I prefer not to do that. No GAMI.
Sample data from today:
6500’, 10C OAT, 29.78”
24.0” Manifold
2500 RPM
9.0 GPH
142-144 kts
If I dial it back to 2200 I see low 7’s fuel flows and mid 130’s. But if I can cruise at 140+ at 9 gph, life’s great.