Fast is relative

[MyNameIsNobody]

Flew to Indy today. I am a LOP guy and for first hour flew at 5500 burning 10.5gph. Had a direct headwind. Went to 5lop burning 11.5gph 25 25 with ram air open and speed jumped from 130 knots to 149. Boom.  1 gph fuel flow increase for a 15 knot increase. Hottest cylinder was 350. Yes I will take that...

 

Edited March 17, 2018 by MyNameIsNobody

[Guitarmaster]

Flew to Indy today. I am a LOP guy and for first hour flew at 5500 burning 10.5gph. Had a direct headwind. Went to 5lop burning 11.5gph 25 25 with ram air open and speed jumped from 130 knots to 149. Boom.  1 gph fuel flow increase for a 15 knot increase. Hottest cylinder was 350. Yes I will take that...
 

10.5 seems really high for LOP ops. I usually see 8.4 at 130 indicated. That's about 40 LOP. At 5 LOP, I would be seeing around 9.5.

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[madjano]

Flew to Indy today. I am a LOP guy and for first hour flew at 5500 burning 10.5gph. Had a direct headwind. Went to 5lop burning 11.5gph 25 25 with ram air open and speed jumped from 130 knots to 149. Boom.  1 gph fuel flow increase for a 15 knot increase. Hottest cylinder was 350. Yes I will take that...
 

GAMI or stock. I've been able to get my stock injectors to run pretty smooth to 40 lop, at about 9ish gph. When I try it w/ram air open it gets rough below 15 lop.

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[ShuRugal]

12 hours ago, Guitarmaster said:

10.5 seems really high for LOP ops. I usually see 8.4 at 130 indicated. That's about 40 LOP. At 5 LOP, I would be seeing around 9.5.

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10.5 seems crazy high to me.  Couple weeks ago i took a trip around the Bay area, and my total fuel consumption / time flying was 8.3 gal/hr.  power settings in cruise were 2350x19" at 7500 msl.  No FF gauge in mine, so just lean to roughness and back off to smooth.

[MyNameIsNobody]

I can lean to 9 or 9.5gph at 5500.  I do not disagree that fuel flow would not appear to be lop at 10.5 or certainly 11.5gph. My primary point is that a gallon of gas an hour makes a massive 15 knot speed increase (indicated and over the ground) in my plane with no cylinder temp penalty. My engine seemed to love it. 

[MyNameIsNobody]

21.6 gallons added to fill tanks on a 2.3 hour flight. First hour was 130 knots at 10.3gph. Finish was at 11.5gph and 150 knots ground speed. Level at 5500 feet. 

[MyNameIsNobody]

13 hours ago, Guitarmaster said:

10.5 seems really high for LOP ops. I usually see 8.4 at 130 indicated. That's about 40 LOP. At 5 LOP, I would be seeing around 9.5.

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I hear you Matt. A direct headwind out of East yesterday. I always calculate my speed in knots over the ground. This was not an average or calculated speed. I never fly at an 8.5gph fuel flow. I am a 15lop to peak fuel flow guy.

[MyNameIsNobody]

A theoretical program had my setting above their power setting. I was 25 squared with ram air open at 5500 feet. A gallon netted 15 knots ground speed gain. I thought that was impressive and worth five bucks. 

[Guitarmaster]

I can lean to 9 or 9.5gph at 5500.  I do not disagree that fuel flow would not appear to be lop at 10.5 or certainly 11.5gph. My primary point is that a gallon of gas an hour makes a massive 15 knot speed increase (indicated and over the ground) in my plane with no cylinder temp penalty. My engine seemed to love it. 

That is true. Sometimes we jump over the dollar to get the dime. I'm on trips I would rather burn in gallon per hour more and get there faster.

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[gsxrpilot]

Where it makes sense to go deeper LOP and take the speed penalty is when it will eliminate a fuel stop.

Now that I fly a 252, it's difficult to back off the 75% power and 100 ROP. I like seeing TAS is the high 180's to low 200's depending on the altitude. But there have been a few long trips where going from 14 gph at 100 ROP to 9 gph at 30 LOP, eliminated a fuel stop. So even at a 15 to 20 knot penalty, I still get there quite a bit sooner.

But all things being equal, I'd rather buy the gas and go fast!

[Bob_Belville]

Where it makes sense to go deeper LOP and take the speed penalty is when it will eliminate a fuel stop.
Now that I fly a 252, it's difficult to back off the 75% power and 100 ROP. I like seeing TAS is the high 180's to low 200's depending on the altitude. But there have been a few long trips where going from 14 gph at 100 ROP to 9 gph at 30 LOP, eliminated a fuel stop. So even at a 15 to 20 knot penalty, I still get there quite a bit sooner.
But all things being equal, I'd rather buy the gas and go fast!

This morning I flew from MRN to VDF. 2nd and 3rd hours were at 65% LOP (8.7 gph) at 8000 and 9000. It appears that tas difference was only 5 ktas vs. 80 ROP 70%. CHTs were cooler. I almost always wind up LOP at 65% power or less.

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[Marauder]

This morning I flew from MRN to VDF. 2nd and 3rd hours were at 65% LOP (8.7 gph) at 8000 and 9000. It appears that tas difference was only 5 ktas vs. 80 ROP 70%. CHTs were cooler. I almost always wind up LOP at 65% power or less.

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You got some numbers to post? 5 KTAS difference would be great but in the few times I have run LOP, it is a 10 knots difference.

Interested in your CHTs and oil in particular.


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[jetdriven]

If you’re leaning it to where it loses more than about 3-5 KIAS it’s too lean. Yes, more than 50 LOP is not only slower but has a higher trip fuel burn because that lean of a mixture  is not as efficient. Pulling the throttle off some and leaning to ~20 LOP is more efficient. Close throttle and go faster on same fuel flow. Yes it sounds odd but it’s real. 

Edited March 18, 2018 by jetdriven

[Marauder]

If you’re leaning it to where it loses more than about 3-5 KIAS it’s too lean. Yes, more than 50 LOP is not only slower but has a higher trip fuel burn because that lean of a mixture  is not as efficient. Pulling the throttle off some and leaning to ~20 LOP is more efficient. Close throttle and go faster on same fuel flow. Yes it sounds odd but it’s real. 

I presume 20° is based on the last cylinder to peak.


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[RocketAviator]

58 minutes ago, jetdriven said:

If you’re leaning it to where it loses more than about 3-5 KIAS it’s too lean. Yes, more than 50 LOP is not only slower but has a higher trip fuel burn because that lean of a mixture  is not as efficient. Pulling the throttle off some and leaning to ~20 LOP is more efficient. Close throttle and go faster on same fuel flow. Yes it sounds odd but it’s real. 

Byron, I’m going to have to try this.... I’ll let you know.  I run basically full MP minus a couple inches and lean much more than 20!  I mainly watch TIT as CHT has never really been an issue at my normal settings.

[aviatoreb]

4 minutes ago, RocketAviator said:

Byron, I’m going to have to try this.... I’ll let you know.  I run basically full MP minus a couple inches and lean much more than 20!  I mainly watch TIT as CHT has never really been an issue at my normal settings.

I think the rockets lop are more tit limited when lop than anything else.

[Bob_Belville]

2 hours ago, Marauder said:

 

You got some numbers to post? 5 KTAS difference would be great but in the few times I have run LOP, it is a 10 knots difference.

Interested in your CHTs and oil in particular.


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Oil temps were very hot. Too hot to blame cowl. When I get the plane back, early May(?), I intend to replace cooler and vernatherm both of which have been to Pacific only a few years ago.

CHTs were acceptable to me though much hotter than yours. It's been a long day, I'm going to bed and will down load the data tomorrow and report. (I was seeing almost 155 ktas on the Aspen at 70% ROP and almost 150 ktas at 65% LOP. (As Byron emphasized, I was only 20 or so LOP. 8.7 gph = 65%. In the past I've run at 8.1 gph to non stop it to NH or WI which is under 60% and it does mean a lot slower, maybe 10 knots. 

[MyNameIsNobody]

My oil temp was 185

[Bob_Belville]

6 hours ago, Bob_Belville said:

Oil temps were very hot. Too hot to blame cowl. When I get the plane back, early May(?), I intend to replace cooler and vernatherm both of which have been to Pacific only a few years ago.

CHTs were acceptable to me though much hotter than yours. It's been a long day, I'm going to bed and will down load the data tomorrow and report. (I was seeing almost 155 ktas on the Aspen at 70% ROP and almost 150 ktas at 65% LOP. (As Byron emphasized, I was only 20 or so LOP. 8.7 gph = 65%. In the past I've run at 8.1 gph to non stop it to NH or WI which is under 60% and it does mean a lot slower, maybe 10 knots. 

@Marauder, @Sabremech, @AGL Aviation, @mike_elliott, @Guitarmaster, @jetdriven

From JPI:

OAT was 7C @ 8000' and 6C @ 9000'. Pretty warm at altitude for March.

CHTs averaged: 354, 340, 355, 335. CHTs max: 383, 361, 378, 368. These are much tighter than before and historically very acceptable. If the Oil Temp had been lower I could have cruised w cowl flaps close.

Oil Temps average: 216, max 228. 

Speed: I was IFR and did not do a proper multi leg speed check. Aspen TAS readout was showing 148-149 KTAS at 9000', 65% LOP, 8.7 GPH. My memory is always suspect but I think that's a good bit faster than before, I'd guess +/- 5 KTAS. (MAP was 22.6 at 8000' and 21.9 at 9000'. Baro was about 30.02, rising as I went south to 30.12 at Tampa.) LOP was about 10,26,12,12 LOP. Gami spread was 0.3 LOP and 0.4 ROP.   

Economy. 3:39 flight, 33 gallons. Avg. 9 gph. 

Joe at Hawk Aircraft Painting is estimating 6 weeks so it will be May before I can get more data.

If one or more of you analytic types want to view the data on Savvy send me a PM to get in.

Thanks for tuning in.

[mike_elliott]

52 minutes ago, Bob_Belville said:

I was IFR and did not do a proper multi leg speed check. Aspen TAS readout was showing 148-149 KTAS at 9000', 65% LOP, 8.7 GPH

Thats now a fast E

 8.7 was about 30 LOP?

[Guitarmaster]

I presume 20° is based on the last cylinder to peak.


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Yes, that is correct. Its measured by your richest cylinder... In other words, the last one to peak.

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[MyNameIsNobody]

I do not have a Sabre cowl, an ARI cowl, a LoPresticowl, or a SWTA cowl.  I have a Laser lower cowl closure. I do not have an oil cooler relocate, Hell I do not even have an oil filter besides screen.  I do not have a dorsal, wing root, flap gap seals or overs. I do have a three blade prop out front.   I do have a 150 knot E into a headwind while burning 11.5 at 5500 (ground speed) while indicating 350ish on highest cylinder that is always 15-20 higher than other three (#2). 4C 4 temp. Cylinders were happy. Oil happy at 185 degrees f. For $10.00 an hour (over 9.5gph at 5500) I have a fast bird, when I want to be fast. Of course, compared to a K or long body, not so much. I am OK with that. 

[Bob_Belville]

Thats now a fast E
 8.7 was about 30 LOP?

Not that far LOP. From 10 to 25. I think I listed earlier...

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[Guitarmaster]

I presume 20° is based on the last cylinder to peak.


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In addition, according to savvy, it's better to do a fast pull through Peak and attack the LOP from the back side..
In other words, pull straight into about 8.5 gallons an hour, set your monitor for ROP and slowly enrichen the mixture until you get the first cylinder that Peaks. Then go lean from there.
Apparently this recommendation was born from seeing fine wire plugs breaking and Tempest coming to the conclusion that pulling through Peak slowly was the cause.

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[MyNameIsNobody]

Return flight from Indy to CID today.  6500 feet vs. 5500 on way out.  11.3GPH 2500 RPM Full Throttle.  Ram air open.  24.5MP indicated.  157 Knots Ground Speed. 323,349, 328, 322 on cylinder temps.  5C temp.  183f on Oil Temp.  Total time on Tach was 2.3 (same as trip out) with 20.02 Gallons added.  When we launched weather in CID was 200 overcast in fog.  Forecast to clear.  Kept watching and just south in Iowa City clear, but CID still 300 overcast.  Right as I was being switched over to CID weather/fog cleared.  Nice!