Slow J

[oldn0tded]

19 hours ago, Alhall said:

Has anyone checked the muffler? It could be blocked some way.

+1

[wishboneash]

2 hours ago, Loogie said:

I flew yesterday, and noted my cruise at 6500ft, 25RPM, 24", 120 ROP(keeps my cyl 368 degrees), RTB was at 5500ft.  The results in smooth air= 158kts both ways.  My J is average and my engine is @ 100hrs SMOH.

 

 

Nice. Seems faster than the average J. As slowflyin asked, what is your FF at this setting? And what is "RTB"?

[bonal]

22 minutes ago, wishboneash said:

Nice. Seems faster than the average J. As slowflyin asked, what is your FF at this setting? And what is "RTB"?

Return to base?

[n824jl]

RE oil temp, what condition is the baffle?  small leaks can make temps rise.  also, flexibility maintains and directs air flow cooling.  Put the aircraft on jacks, raise the gear and check the fit of all gear doors.  Small amounts of drag from ill-fitting doors make significant  reductions in speed.  Also, if the powerplant has been removed, are the washers and mounting biscuits(vibration isolators) installed properly?  Good luck

[Mcstealth]

On 11/30/2015, 11:56:54, gsengle said:

Def check the lifters, I had a similar problem in an arrow, with no other symptoms, I had an intake valve not opening far enough.

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How was this issue discovered?

[gsengle]

What happened was I started having the cylinder drop out on very short final. Changed some plugs. Then it decided to do it in cruise. Just wasn't getting enough air. But no engine monitor on that plane made it harder to diagnose. But had been a bit anemic for a while leading up to the full blown issue...

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[Guitarmaster]

On November 29, 2015 at 8:29:59 PM, Llcrt said:

I own a 77 J model that will only true out at 160ish MPH or 140 knots.  It appears to be making good power, about 27" manifolf pressure on take off at 700 feet.  Typically in the Tesas summers, she only climbs at about 700 fpm, and the oil temp really starts to heat up.  I think my high oil temp is a result of my lower speeds.  The only 2 things I can think of to do now is to re-rig my flight controls because my right flap stays down ever so slightly and the ailerons are working to roll the plane back to the right.  Could be a little bit of drag.  The other thing that I was thinking was maybe a worn camshaft, but I have no oil in the filters when I cut them open and the engine appears to be running smooth.  Anybody have any ideas?

Is this a recent development or has it always been slow?  

 I have an F that was mis-rigged  and I was losing 9 knots.  I am getting close to being properly rigged and I true at 147KTAS.

[Loogie]

13 hours ago, slowflyin said:

Loogie,

Do you recall what your ff was on this run?

 

11.6 GPH average

RTB means return to base

[Mcstealth]

14 hours ago, gsengle said:

What happened was I started having the cylinder drop out on very short final. Changed some plugs. Then it decided to do it in cruise. Just wasn't getting enough air. But no engine monitor on that plane made it harder to diagnose. But had been a bit anemic for a while leading up to the full blown issue...

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And how did the mechanic finally ended up diagnosing it?

[gsengle]

I forget the details but had to open up and measure...

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[cnoe]

Loogie's numbers are similar to mine. Today I ran a N E S W track at 4,500 msl, 75F ROP, 25+", 2,500 rpm averaging 157.25 kts. Fuel flow at that setting was 12.3-12.5 gph on the JPI.

When I stepped up the power a bit to 100F ROP and 2,600 rpm the average speed increased to 159.5 kts with FF increasing to the low 13s. Even at this higher power setting the highest CHT was 374F (OAT 57F).

I typically run 15-30F LOP at 150 kts.

My '78 J is stock w/ 550 TSMO. I have the fixed step and a towel-bar antenna on the tail but no draggy belly strobe.

Keep looking and you'll get your speeds back in line. And please let us know what does the trick.

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[wishboneash]

18 hours ago, cnoe said:

Loogie's numbers are similar to mine. Today I ran a N E S W track at 4,500 msl, 75F ROP, 25+", 2,500 rpm averaging 157.25 kts. Fuel flow at that setting was 12.3-12.5 gph on the JPI.

When I stepped up the power a bit to 100F ROP and 2,600 rpm the average speed increased to 159.5 kts with FF increasing to the low 13s. Even at this higher power setting the highest CHT was 374F (OAT 57F).

I typically run 15-30F LOP at 150 kts.

My '78 J is stock w/ 550 TSMO. I have the fixed step and a towel-bar antenna on the tail but no draggy belly strobe.

Keep looking and you'll get your speeds back in line. And please let us know what does the trick.

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I tried mine today between LVK to SAC and back (5000/4000 ft). FF was 11.5 gph, ~25 to 26" MP and 2500 rpm, OAT=12C. CHTs below 370F, oil temp ~190F. I was seeing 152 KTAS. I have a lot of antennas which could be an issue. I guess I am about average to slightly slow.

[cnoe]

1 hour ago, wishboneash said:

I tried mine today between LVK to SAC and back (5000/4000 ft). FF was 11.5 gph, ~25 to 26" MP and 2500 rpm, OAT=12C. CHTs below 370F, oil temp ~190F. I was seeing 152 KTAS. I have a lot of antennas which could be an issue. I guess I am about average to slightly slow.

That's really close to what I was seeing (154 kts) at 2,400 rpm on my electronic tach. Your fuel flow is also lower than mine at 4,500' WOT and 2,500 rpm. Maybe you were running a little leaner than me or perhaps you have a little mechanical tach error?

Still, 150+ kts @ 11.5 gph would make any Arrow or Cessna RG owner green with envy! 

[wishboneash]

1 hour ago, cnoe said:

That's really close to what I was seeing (154 kts) at 2,400 rpm on my electronic tach. Your fuel flow is also lower than mine at 4,500' WOT and 2,500 rpm. Maybe you were running a little leaner than me or perhaps you have a little mechanical tach error?

Still, 150+ kts @ 11.5 gph would make any Arrow or Cessna RG owner green with envy! 

I have an EDM-900 so the tach is accurate. Also the mechanical tach reads similarly. I too normally run 25-30 LOP at higher altitudes burning 10.5 gph giving 148-150KTAS if I recall correctly.

[ArtVandelay]

I have an EDM-900 so the tach is accurate. Also the mechanical tach reads similarly. I too normally run 25-30 LOP at higher altitudes burning 10.5 gph giving 148-150KTAS if I recall correctly.

Ditto, except my FF is closer to 8gph, I got all the speed mods and remove my tie down rings.

[Hank]

51 minutes ago, wishboneash said:

I have an EDM-900 so the tach is accurate. Also the mechanical tach reads similarly. I too normally run 25-30 LOP at higher altitudes burning 10.5 gph giving 148-150KTAS if I recall correctly.

Wow! You beat my C by 10 knots, at the cost of 1.5-2.2 gpm . . . Or do I have a fast C? 

[wishboneash]

27 minutes ago, Hank said:

Wow! You beat my C by 10 knots, at the cost of 1.5-2.2 gpm . . . Or do I have a fast C? 

This is depressing 

[cnoe]

1 hour ago, wishboneash said:

I have an EDM-900 so the tach is accurate. Also the mechanical tach reads similarly. I too normally run 25-30 LOP at higher altitudes burning 10.5 gph giving 148-150KTAS if I recall correctly.

It's not tach error then. All our fuel flow readings are subject to the peculiarities of the specific installation so I suspect that's where the FF difference is. My k-factor setting may be just a bit different. Fuel consumed is easily within a gallon of what I pump back in but there is some minor variation.

The only aerodynamic advantage I might possibly have is the lack of the belly strobe which really does hang out there on most planes. And weight matters too; I'm light and with all my gear I only add 185# or so to the 45 gallons of fuel I was carrying on this test flight (making my total weight at ~2,195# or 545# below gross).

[bonal]

42 minutes ago, Hank said:

Wow! You beat my C by 10 knots, at the cost of 1.5-2.2 gpm . . . Or do I have a fast C? 

Hank I thought your C was running in the high 140's I figure you out run me by a knot or two but based on some other data I think I might have you in climb  what are book speeds for a J

[cnoe]

1 hour ago, wishboneash said:

I have an EDM-900 so the tach is accurate. Also the mechanical tach reads similarly. I too normally run 25-30 LOP at higher altitudes burning 10.5 gph giving 148-150KTAS if I recall correctly.

I'm a bit confused now (which happens more than I like). 

You said you were doing a 4-5K' speed run burning 11.5 gph (which I assumed was ROP), but then you said you're still burning 10.5 gph at altitude running LOP.

My fuel flow running LOP at 7-9K' is usually right at 9.0 gph (making 150 kts when light and a bit less when heavy).

I'm just surprised your fuel flow only varies 1 gph between a high power setting and a LOP setting.

[kmyfm20s]

Here my speeds when I was breaking in a new set of cylinders a few years ago when I had my J. I was at 1500' WOT/2700rpm.

 

[cnoe]

2 minutes ago, kmyfm20s said:

Here my speeds when I was breaking in a new set of cylinders a few years ago when I had my J. I was at 1500' WOT/2700rpm.

 

So it was YOUR M20-J that earned the name 201. Wow! 

[wishboneash]

36 minutes ago, cnoe said:

I'm a bit confused now (which happens more than I like). 

You said you were doing a 4-5K' speed run burning 11.5 gph (which I assumed was ROP), but then you said you're still burning 10.5 gph at altitude running LOP.

My fuel flow running LOP at 7-9K' is usually right at 9.0 gph (making 150 kts when light and a bit less when heavy).

I'm just surprised your fuel flow only varies 1 gph between a high power setting and a LOP setting.

You got me! I should have checked my numbers before posting from (bad) memory. I went back and checked my JPI data. It is close to 9 gph and about 146 KTAS. I have been running more ROP recently. Still not exactly a fast J!

[cnoe]

Just now, wishboneash said:

You got me! I should have checked my numbers before posting from (bad) memory. I went back and checked my JPI data. It is close to 9 gph and about 146 KTAS. I have been running more ROP recently.

 

Just now, wishboneash said:

 

Thanks for the clarification; that sounds right.

You know we can't have the "C crowd" on here bragging about their superior fuel consumption AND speed. 

[wishboneash]

Just now, cnoe said:

 

Thanks for the clarification; that sounds right.

You know we can't have the "C crowd" on here bragging about their superior fuel consumption AND speed. 

Shouldn't post on the "General Mooney Talk"! Haha.