Fuel Flow at Full Power

[kortopates]

25 minutes ago, carusoam said:

Thanks TJ,  TCDS is the document I was thinking of....

From IO550 Experience...

Max Power Using the EGT method comes in a range from 200°F to 300°F ROP... (calibrated gauge on the instrument panel, blue box method...)

This is engine specific, but can be extended to other NA engines...

As for CHT data... it would be wise to specify the ignition timing that you are using while comparing these data points... or if you have changed the CR at all.... As one of us has done recently...  (firewall forward STC thread...)

Some IO360s Are Set To 20° And Others have been Set to 25° BTDC...

The IO550 is Set to 22° BTDC....

The further BTDC... the more fuel is converted to power... the cost is heat generated inside the cylinders... and increased risk, decreased safety margin, of piston melting ping...

It would be great to change timing in cruise to something like 30° BTDC under low power conditions... (Thinking out loud after seeing electronic ignitions this week)

Ordinary PP thoughts only, not a mechanic...

Best regards,

-a-

This is another Continental vs Lycoming thing and of course they are very different. Although we adjust  Max redline FF, idle FF and mixture on the Continentals we can only adjust idle mixture on the Lycoming as @Clarence said above.

With all the data I see at Savvy, the nominal max FF for sea level departure at 2700 rpm is about 18 1/2 GPH for the 200HP FI IO-360's  and about 16 1/2 GPH for the 180HP Carbureted O-360. (So @Hank is doing real well seeing 18 GPH with his carbureted O-360 - does it have power flow exhaust?)

Powerflow exhaust is an example of when some planes need to have their max FF adjusted up a bit since they can run even hotter after the mod. 

[carusoam]

Fabulous supporting data, Paul!  

Best regards,

-a-

[ArtVandelay]

Thanks TJ,  TCDS is the document I was thinking of....
From IO550 Experience...
Max Power Using the EGT method comes in a range from 200°F to 300°F ROP... (calibrated gauge on the instrument panel, blue box method...)
This is engine specific, but can be extended to other NA engines...
As for CHT data... it would be wise to specify the ignition timing that you are using while comparing these data points... or if you have changed the CR at all.... As one of us has done recently...  (firewall forward STC thread...)
Some IO360s Are Set To 20° And Others have been Set to 25° BTDC...
The IO550 is Set to 22° BTDC....
The further BTDC... the more fuel is converted to power... the cost is heat generated inside the cylinders... and increased risk, decreased safety margin, of piston melting ping...
It would be great to change timing in cruise to something like 30° BTDC under low power conditions... (Thinking out loud after seeing electronic ignitions this week)

According to Lycoming, max power occurs from 100°-200° ROP.
It would be great to change the timing based on RPMs (not if in cruise or not), the higher RPM, the more advanced the spark required. For those that race or just run 2700 for fun will benefit from 25°, if you reduce your RPMs to 2400-2500 cruise, 20° may be better. Don’t really know since I’ve never seen data from dynamometer testing. If you advance the timing too much you risk the combustion pressure peaking BTDC.
I wonder if those with electronic ignition, what do they use for timing, and I assume that the stamped timing no longer applies, and it varies the timing.

[MikeOH]

11 hours ago, Bob - S50 said:

A bit off track, and see if others agree, but if you CHT's are high, don't reduce RPM, that will most likely make it worse.  If you want to reduce power because everything is hot, and assuming you are still full rich, do it with the throttle.

Well, all I know is that backing off the rpm drops my CHTs to livable numbers (380 in climb); reducing rpm or MP would seem to reduce power, I would think.

[MikeOH]

10 hours ago, 1964-M20E said:

The fuel flow on the servo at full throttle may not be adjustable but you can ensure that when the red knob is pushed all the way in the mixture lever on the servo is in the full rich position.  This is linkage adjustable.

Excellent suggestion!

Thank you

[MikeOH]

8 hours ago, Marauder said:

That is where mine has historically run:

2016

 

2017

 

2018

Very good data there!

It strongly suggests that I do NOT have a fuel flow issue.  I guess I need to look elsewhere for my high CHTs and Oil Temp.  Your data are a carbon copy of mine....except your CHTs look great!

[MikeOH]

7 hours ago, kortopates said:

This is another Continental vs Lycoming thing and of course they are very different. Although we adjust  Max redline FF, idle FF and mixture on the Continentals we can only adjust idle mixture on the Lycoming as @Clarence said above.

With all the data I see at Savvy, the nominal max FF for sea level departure at 2700 rpm is about 18 1/2 GPH for the 200HP FI IO-360's  and about 16 1/2 GPH for the 180HP Carbureted O-360. (So @Hank is doing real well seeing 18 GPH with his carbureted O-360 - does it have power flow exhaust?)

Powerflow exhaust is an example of when some planes need to have their max FF adjusted up a bit since they can run even hotter after the mod. 

Oh, geez...now I have contradictory data from Marauders....I don't know what time it is, anymore!!

I do have a Powerflow exhaust, as well.  I've also heard a 10:1 rough rule-of-thumb...200HP needs close to 20 gph.

[kortopates]

11 minutes ago, MikeOH said:

Oh, geez...now I have contradictory data from Marauders....I don't know what time it is, anymore!!

I do have a Powerflow exhaust, as well.  I've also heard a 10:1 rough rule-of-thumb...200HP needs close to 20 gph.

We can also get a good sense of how rich your mixture is by EGTs (especially TIT with Turbos).  Chris @Marauder EGTs are all right where they should be from mid 1200 to mid 1300s'. I get concerned when I see them above 1400F full power and full rich. CHTs are too influenced by airflow to trust them as a proxy for mixture.

[chrixxer]

FWIW, my F (IO-360-A1A) sits right around 16.3 at take-off power, per the FS-450 (which is almost precisely dialed in; it might be off a percentage or two, I've never been off by more than 0.5 gallons even on a 6 hour flight).

[MikeOH]

1 hour ago, kortopates said:

We can also get a good sense of how rich your mixture is by EGTs (especially TIT with Turbos).  Chris @Marauder EGTs are all right where they should be from mid 1200 to mid 1300s'. I get concerned when I see them above 1400F full power and full rich. CHTs are too influenced by airflow to trust them as a proxy for mixture.

Hmm, at take-off my EGTs are in the 1200-1300 range, but at cruise (LOP, 8.5 gph) they run in the mid to high 1400s.  Anything to worry about there?

[MikeOH]

Just now, chrixxer said:

FWIW, my F (IO-360-A1A) sits right around 16.3 at take-off power, per the FS-450 (which is almost precisely dialed in; it might be off a percentage or two, I've never been off by more than 0.5 gallons even on a 6 hour flight).

Thanks for that!  My totalizer is similarly accurate; so, I believe my 16 gph numbers.  What do you see for CHTs on take-off?

[chrixxer]

1 minute ago, MikeOH said:

Thanks for that!  My totalizer is similarly accurate; so, I believe my 16 gph numbers.  What do you see for CHTs on take-off?

Depends largely on OAT, though its mostly oil temp that limits my climb-out performance. Also, it seems my baffles weren't reinstalled properly a while back (before I got the plane), so we'll see what things look like from tomorrow onward (er, well, once I get the JPI (re)installed...)

[Hank]

9 hours ago, kortopates said:

With all the data I see at Savvythe nominal max FF for sea level departure at 2700 rpm is about 18 1/2 GPH for the 200HP FI IO-360's  and about 16 1/2 GPH for the 180HP Carbureted O-360. (So @Hank is doing real well seeing 18 GPH with his carbureted O-360 - does it have power flow exhaust?)

No power flow exhaust. No fuel flow. The 18.2 is from my Owner's Manual. 

[MikeOH]

4 minutes ago, chrixxer said:

Depends largely on OAT, though its mostly oil temp that limits my climb-out performance. Also, it seems my baffles weren't reinstalled properly a while back (before I got the plane), so we'll see what things look like from tomorrow onward (er, well, once I get the JPI (re)installed...)

Interesting...I'm having high oil temp issues, as well.  But, they are tending to happen during cruise, not so much on climb out.  Definitely OAT correlated, but not perfectly.  That is the delta between OAT and Oil temp is not a constant, but oil temp is definitely lower at lower OATs.

[kortopates]

7 minutes ago, MikeOH said:

Hmm, at take-off my EGTs are in the 1200-1300 range, but at cruise (LOP, 8.5 gph) they run in the mid to high 1400s.  Anything to worry about there?

You're fine if you're seeing that (1200-1300) range at sea level and 2700 rpm.

Cruise EGT isn't even related since you're leaning to that; it's more of function of your % power (8.5 GPH isn't that high either).

[MikeOH]

6 minutes ago, kortopates said:

You're fine if you're seeing that (1200-1300) range at sea level and 2700 rpm.

Cruise EGT isn't even related since you're leaning to that; it's more of function of your % power (8.5 GPH isn't that high either).

Good!  That's what I thought, but appreciate the confirmation:)

It's interesting that several pilots are reporting near my number of 16, but the Savvy data is up around 18...going by the statistics suggests I should get to the bottom of this.  I'm going to start with making sure the mixture control is really going full on the FI Servo.

I also wonder if there are slight version variations in FI Servos and, given how old our planes are, that some may have had an improper FI Servo installed??

[Bob_Belville]

30 minutes ago, MikeOH said:

Hmm, at take-off my EGTs are in the 1200-1300 range, but at cruise (LOP, 8.5 gph) they run in the mid to high 1400s.  Anything to worry about there?

No. Sounds perfectly normal. 8.5 gph is just under 65% LOP for a 200 hp engine. 

[kortopates]

50 minutes ago, MikeOH said:

Good!  That's what I thought, but appreciate the confirmation:)

It's interesting that several pilots are reporting near my number of 16, but the Savvy data is up around 18...going by the statistics suggests I should get to the bottom of this.  I'm going to start with making sure the mixture control is really going full on the FI Servo.

I also wonder if there are slight version variations in FI Servos and, given how old our planes are, that some may have had an improper FI Servo installed??

We see significant amount of variation in max FF, and you're not taking off from sea level either. KPOC is 1014' which reduces your MAP by a full 1". You're good. 

As I said above, I wouldn't be the slightest bit concerned with those EGTs.

[chrixxer]

2 hours ago, kortopates said:

you're not taking off from sea level either

Neither am I ... KTOA is at 102'!  

[kortopates]

12 minutes ago, chrixxer said:

Neither am I ... KTOA is at 102'!  

 

2 hours ago, kortopates said:

We see significant amount of variation in max FF

where are your EGTs?

[Bartman]

22 hours ago, jaylw314 said:

I'd check the air filter and intake first!!

Yeah, you never know what you might find in there. Ask @chrixxer

[David Lloyd]

16 GPH flow seems a bit low to me but since you are climbing and max flow stays pretty constant and as manifold pressure drops with altitude less horsepower is made requiring less fuel so as you climb things pretty much correct themselves.  

A couple posts mentioned timing.  20 Or 25.  Which is yours? Is your timing set correctly?  I have found this to be equally critical to cylinder head temps as fuel flow.  Being experimental I can monkey around with timing.  20 Degrees BTDC my cylinder temps are cool.  I can climb at low airspeed on a hot day.  26 Degrees BTDC and I must be careful with the mixture to avoid redline CHTs in cruise.  9.5:1 Pistons put me closer to detonation than your 8.7:1 compression ratio.  23 Degrees works well for me with CHTs under control.  Someone mentioned hot oil temps.  Here again with hours piddling with marginal cooling I have found a direct correlation between CHTs and oil temps. No kidding, right? Wait.  If cruising a full power rich of peak mixture with CHTs around 400 degrees I will have oil temps of around 203-205.  Pull the mixture to lean of peak and CHTs may come down to 365-370 and after a while oil temps will ease of to about 190. 

Edited July 31, 2018 by David Lloyd

[jaylw314]

37 minutes ago, David Lloyd said:

16 GPH flow seems a bit low to me but since you are climbing and max flow stays pretty constant and as manifold pressure drops with altitude less horsepower is made requiring less fuel so as you climb things pretty much correct themselves.  

A couple posts mentioned timing.  20 Or 25.  Which is yours? Is your timing set correctly?  I have found this to be equally critical to cylinder head temps as fuel flow.  Being experimental I can monkey around with timing.  20 Degrees BTDC my cylinder temps are cool.  I can climb at low airspeed on a hot day.  26 Degrees BTDC and I must be careful with the mixture to avoid redline CHTs in cruise.  9.5:1 Pistons put me closer to detonation than your 8.7:1 compression ratio.  23 Degrees works well for me with CHTs under control.  Someone mentioned hot oil temps.  Here again with hours piddling with marginal cooling I have found a direct correlation between CHTs and oil temps. No kidding, right? Wait.  If cruising a full power rich of peak mixture with CHTs around 400 degrees I will have oil temps of around 203-205.  Pull the mixture to lean of peak and CHTs may come down to 365-370 and after a while oil temps will ease of to about 190. 

Damn you and your experimental stuff!  We are stuck with only 20 and 25 deg BTDC as choices.  I tried to get 22 deg by trying to convince my IA to retime the mags while not wearing his glasses, but he just rolled his eyes.

[EricJ]

I happened to look today and mine is flowing 17.9 gal/hour at takeoff and early climbout.    Apparently that's within the typical range, but is another data point.

 

[MikeOH]

Just wanted to thank everyone for their input; most appreciated!

After I sort this out, I'll post back...who knows, it may well be more than one thing responsible for my high oil temps and having to climb at reduced power to keep my CHTs under 400....fuel flow was a thought, but timing, baffling, vernathrem, plugged oil cooler...