M20K Fuel Flow

[Northern Mooniac]

I had my fuel flow set to spec, which is 40in and 24gal/hour

But with the merlyn and intercooler I don't ever use more than 37" on take off. Should I have this adjusted to be 24g/h at 37"?

[N231BN]

I would certainly think so, what does the intercooler STC paperwork say?

Edited October 16, 2017 by N231BN

[kortopates]

Yes, that is exactly what the STC instructions say to do, set max fuel flow for 100% power per the intercooler temperature table they gave you which should be about ~37.5" MAP. At Savvy, we like to see Continentals high FF number from their specified range of 23.0-24.7, plus 0.5 to 1.0 GPH above that so would prefer to see in the range of 25.2-25.7 GPH at ~ 37.5" 

[Northern Mooniac]

Thanks guys! I'll get it adjusted to that. I was reading another fuel flow article and realized mine isn't setup right. this is likely why my #1 cylinder is already hot on climb. sits at 410 during 110kt climb 500-700ft/min sure would be nice to get that 1000ft/min climb out!

[Northern Mooniac]

Here is the official fuel setup from Turbo Plus. According to my mechanic, it's no different? Am I missing something?
 

 

TSIO360 Fuel Setup - NEW 08.pdf

[carusoam]

We also have the Turbo Plus Guy here somewhere.

A search will probably find him.

Having Paul, from Savvy, supplies the logic.  

Check in with the turbo plus guy for the proper document/data to make sure you have it right for the hardware that you have.

@Turboplus has a thread detailing a few recent installations they have completed..

 

PP thoughts only, not a mechanic...

Best regards,

-a-

[johncuyle]

22 hours ago, Northern Mooniac said:

Here is the official fuel setup from Turbo Plus. According to my mechanic, it's no different? Am I missing something?
 

 

TSIO360 Fuel Setup - NEW 08.pdf

Process is basically the same, the difference is the MP at which 100% horsepower is achieved.  Without the intercooler it is 40" on a standard day.  With, it is adjusted based on temperature drop across the intercooler.  Ballpark, you should be flowing around 25GPH at 40" on a standard day without the intercooler and about 25GPH at ~36" on the same day with the intercooler.  My fuel flow was low before the install.  LASAR fixed it when the intercooler went in and between the additional fuel and the intercooler my CHTs are like 40dF cooler in climb.  100% power climbs at 90KIAS on a standard day yields a bit over 1000FPM climb and CHT below 380.  At 115KIAS using book standard climb power settings (with MP adjusted down, of course) I can set the cowl flaps in trail, climb at over 500FPM, and still stay cooler.  The intercooler was worth every dollar and pound of useful.

[carusoam]

Great detailed Pirep, JC!

Best regards,

-a-

[kortopates]

On 10/21/2017 at 12:08 PM, Northern Mooniac said:

Here is the official fuel setup from Turbo Plus. According to my mechanic, it's no different? Am I missing something?
 

 

TSIO360 Fuel Setup - NEW 08.pdf

The difference is very clear, exactly as @johncuyle says above. The mechanics that don't know any better, adjust your max FF for 40" redline (really overboosting it by 3" with the intercooler)  and then when you take off at real intercooler redline of ~37" your FF is a few GPH's too low. Good chance TIT is climbing above 1450F with everything forward - which should have your attention before liftoff - and CHT's will escalate. 

[Northern Mooniac]

Hey Guys, so we turned up the fuel flow today, so now i'm getting about 22gph on take off at 37in. what a difference in power. I was climbing out at 1200ft/min today. There was a wicked 35kt headwind and it was about +8 cecius, but my cht's were low it was pretty awesome.

Now my issue is running LOP. I would do 10.5gph no problem and now it runs rough, but if I push a little more fuel into it I was getting a smooth engine at 11 to 11.5gph or 75% power. at 70% or 10.5 it didn't run smooth.

I can't see how increasing the fuel flow would affect that?

[johncuyle]

On ‎10‎/‎23‎/‎2017 at 2:33 PM, Northern Mooniac said:

Hey Guys, so we turned up the fuel flow today, so now i'm getting about 22gph on take off at 37in. what a difference in power. I was climbing out at 1200ft/min today. There was a wicked 35kt headwind and it was about +8 cecius, but my cht's were low it was pretty awesome.

Now my issue is running LOP. I would do 10.5gph no problem and now it runs rough, but if I push a little more fuel into it I was getting a smooth engine at 11 to 11.5gph or 75% power. at 70% or 10.5 it didn't run smooth.

I can't see how increasing the fuel flow would affect that?

Me neither, but I have also noticed that leaning is trickier since getting the pressure adjusted.  On the ground at idle I don't seem to be able to lean as aggressively as I used to, and it seems to require a little more fiddling to get it leaned out in cruise as well.  I don't have experience with flying it without the intercooler and at correct FF (it was low before I went in) so I'm not sure whether it is due to the combination of changes or just the FF adjustment.  I can still get it to run lean, though, it just isn't quite as easy.

[Northern Mooniac]

ironically, I can get it to lean out to 75% power and keep temps in check where as before I could not get it over 70% without TIT getting too high. i'm trying to run 70% power to balance engine life and speed so hoping to stay out of that 75% zone...hopefully have some flights coming up so we'll see how it goes.

[milotron]

What rpm are you running at? Typically 2500 runs LOP better than lower, but should try it out. I can run 2400 or 2500 at 65%LOP no problem. I had been running 2500 all the time but I find 2400 a bit quieter with no real performance change.

 

I need to try different settings at higher power at LOP. When I have run 75%  I have gone ROP due to engine roughness, but my GAMI spread is over 0.6GPH.

 

iain

[Northern Mooniac]

So I went for  flight today. and I found that I can run 10.5gph lop but with 30in MP. if I ran higher than 31 I could only get the engine to run smooth at 11.5gph.

The interesting part is that now I can ROP at 15gph.

Im getting about 145-150 true off my aspen with lop and 160-165 rop. very interesting!

[N231BN]

What do you have for a FF instrument?

[Northern Mooniac]

JPI830 i haven't been up in a few weeks. busy with work and working on my ifr. i'm going to try using the low boost on take off and see if that helps.

[N231BN]

Ok, I was wondering if you were still using the stock FF as they all eventually turn unreliable. FYI, 22 gph is on the low end for takeoff FF. SID97-3g lists it at 23.0-24.7 gph.

[N231BN]

One more thing, ref. post #10 what manifold pressure and TIT are you running?

 

 

 

 

[jlunseth]

We have had several threads on this.  You were right to get the fuel flow adjusted.  On a normal day you probably don't hurt the engine with a fuel flow that is down a couple of gallons, but on hot day you certainly can, and I have not run into an A&P yet who understands that the fuel flow setting with the intercooler needs to be different.  You need to show them the Turboplus STC.

For LOP, I do the "big pull."  The big pull is something they teach at the APS seminar.  I make a slight throttle setting first, typically I dial the MP back to 35" from whatever takeoff MP was.  Then I dial the RPM back to my desired cruise setting,  I typically use 2450.  Once those settings are made, I pull the fuel flow back in one smooth pull until I feel the aircraft slow.  It is very perceptible.  That means you are on the lean side of peak.  Usually it means I am seeing 10.9 or something, for a fuel flow, but that is just temporary, because from there I adjust to my final setting.  The fuel flow and throttle are interlinked, so a change to one means a change to another.  The big pull has caused your fuel flow to reduce, but your MP is now also down somewhere in the 33 range.  Now you need to tweak both of them to get to the setting you want.  I shoot for 34" of MP and a fuel flow of 11.0-.2.  That is about 71% power.  You will want to adjust fuel flow to keep TIT at or under 1600.  Don't worry about the EGTs. As long as they are stable (not jumping around or one much higher than others) you are fine, and those instabilities, if they happen, are signs of some problem in the engine and not with your fuel flow setting.  This is about as much power as I can make LOP, and keep the TIT at or under 1600.

This works for my aircraft up to somewhere in the mid-teens.  If I go higher there is not enough cooling, and I have to go ROP to keep the TIT in line.  I am not leaning from peak TIT in making this setting by the way.  What I have done, is used my JPI930 enough times, leaning by EGT for the cylinder nearest peak on the LOP side, to know what my settings should be, and after that it is just a matter of keeping the TIT far enough under redline to keep the turbo healthy.  

People ask me "why 34", that is too high a power setting."  They are thinking in ROP terms, where power is dictated by MP.  On the LOP side, fuel flow determines %power.  The reason for the 34 is to make sure all cylinders are far enough LOP.  LOP is a matter of creating a lean air/fuel mixture, which you can do either by leaning the fuel with MP constant, or adding air with the fuel flow constant.  So that is what the 34" does, it adds air in order to make the mixture more lean.  When you add the air, you just have to make sure you tweak the fuel flow to get it back to that 11.0-.2 range because changing the throttle setting will change the fuel.  In the TSIO360LB, if you make these settings but use, say, 29" of MP, or 32", you are right around peak at 29 and maybe a little on the rich side, and just a few degrees LOP at 32, say 10 or so, and since the cylinders don't all run at the exact same setting, you may have a couple that are closer to peak.  Those are "red box" settings.  You are making pretty much the same power as at 34, but at a richer setting.

If I need to throttle down for some reason, say I have made my 34 and 11.1 setting and am nearing an airport so I want to slow the plane to 120 kts, I just leave the fuel flow alone and throttle back to 24-24.5 MP (it varies with the day).  Because the throttle and fuel flow are interlinked, the linkage will attempt to keep the same fuel/air ratio at the new MP setting, so the engine is running nicely LOP at your lower power setting (its probably in the 9's, but I don't even pay attention to it). and you are at a nice 120 kt approach speed.  I don't pay attention to the fuel flow at this lower power setting, by the way, not because I am being careless about the engine, but because I am now under 65% power, and under 65% you can run the fuel/air anywhere you want without hurting the engine.  It just keeps the cylinders cleaner to be at a nice LOP setting.

The one other thing to be mindful of is that when the fuel flow is set properly, it is probably going to be quite rich at idle.  When you are on short final the engine will tend to "burble," because it is overly rich.  This can be easily cured by leaning out further, with the prop driven by the descent you can lean out quite far and the engine will run smoothly.  You just need to remember to push the fuel flow in for a go around, and on the ground you need to push the fuel flow in some because with the aircraft is now moving more slowly, the engine can die without added fuel.  It does not happen in the air, it just happens on the ground as the plane slows.  The other way of handling this is to let the aircraft get behind the power curve during short final, so that you need to increase power to keep airspeed up, and when you do that, you are operating at a higher power setting and can push the fuel flow forward without creating the burbling.  The burbling is not unsafe, the engine is not going to quit, people on the ground will just constantly tell you there is something wrong with your engine when there actually is not.

Edited November 18, 2017 by jlunseth

[milotron]

1 hour ago, jlunseth said:

The burbling is not unsafe, the engine is not going to quit, people on the ground will just constantly tell you there is something wrong with your engine when there actually is not.

Love the burble!  Every instructor who comes up with me panics on short final when they hear that thinking the engine is going to die!

Fire breathing Mooneys!

[Emmet]

Are the 34“ with intercooler?

[jlunseth]

Yes, I have an intercooler.  The 34" is with an intercooler.  I use 36-37" for a takeoff setting, so it is a little less than takeoff.  You could go even leaner of peak if you set the MP higher, like 36, but I just think that would work the turbo too hard.

[jlunseth]

10 hours ago, milotron said:

Love the burble!  Every instructor who comes up with me panics on short final when they hear that thinking the engine is going to die!

Fire breathing Mooneys!

Yes, and the last Mooney instructor I flew with worried about whether the engine was going to die in the air, if I was leaning it so far it would quit on the ground without more fuel.  No, it doesn't.  I suppose you could pull it far enough to cut off all fuel, don't do that.  Pull it out far enough to smooth the engine.