My plane *is* slow! Please help.

[Slick Nick]

On 9/11/2024 at 9:01 AM, AndreiC said:

As I said earlier, I am hoping to get as much as can from what I have now. I don't have the money to replace a perfectly good prop for a couple of knots. If at the end of all investigations it turns out the prop is costing me all this speed loss, so be it. 

The plane was perfectly clean, with smooth leading edges.

I will see if my mechanic can borrow the Mooney rigging tools, to check the controls, at the annual. I'll also get the gear checked.

It’s the prop that’s killing your speed though. You’re pretty much getting what you should be with that prop out front. They make a huge difference in cruise speed, depending on the profile, which is why they aren’t that popular on the 4 cylinder Mooneys to begin with. Never mind the whole “3 blade prop on a 4 cylinder engine” harmonics argument, that’s another story. 

[Echo]

Going rich of peak up high is a pretty cheap speed mod.  Without mods THAT s what you should do if you want more speed.  See what you get.  Your plane is NOT slow.  It IS a Mooney after all.  Enjoy.

[Kelpro999]

Throw a large bag of dog food in luggage area , that’ll wake up that pup.

[AJ88V]

On 9/11/2024 at 11:01 AM, AndreiC said:

As I said earlier, I am hoping to get as much as can from what I have now. I don't have the money to replace a perfectly good prop for a couple of knots. If at the end of all investigations it turns out the prop is costing me all this speed loss, so be it. 

The plane was perfectly clean, with smooth leading edges.

I will see if my mechanic can borrow the Mooney rigging tools, to check the controls, at the annual. I'll also get the gear checked.

This is a wise and mature attitude.  All Mooney owners want more speed and in the practical sense, it's ultimately about bragging rights.  What you have is a lovely plane that delivers more knots per horsepower and more nm per gallon than just about anything else in the air, and you're doing it at a bargain price to boot!  Enjoy!

[Ragsf15e]

On 9/11/2024 at 10:19 AM, AndreiC said:

For these numbers, how close to standard atmosphere (ISA) were you? (I see you're in AL, so you may be much hotter than ISA.)

I am puzzled by the fact that with basically the same engine (IO360-A1A) I am nowhere near 70F ROP with 10.3 gph. I know my fuel calibration is accurate, because when I fill up the tanks it is within less than one gallon. Yesterday I was at 8500 ft but ISA+15 (so closer to 10500 DA), and at peak I was at 9.4 gph. To get to 70F ROP I probably would have needed at least 11-11.5gph.

Your ff of 11-11.5 to be ~100rop at 8500’ would match mine.  Heck, it might be 11.5-12 there if he’s at isa.

Running at peak is fine if you’re running low enough power, but if you’re trying to maximize speed, you’re going to have to be rop to get maximum power.

[Shadrach]

53 minutes ago, Ragsf15e said:

Your ff of 11-11.5 to be ~100rop at 8500’ would match mine.  Heck, it might be 11.5-12 there if he’s at isa.

Running at peak is fine if you’re running low enough power, but if you’re trying to maximize speed, you’re going to have to be rop to get maximum power.

I would submit that running at peak is OK at most cruise MP and RPM settings, provided you use the richest cylinder. The approximately 5% delta in power between peak and ROP just is not that large. 

Assuming the WOTRAO and 2500, 11.5 seems high at the 10.5K DA  @AndreiC describes. According to book power charts. At 2500, 2600rpm is no setting 100ROP setting at ISA 10,000' that consumes 11gph much less 11.5gph.  At 2700rpm and 100ROP, fuel flow would be around 11GPH...interpolated from the POH.

[Ragsf15e]

1 hour ago, Shadrach said:

I would submit that running at peak is OK at most cruise MP and RPM settings, provided you use the richest cylinder. The approximately 5% delta in power between peak and ROP just is not that large. 

Assuming the WOTRAO and 2500, 11.5 seems high at the 10.5K DA  @AndreiC describes. According to book power charts. At 2500, 2600rpm is no setting 100ROP setting at ISA 10,000' that consumes 11gph much less 11.5gph.  At 2700rpm and 100ROP, fuel flow would be around 11GPH...interpolated from the POH.

Yes, but @AndreiC and I were replying to @0TreeLemur saying that 10.3gph was around 70rop at 8500.  In my experience, my ff is higher than that there.  Maybe if it’s very hot?

[AndreiC]

1 hour ago, Shadrach said:

I would submit that running at peak is OK at most cruise MP and RPM settings, provided you use the richest cylinder. The approximately 5% delta in power between peak and ROP just is not that large. 

Assuming the WOTRAO and 2500, 11.5 seems high at the 10.5K DA  @AndreiC describes. According to book power charts. At 2500, 2600rpm is no setting 100ROP setting at ISA 10,000' that consumes 11gph much less 11.5gph.  At 2700rpm and 100ROP, fuel flow would be around 11GPH...interpolated from the POH.

This is what has been puzzling me too. Maybe the key words here are "provided you use the richest cylinder". I have been leaning using my EDM 700, stopping when the first EGT peaks. This (I guess) means that I am using the *leanest* not the richest cylinder. I hope operating this way has not damaged something in my engine (I always run well below 75%, closer to 70% or 65%). But next time I go I will try to use the richest cylinder for leaning to peak. 

Question: when going for 100 ROP, do you use the richest or leanest cylinder for reference?

[201er]

28 minutes ago, AndreiC said:

Question: when going for 100 ROP, do you use the richest or leanest cylinder for reference?

Depends on what your purpose is! If you're trying to go as fast as possible, gonna want to be around 80-100 ROP on the median cylinders (like 70, 90, 100, 120). That will probably give you the best possible power. But, it will also get quite hot. If you're trying to conserve cylinders, you'll probably want to be at least 100ROP on the leanest cylinder and richer on the others. You may not even be able to accept 100 ROP and need to go even richer (on leanest) to keep the CHTs below 380.

[KSMooniac]

If flying ROP, you want to use your LEANEST cylinder as the reference point, so that all of your cylinders are richer than the first to peak when leaning from the rich side, then enrichening to whatever setting you're trying to use.  If you confuse this, you might think you're setting 100 ROP, but one or more jugs might end up at 60 ROP which is a bad setting if running more than 65 or 70% power.  use the leanest cylinder as a reference, and you might end up with 100, 110, 120, 130 on all of them... much better.

The converse is true... when running LOP, you want to reference the RICHEST cylinder so that all of the others are safely leaner than your reference cylinder.  The bad situation here if you mix it up is that you set a cylinder at 20 LOP, but you used the leanest cylinder and you'll end up operating one or more at 20 ROP, which is a horrible place to be if running more than 65% power.

For those with IO-360 engines, I'd encourage everyone to chase down all induction leaks and try to get the fuel:air ratios balanced across all 4 cylinders.  the Lycoming IO-360 can be very well balanced, even without GAMIjectors.  I figured out my richest and leanest cylinders and swapped injectors (after verifying no induction leaks) and got my GAMI spread down to 0.0.

[Will.iam]

If you do have a cylinder in the red zone and at 75% you will know it soon enough as that cylinder will be climbing up past 400cht. If you richen or lean enough to get all the cylinders below 400 (lycoming 380 continental) you will see a fuel flow will also be outside the red box area. In very cold temps in winter drop your limit another 20 degree to be safe. 

[AndreiC]

Even in climbs I do not see CHT’s over 370, so I hope my misadventures did not damage anything. But thanks for the advice, I will keep it in mind. (My concern was that as I now understand it, by running at peak but using the leanest cylinder as reference, ai may have been running with a few cylinders 20 ROP, which is bad.) I’ll adjust my leaning procedure. 

My EDM-700 reports a difference of about  50F between the highest and lowest EGT. Is this what the GAMI spread is?

[KSMooniac]

24 minutes ago, AndreiC said:

 

My EDM-700 reports a difference of about  50F between the highest and lowest EGT. Is this what the GAMI spread is?

No, it is the difference in fuel flow between the first and last to peak.  

I'd suggest taking the www.advancedpilot.com online seminar... it is not free but worth way more than the cost.  I took the live version 17 years ago and learned more in a weekend than in some of my college courses.

[Hank]

18 hours ago, Echo said:

Going rich of peak up high is a pretty cheap speed mod.  Without mods THAT s what you should do if you want more speed.  See what you get.  Your plane is NOT slow.  It IS a Mooney after all.  Enjoy.

Thus is quite a surprise to me, I thought the E would significantly outperform my little C. We're much more comparable than I imagined! At 7500 msl, 2500/21" the E is faster but the C goes farther . . .

The important thing is that they're both Mooneys!

[0TreeLemur]

4 hours ago, Ragsf15e said:

Your ff of 11-11.5 to be ~100rop at 8500’ would match mine.  Heck, it might be 11.5-12 there if he’s at isa.

Running at peak is fine if you’re running low enough power, but if you’re trying to maximize speed, you’re going to have to be rop to get maximum power.

Sorry for my delayed response.  I've been flying.  A lot.

That's recent performance between AL and MI, it has been warm.   T=11C at 8500'.  At least 14C above ISA.

[Ragsf15e]

5 hours ago, AndreiC said:

This is what has been puzzling me too. Maybe the key words here are "provided you use the richest cylinder". I have been leaning using my EDM 700, stopping when the first EGT peaks. This (I guess) means that I am using the *leanest* not the richest cylinder. I hope operating this way has not damaged something in my engine (I always run well below 75%, closer to 70% or 65%). But next time I go I will try to use the richest cylinder for leaning to peak. 

Question: when going for 100 ROP, do you use the richest or leanest cylinder for reference?

These guys got you straightened out. Don’t run peak on the leanest.  If you run peak on the richest, the others are by definition lean of peak and should be cooler.  The converse leaves 3 cylinders in a bad spot just rich of peak.

If you want raw speed, closest relatively safe power setting is around 100 rich of peak from the leanest.

In all cases, keep an eye on your chts as they should remain below 400ish (I keep mine below 380ish). If you’re at peak/lop, leaner is cooler.  If you’re rop, richer is cooler.

Egt values are pretty meaningless.  You just need to know what order the cylinders hit their peaks and how far you are on either side of peak for the richest (running lop) or leanest (running rop).  Your gami spread is the difference in ff from first peak to last.  The tighter that is, the easier it is to get all the cylinders near the same setting (peak, lop or rop) which helps it run smoothly.  Typically this is more important at peak or lop.  
 

Ask if you have more questions!

Edited Friday at 11:08 PM by Ragsf15e