Optimizing 201 engine performance

[Oldguy]

On the ROP side, reducing fuel will raise CHTs - on the LOP side adding fuel will raise CHTs.

Think of a curve with ROP and LOP on either side - like they actually are. Adding fuel makes you richer on the ROP side and moves you farther from the peak and reduces CHT. On the LOP side, reducing fuel moves you further into the lean side and reduces fuel. If you were truly LOP in your test, adding fuel would move you closer to peak and raise CHTs.

As a reminder, EGT readings are relative and CHT numbers are absolute. For EGT we are looking for the direction of change. i.e. increasing is moving closer to peak and decreasing is moving away from peak. This is true LOP and ROP. To manage your CHT temps, you need to know which side of peak you are on.

When setting my J up for cruise, I fly LOP by using my EDM 830. I honestly cannot tell you what any of my EGT numbers are with the exception that they go negative. My CHT temps, on the other hand, I watch like a hawk. They typically run under 365 in every season except summer down here in Alabama when they can broach 375 or so. In fact, I think the EDM 830 has an alert you set for max CHT, but nothing is available for max EGT.

Look in the pilot guide for your JPI and see about the steps to calibrate your fuel flow as it really does sound a large amount off. You are getting there, and you are getting to fly your plane. All in all, doesn't sound too bad.

[Oldguy]

Found this for Continental engines, but it should help show the relation to LOP/ROP operations. There is probably one for our Lycoming IO-360 but its is Sunday and I am still somewhat under the weather.

[Bob_Belville]

A little conversation about the power of your JPI 700' fuel information:

If you aren't doing so you should record and then reset the USD (fuel used since last reset) to zero at each fill up and compared USD to actual fuel required to fill the tanks. If you put this data in a spread sheet you'll be able to determine the accuracy of your fuel flow transducer. Your manual will describe the process for adjusting the fuel flow factor if there is a consistent difference between actual and JPI fuel USD. N.B., the USD and the FF will likely be off by the same percentage. I.e., if the JPI USD averages 10% more than the actual fuel used it probably means the indicated JPI FF is 10% higher than the actual fuel flow.

I have an EDM 930 but I suppose the fuel flow technology is essentially the same. My USD vs. actual is well under 0.5%. IOW, when I fill the tanks I will match the USD within 0.2 gallons on average. Literally, my last 11 flights USD totaled 231.6 gallons and the actual pumped was 231.7. (Since "full" depends upon how level the plane is and how patient the person on the nozzle is, it is recommended to look at a running total of several hundred gallons.)

In addition to being able to trust the FF displayed it is really helpful to know that if the USD says I have 10 gallons remaining I won't have less than about 9.8 gallons to get to the ground and a fuel pump.  

[cnoe]

I deliberately pulled mixture back and saw the EGT rise to 1504 before it started to fall off again... (then after bumping mixture richer)...This had me at 22" MP, 2550 RPM, WOT, 1460 EGT and 365 CHT.

 

Assuming you are referring to the LAST cylinder to peak when leaning you were then running ~44F LOP which is pretty dang lean at 22" MP and decreases power significantly. Necessarily the other 3 cylinders are running even more lean and providing even less power. Remember the power curve slopes continually downward as you lean beyond ~80F ROP.

 

You might regain substantial power by enriching to 10F-15F LOP (or even peak EGT at that power setting) as long as your CHTs stay below 380. That might give you 150 KTAS or close to it.

 

 

Sent from my iPad using Tapatalk

 

[Bob - S50]

Agreed.  When I lean, my richest cylinder is usually less than 10F LOP and the leanest is usually about 40F LOP.  The other two are somewhere in between around 20-30F LOP.

[Bob_Belville]

Here's an real world LOP example on the 930. All cylinders are LOP but not enough to get a big speed drop off. FF is 8.2 GPH for 61% power. I suppose KTAS was about 145. Unless the headwind is really strong this would be a good economy set up. CHTs are below 340F and OilT is below 200F. Happy, happy, happy.

[mccdeuce]

10 hours ago, cnoe said:

Older Js are indeed slower than newer ones, but not by that much. Mine is a stock 1978 model that I consider to be middle-of-the-pack in terms of speed. When moderately loaded running LOP I routinely see right at 150 KTAS w/ fuel flow of ~9 gph. 

My last speed check running 80F. ROP (GPS 3-direction confirmed) showed 163 KTAS at 75% power and 11.1 gph FF.

Jetdriven's '77 J is a few knots faster than mine, and @Mike_Elliott routinely flies a J (N984VW) that puts us all to shame.

I know that some will say that I should revert the timing back to 25deg. (I have an a3b6) but I also have electronic ignition with variable timing so roughly 30deg at altitude and the electronic really does all the work. (2 deg per 1" MP)  I will have to do some more testing for sure. I am also a bit plagued by cooling at the moment but I think I have found a spot to drop 10-15degs. 

Recently checked my rigging but can't hurt to check again. 

[Bug Smasher]

On 5/30/2017 at 0:58 PM, Bug Smasher said:

Guys, thanks for all the great info! I'll find out my GAMI spread on my way to Sedona on Thursday and report back.

Spread was closer to 1gph. Might be time to upgrade to GAMIs.

[jaylw314]

5 minutes ago, Bug Smasher said:

Spread was closer to 1gph. Might be time to upgrade to GAMIs.

That's not great, but not terrible.  My GAMI spread is 0.7 gph, and I can get about 20-30 degF LOP at most power settings.  It still doesn't explain the high indicated fuel flow rates...

[Shadrach]

On 5/29/2017 at 3:36 PM, gsxrpilot said:

Hi Chris, 

Welcome aboard. Just a couple of notes. Temps won't go down as you approach LOP. They will go down as you go PAST Peak. That's leaving ROP and transitioning to LOP

A quick point of order here... it's good to be doing this as you're learning, above 8000 or 9000 ft. You really can't make enough HP up there to damage the engine even running it in the worst possible way.

First go out and find Peak. Assuming you start at full rich on the mixture, pull the mixture back (leaning). As you do so you should see EGT's all rising. EGT's are the only numbers used to find Peak. As you keep on leaning, (pulling the mixture back), the EGT's will continue to rise and then will start to fall. The point where the EGT's are at their maximum temperatures is Peak. Note your fuel flow at Peak. Note the EGT's at Peak. Peak is a bad place to run your engine for any length of time, and this is why you learn this procedure at high altitude.

If you continue to pull the mixture back, the EGT's will continue to drop and you are going LOP (Lean of Peak). At some point, the engine will start to run rough. You are now a little TOO LOP. So add a little mixture back just to smooth out the engine. Note the EGT temps now. The difference between this value and the EGT's at Peak will be how many degrees LOP you are. Note fuel flow again. And report back to us.

Good explanation, but there is absolutely nothing wrong with running at peak EGT.  It is a fine power setting provided the richest cylinder is used to set power.  My engine runs quite cool at peak EGT and does so very smoothly. If I were to record CHT at peak vs 100 ROP, I would bet that peak would be cooler.

[Shadrach]

On 5/30/2017 at 2:20 PM, Bug Smasher said:

What is the consensus on running LOP without GAMI injectors on a fuel injected 360 Lycoming? 

95% of them will run just fine.  3% will run just fine after the intake leaks are fixed. 2% might need ignition system work.  Yes I made all of those stats up, but I've yet to come across an IO360 that can't be made to run smoothly LOP without GAMIs.  I am sure they exist, but it's rare situation .

[Shadrach]

On 6/4/2017 at 5:35 PM, Oldguy said:

Found this for Continental engines, but it should help show the relation to LOP/ROP operations. There is probably one for our Lycoming IO-360 but its is Sunday and I am still somewhat under the weather.

This is a good graph for conceptualizing the mixture spectrum and how it relates to EGT/CHT, but I think the the avg EGT/CHT numbers are on the high side for an IO360 in a Mooney.  One thing it does illustrate nicely is the fact (as I stated earlier) that peak EGT generates lower average CHTs (as well as lower mean cyl pressure) than the 100ROP.

[Shadrach]

On May 29, 2017 at 2:52 PM, Riddle78 said:

Mooney Gurus,

First time posting and I've really enjoyed reading the wealth of knowledge and experience on this forum. I'm sure this is covered somewhere in the 12,000 plus posts on this website but I haven't been able to uncover a thread that speaks to this (so I apologize in advance if there is one). I've owned a '77 201 for almost two years now and I'm not sure I'm setting my cruise power effectively. For example, my last cross country took place in the following conditions:  altitude 9,500, OAT 11C/53F, hottest CHT 385, hottest EGT 1363, 2500 RPM, throttle firewalled, and consuming just shy of 12 GPH. I consistently stayed between 145 and 150 KTAS...is that what I should expect? I thought I could be squeezing a little more out of it, even at that altitude. 

I'll be honest I don't quite grasp the whole LOP and ROP discussion, and I hesitate to take the CHTs above 400 if I don't have to. At what point does the temp typically fall back off as I approach LOP? I'm a total amateur in this regard and I hope someone can make me smarter (and help my motor last longer) with any perspective or advice. Thanks very much in advance.

Chris

Chris,

Don't over complicate this.

1) Determine your richest and leanest cylinder.

2) Climb to an engine safe altitude of say 6500'

3) pull the mixture until the plane runs slightly rough and enrichen until smooth.

4) looking at your richest cylinder, determine your setting

When performing step four, simply observe the EGT at which the engine begins to get rough and then slowly enrichen to peak and note the temp. That will tell you exactly how far your engine will run LOP and if you have FF installed, you should note that at each setting as well.

If the EGT fails to peak while performing number step four, then you know your engine will not run smoothly lean of peak as it began running rough before your richest cylinder peaked.

The GAMI test is nice and is precise if trying to modify injectors, but the engine is conforming (even F/A distribution) than all you really need to know is that it runs well LOP or it does not.

I've been at this so long that if I got a new plane, this is what I would do first.  I would have no qualms about running any IO360 in LOP cruise on my first flight by using the method above.

If my engine failed to run well LOP, then I would do a GAMI test to try to determine why and where the problem was. Otherwise, I would expect it to run as any other injected Lycoming.

Edited June 7, 2017 by Shadrach