LOP the horse is not dead

[drgwentzel]

Flyers,

Sorry to beat a dead horse with this but here it goes:

Ok...'71 Cessna Cardinal RG, I just put in a JPI EDM 800. *I do *not* have GAMIjectors and i have about 1700 hours SMOH.

Question: *What is the difference between the GAMI Lean Test and just using the EDM 800's Delta Fuel Flow (GAMI Spread) that you can pull up easily after leaning LOP and holding the LF Button down? *The manual GAMI lean test requires a safety pilot (if doing it with pen and paper) and at least 1.0 on the Hobbs if you do it correctly by the longhand method. *Is the EDM less accurate than paper? *

Question/statement: *my GAMI Spread by the EDM automatic calculation has varied from 0.2, 0.5 and 0.7 twice in 4 flights. So what is a pilot to believe? *I think GAMI recommends less than 0.5 GPH delta for LOP operation. *The delta fuel flow appears to be a dynamic figure, am I safe to operate LOP with these figures? *My guess would be no. *

Question: *in reading about LOP operation on an IO360 I hear people saying to lean to about 35 degrees LOP. *Hey! *There are 4 cylinders here and each one of them has a different figure. * *If any one is 35 LOP the others are not. *Which cylinder should be 35 deg lean of peak? *The first or the last to peak? *My guess is the last to peak.

My IA says to never run a Lycomming LOP. *Only big bore Continentals should be run this way. *What is Lycomming's stand on this? *

My IA also opines that GAMIjectors in an IO360 are "overkill" and totally unnecessary and a waste of money.

He also has the position that if I have run the engine ROP for its 1700 hours, running it LOP for the last 300 would cause trouble and be potentially detrimental. *He did not explain his thinking or provide any science and I had no intention of debating him on the subject as I have no experience to offer other than common sense, gut feeling and what I have read on the Cardinal Flyers website and aviation newsgroups such as this one.

What say the group?

Gene Wentzel - '71 177RG

 

[Bayou Boy]

I don't speak for the group but I would tell you to go over to avweb and read the savvy aviator columns that concern LOP operation. I run a lycoming io540 in my PA-32 without an engine monitor or gamis and can most assuredly run LOP. Above 8500ft at full throttle and 2400rpm I run 13 gph: well LOP. I can get down to 10 gph before roughness.

 

[SCCutler]

1. The GAMIjectors are flow matched - but your factory injectors may be close enough that you can still run LOP- try it;

2. THere is no reason of any kind why a Lycoming cannot be run LOP;

3. If you fly at 65% or less (somewhere in there), you ain't gonna hurt it anyway;

4. Try at 8,000 or so (where you simply cannot develop enough power to hurt the engine anyway); using "lean find" mode on your JPI, pull until you identify peak, note fuel flow there, pull back until the temperature of the first-to-peak cylinder (it'll be blinking) is around 35* lower and stable. If the engine is running smoothly (and you'll see on the JPI right away if any cylinder is not making power), you're good to go. Note the fuel flow and that'll be your target for similar power settings.

 

[Ted]

The summary is that, it's really pretty simple.

If you'd like to fly up to Williamsport, I'd be glad to give you some instruction in operating your engine LOP or ROP with your engine monitor, and explain how to make the most of it and interpret it.

 

[kgruber]

LOP-SOP

 

[Lance F]

Your IA is woefully uninformed. Wonder what else he's telling you that is absolutely wrong?

 

[Ted]

Your IA is woefully uninformed. Wonder what else he's telling you that is absolutely wrong?

Few IAs fly, and those that do probably don't fly with any sort of significant instrumentation. So they are typically the last people you should be getting advice from on engine management.

 

[SCCutler]

Few IAs fly, and those that do probably don't fly with any sort of significant instrumentation. So they are typically the last people you should be getting advice from on engine management.

Like you'd have even a clue about Lycoming engines....

 

[n20junkie]

When you use less fuel you use less lead.

Lead is there for exhaust valves.

LOP engines tend to have exhaust valve issues.

We ran our columnia ROP. The exhaust valves look great and the service center couldn't believe us when we said we run ROP. But after the borescope was done their opinions changed.

If you take the airspeed you fly while LOP. Then just pull the manifold pressure bace to obtain that airspeed while remaining ROP, the difference is about 1 GPH. So why all the fuss over LOP. At least in a turbocharged acft.

I build very high HP engines, I also tune them. We never ever go LOP. Its not worth the risks during cross over. The crossover is where much of the damage is done. Even a few seconds at peak can torch a turbo and warp a valve.


Oh and I am an IA, but I am also and ATP. So this is combined knowlege gained from flying planes, then tearing those very engines down.


Ask cessna how the LOP stuff is working out on the 400 series singles. Not one I have ever heard of making it past 600 hours without torching the valves.

 

[Ted]

Like you'd have even a clue about Lycoming engines....

Or any other, for that matter!

When you use less fuel you use less lead.

Lead is there for exhaust valves.

LOP engines tend to have exhaust valve issues.

We ran our columnia ROP. The exhaust valves look great and the service center couldn't believe us when we said we run ROP. But after the borescope was done their opinions changed.

If you take the airspeed you fly while LOP. Then just pull the manifold pressure bace to obtain that airspeed while remaining ROP, the difference is about 1 GPH. So why all the fuss over LOP. At least in a turbocharged acft.

I build very high HP engines, I also tune them. We never ever go LOP. Its not worth the risks during cross over. The crossover is where much of the damage is done. Even a few seconds at peak can torch a turbo and warp a valve.


Oh and I am an IA, but I am also and ATP. So this is combined knowlege gained from flying planes, then tearing those very engines down.


Ask cessna how the LOP stuff is working out on the 400 series singles. Not one I have ever heard of making it past 600 hours without torching the valves.

Your experience isn't representative of anything I've seen, other than people who say they're running LOP (and may be), but are doing it incorrectly and then yes, torching valves, cooking turbos, and other such things. But there are no shortage of people on this board and elsewhere who have had very, very good luck with LOP operation. In airplanes I've done it for over 2000 hours of piston engine time, on stands even longer. No engine problems that I've seen have been caused by LOP operation.

The lead isn't there for exhaust valves (other than to cause them to stick). It's there as to boost the anti-knock characteristics of the fuel. Also, your Columbia may only have a 1 gph difference ROP vs. LOP, but that's not representative of what I've seen on most aircraft.

Most mechanics I see that talk about LOP "Issues" are really talking about people just running their temperatures too hot - CHTs, EGTs, TITs. Unlike a turbine where red line is a goal, on pistons, that's not the case. The engines you build (I'm assuming automotive) are probably not particularly well-suited to LOP operation. Most aircraft engines (although not all) tolerate it well. They also tolerate ROP operation well. The trick with either of them is doing it correctly.

 

[Geico266]

Lycomings run LOP nicely.

The trick to doing it safely is balancing the injector fuel flow so that the EGTs peak at the same fuel flow.

To set the engine up each EGT must have it's own temp gage, and you should have a fuel flow meter, and a clip board. You will need a passenger / safety pilot. Start at 7000 MSL and sqare the engine up 2400 RPM and 24" MP. Start with the fuel flow .5 GPH rich. Write down all EGT's. Lean .2 gallons and let the engine temps settle for a min or so then record the temps again below the first readings. Continue until all cylinders have peaked.

With the above info contact a company that sells and serves engines for your plane and injectors and give them the info. They will be able to sell you replacement nozzles for your injectors to adjust the flow to match. After you install the new nozzles repeat the test. The EGT's should peak at he same time. The temp is not important, it is geytting them to pesk at the same time that is the key to successful LOP operations.

Do not try and drill out the nozzles. They are honed, not drilled.

 

[Ted]

The trick to doing it safely is balancing the injector fuel flow so that the EGTs peak at the same fuel flow.

While that does help (and from what I've seen, the GAMIjectors do seem to work well on the IO-360s), on my parallel valve IO-540s, the stock injectors work very nicely and run LOP just fine.

 

[Geico266]

While that does help (and from what I've seen, the GAMIjectors do seem to work well on the IO-360s), on my parallel valve IO-540s, the stock injectors work very nicely and run LOP just fine.

Stock injectors work just fine. Each injector has a flow nozzle that can be easily replaced with a larger or smaller diameter so that the flow is the same to each cylinder based on EGT's. Obviously, different manufacturers have different injectors, but they all (I think) have replaceable nozzles.

Have you run the flow test?

 

[Ted]

Have you run the flow test?

Nope. But the plane doesn't have anything more precise on fuel flow than the factory fuel flow gauge. The primary purpose of the flow test is to see how balanced things are. If your engine is balanced well from the factory, you can still run LOP fine. You may not be able to run quite as lean prior to the engine getting rough, but that doesn't mean that you can't still run LOP happily.

In the case of my Aztec, it's not worth putting GAMIs on. The 310 would benefit from it, but I'm still doing fine 300 hours later on it without them (yes, running LOP).

 

[Lance F]

I have run a Lycoming IO360A3B6D on my Mooney for 6 years or so. At a Sun n Fun some years ago I gave full payment to GAMI at their booth for a set of injectors. On the flight back from Lakeland we did the GAMI test. I sent tGAMI the numbers, and they sent me back my check...literally. We had at most a .2gph difference between all 4 cylinders with the stock injectors.
I know of many Lycoming owners that do not need GAMIs to operate LOP very smoothly.

And the fuel savings is significantly better than 1 gph.

And to Gene, the OP, I say to do a little research on the matter. One cannot say run 35deg LOP as a blanket statement. A lot depends on altitude. For example, at 3000' I might be 35deg LOP, but at higher altitudes ( say above 8,000') I'll only be about 5 deg LOP.

 

[Ted]

And to Gene, the OP, I say to do a little research on the matter. One cannot say run 35deg LOP as a blanket statement. A lot depends on altitude. For example, at 3000' I might be 35deg LOP, but at higher altitudes ( say above 8,000') I'll only be about 5 deg LOP.

It's also dependent on the airplane. If you're looking at turbocharged aircraft, you might find yourself running leaner than that simply to keep your temperatures happier (specifically turbo and CHT).

 

[Geico266]

Nope. But the plane doesn't have anything more precise on fuel flow than the factory fuel flow gauge. The primary purpose of the flow test is to see how balanced things are. If your engine is balanced well from the factory, you can still run LOP fine. You may not be able to run quite as lean prior to the engine getting rough, but that doesn't mean that you can't still run LOP happily.

In the case of my Aztec, it's not worth putting GAMIs on. The 310 would benefit from it, but I'm still doing fine 300 hours later on it without them (yes, running LOP).

Give the test a try for fun. If you have a vernier mixture control each notch on the handle is .2 GPH.

Can you monitor each cylinder EGT?

 

[Geico266]

I have run a Lycoming IO360A3B6D on my Mooney for 6 years or so. At a Sun n Fun some years ago I gave full payment to GAMI at their booth for a set of injectors. On the flight back from Lakeland we did the GAMI test. I sent tGAMI the numbers, and they sent me back my check...literally. We had at most a .2gph difference between all 4 cylinders with the stock injectors.

Gami's are nice, no doubt. Glad you nailed it on the first run.

Here is a sample of the test run on my engine after adding two new nozzles. The red EGTs are where it peaks. The goal is to get them to peak at the same fuel flow, or within a range. Usually, .2 GPH is the goal.

 

[Ted]

Give the test a try for fun. If you have a vernier mixture control each notch on the handle is .2 GPH.

Aztec has levers, like most twins (actually, all of the ones I've seen). And also, "each notch" won't be correct on every aircraft, given variations in carburetors, linkages, etc.

Can you monitor each cylinder EGT?

You betcha. Got full engine monitors on the Aztec and 310. The fuel totalizer hasn't been a hugely important upgrade - the plane's factory one works sufficiently.

I've done no shortage of mixture distribution runs on aircraft engines. Probably over 500. Believe me, I know how they work and what you learn from them...

 

[Geico266]

I've done no shortage of mixture distribution runs on aircraft engines. Probably over 500. Believe me, I know how they work and what you learn from them...

Good, then maybe we can teach the other plane owners what we are talking about.

It is difficult to get the info across so everyone understands it. I can only type with one finger!

 

[airguy]

In my C-172 with IO360, I have the GAMIjectors and run LOP in cruise every flight. I don't have any experience with the factory injector nozzles, we bought the airplane with GAMI already on it, but we can run deep LOP (throttle full open) and control power with mixture all the way down to about 2100 rpm before my #3 cylinder loses fire.

I typically cruise between 6k and 8k, 120kts true, at 7.6 to 7.8 gph, 2500 RPM WOTLOP. I do run nicely ROP during the climb, to keep the engine cool while airspeed is lower.

 

[Geico266]

I never have understood the mystery and myths about running LOP. It makes sense to me given the proper set up and instrumentation. I have even seen carb engines run LOP, but that is rare. No way to adjust the flow to each cylinder.

Hopefully, I do not come off as a "know it all" or expert as I am neither. I have just spent a ton of time learning the "ins and outs" of LOP and have set up several engine to run LOP. A properly set up engine running LOP burns less fuel, runs cooler, and seems happy to me. BTW, I only burn cargas.

The experimental world is rich with learning experiences and opportunities to learn.

 

[Jaybird180]

I typically cruise between 6k and 8k, 120kts true, at 7.6 to 7.8 gph, 2500 RPM WOTLOP. I do run nicely ROP during the climb, to keep the engine cool while airspeed is lower.

Don't have POH handy, but I recall that factory flow should be about 8.6 at this setting (???). While any fuel savings gain is significant this is within the 1GPH that someone argued above. I think the point of argument was diminishing returns for increased risk. Not sure I agree with the argument, but I can empathize.

 

[Ted]

Don't have POH handy, but I recall that factory flow should be about 8.6 at this setting (???). While any fuel savings gain is significant this is within the 1GPH that someone argued above. I think the point of argument was diminishing returns for increased risk. Not sure I agree with the argument, but I can empathize.

Scale it up to a bigger engine, where the savings really kick in. And, when done properly, your engine runs happier, so you actually have decreased risk.

 

[Sac Arrow]

Also, if you're flying a Cherokee or Skyhawk with an I0 360 or smaller engine with no instrumentation, and you follow the leaning procedure of "lean it out until it runs rough then give it a turn richer to smooth it out" you are PROBABLY running it LOP anyway.

 

[skidoo]

Scale it up to a bigger engine, where the savings really kick in. And, when done properly, your engine runs happier, so you actually have decreased risk.

I have a little bigger engine. My POH numbers to get 120kt true for the TIO540 is 2100 rpm, 20" mp, and 9.8 gph. That is a factory ROP number and for 3100 lb gross, vs 2500lbs or so gross for the 172. It recommends for Best Economy to run AT PEAK which could be a bit less. I haven't tried it. My POH allows for running AT peak but not LOP. The only way to operate AT peak and keep it under red-line is to operate at lower power levels. So, I guess the logic is that if one is concerned about economy, he is willing to go slower.

The difference in the turbo 182 at 9.8 gph and 7.8 gph in a lighter 172 it not that much, especially if the book number for the 172 is 8.6 gph. Sounds like 1ghp or so difference between book and LOP may be about right. And, may be even less of a difference from running AT peak which is allowed by my POH. With the engines going from $50 to $65K, I think I will be sticking with my POH recommendations.

 

[SCCutler]

With the engines going from $50 to $65K, I think I will be sticking with my POH recommendations.

With engines at $50k to $65k, I'm more likely to roll with the guys whose recommendations are founded in science. The APS / GAMI guys are the gold standard of engine operation knowledge.

I watched a TCM IO520 torn down, and it was like a new engine inside, measured out to new tolerances in bearings, cylinders were beautiful, looked like new inside, minimal deposits. Engine had 2,650 hours, cylinders had 2,050 hours. The A&P (a DER) said if it had been a prop strike tear down, he'd have put it back together and flown another thousand hours.

The science has proven: LOP (done right) is less stressful on the engine in every measurable way, and it saves a raft of money, besides.

 

[airguy]

Don't have POH handy, but I recall that factory flow should be about 8.6 at this setting (???). While any fuel savings gain is significant this is within the 1GPH that someone argued above. I think the point of argument was diminishing returns for increased risk. Not sure I agree with the argument, but I can empathize.

It's 12% - scale it to whatever engine size you want, I'll take it all day long...

Increased risk is questionable, and I would say negligible with proper instrumentation and attention to detail.

 

[skidoo]

It's 12% - scale it to whatever engine size you want, I'll take it all day long...

Increased risk is questionable, and I would say negligible with proper instrumentation and attention to detail.

This subject with real numbers interests me. My first thought here was OK, 10-12%, great. But, what happens to the speed from the book value? Then, I remembered that I have a 172S POH that came with the King Instrument course. So, off to check some numbers. It shows @ 8000 ft, 9.4 GPH at 119 KTAS at 2600 rpm, and 8.6 GPH at 112 KTAS at 2500 rpm.

I don't know how close this is to your model, but my understanding is that you lose some power and airspeed as you lean beyond peak. If this is true, then I don't understand how you get faster than POH numbers at a lower rpm and LOP.

I find it interesting, however, that for 120 KTAS at 8000 ft, the book GPH is pretty close to the same as my 182.

 

[Sac Arrow]

With engines at $50k to $65k, I'm more likely to roll with the guys whose recommendations are founded in science. The APS / GAMI guys are the gold standard of engine operation knowledge.

I watched a TCM IO520 torn down, and it was like a new engine inside, measured out to new tolerances in bearings, cylinders were beautiful, looked like new inside, minimal deposits. Engine had 2,650 hours, cylinders had 2,050 hours. The A&P (a DER) said if it had been a prop strike tear down, he'd have put it back together and flown another thousand hours.

The science has proven: LOP (done right) is less stressful on the engine in every measurable way, and it saves a raft of money, besides.

Before I got my Turbo Arrow, it had always been flown at about 100 degrees ROP. I was dismayed with the economy and started playing with LOP, and ran it LOP at 65% or less at cruise. Compressions actually increased, and the A&P said the depositions were starting to go away. I'm pretty sold on it.

 

[n20junkie]

Or any other, for that matter!



Your experience isn't representative of anything I've seen, other than people who say they're running LOP (and may be), but are doing it incorrectly and then yes, torching valves, cooking turbos, and other such things. But there are no shortage of people on this board and elsewhere who have had very, very good luck with LOP operation. In airplanes I've done it for over 2000 hours of piston engine time, on stands even longer. No engine problems that I've seen have been caused by LOP operation.

The lead isn't there for exhaust valves (other than to cause them to stick). It's there as to boost the anti-knock characteristics of the fuel. Also, your Columbia may only have a 1 gph difference ROP vs. LOP, but that's not representative of what I've seen on most aircraft.

Most mechanics I see that talk about LOP "Issues" are really talking about people just running their temperatures too hot - CHTs, EGTs, TITs. Unlike a turbine where red line is a goal, on pistons, that's not the case. The engines you build (I'm assuming automotive) are probably not particularly well-suited to LOP operation. Most aircraft engines (although not all) tolerate it well. They also tolerate ROP operation well. The trick with either of them is doing it correctly.

What happens if you run unleaded fuel in an engine designed for leaded?

Something happens very specifically.

 

[Ted]

What happens if you run unleaded fuel in an engine designed for leaded?

Something happens very specifically.

You're thinking automotive. I'm guessing that's what you're used to, given what you've implied. In aviation, lead is put in the fuel as an additive for knock resistance.

I offer an advanced engine management course that goes into more details.

 

[Apache123]

You're thinking automotive. I'm guessing that's what you're used to, given what you've implied. In aviation, lead is put in the fuel as an additive for knock resistance.

I offer an advanced engine management course that goes into more details.

What he said.

After reading through the data (Deakin's articles are great), I joined the LOP camp. I pull the mixture lever waaaay back in my carb'd Lyc 320s and I'm pulling the same airspeed at 11.5GPH rather than 16GPH.

Also, if you can, I recommend the old P&W Engine Data / Analysis books. They cover a lot of these topics in detail.

 

[gprellwitz]

What happens if you run unleaded fuel in an engine designed for leaded?

Something happens very specifically.

Other Grant ,
not sure if you're aware, but Ted has some pretty good aircraft engine engineering chops that many of us are aware of. As he heats, he offers an advanced course in running the engines too.

 

[Jaybird180]

It's 12% - scale it to whatever engine size you want, I'll take it all day long...

Increased risk is questionable, and I would say negligible with proper instrumentation and attention to detail.

Are fuel flows really proportionate with displacement size? I would be surprised if the answer were yes.

Surprise me.

 

[SCCutler]

Yeah, well, *I* want to hear from someone with an engineering degree.

Preferably, someone who has actually worked, as an engineer, for a major aircraft engine manufacturer.

It would help if this someone were working in the aviation industry, and was a professional pilot. Hell, maybe even married to one.

But what're the odds of that happening?

 

[Jaybird180]

With engines at $50k to $65k, I'm more likely to roll with the guys whose recommendations are founded in science. The APS / GAMI guys are the gold standard of engine operation knowledge.

I watched a TCM IO520 torn down, and it was like a new engine inside, measured out to new tolerances in bearings, cylinders were beautiful, looked like new inside, minimal deposits. Engine had 2,650 hours, cylinders had 2,050 hours. The A&P (a DER) said if it had been a prop strike tear down, he'd have put it back together and flown another thousand hours.

The science has proven: LOP (done right) is less stressful on the engine in every measurable way, and it saves a raft of money, besides.

Is there a typo somewhere in there?

 

[Ted]

But what're the odds of that happening?

I wonder where we could find such an individual...

Is there a typo somewhere in there?

No. The required action at a prop strike is that certain components be replaced (like the propeller), but otherwise it's a condition inspection. So upon inspection, it is reassembled.

In fact, my recollection (although it's been a while) is that the minimum required at a prop strike is that you replace the prop (duh) and change the gear on the back of the crankshaft. As I recall, you legally may not even need to tear down the engine (although most people choose to for obvious reasons).

 

[SCCutler]

Is there a typo somewhere in there?

Nope.

It was a tear-down preparatory to overhaul. It was after the A&P looked at the engine's internal condition that he made his observation. He felt the engine appeared to be like new inside, and ascribed much of that to LOP ops.

 

[Amelia]

Local A&Ps seem to think LOP is a bad idea for my TSIO-360LB. I should run 50 to 100 ROP. And others say LOP offers a big savings, runs cooler, and I should always run LOP. I've tried it both ways, and I really can't tell the difference in how the engine sounds- seems happy either way. A Mooney engineer suggested ignoring the Mooney 231's POH, that 31" and 2500 RPM was ideal cruise setting for all altitudes. I love simplicity. Does that work with LOP? Oh, help. Somebody just tell me what settings to use, and reassure me I won't wreck the engine...?