This seems to be a subject every pilot has an opinion on...

My experiences with automotive tuning tells me that on a fuel injected engine, it should be really easy to lean out into the mid 15 to 16:1 O2 levels at lower power settings. I used to cruise my 11.5:1 compression LS1 V8 around these levels all day with no change except excellent fuel economy on the highway. On 93 octane. I have no idea what these numbers equate to as far as EGTs on a standard, aircooled aviation engine though.

I know a lot of people that run around 100* ROP with the attitude that "fuel is cheaper than an overhaul." I can't argue with that logic, especially since it's their planes and their engines!

I'm just curious if anyone on here has delved into the science and what kind of ROP vs. LOP actual practices everyone on here uses.

This may give you some insight...................Rob

http://www.eaavideo.org/video.aspx?v=2534345030001

This is one of the most heated topics in aviation. If you want a good understanding of internal combustion in aircraft engines I don't think there is better source than this series of articles.

http://www.avweb.com/news/pelican/

I myself have had good luck with WOTLOPSOP.

Paul

CamTom12,

Modern aircraft engines are anything but. The fuel injection systems on certified aircraft engines are the equivalent to 1960's automobiles. Highly inefficient.

The engines themselves are also ancient design. How awesome would it be if an aircraft engine manufacturer decided to invest the money (tens of millions I'm sure) to build (and certify) a modern aircraft engine, liquid cooled, electronic ignition, electronic fuel injection, etc. We would burn less then half the fuel we do today and TBO would be 5,000 hours plus. And we could all run on pump gas instead of avgas.

When I was a kid in the 60's automobile engines never got past 100,000 miles without at least a valve job, and a complete overhaul was usually called for. Today's engines easily go to 250,000 miles without ever opening them up.

As scary as this sounds (can't believe I'm saying this) if it wasn't for government fuel economy regulations, the Big Three would never have improved their engines and new cars today would still get 10mpg and need an overhaul at 100,000 miles. I should say that Japanese imports had an impact on improvements as well, but it was minor compared to government regulations.

This is kind of interesting:
http://www.quietaviation.com/programs/qtpower.html

CamTom12 wrote:This seems to be a subject every pilot has an opinion on...

My experiences with automotive tuning tells me that on a fuel injected engine, it should be really easy to lean out into the mid 15 to 16:1 O2 levels at lower power settings. I used to cruise my 11.5:1 compression LS1 V8 around these levels all day with no change except excellent fuel economy on the highway. On 93 octane. I have no idea what these numbers equate to as far as EGTs on a standard, aircooled aviation engine though.

I know a lot of people that run around 100* ROP with the attitude that "fuel is cheaper than an overhaul." I can't argue with that logic, especially since it's their planes and their engines!

I'm just curious if anyone on here has delved into the science and what kind of ROP vs. LOP actual practices everyone on here uses.

I know a lot of people that run around 100* ROP with the attitude that "fuel is cheaper than an overhaul." I can't argue with that logic, especially since it's their planes and their engines!

Let’s do the math, TBO= 2000, FUEL= $5.50 2000 X $5.50 = $11000.00 That’s @ one GPH, so do you think fuel is cheap?. AS for me, most people flying my aircraft and engine combo, burn 10 to 12 GPH, I run LOP on most cylinders, I average point to point 8.7 GPH, Before engine monitors there was an unforgiving boogie man monster that at any second could destroy your engine if you ran to lean, (actually running just right, and produced max btu/cyl pressure). Another point is carbon build up on an engine that is run ROP and contaminants in the oil all contributing to a shorter engine life. Mike Bushes Webnars are excellent.

Anyone interested in LOP and fuel efficiency needs to speak with my friend Klaus Savier at Light Speed Engineering in Santa Paula, CA. If you are lucky enough to fly an experimental airplane, Klaus' LSE ignition system will increase available power and torque by 10-12%, and decrease cruise flight fuel burn by perhaps double that.

Klaus has done a lot of research and 25+ years of testing... something very few modifiers and hot-rodders and "gurus" have done. I actually squeezed my fat ass into the back of his airplane on one of his test flights in 1988,a nd saw the performance and efficiency of this system first hand.

Klaus has set, broken, and re-broken many speed and efficiency records. His airplane will make 200 MPH, with two people aboard, if I recall, at under 3GPH. The same airplane has been clocked at well over 240 MPH at Reno. All with a modified O-200.

He explained to me that his system allows what he calls a "hyper-lean" cruise condition, with LOWER temperatures and pressures than normal ROP and LOP operations.

Some of this has no relevance in bush flying, but lots of it does. Because you can use all this capability to greatly extend fuel range, or climb power, or the ability to hand start an airplane safely and thus eliminate the weight of the starter.

I believe field approvals for this system have been done, although likely not for the faint of heart.

Papa Victor wrote:I myself have had good luck with WOTLOPSOP.

What the heck?! hahahaha



Thanks for the replies, I'll check those links out.

What started this train of thought is my friend's TU206 munched a couple of cylinders on a nearly TBO engine that had been running for almost 30 years. He's got a new motor freshly installed and we were talking about what he could do to make sure this is the last engine he has to put in it. It was pretty expensive!


EZ, I'll surely be looking into that if my experimental purchase goes through! (I'm on a two year hold because of moves and schooling, but I think the owner is "waiting" for me!)

MAU MAU wrote:This may give you some insight...................Rob

http://www.eaavideo.org/video.aspx?v=2534345030001

This is exactly what I was looking for, and corresponds with my automotive experience as well (plus some labs we did in thermo way back when).

Here's the first video which hits the basics before getting into the advanced stuff in the one you posted: http://www.eaavideo.org/video.aspx?v=2274677932001

I sent links to both videos to my ROP friends for their thoughts.

CamTom12 wrote:This seems to be a subject every pilot has an opinion on...
I know a lot of people that run around 100* ROP with the attitude that "fuel is cheaper than an overhaul." I can't argue with that logic, especially since it's their planes and their engines!

I cannot understand this logic. How is putting more energy and hence stress into and engine supposed to help it last longer? At higher power settings it appears that 50-100*F ROP is the very worst place to be running the engine, people only get away with it by the sheer luck of the way they run their plane in many cases, either at high altitude (lower power) or at cruise throttle settings when they lean.

Here's a CHT / EGT curve to illistrate the point, where RED is the "wrecking your engine area" for leaning at different power setttings. The LEFT side of the peak is LEAN.


Note that at economy cruise power settings (below 60%) it's almost impossible to lean incorrectly, there is no red zone anymore. This is how guys can run 50 ROP and not shred their motors.

From the link in the first reply to OP, I like # 18 the most:
http://www.avweb.com/news/pelican/182084-1.html

Here are some good debunkers:

Some Old Wives' Tales (OWTs)

From this comes a few pernicious OWTs, all with a modicum of truth.

"Never run lean of peak!" That's right, you can't in most flat engines, because their uneven mixture distribution causes them to run too rough.

"Leaner is hotter!" That's true only up to the point of maximum CHT, which occurs at around 35° F to 50° F ROP for most engines. Leaning beyond that point makes 'em run cooler. Naturally, if your engine gets the shakes at lean mixtures because of poor mixture distribution and the resulting uneven cylinder-to-cylinder power, then the only leaning range left to you is on the rich side, and if limited to that area, leaner is hotter!

"Leaning too much will burn your valves!" True (at higher powers), unless you continue leaning to the lean side of peak EGT (where leaning makes cylinder heads and valves run cooler), or you operate at sufficiently low power settings that valve temperatures remain acceptably cool even at peak EGT. (This works out to around 60% to 65% of rated power, on most of the flat "big bores".)

These are the kinds of things running through factory tech reps' minds when they scream (as a Lycoming rep did to me awhile back), "I wouldn't recommend lean-of-peak to my worst enemy!" Neither would I, in his stock engine with its lousy mixture distribution!

I have to agree with Cam Tom 12,pilots and or aircraft owners are a very opinionated bunch (sometimes not correctly- or it is passed down obsolete information) I have a long history with motorcycle repair and four stroke (not two stroke) engines if given equal fuel distribution will last a very long life at the old lean settings.
I recently installed 6 ECI-Tittan cylinders on our o-470K 180,as well as an insight g-2 engine monitor. With a lot of attention on the top end build as well as mag timing and I believe the Venturi intake seats, I am now running our carbureted o-470 lean of peak. Fuel burn is much better than book.

Engine: IO-520D with GAMI injectors

Climb: Rich

Cruise:
The sweet spot for me in cruise is usually 4500-5500' as I can acutally use WOT and I target a MP of around 24-25". Generally I set my RPM at 2300-2350 and run about 50-60 deg LOP. Fuel flow to get this is usually around 10.8-11.4 g/h. Consequently, on the ROP side of things, I will generally set 23 squared and set fuel flow at 16 gph to keep egt 120-150 deg ROP. Speed difference is about 5 mph. Fuel savings is about 4.5-5.0 g/h. Fuel prices are over $6 here so maybe $30 per flight hour in fuel savings. I've saved enough fuel already to buy new cylinders if my valves all melt as some predict. More important than just the money is the ability to increase my range by 200 NM per tank of gas. This can make a huge difference when flying in areas with limited fuel options.

Cylinder temps when ROP are much more uniform because the fuel is helping to cool. When LOP, aircooling is much more important and I have learned that it is more difficult to keep temps in check when flying slowly on skis. In high-speed cruise on small tires, it is actually hard to keep your cylinders warm.

I had beers with the gammi guys at Osh KOSH and since then I've been running my 185 wide open throttle 2500 rpm and lean of peak. It's simple and it's a dream. 11 gph and cruising at 130-140 kts.

Durango Skywagon wrote:I had beers with the gammi guys at Osh KOSH and since then I've been running my 185 wide open throttle 2500 rpm and lean of peak. It's simple and it's a dream. 11 gph and cruising at 130-140 kts.

I have a good friend with a 185 on floats that runs 25^2 and leans by fuel flow. Something like 16gph I think. He's got a 6cyl EGT/CHT scanner but uses it primarily for troubleshooting if something feels amiss. His leaning/richening is all by fuel flow - he's got a system down with as many hours as he's flown that plane.

I sent him both of those video links, I'm curious if he'll modify his leaning at all but it's all personal choice/preference.

I also sent them to another good friend with a TU206 and he's interested in the videos for knowledge but "skeptical, because you never hear of LOP success stories, and my A&P told me that while it's possible it's not recommended."

So, who knows what they'll both end up doing?

CamTom12 wrote:

Papa Victor wrote:I myself have had good luck with WOTLOPSOP.

What the heck?! hahahaha

Wide open throttle lean of peak standard operating procedure.

I operated the IO540 in my comanche this way. Power was only controlled by mixture until landing. After take off I would do the "big pull" (mixture)to lean of peak. I controlled CHT's with mixture. Leaner is cooler on the lean side of peak. Max power was dependent on the max CHT's I wanted. Then on landing I would do the "big pull" again but this time it is the throttle. I would pull the throttle on final approach, back to 15" which would automatically take me to ROP(with out touching the mixture knob) and temps would remain stable and cool.

None of this can be done if the engine isn't running smooth. And if you need power you have to train yourself to go mixture rich first!!

These discussions are fun because it goes against a lot of peoples engrained beliefs.

Definitely watch Mike Busch's webinars...both of them. Also read John Deakin's articles on Avweb's Pelican Perch. Mike says for ROP you should be 100-120 ROP. But if you can run LOP, I don't know why you wouldn't!

X2 for Mike Busch. I think it is worth the cost to belong to EAA just to get the Sport Aviation Magazine where Mike has a monthly column.

When I bought the 185 I could not keep cylinder head temps under 400 degrees without running way ROP and keeping the cowl flaps open. This was surprising as I never had any temp problems with my old T-210. I replaced all he baffling and added the "gills" to the side of the engine for additional air flow. Didn't change anything.

Next I read Mike Busch's comments on LOP and gave it a try. I did not have Gamis but did have a JPI 700 engine monitor. After reaching cruise I would be running about 2,400 rpm and would lean till the engine started running rough. I would richen slightly and cyl temps would be less than 380 degrees which is the recommended max for temps. I still could only partially close the cowl flaps but this was by far the best way for me to control temps. At 5,000 msl I would be burning around 12 +/- gph. FF