1954 C-180, O-470S with 550-ish hours on it now.

The airplane does lots of local flying, and as a result is often not leaned very well.

I am pretty anal about leaning on long flights, running 20-40 LOP anytime I fly it (it's a super freak of an O-470 - runs *absolutely* smooth lean of peak right up until it quits at 60+ LOP).

I took it to OSH from SoCal a few weeks ago, and was curious what 30+ hours LOP would do to it, so here are before and after pics of the exhaust valves. Thought some here would find it interesting. I certainly did.

I'm surprised at the change.

#1 before


#1 after




#2 before:


#2 after:



#3 before:



#3 after:



#4 before:


#4 after:



#5 before:



#5 after:



#6 before:


#6 after:


The tops of the pistons changed dramatically as well, but the pics are marginal.

That is really interesting - thanks for posting.

The exhaust valves are much cleaner for sure.

The difference in the amount of carbon is significant. There was so much before that the light on the borescope was barely adequate. In the 'after' pics, the cylinders were much cleaner and reflected far more light which allowed for far better exposures. Same exact borescope for both sets of pics.

At least they're symmetrical w/no hot spots.

Cannon, is yours the 180 that is supposedly in that hangar out at the old Brennan airstrip in Moorpark, next to Tierra Rejada farms? I've always heard there was a 180 in that hangar, but I've never seen anyone fly there. In the last few years, it looks like they cut off part of that strip, but the hangar and windsock are still there. I saw "Moorpark" under your avatar photo, and I just had to ask...

My Bonanza has the IO-520BA 285HP - I fly it LOP at 11GPH. I have a JDM Engine analyzer (critical for LOP operation). In my opinion, if you want to extend the life of your engine beyond TBO and save at the pump, installing the right injectors and instruments to monitor your engine will pay for itself in months.

Jim

What kind of EGT resolution are you able to get with your carbureted 470? I've always heard that LOP isn't recommend with carbureted engines because you can't get the resolution with the smallest twist. Or perhaps it was because unless the induction and cylinders are just so, you can't get even readings like you can with balanced injectors?

Z - what do you mean by resolution and smallest twist?

I have been told the shape of the induction pipe system and the resulting uneven airflow and hence uneven fuel distribution per cylinder is to blame for the O-470's difficult nature for LOP ops.

Battson wrote:Z - what do you mean by resolution and smallest twist?

I mean: What is the finest degree to which you can adjust EGT temps with a carburetor? Does the mixture control on a MS design carb allow for as fine an adjustment as that in an injected system? How sensitive do your fingertips have to be to twist the knob to such a fine degree?

The key to LOP ops is minimizing the EGT spread. In carbureted engines, the fuel is "injected" into the induction system at the carb, then distributed to the various cylinders via very different length induction tubes. This creates very imbalanced mixtures at the cylinder, which causes uneven EGTs.

With injection, the fuel is injected right at the cylinder, so assuming you have balanced injectors, the EGTs will be much better balanced.

With a carbureted engine, using partial carb heat will significantly improve the balance of the EGTs, and permit LOP ops. A multi probe EGT gauge is essential in my opinion, to play this game.

MTV

mtv wrote:With injection, the fuel is injected right at the cylinder, so assuming you have balanced injectors, the EGTs will be much better balanced.

I have been fiddling with a small imbalance on my #2 cyl. It was running slightly rich then cutting shortly past peak.
Removed and ultrasonically cleaned the stems and orifices.
Now it leans like well tuned piano plays.
I was seeing 130 KTAS at 37 L/hr (9.8 Gal/hr) on the way home last weekend, I was happy with that from a lazy 540.

Great pictures, Cannon. Do you have any idea what the GAMI spread is on your engine (difference in fuel flow at peak EGT for the leanest cylinder - fuel flow at peak EGT for the richest cylinder)? If it's 1 gph or less, that would explain why you can run LOP, although GAMI likes .5 gph or less. http://www.gami.com/gamijectors/leantest.php.

The intake on the O470L I used to run looked like a home plumbing experiment, but the engine purred. I have no idea what the spread on that engine was, though, because I didn't have the 6 place engine monitor + fuel flow. Anyway, I figure I can replace one cylinder/year on the IO520F with the money I'm saving on fuel running LOP vs. ROP. The JPI with fuel flow has already paid for itself. Considering everything else that can go wrong with cylinders (mostly crappy workmanship), I think that's a pretty sensible trade off.

CAVU

Awesome pics! Thanks for posting them. I'm running an IO470 and with a Gami spread of 0.2, it runs very nicely LOP. At 6 months after annual, we pulled one set of plugs while doing some maintenance. My mechanic asked when we cleaned them last. I told him about 50 hours ago. He said, "You're running LOP?" I said "Yes". He replied that it looked like we had just cleaned and gapped them the day before. Good to see the positive effects of LOP ops.

My airplane is not the one, but I do know the owner of the 180 that still lives there, along with a Scout.

The airstrip was put up for sale 6-8 years ago, and a neighbor decided to buy it. He wasn't a pilot, but now had a great airstrip so he decided he should learn. The owner of the 180 was an existing hangar tenant, and helped him locate an airplane (the Scout).

The two of us taught him how to fly in the Scout out of that airstrip. That was a lot of fun. It's a great little strip, but people often called 911 when we landed, thinking that an airplane had crashed. The police and fire dept knew us well, as they had to send someone out just in case. Unless you know it's there, you cannot see the strip from any nearby road. Nobody realizes its there.

EZFlap wrote:Cannon, is yours the 180 that is supposedly in that hangar out at the old Brennan airstrip in Moorpark, next to Tierra Rejada farms? I've always heard there was a 180 in that hangar, but I've never seen anyone fly there. In the last few years, it looks like they cut off part of that strip, but the hangar and windsock are still there. I saw "Moorpark" under your avatar photo, and I just had to ask...

CAVU wrote:Great pictures, Cannon. Do you have any idea what the GAMI spread is on your engine?

CAVU

No idea. I only have a single point probe, and thus only run that way at lower power settings (22/23 or less). I figure I can't hurt it that way. For reference, it runs smoother than a GAMI'd 550 we had in a Bonanza several years ago. That engine always had a slight, but noticeable, shake anywhere LOP. Judging by the change in all six cylinders of the 470, all are LOP, though I have no idea where they are individually.

Interstingly, if I run LOP at lower altitudes (which required a partially closed throttle plate), it is not as smooth. The cocked throttle definitely messes with the distribution. Partial carb heat won't fix it, either.

Zzz wrote:I mean: What is the finest degree to which you can adjust EGT temps with a carburetor? Does the mixture control on a MS design carb allow for as fine an adjustment as that in an injected system? How sensitive do your fingertips have to be to twist the knob to such a fine degree?

It's pretty touchy.

Once level with the prop pulled back, I pull the mixture fairly quickly until I feel the power fall off, then forward just a tad (maybe a half turn back towards rich). This puts it in the ballpark of peak EGT. I let it sit for a minute or two until the EGT stabilizes, then go further rich very slightly (1/4 turn max) to which way the EGT moves. If it falls, I know I'm ROP. If it rises I know I'm LOP.

Either way, I lean or enrich *very* slowly to find peak EGT. This can take several minutes as the probe is slow to respond. By slowly, I mean I turn the mixture knob enough to take up the slack in the vernier, then just a few degrees more and wait. Repeat until I get peak EGT.

From there I do the same thing to go LOP. From peak EGT, it requires very small adjustments and a lot of patience. If I'm down to 15 LOP, sometimes I'll overshoot to 25-30 LOP even with the smallest movement of the vernier. I can't imagine it's even possible without a vernier mixture knob.

I can usually move the EGT a couple of degrees either way, but it literally feels like I'll take up the slack in the vernier, put a touch of pressure on it, and even that slight pressure is enough to move the EGT. So it's touchy, but very doable. Definitely more sensitive than the IO-550 was.

mtv wrote:The key to LOP ops is minimizing the EGT spread. In carbureted engines, the fuel is "injected" into the induction system at the carb, then distributed to the various cylinders via very different length induction tubes. This creates very imbalanced mixtures at the cylinder, which causes uneven EGTs.

With injection, the fuel is injected right at the cylinder, so assuming you have balanced injectors, the EGTs will be much better balanced.

With a carbureted engine, using partial carb heat will significantly improve the balance of the EGTs, and permit LOP ops. A multi probe EGT gauge is essential in my opinion, to play this game.

MTV

Dead on MTV... Do not try LOP ops without injection and a multi-probe - You'll burn up cylinders.

AS far as burning up cylinders LOP without fuel injection, I totally disagree and have paid for my next overhaul in fuel savings by now. Bout 1400 hours LOP on 0-470's and yet to see any downsides other than a tremendous amount of fuel savings and a cleaner engine.
A good multi-probe engine analyzer is an excellent tool for sure. There is some technique involved for running LOP on carburated engines at varying altitudes, but we've tore that up in other threads already. Whatever you do, just don't run 30-50 ROP at higher cruise power settings, THAT is where cylinders/engines get "burned up"!!!!!!!!!

From Mike Busch:

"When power gets down to about 60 percent, the avoidance zone disappears and you can run the mixture pretty much anywhere you please without overtemping or overstressing anything."

"Today, with tuned fuel-injector nozzles and digital engine monitors, we are able to operate these engines deep in the LOP regime without roughness. Even most carbureted engines can be operated at least somewhat LOP if the pilot knows what he's doing."

Sounds to me like Cannon falls into the category of knowing what he is doing.

I know we've all read it (or should have by now), but here it is again.

http://www.avweb.com/news/savvyaviator/savvy_aviator_59_egt_cht_and_leaning198162-1.html