An airplane that is somewhat short on fuel endurance is the PERFECT candidate for a fuel flow computer. I don't care who you are, if you fly much, and you fly a range challenged airplane, sooner or later, you are going to get into fuel issues.

The fuel flow computer really helps to mitigate those circumstances, and gives you a better handle on what's going on.

You ask the question: How many different power settings do we have to experiment with before we settle on one we use? Words to that effect, anyway. Too lazy to actually cut and paste.

I ALWAYS use different power settings. Like almost every time I fly. Assuming I have a fuel computer, that is.

You are proud of your clean plugs, but you could well be frying a valve in the process of running those clean plugs. The leaner they get, the cleaner they burn. Right up to big bucks.

I'd rather know what is going on with the atmosphere and my airplane, than worry about clean plugs.

I'd rather clean the plugs every 50 hours (which I do regardless) than lean the hey out of an engine and fry a valve.

Been there, done that, with a single probe egt, and poor leaning practices.

MTV

watkinsnv wrote:I very much dought that I'll be frying any valves. I fly at reduced power settings With my Lyc O360 in the Cessna 170B Like I said I'll give up that gallon you seem to want to save, to cool those valves and I'm not in any hurry to miss any fuel stops to get any where. Its not poor leaning practices that hurt engines its people trying to be smarter than they should be. Thinking they can get more perfomance out of there engine. They can go that much farther in that much time using only that much fuel. Can't say that i've been there. Lance

Assuming by reduced power you mean 65% or less your mixture setting is irrelevant. You cannot damage anything with the mixture control.

Lance,

Here's a quote from your first message: "I lean aggressively and after 150hrs I just pulled my plugs for the first time and they were in great shape, with no deposits"

So, I guess I don't know what you mean by "lean aggressively". Lycoming recommends best economy at one mixture, and best power at another. In your next message, you stated that you lean till engine roughness, then richen the mixture. That is not leaning aggressively--it's pretty normal in fact.

Bonanza Guy is correct that, at lower power settings, it's not possible to damage the engine by leaning.

In fact, Lycoming says you can run the engine AT peak EGT for maximum economy. But, don't fool yourself that you can't fry a valve by actually leaning aggressively. A lot of this has to do with the specific installation. Every installation is VERY different in temperatures and which cylinder peaks first. Also, the carburetor itself has a pretty dramatic effect on fuel distribution to the four cylinders, and there are different nozzles, etc that will affect fuel flows and EGT's.

I understand your point, and I agree that the biggest benefit of the graphic engine monitors isn't to assist in leaning, but rather for the other benefits noted earlier.

MTV

65% power is not a magic number that guarantees no problems. Temperature is also a limiting factor, and mixture affects temperature. The strength of aluminum drops significantly over 400df. It's quite possible on warm days to lean to the point where CHTs exceed 400df at power settings below 65%, especially at high DAs. The internal pressures may not be excessive, but excess heat alone can cause problems.

The APS guys have done exhaustive research on this. Here's an article on the subject. http://www.swaircraftappraisals.com/MeyersForum/Engine%20Info/Engine%20Operation/Pelican's%20Perch%20Mixture%20Magic.htm [sorry--not sure why this won't show up as a link] Deakin and TCM recommend not running at CHTs over 380 regardless of the % power.

Cruising at DA of about 15,000 last weekend, the IO520 was making well under 65% power at peak EGT. I still had to open the cowl flaps a couple of notches to keep CHTs below 380. An alternative would have been to keep the cowl flaps closed and richen the mixture, but, at such a low power setting, using more air for cooling seemed like the better choice.



CAVU

I was going to bring up that 65% power, I believe is a magic number for Lycomings, but that doesn't of course mean that it is a magic number for all other engine makes.
I believe that Lycomings recommendation for economy cruise is to run it at peak EGT at or below 65% power. I think the next sentence say's that for maximum engine longevity run it at 50 deg rich of peak, so I run it 50 deg. rich of peak. For me that increases cruise speed by two knots and costs one GPH.
Lean of peak on our C-210 which has the IO-520 Conti. works wonderful if you don't mind a loss of 5 kts cruise, but on my Maule with the IO-540 Lyc. it doesn't work as well. On the Lyc. The leaner it get's, the less power it makes.
Point is that what works for one doesn't work for the other, you can't even use the same warm starting technique.

Thought that I'd update this thread a little.

I bought the JPI and love it. Just reading up on what the measurements actually mean and how variations effect different things has been fun.

We put the PowerFlow exhaust system and the Challenger Air Filter on last weekend. Couldn't fly it due to winds (14G22 @ 90 degrees off of the runway) but the static RPM increased 100 RPM.

This weekend we'll finish under the cowl with the HID landing lights, the Safe-Heet oil heater system, converting to multi-cylinder priming, and changing the ring mount CHT probe on #1 to a bayonet probe.

Next weekend is the Landes Nose Fork with the 8.50 x 6's, installation of the Aero 553 CO detector, and replacement of the post light.

The Sportsman STOL kit is sitting on the hangar floor for a Christmas installation and the paint job is scheduled for 1 Mar 08 which will include the horizontal stabilizer boots and (maybe) the VG's.

Lets see - headers, big wheels, new paint. Now all I need is twin CB antennas and a rebel flag for the back window and I'll be a REAL REDNECK PILOT.

KR5T wrote:Lets see - headers, big wheels, new paint. Now all I need is twin CB antennas and a rebel flag for the back window and I'll be a REAL REDNECK PILOT.

Nah, for that you would need neked lady mudflaps, too.

tom

Gun rack! Where is the gun rack?

Skystrider wrote:Gun rack! Where is the gun rack?

In Oklahoma, H&K P7M8 in shoulder leather under the right arm. Everywhere else, 10mm Commander under the arm. In all situations, SOCOM 16 in the back.

I have the JPI monitor and have been very happy with it. Also have the JPI EGT/CHT and am very happy with it. Another thing that I like alot about the fuel monitor is that in the lower 1/2 of my fuel tank it lets me know how much fuel is left. Before I had the JPI my tanks were registering empty with probably an hour or so of fuel left. I was pretty sure I had fuel, flying by time. But looking at the E on the gauges gave me a pretty uneasy feeling. The gauge has been very fuel flow monitor.

FWIW Gary