Leaning engines using Mike Busch Method

[carusoam]

EB,

It was used in the Corvette in the mid 80’s on up. The IO550 install in the Ovation began using it in '94. The Bravo doesn't have it. The Acclaim does it with two turbos. Even injection molding machines use it today to balance polymer flow between mold cavities.

I'll try to post a photo... No photo coming, unable...

Fuel flow is challenging to control, but air is compressible, temperature sensitive, and has a very low viscosity/Reynold's number making it somewhat sensitive to flow geometries such as sharp corners in engine intake manifolds, or variable lengths of the tubes. Add to that, the flow is not continuous, each intake runner handles air flow once per two RPMs. The driving force of the flow is the vacuum created by each individual cylinder - atmospheric pressure on the back side of the air filter.

Starting fresh would be like inventing the trumpet.

In the 70's, tuned port fuel injection was not as common as it is today. Fortunately it is common now. Mooney modernized intakes with the 6 cylinder engines, leaving the fours to languish a bit.

We would probably benefit to see what the "new" designs for IO360s used by others...?

In LOP Ops, controlling air flow is as important as controlling gasoline flow... Finding an intake system that works from an existing plane would be a nice place to start....STC would need to lead.

Well, that's my theory.

Gentle curves are good, corners are not, they lead to dead spots in flow channels...

Tuning the pipes is where it be for LOP...

Best regards,

-a-

[jetdriven]

Marks, with CHT's under 300 deg you run the risk of lead fouling. Lead scavenging is a function of sufficient CHT and ethylene dibromide (C2H4Br2) in the fuel. If your plugs show lead deposits then your CHT's are low.

http://www.avweb.com/news/maint/182849-1.html

I have only seen CHTs below 300 when at 30-40% power, and I dont have lead fouling. 

[PTK]

I am taking shortcuts when I just lean to a fuel flow, but within the constraints of my operating environment, I think that I am safe in doing so.

Jim

Jim, just curious what your GAMI spread is. That's one thing that hasn't been mentioned much in this discussion. I think it's very relevant when leaning by ff to make sure that all cylinders are on lean side (and that ff is setup correctly.) I do the same thing. I operate out of sl airport. Once out of 1K or so I setup cruise climb at 2450 RPM and lean to target EGT all the way up. Then I pull mixture back to 9 gph which puts me well lop. Then tweek from there. My gami spread is 0.2 gph stock injectors.

[PTK]

For a couple reasons Jim. Since high (take-off) RPM retards timing (and pp) and I'm going to be leaning anyway (which also retards timing and pp) I want to avoid high RPM leaned and keep engine happy. Also prop has been balanced there and feels good.

[marks]

I often run 25 LOP and at 8.2 GPH or so at 2,500 RPM and usually one or two cylinders are just below 300. In winter I put packing tape over about 60% of the oil cooler and the oil temps are about 190 or so in winter set up like that. I can believe the warnings about lead at low CHT and really don't know how to keep the temps up. If I increase power to ROP at 10 GPH the cylinders warm up to 320 or so. In summer the problem isn't so noticeable but at 8.2 GPH the engine always seems cool. BTW I installed GAMIs and my spread is about .2 or .3

[Hank]

For a couple reasons Jim. Since high (take-off) RPM retards timing (and pp) and I'm going to be leaning anyway (which also retards timing and pp) I want to avoid high RPM leaned and keep engine happy. Also prop has been balanced there and feels good.

 

How did you get variable timing on your engine? I wasn't aware that Lycomings had that option. Higher RPMs increases % Power, but running LOP should push you further lean. Spark timing is always at the same spot [20º/25º before TDC].

[PTK]

Yours doesn't have variable timing?! I'm not talking about mag timing Hank! High RPM retards combustion event and so does leaning. By reducing RPM slightly and leaning the combustion event doesn't retard, (as you know.)

[PTK]

OK. But it is costing you about 7.5% of your total power and a larger percentage of your excess power, which is needed for the climb. If it feels good, though, I say do it.

Jim

Simply a matter of personal preference Jim. The engine feels smooth, it's a lot more quieter and happier.

"If you pulled the RPM back...you can leave it there, or run it back up to full redline RPM...The choice is yours. Or pick a smooth RPM in between..." John Deakin

[jetdriven]

Deakins comment was made for cruise RPM.  Pulling the prop back on climb is unneccessary. There is no limitation on 2700 RPM, it is even listed as a cruise RPM.

[PTK]

Byron, actually it's from his article #64 "The Climb." I understand your point and I don't disagree. As I said, just my preference.

[jetdriven]

Here is some more from his article, found here: http://www.avweb.com/news/pelican/182176-1.html

 

"I rudely left you hanging last month, right at liftoff, full power. It's worth noting that you could have left the engine running at that power setting for the entire month, and two months more. Assuming a total of about 750 hours in a month, almost all these "big-bore" flat six (and flat four) engines should happily run continuously at that power setting for three full months, and probably well beyond, as continuous running is known to be "better" for them. I would not be even a little surprised at 10,000 hour TBOs on any of these engines, if run continuously, paying attention to temperatures and pressures.

It's not the power you pull that determines maintenance, repairs, and TBO, it's the temperatures and internal pressures you run, and how you abuse your engine with cold starts to instant high RPM. Sadly, during the last ten years or so, it has been more an issue of quality control at the factories than engine management. Lycoming and TCM crankshafts have broken, and factory-installed exhaust valves on TCM engines appear to fail prematurely, no matter how you run the engine.

Please get away from that feeling that you are somehow abusing your engine, and that you need to reduce from takeoff power right away to "save the engine."

The sole exception is when you have an engine with a LIMITATION regarding takeoff power, sometimes five minutes, sometimes less. Please do observe that limitation, there MAY be something the factory knows. Again, I refer ONLY to a genuine LIMITATION, in the "Limitations" section of the POH, and NOT the text written in the "How to fly" section."

[aaronk25]

Packing tape works well??? Was just thinking how to restrict some airflow to the oil cooler. Also seeing 170s at -20c cruise temps.

[bd32322]

Packing tape works well??? Was just thinking how to restrict some airflow to the oil cooler. Also seeing 170s at -20c cruise temps.

Was told to use aluminum foil tape which works .. I was running 160-170s in the winter months before the tape also ..