Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

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diamondback0320
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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby diamondback0320 » Tue Feb 12, 2019 10:36 pm

Not to hijack but have a question as well..my pacemaker ignition is set at 22.0..2300..27.0..7.5..180 SV wide deck 9:5:1 pistons fresh motor with 65hrs..is that too much timing..how do ya know..plugs look a little light but not snow white & running avgas..runs strong & doesn't get hot..would 25.0 & 10.0 be better? Thanks

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby Moritz » Tue Feb 12, 2019 11:37 pm

Check aircraft spec

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby Slidin Gator » Wed Feb 13, 2019 4:45 pm

diamondback0320 wrote:Not to hijack but have a question as well..my pacemaker ignition is set at 22.0..2300..27.0..7.5..180 SV wide deck 9:5:1 pistons fresh motor with 65hrs..is that too much timing..how do ya know..plugs look a little light but not snow white & running avgas..runs strong & doesn't get hot..would 25.0 & 10.0 be better? Thanks

To my knowledge, all Lycoming motors, other than the O-435 and O-290, have a timing spec of 25 degrees BTDC. The 290 and 435 call for 15 degrees. But, the old airboater rule of thumb is to advance the impulse mag as far as you can and still start it and match it with the other mag. That timing setting would normally put you around 27 to 30 degrees.

As long as the motor is running cool, not detonating and makes power continuously at WOT then you are probably in good shape. Give it a try at 25 degrees, if you don't notice much performance difference, then you are probably better at 25. Make sure you run 100LL on those settings, you would want to dial it back to 22 if you ever run CM fuel. The ability to adjust timing in the field for situations like that is a huge advantage of this ignition system.

As for temp, I am talking about cylinder temps not oil temp. As noted in this thread, my oil temp runs fine but my cylinder temps are high. I will see 550 on the CHT gauge before the oil temp starts to move the needle.
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby diamondback0320 » Wed Feb 13, 2019 5:22 pm

Ok..I only run avgas..I haven't checked cylinder temp last couple trips but had B4 that few times with ir gun & didn't see any over 300ish

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby diamondback0320 » Wed Feb 13, 2019 5:25 pm

But I'll put it back to 25°..I see you have the 2nd # at 2000 & mine is at 2300.. should I change that?

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby diamondback0320 » Wed Feb 13, 2019 5:34 pm

The builder that actually installed it on the motor when built had it at 2200..1900..27.5..7.5, just wondering what's best all around performance and not too much timing.. thanks for your input

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby Slidin Gator » Wed Feb 13, 2019 8:43 pm

diamondback0320 wrote:The builder that actually installed it on the motor when built had it at 2200..1900..27.5..7.5, just wondering what's best all around performance and not too much timing.. thanks for your input

That's really your job to figure out, what does your Frankenstein like best? That's what's cool about the system, it's easy to adjust and test different settings. 25 degrees is safe.
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby diamondback0320 » Wed Feb 13, 2019 10:17 pm

Ok thanks

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby rowdy1 » Sun Feb 17, 2019 12:45 pm

I spent all day with mine yesterday. I installed the afr gauge, re-clamped all of the intake hoses and changed the fuel pump to get 6psi. I also move the stock settings on my Pacemaker. I retarded the base timing to 18 and total timing to 22.5 . Bottom line---it still runs hot. AFR is:

800 15.1
1200 14.3
1800 12.9
2200 11.5
2750 11.2

The problem is I still have very little color on the plugs. More than before, but still not that toast color I like.

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby CarMotorBarge » Sun Feb 17, 2019 4:58 pm

How does the timing mark on the ground strap on the spark plugs look? For a given RPM and timing, the timing mark needs to be in the elbow of the ground strap. There is a ton of data on the Internet about this.

Throw some new plugs in and run the motor at 2000 RPM for a couple of minutes on the table. If the timing mark is below the elbow on the ground strap, you need more timing. If the timing mark is beyond the elbow, you need less timing.

You will need to repeat this process every 250 RPMs from idle to WOT.
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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby kwanjangnihm » Mon Feb 18, 2019 6:08 pm

Test - bumping topic up!
" I don't care who you are back in the world, you give away our position one more time, I'll bleed ya, real quiet. Leave ya here. Got that? "

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby rowdy1 » Mon Feb 18, 2019 7:37 pm

Slidin Gator,
You get that thing fixed yet? Hurry up I need help with mine!

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby MJD291 » Mon Feb 18, 2019 8:00 pm

From the first post you said you set the econimizer screw full rich CW? Wouldn’t that be leaning it?
I LOVE THE SMELL OF AV GAS IN THE MORNING. IT SMELLS LIKE..... VICTORY

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby Slidin Gator » Mon Feb 18, 2019 8:41 pm

MJD291 wrote:From the first post you said you set the econimizer screw full rich CW? Wouldn’t that be leaning it?

MJD,
I honestly hope you are correct, I will easily call dumba@@ on myself vs. fighting it! Per my understanding of my discussion with GMAC76, CW (staring down the screwdriver) is full rich on the economizer, both the 6AA and 4-5. Per John Fenner's earlier post, CCW on the Aneroid (on the 6AA only) is further rich. Drilling the jet is the only option to go richer on the 4-5. Since I have the O2 sensor set up, I guess I should kick myself in the A and go make sure :slap:

I have yet to attempt any adjustment on the 6AA Aneroid, only full CW on the economizer. I am presently running Autolite 386 plugs and see no oil fouling issues. I need to go colder on my plugs. I just ordered 373 plugs today. They are non-resistor but colder heat range. I will have to see how they work on my dog tracking electronics, but they should pull cylinder temps down. I have 3 days of hard running planned for this coming weekend, so I will see if they make any difference.

4 out of 6 cylinders always remain below max. recommendation (<500). #3 & 4 will push to 600 (and beyond if I let them). Good thing I have 3 spare cylinders on hand, maybe I need to order some more. :scratch:
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby Slidin Gator » Mon Feb 18, 2019 8:58 pm

rowdy1 wrote:I spent all day with mine yesterday. I installed the afr gauge, re-clamped all of the intake hoses and changed the fuel pump to get 6psi. I also move the stock settings on my Pacemaker. I retarded the base timing to 18 and total timing to 22.5 . Bottom line---it still runs hot. AFR is:

800 15.1
1200 14.3
1800 12.9
2200 11.5
2750 11.2

The problem is I still have very little color on the plugs. More than before, but still not that toast color I like.


I need to send you my O2 test rig to calibrate them.. For reference, here are the readings I got on the AA6.

Slidin Gator wrote:I decided to quit guessing and got a wide band fuel/air sensor and mounted in a section of pipe to push into my mufflers.

Here are the readings I got:

PORT Bank
RPM
500 15
1000 13
1500 13
2000 13.3
2500 13.5
2735 11.3 WOT

STBD Bank
RPM
1500 14
2000 14
2500 12.8
2735 10.5 WOT


These seem to be in the same ball park at least!
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby Slidin Gator » Mon Feb 18, 2019 9:13 pm

CarMotorBarge wrote:How does the timing mark on the ground strap on the spark plugs look? For a given RPM and timing, the timing mark needs to be in the elbow of the ground strap. There is a ton of data on the Internet about this.

Throw some new plugs in and run the motor at 2000 RPM for a couple of minutes on the table. If the timing mark is below the elbow on the ground strap, you need more timing. If the timing mark is beyond the elbow, you need less timing.

You will need to repeat this process every 250 RPMs from idle to WOT.

CMB you just sorted out my need to learn something new every day, I have never heard of this before but I have now. Just when I thought I had spark plugs figured out too, thanks :slap:. From my read, this procedure is for optimizing timing for maximum power over the operating curve, hence the 4 second links that Goggle came up with!

It appears that Rowdy is testing out my thinking on variable timing from a heat budget standpoint, retard the timing to substitute for a richer fuel mixture, less fuel burned in the cylinder, more burned in the exhaust, to lower cylinder temps. So trading off some cylinder temp for exhaust temp. Always interested in different thoughts.
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby CarMotorBarge » Mon Feb 18, 2019 10:09 pm

Yes, what I suggested is for optimizing power (efficiency) across the entire RPM range. Timing is affected by RPM and AFR. Every 250 RPMs the timing is optimized to get the optimal fuel burn for the given RPM and AFR.

Also why wouldn't you want to optimize the power? Burning fuel in the exhaust manifold sounds like a waste of power and fuel mileage.
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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby Slidin Gator » Mon Feb 18, 2019 11:44 pm

CarMotorBarge wrote:Also why wouldn't you want to optimize the power? Burning fuel in the exhaust manifold sounds like a waste of power and fuel mileage.

You got me there for sure. Just trying to figure out the best way to keep these overgrown VW motors cool.

Used to keep a 6 pack in the glove box of my buddies bug. It was hot in the summer but it worked good in the winter.
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby CarMotorBarge » Tue Feb 19, 2019 6:32 am

You need to set the timing for optimal power. You want to get the best fuel burn. This will actually make the engine run cooler. Too little and too much timing will make an engine run hot.

Also are you using AV gas or 93 octane?
14x7.5 Al David hull with 14 inch transom
419 CI Horsepower Barn LS3 with 2.88 Ox Box swinging 4 blade 83.5" R
GTO Rigging and B&S Tilt Trailer

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby Slidin Gator » Tue Feb 19, 2019 5:05 pm

100LL. What I have found is that the motor runs about 50 degrees cooler at 22 degrees timing (vs 25) when operating between 2,000 to around 2,500 RPM. But it needs 25 degrees for maximum power to 2,800. I am working on wiring in a switch to adjust the timing as needed.
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby CarMotorBarge » Tue Feb 19, 2019 5:43 pm

You aren't running the pace maker system?
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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby Slidin Gator » Tue Feb 19, 2019 8:23 pm

CarMotorBarge wrote:You aren't running the pace maker system?

Yes, I am running that system. The switch is to switch between different timing curves pre-set on the unit.
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby Slidin Gator » Sat Feb 23, 2019 11:11 am

Looks like some success on my end. I installed my timing retard switch, swapped wires on #4 jug fan (so it is sucking up now) and put in colder Autolite 373 plugs. Now my hottest cylinder is #3, the one without a fan and it is hitting 500, #4 with fan is 450 and the rest are cooler. I am hauling 3 hunters, 3 dogs and one big fat sow right now and still staying cool enough to call it good. A shroud and another fan and I think I may have this licked.
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby rowdy1 » Mon Feb 25, 2019 10:15 pm

Do you think its the plugs that made the difference? If so I'll buy some tomorrow!

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Re: Tuning a Lean Running O-540 & 6AA / M5-4 Carbs

Postby Slidin Gator » Tue Feb 26, 2019 7:47 am

Rowdy,
It’s everything thing making a small difference but the plugs definitely help. I Won’t have a chance to pull a few plugs to see what they look like until this weekend, but motor temps are cooler for sure. They are cheap enough so you should give them a try. I set the gap at .025.

Swapping fan direction made a significant change too.
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.


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