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sarg314(at)gmail.com
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 Posted: Wed Mar 02, 2011 8:47 am Post subject: leaning engine |
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I have a Bart Lalonde IO-360-B2B with AFP injection in my 6A with about 36 hours on it. I have a VM-1000 engine monitor with it's "leaning mode" to help me lean it. It just watches the EGT's until they peak and flashes the display to alert you to the peak.
The leaning mode worked initially. My first problem with it occurred when a EGT wire fell into contact with a spark plug wire. That made the EGT readings so noisy that it couldn't detect peak EGT. I re-arranged the wires and that seemed to fixed that problem. Now however, when I start leaning, the thing doesn't detect a peak until I've leaned so much that the engine has started missing. Is this indicative of a EGT temp reading problem, or an engine/fuel injection problem? Could a bad injector nozzle do this?
The EGT temps of the 4 cylinders are pretty even.
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Tom Sargent
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recapen(at)earthlink.net
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| Posted: Wed Mar 02, 2011 9:39 am Post subject: leaning engine |
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Tom,
I have no experience with the VM1000 - but the Peak-detect mode on my AFS3400 determines peak the same way.
If I recall correctly, the original VM1000 EGT thermocouples are similar to the ones that AFS uses. My understanding is that the heat generates electricity via dissimilar metal activity and it is a very low voltage and amperage.
You may have toasted the EGT circuit in the DPU with the gozillion volt spark.
With the EGT's pretty consistent and even, it sounds like the engine is running fine - injection and all. Remember, it doesn't matter what the temps are, only that the ups and downs track together and peak at the same fuel flow rate
Since balancing my injector flow (AFP also), I can pull the mixture pretty coarsely and I'll get peak detection about 30 LOP and can then adjust accordingly - but well before it starts missing. Have you done any work towards balancing your injector flow? There's lots of documentation on how to do this - and I'll be happy to share my method with you...
Ralph
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rvmills(at)sbcglobal.net
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| Posted: Wed Mar 02, 2011 11:55 am Post subject: leaning engine |
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Tom,
I have a VM-1000 on my RV-6 (IO-540 with Bendix FI) and see somewhat similar results (minus the engine stumbling).
Airplane had 400 hours when I bought it (with the VM in it) and I've used that leaning mode a lot in the 3+ years I've owned it. Now the VM has over 800 hours and is 13 years old (just for perspective).
When I lean, the VM peak indication almost always happens when the leanest cylinder is lean of peak. On my motor, 2 and 5 are always the first to peak. After much experimenting, I've found that once I get that peak indication (the flashing) if I switch to the EGT for the cyl that peaked first, I can then richen to where I want that cylinder, knowing that the other cylinders are richer. I run 50 ROP on the leanest, and that puts the others about 80-110 ROP (on my engine), and that is my practice up hi, where I can't hurt the motor by being too close to peak.
One thing I've noted is that how slowly I lean has an impact on how lean of peak that leanest cylinder will go before it flashes. I lean pretty slowly over time, but if I go excrutiatingly slow, that peak indication happens much closer to actual peak. With my normal method, the peak happens consistently at 1 gph FF less than actual peak, and my 50-110ish ROP setting is another 1 gph FF higher. For example, if it flashes at 11 gph, real peak on the leanest cylinder is 12, an my preferred EGT setting is 13. It's very consistent. And I know those fuel flows make most of you cringe! 
In other experiments, I have found that most of my cylinders peak within .2-.4 gph FF of each other, with an outlier that is .6 gph from the leanest. I've considered GAMIs, but haven't gone there yet. I have 10:1 pistons, so I choose to run ROP and pay a little extra in fuel for the cooling (just one technique). If I wanted to run LOP, I'd definitely balance the injectors more, then spend more time testing with that leaning mode, to see where each cylinder went LOP.
My VM has behaved this way since I bought the plane, so I don't know if your wire contact could have caused the issue...just can't speak to that.
Perhaps try some really slow leaning up above 8k and/or below 75% power: drop .2 gph and write down all 4 EGT readings, then repeat over and over until all 4 are 25-30 LOP (or wherever the smart LOP flyers suggest) or until the engine start to run rough. See how close to each other in FF they each peak, and see where the VM flashes at you. It may reveal an injector balancing issue, or it may show that you are more LOP than you think when the VM flashes. Takes a bit of a X-C to do it, but it burns up time enroute!
Hope this isn't TMI, and that it helps...Goose is already going to gimme heck for being verbose!
Cheers,
Bob
On Mar 2, 2011, at 8:20, thomas sargent <sarg314(at)gmail.com (sarg314(at)gmail.com)> wrote:
[quote]I have a Bart Lalonde IO-360-B2B with AFP injection in my 6A with about 36 hours on it. I have a VM-1000 engine monitor with it's "leaning mode" to help me lean it. It just watches the EGT's until they peak and flashes the display to alert you to the peak.
The leaning mode worked initially. My first problem with it occurred when a EGT wire fell into contact with a spark plug wire. That made the EGT readings so noisy that it couldn't detect peak EGT. I re-arranged the wires and that seemed to fixed that problem. Now however, when I start leaning, the thing doesn't detect a peak until I've leaned so much that the engine has started missing. Is this indicative of a EGT temp reading problem, or an engine/fuel injection problem? Could a bad injector nozzle do this?
The EGT temps of the 4 cylinders are pretty even.
--
Tom Sargent
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sarg314(at)gmail.com
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| Posted: Wed Mar 02, 2011 12:25 pm Post subject: leaning engine |
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Ralph:
No, I haven't done anything about balancing injector flow. I assume that's in my AFP manual? Is it hard?
I've considered that the proximityof the spark plug wire might have induce too much voltage in the Thermo C. circuit, enough to damage it even. That might not be too hard to fix, though. You can still get parts for the VM1000, at least as of about a year ago.
On Wed, Mar 2, 2011 at 10:36 AM, Ralph E. Capen <recapen(at)earthlink.net (recapen(at)earthlink.net)> wrote:
[quote] --> RV-List message posted by: "Ralph E. Capen" <recapen(at)earthlink.net (recapen(at)earthlink.net)>
Tom,
I have no experience with the VM1000 - but the Peak-detect mode on my AFS3400 determines peak the same way.
If I recall correctly, the original VM1000 EGT thermocouples are similar to the ones that AFS uses. My understanding is that the heat generates electricity via dissimilar metal activity and it is a very low voltage and amperage.
You may have toasted the EGT circuit in the DPU with the gozillion volt spark.
With the EGT's pretty consistent and even, it sounds like the engine is running fine - injection and all. Remember, it doesn't matter what the temps are, only that the ups and downs track together and peak at the same fuel flow rate
Since balancing my injector flow (AFP also), I can pull the mixture pretty coarsely and I'll get peak detection about 30 LOP and can then adjust accordingly - but well before it starts missing. Have you done any work towards balancing your injector flow? There's lots of documentation on how to do this - and I'll be happy to share my method with you..
Ralph
--
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