A

armondo

Active Member
I'm flying an RV6--0360 with the following electronic system:
Electroair fires lower plugs. Slick Mag upper plugs. Dropoff on electro air 20 rpms. Dropoff on Mag 210 rpms. New mechanic says it's excessive. Mag checks perfect. Since the Mag check is between two different systems, one being much more efficient than the other. Therefore, I think there is no problem. What do you think?
 
How long has it been doing this???

Does the electronic ign advance the timing?? If so, by the time you are up to 1700 or whatever RPM, you are not in time with the mag-------therefore you are not only switching off one ign system, you are changing the timing at the same time.

Typically, retarding the timing will show a RPM drop---------and that is what may be happening when you turn off the electronics.
 
armondo said:
I'm flying an RV6--0360 with the following electronic system:
Electroair fires lower plugs. Slick Mag upper plugs. Dropoff on electro air 20 rpms. Dropoff on Mag 210 rpms. New mechanic says it's excessive. Mag checks perfect. Since the Mag check is between two different systems, one being much more efficient than the other. Therefore, I think there is no problem. What do you think?
Click to expand...
210 RPM is excessive. If the Mag checkes out perfect, then perhaps check timing, spark plug or wires.
 
210 RPM is fine as long as your mag checks out, and you said it did. You are not comparing apples to apples when you do a 'mag' check during run-up. You are checking two different systems and they are not the same. You are not comparing two systems during the check, you are only telling yourself that each system is actually firing and the engine is firing smoothly on each. It's going to drop more when you turn off the mag, because like you said, the EI is so much more efficient with it's advanced timing. I have one Plasma III and one mag, and when I do my preflight 'mag' check, I get no drop at all when I turn off the mag and about 200-250 when I turn off the Plasma. There is nothing wrong with my mag - it just can't keep up with the EI. No drop with the mag turned off because the mag is essentially not doing anything important (the cylinder has already fired) - unless the EI quits.
 
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What he said

Yeah, what Scott said.

I have the same setup as Scott. BTW the Plasma fires the top plugs which tend to stay cleaner anyway and thus cause even more drop when switching to the bottom plugs, which are mag fired.

I get a 200 drop on the mag and only a 20 drop when the plasma is firing alone - Just like Klaus said would happen when he sold me the Light Speed Plasma 3.

As I get close to needing a 100 hour spark plug service the Plasma begins to show more RPM drop, but after the plugs are all cleaned and gapped I'm back to only a 20 or so RPM drop when I turn off the mag.

My other mag is almost brand new, so it would seem it should be fine, but it still gives the 200 drop. I believe its for exactly the reason Scott (and Klaus) explained.
 
Same here

What Scott and Fastwind said.
If you don't like the 200 rpm drop run it up at higher rpms
And your drop will be less.
There is quite a difference in rpm drop on my 540 between doing a run up
At 1700 and 1800 rpms.
 
As a reference my IO-360 at 1700 RPM drops about 90-100 RPM and my Lycoming manual says up to 150 RPM is acceptable. Of course it might different if your plugs are on top or bottom. When I had slick mag on both sides, each one had one set on top and one set on bottom to even out the performance. Now my Slick Mag fires the top plugs and PMAG fires the bottom.
 
High mag drop with Electroair

Just wanted to add that I have experienced a 200+ mag drop which recovers to about 100 within a couple seconds. The mag is 1 year old and the other half of the system is a Jeff Rose system from about 12 years ago. I am the second owner after the builder. The previous A&P who did CI's on it said that it had always been that way and not to worry but I finally have a reasonable explanation that gives me some reasons - thanks! I also recently replaced the top plugs (mag) due to occasional missing on mag runup. The old plugs had resistances of about 4k, 4,4k, 8k and 12k - problem solved. Aside from plugs and wires, I believe the only repairs required for the ignition was the magnetic pickup 4 years ago. Aerosport O-320-D2A. Runs great and good on fuel!
 
RPM Drop

I had both the Jeff Rose & Electroair configs on the same plane (IO540) with no noticeable performance difference. The setup / connections on the Electroair is straightforward; Jeff Rose not so much!

At 1800 RPM the mag drop was 75 to 100 RPM & the EI was 20-30 for both configs. Clearly, the engine sound was robust and strong when the Electroair was operating. I do not have any empirical results between all mag / mag&EI as yet. But, will be installing the Electroair on N1XS & plan to do before & after tests.

Perhaps, Ernst observation on the 1700 vs 1800 RPM mag test bears some merit.
 
Advance

I agree with the above posts except if I read correctly it's backwards. The Rose or Electroair system, if the advance is hooked up, will be near 40 degrees advance at idle vs 25 for the mag. So a large drop when the EI is turned off would be normal and slight or no drop when the mag is off since the firing event is already in progress by the time it fires.
If you unhook and plug the vacuum line, then you can really compare the two since the Rose should go back to 25 degrees +- with no advance signal.
Its the advance much more than the stronger spark that makes the difference in RPM drop.
Tim
 
tim2542 said:
I agree with the above posts except if I read correctly it's backwards. The Rose or Electroair system, if the advance is hooked up, will be near 40 degrees advance at idle vs 25 for the mag. So a large drop when the EI is turned off would be normal and slight or no drop when the mag is off since the firing event is already in progress by the time it fires.
If you unhook and plug the vacuum line, then you can really compare the two since the Rose should go back to 25 degrees +- with no advance signal.
Its the advance much more than the stronger spark that makes the difference in RPM drop.
Tim
Click to expand...

Correct.....and Mixture control has a lot to do with this too.

Despite doing what your instructor taught you, do not do mag checks full rich. Do them on the lean side of peak, and a 200+ RPM drop is perfectly normal.
 
I've been in this exact situation with a customers 6a. If you turn the electronic off, and you get a 200+ drop with the mag, that is borderline too much. How many hours does the mag have on it?

In my case, the Electroair had a bad computer, it dropped 50 RPM, then kept sluffing off RPM the longer it was left on the EI by itself.

As mentioned, if the mixture is too rich or too lean, it can also contribute to excessive mag drop.

If it's got lots of hours on the mag, get it overhauled, time it to 25, and enjoy another 500 hours.
 
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