LSE ignition rpm drop during run-up

Hello Gang,
I have an IO-360 (angle valve) with a mag on one side and a Plasma III on the other. When I do my run-up and I turn off the Plasma (i.e. mag running) I get about a 50 rpm drop. When I turn off the mag (i.e. Plasma running) I get about an 80-100 rpm drop. I would have expected it the other way around or very little rpm drop when turning the mag off, since the Plasma is supposed to be more efficent and/or produce more power. Is this normal? What has the experience in the field been? I do my run-up at 1700-1800 rpm with the mixture full rich. I haven't checked my timing with a timing light yet, but I did set the timing in accordance with the manual at 5 deg. after TDC (about two teeth on the ring gear) since I have 8.7:1 compression.

Thank you!
Jerry

LSE RPM drop

Mine is essentially zero (also have a mag) on an O-360. I would verify the timing. Note that I get no digital RPM indication when running on the LSE only. But by sound the RPM sounds so close to that when both mag and LSE are on that I assume essentially no RPM drop (on LSE only).

NO DROP!

I have a 0320, one mag and a lightspeed. I do my run up at 1600 and get NO drop when I shut off the MAG!! Well..... maybe 10 rpm or so. But when I shut down the lightspeed, I get about 150 rpm drop. And that is what I expected.

So, you are right, It's NOT RIGHT!

Warren

LSE drop greater than Mag

Jerry,
I, too have also experienced the very same thing: more RPM drop when switched to Plasma than switched to magneto. Both times that this occurred it was the same problem. One of the contacts at the LSE coils was loose. I now keep a few extra 90 degree bayonet-style connectors in the repair kit so as to be able to fix the problem if away from home.
Of course, your problem may be a faulty coax or coax connector at the brain box or fouled plugs or...
Anyway, it is worth taking a look.
Mark

RV8Squaz said:

Hello Gang,
I have an IO-360 (angle valve) with a mag on one side and a Plasma III on the other. When I do my run-up and I turn off the Plasma (i.e. mag running) I get about a 50 rpm drop. When I turn off the mag (i.e. Plasma running) I get about an 80-100 rpm drop. I would have expected it the other way around or very little rpm drop when turning the mag off, since the Plasma is supposed to be more efficent and/or produce more power. Is this normal? What has the experience in the field been? I do my run-up at 1700-1800 rpm with the mixture full rich. I haven't checked my timing with a timing light yet, but I did set the timing in accordance with the manual at 5 deg. after TDC (about two teeth on the ring gear) since I have 8.7:1 compression.

Thank you!
Jerry

Click to expand...

I have a standard O360 with timing set at 21 degrees (standard compression setting for the LSI) and would not have any drop when I turned off the mag. However my good friend who's hangers with me and who's plane I work on often has the same thing you are having. The difference is he has high compression and the timing is setback an additional 5 degress (should be 16 with a light) like yours. I have checked his over extensively and have come to the conclusion the timing difference with the higher compresion causes the drop on his and not on mine. So I would have to say from what I have seen yours is normal.

Another data point.

I have the Plasma III and a Slick mag on my ECI 0360/RV9a. I do my run up at 1700 rpm and see a 10-20 rpm drop when running w/o the mag and a 50-70 rpm drop when the PIII is turned off. I have the standard 8.5:1 compression.

Cheers,

db

Hey Guys,
Thanks for all of your replies. It sounds like I need to get a hold of a timing light to check it out and know for sure. I don't think anything is drastically wrong because the engine actually runs great. I'm getting expected airspeeds, temps, and fuel flow. Yesterday it was about 40 deg F and I had about half tanks and was climbing out at 2900-3000 fpm at best rate! It's just something that's been bugging me. I welcome more inputs especially if you have the same engine and setup I do. As always thanks to everyone. I appreciate your help very much!

Jerry

Hello Gang,
I finally got around to checking the Plasma III with a strobe light. I ended up having to advance the timing using the Hall effect transducer about 4-5 deg to get the 16 and 35 deg timing specified in the instructions for my engine with 8.7:1 compression. The timing is set such that the green light on the transducer is on with the #1 cylinder right at TDC. I initially had it set so the green light would turn on with the #1 cyl 5 deg after TDC, but had to advance it about 4-5 deg to get it to time properly with the strobe light. Anyway, I feel it was successful. The RPM drop with the magneto off is now only about 50-60 RPM. I just hope I didn't advance it too much.
I was unable to check the timing of the mag with the strobe. We couldn't get the strobe light to work when I had it connected to the mag lead of the #1 cylinder. Is there a reason for this?

Jerry

Check your manifold pressure sensor line

I had the same problem and almost by accident found that the manifold pressure sensor line had come unstuck, meaning the LSE wasn't retarding? the timing at low RPM.

I think there's a couple of things comming into play here. If you have a lightweight prop your engine will be more suceptable to a rpm drop than if you are using a heavier cs prop. also since the lightspeed uses a combination of mp and rpm to calculate the timming, temp, prop pitch and or DA will have an affect also. I think if you add or subtract rpm you will find a sweetspot that will show very little drop on the ei mag.
At least thats the way mine works.
Tom\RV3
160+
10:1
Lightspeed/slick mag
catto prop