Hi RPM drop on my LSE Plasma II

Mattituck installed the plasma II EI on my new IO-320. All test bed figures looked great. Now that the engine is installed and flying i am having an issue. After confirming all parameters of my plasma II installation (verified timing , wiring, troubleshooting all coils, checked plugs, mixture setting, etc) I have still not been able to determine why I get a 120-150 drop in rpm when I run only on my plasma II during a mag check. The slick mag drops @ 90 which is normal, but the EI should be very little, maybe 25rpm. The engine also appears not to be making full power - only 82% on take off WOT. Any ideas? All parties appear to have exhausted ideas. Has anyone had a similar experience??

Verify the vaccum line is hooked up to the LSII, I've seen this symptom (mag drop)with this line disconnected.

Calls

I have found both Mahlon at TMX and Klaus at LS to be excellent. Have you called both for some help? Klaus doesnt seem to like emails and message board info nearly as much as a direct call where he can help. Just ensuring you tried that path?

Here's a few ideas.

First: Troubleshoot according to the manual.
Second: Talk to Klauss. Don't bother talking to Klauss if you haven't done the troubleshooting exactly as stated in the manual. Klauss will make his frustration evident, which will in turn anger you.

Here are some thoughts. Have you checked lightspeed timing with a timing light per the manual?

Are you sure you are only getting 82% power? Is that all you should be getting in your conditions? Your EFIS displays power based on some combination of fuel flow, rpm, and manifold pressure, depending on the brand. It would be possible (in theory) to have a fuel leak after the fuel flow sensor, while in a dive with the prop windmilling and both ignitions turned off. Your EFIS would tell you 100% power even though the engine isn't running. That's an extreme example, but until you get to know your plane and make sure all of the parameters are set up properly, don't place too much faith in that %power number. It's just an approximation. Also Don't forget that you loose ~3% power per 1000' of density altitude. If you are flying out of a high density altitude airport, 82% sounds about right.


Also remember that you can only display full power at redline. If you have less rpm than that, power display will be lower proportionately.

After insuring your lightspeed timing, try your runup like this. Run up to ~1700. Pull the mixture knob until max rpm. Now perform your ignition test. Don't forget to push the mixture knob forward again for takeoff! You need that extra fuel flow for cooling.

Hope this helps!

Guy

Thanks for your input

Thanks guys - I have done all that has been suggested. Talked to both parties, provided all of the requested data points, verified timing as specified in manual, performed all troubleshooting as detailed as well. Hi end performance is probably within spec - just concerns me that I get such a large rpm drop when running only on the plasma II - just should not be that way. I plan to pull all connectors and reseat them. Thanks again!

Hey Mark,

Have you checked to make sure your ignition switches aren't backwards? In other words, does the switch labeled for you mag actually connect to your mag and vice versa?

Yes , I also confirmed ignition wiring

Including the switch . . . All good. I will contact both Mahlon and Klaus tomorrow. Thanks again!

I'll provide a little explanation of why there is an rpm drop when you shut off one ignition. With two mags, the flame-fronts from identically-timed magnetos reaches the center of the combustion chamber at about the same time. When you turn off one mag, the other must now supply the combustion for the whole cylinder, which takes a little longer in time, therefore the combustion is later and doesn't reach peak pressure until later, and so the power drops.
Typically the EI is timed at the same base timing as the magneto, and it depends on lower MAP and rpm to increase timing above the base value. If the MAP input is disconnected from the EI there will be no advance except the small amount from rpm. Under this condition, the drop should be about the same for the EI and the magneto. If the EI is functioning properly, under the low MAP which is available at run-up rpm, the EI will be much advanced over the magneto. The combustion process will be almost complete before the magneto fires, so the magneto will not contribute anything to the power, and very little rpm drop occurs.
All of this being said, if you get a larger drop on one then you are going from an ignition which is much advanced over the other. It seems to me, from your symptoms, that the EI is operating at much lower advance than is the magneto, and you need to use a timing light to check both of them.

Easy way to check your advance between the two systems is look at your EGT's during runup. You should see much higher EGTs with only the mag on than the Lightspeed due to the lack of advance on the mag.

Basically the symptoms seem to suggest that the unit is not coming out of TDC timing used for starting. This can be verified with a timing light.

Checked timing again today . . .

elippse said:

Basically the symptoms seem to suggest that the unit is not coming out of TDC timing used for starting. This can be verified with a timing light.

Click to expand...

Definitely getting some crazy results when checking the timing with the strobe. The EI appears to be firing 4 times somewhere around the correct advanced mark (which is 35deg advanced for a hi compression jug). This is a plasma II+ which has one spark, not several triggers like the III.

Today also did lots of searching for possible mp leaks. Non found but will test fly again tomorrow. Klaus and marlin have offered lots of suggestions. May be time to send the plasma II back to LSE for a bench test.

I will post my flight test results later this weekend. Thanks for your comments.

The engine also appears not to be making full power - only 82% on take off WOT. Any ideas?

On your MAP reference, is the MAP source tee?d to supply the LSE and engine monitor together? Possible leakage? Just a thought.
Thomas S.
AirVenture Presenter 07/26/11
http://www.eaaapps.org/presenterinfo.aspx?id=1470

Just curious, do you have a restrictor in the MAP sensor line? Would pulsations in the MAP sensor line wack out the EI brain box?

No restrictor

On mp lines. Is this recommended? My a&p feels it is a good idea but doesn't know if this is having any effect on my issues.

It can't be good for it. a smooth manifold pressure indication to the brain box has to be better than a pulsating signal.

If the MAP line was too restricted, the MAP wouldn't be as high and the unit would be more advanced giving more, not less power. If the EI is operating at TDC the power will be much lower. It isn't necessary to provide a restriction to smooth the MAP; that is handled inside the unit electronically.