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And yes, the CPI box's "gauge mode" does give a quick crosscheck for actual timing being delivered to the engine. If all else fails, one can just plug in the desired timing directly from the CPI box controls. Good food for thought for all EI systems. |
Scott did you change out the MP sensor with he box change out? Or find any fault in the original MP sensor?
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Just some more info on GM MAP sensor failures used in the EM-5. Most have failed open or shorted (essentially 0 or 5V) but we have seen a couple fail with a floating voltage. This type of failure is harder to detect on many systems- especially those with no timing display available to the pilot.
With the floating failure, the MAP could go anywhere and the timing would follow the programming in the case of our products. This could be bad news at WOT and low altitude if it gave you an extra 10 degrees of advance. You could also have an issue where the MAP line becomes disconnected. This is fairly safe with SDS products since there is usually no MAP advance at 30 inches (sea level conditions) and if it happened at 8000 feet, you might get some advance but the engine would take that safely in most cases because you are below 75% power anyway. With the CPI and other SDS products using the internal MAP sensor, we just haven't replaced one in the last 17 years so these parts are exceptionally reliable given that track record in the tens of thousands of hours. |
Scott is your Plasma box mounted hot side or cold side of the firewall. Just curious.
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- The LightSpeed MP sensor is internal to the box. - The Plasma II+ system allows for external LCD indication of RPM, MP and some bias control of ignition advance. - For external ignition advance control, you install a potentiometer on the panel for each ignition. On initial install, the ignitions work correctly, but only after I fixed a multitude of Klaus supplied wire harness cold solder joints. On connecting the external potentiometer timing advance went to hard full advance (40+ degrees if I remember correctly). Calling Klaus I was told I screwed up the wiring. After three more calls he let me send him one of the six Plasma II+ ignitions (on my dime) to look at (we were installing these on three separate RV-8s). When he got the ignition he told me he found the problem - a wrong resistor on the board. He fixed the one I sent him and provided the correct resistors for ME TO DO A FIELD REPAIR of the other five boxes. Klaus never reimbursed me for my cost, my time or said thank you for finding a production problem with his ignition. The saga continues over the next 300 hours - including hard in flight failures. I pulled both ignitions at that point an installed pMags (now with 600 trouble free hours). Sorry for the long tale, but perhaps someone else will benefit from my experience. Carl |
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In fairness, we don't factually know the MPS was the culprit, just that advance pegged at 43, and advance is a MPS circuit function. It could have been some other software or hardware fault. |
Thanks for the comment Carl.
It is that kind of info that makes me wonder if we'll even attempt a repair. Am I going to trust this thing? I have no intent of requiring the pilot to actively monitor ignition timing in order to stay safe... |
I do have the single LS Plasma II + I know it has the Hall effect sensor and module that installs directly into the mag position. The CPI " box" is mounted on the back side" cold" of the firewall but now that I think about it the MP sensor that is mounted in my case behind the Inst panel actually feeds my Dynon and the vacuum line is " teed" to the LS plasma. (Been a while "2007")
BTY i checked my mag timing today which was off considerably , about 35Deg BTDC (I guess partly due to internal wear) has about 350 hours on it. Also the LS required a touch up to get the green light "off" at the #1 TDC position. Have not run engine since adjustments. Thanks Dr Dan for helping me with my memory! |
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That's the open failure. Ross, check me; is there any practical reason to worry about a shorted failure? We're all setting the base timing with high manifold pressure, so a shorted sensor (5V signal) shouldn't make any difference. |
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