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Increasing CHTs

scard

Well Known Member
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So, recently we noticed it becoming very difficult to manage CHTs, mainly #3 & #4. The change was so slow that we barely noticed. With summer upon us it is a glaring issue. 3 and 4 passing 415deg by downwind on the first takeoff of the day. Wow, that just isn't normal. Cruise CHTs seem higher too. Are we sure this isn't just our imagination or an instrumentation problem? We finally declared that it isn't our imagination. Now what?

... I'll let that dwell for a few minutes then followup with findings :).
 
My 10 has 9.5:1 compression and does the same thing on hot days....worse when fully loaded. I depart WOT and Max RPM, I have to keep the nose over at 125 kts else the CHTs go wild.

Somewhere on this board I read that backing off the RPM to 2400 shortly after take off is helpful. So, I do that now and it makes a big difference. I can keep the climb rate up for longer wo having to also reduce throttle.
 
My guess...

Time to look at intakes to the cylinder, and possibly replace gaskets and sump fittings. Those two cylinders are likely running lean.
 
I like the intake idea. Yeah, I look at those often and have a stack of gaskets that I use often.

However, the rest of the story... So, OSH is coming AND we have an airshow performance coming up so it is time to make some kind of declaration that fixes any doubt. Time for a targeted flight test. Yep, up and out on downwind coming through 400deg, grrrrr.... Cool it off and setup a 130kt climb at 300fpm. CHTs climbing again. Yep, I call BS. Level off at 5k' in 70deg air doing 140kt in low cruise. Still way higher CHT than we know. (pilot tuned to the airframe with 1800hrs) What causes sneaking / no major change high CHT?... As I orbit the airfield at 5500'.

Hmm, Right lightspeed ignition off. No change. Ok back on. Left side Slick mag off. CHT immediately drops. Wow, still falling. Pull up into a 90kt climb and CHT still falling. Hold what you've got and turn it back on. Yep, here come the CHTs at high speed.

Yep, Houston we have a problem, and a diagnosis. The timing was off on the Slick mag by 3.5 teeth. Wow, that is huge and a first for this airframe. I haven't pulled it to check the e-gap yet, nor has it been test flown yet due to the shop build. I'm still thinking about this thing that is accepted as mag drift. It is either vibration in the mounting clamp or internal wear.
 
Scott, just a data point.

The P-mag's "A" Curve starts at 26.2* BTC.

I have found that by dialing them back 1.4 degrees to 24.8* BTC, my CHT's came right down in line. (This was done some time ago.)

I have been playing with the max advance feature on the P-mags and can dial in my CHT's with timing in flight rather than fuel.

Can you play with the max advance setting on the Light Speed? It might help.
 
The timing was off on the Slick mag by 3.5 teeth.
Is your Slick subject to the Service Bulletin that requires action if the timing drifts x# of degrees? Sounds like one possibility is that yours is doing what the SB suggest has happened to a fair number of others.
 
Good job on diagnostics Team Card.

Very interesting - Mahlon said (somewhere) that the lower plugs had more influence than the top in some installations/conditions. One might conclude in this case the top plugs are not doing much, even advanced. Just observed a friends 540 with large mag advance in only 20hrs on a new Lycoming. Within the SB limits. Odd you did not see this in the static mag drop test, he did. Is that because it is not WOT? (and carbed)

At what point is a mag internal inspection in order?

So many questions.
 
Bill, I would say an internal mag inspection is a good thing to do any time you get an uneven drop that can't be fixed at the spark plug end. People seem to be scared to open magnetos. There's only like six parts inside. Sure makes me feel better than just asking for opinions and "wondering" about it. I say, rip em apart and make em sparky.
 
Scott, you were almost ten degrees off. If you didn't find that the mag was loose at the base you should have that apart before you go anywhere. I'm guessing the breaker cam is shot. If so, pretty soon the points won't be able to break period. That's if your timing was late/retarded. If it was advanced you may have a distibutor gear coming apart. I've seen the "bad" cams wear to nubs in just a couple hundred hours.
 
After sleeping on it, I AM going to pull it apart today for a look-see and check the e-gap. Luckily I'm not one of those afraid to dig into a mag. I even have a spare on the shelf if needed.

Oh, and it was advanced.
 
So, recently we noticed it becoming very difficult to manage CHTs, mainly #3 & #4. The change was so slow that we barely noticed. With summer upon us it is a glaring issue. 3 and 4 passing 415deg by downwind on the first takeoff of the day. Wow, that just isn't normal. Cruise CHTs seem higher too. Are we sure this isn't just our imagination or an instrumentation problem? We finally declared that it isn't our imagination. Now what?

... I'll let that dwell for a few minutes then followup with findings :).

I believe CHT's are directly related to OAT change. If you see a 70F change in OAT, you will see a 70F change in CHT.

You may not have a problem.
 
As the cam wears down it breaks the points late. Same for worn points, the breaker half that the cam pushes gets farther from the cam. Retiming the mag makes it pop at the proper time, but internally the point break is moving away from e-gap which is of course the magic position where the rotating magnet has maximum flux relative to the core lams. It's physical, you can feel it. Moving point break away from that spot rapidly reduces spark output. Pretty much all the wear and the rotational forces push the mag towards retard. If your points grow a stalactite, which they do because one point deposits material onto the other point you have a pit on one side and a spike on the other. If the breaker halves shift then the spike rests on an unworn spot making them taller. This will cause advance. Also as the cam wears in it leaves a tall nub at the top and/or bottom of the cam. You retime a couple degrees. Couple years later you retime a couple degrees. Then the cam moves in it's slot and/or the breaker halves shift and a tall nub is suddenly breaking the points early (where they used to break). That's the only advancing mechanism I know of (unless you jumped an accessory case gear or something in your impulse coupling is not snapping all the way back).
Anyone else think of another advance mechanism?
 
Ok, just back from the hangar. I opened it up and there are no internal issues. It looks great inside and the e-gap was pretty much spot on. I'm comfortable that it must have loosened just enough to slip on the accessory case. We're waiting on a prop cable (tomorrow) for a test flight. I'll bet we can stick a fork in this one. I'm looking forward to CHTs being back in line without all that advance.
 
I'll reopen this for the peanut gallery. We ended up putting a new mag on it. Still high CHTs on all but #1 cyl, also corresponding higher oil temp. I'm relating these temps to what we know they have always been in the last 1600 hrs. About 30+ deg hotter cht and +10 deg oil temp. Remember this is a left impulse coupled mag, a right Lightspeed, O-320. All intake tubes are tight and clean.

Tanya went out and flew around mostly straight and level in our normal cruise profile at 4500' doing 145 TAS for a half hour. We would expect to see CHTs at around 350, which is where #1 was, but 2,3,4 were 386+ and very difficult to keep under 400 in any climb. Mag drop checks were fine. She flew around on only the lightspeed for 10min and all temps were exactly in line with our normal expectations. Are we just making less power with the mag off, thereby cooler? I would think the lightspeed can support near complete combustion based on its very low mag drop during runup.

What gives? I'm running out of ideas. Is there a failure mode in the mag harness that could produce advance (I don't think so). I'm thinking about hanging a timing light off of each plug to see if I can find anything interesting (doubt it). I'm also thinking about experimenting with making the mag "late to the party".
 
Perhaps looking at it from the LightSpeed side might be worthwhile.

If you assume the mag is timed correctly, the results you find with running just the LightSpeed is opposite of expected (the Lightspeed should be 30+ degrees of advance at that power level and would show little drop when turning off the mag). Things to explore:
- Is the Lightspeed timed correctly (timing set when at TDC - NOT 25 degrees BTDC)? Use a timing light with the Manifold Pressure line disconnected to verify. Do this again with the Manifold line attached and see if you get any advance (may not depending on what RPM you are at)
- If this is a LightSpeed Plasma II have you connected the external pot to control timing?
- Don't assume the LightSpeed is functioning correctly.

After you have eliminated the LightSpeed then go back and figure out why the mag timing is off.

Carl
 
Time to look at intakes to the cylinder, and possibly replace gaskets and sump fittings. Those two cylinders are likely running lean.

Minor intake leaks only affect the engine at reduced throttle. At wide open throttle there is no differential pressure to force air in downstream of the carb or FI body. Only when the throttle is mostly closed or closed does it have an effect. It is easy to test by recording egts at 23" then at 13" or so. If egts go up there is probably a leak.
 
Baffles?

You may have already mentioned it, but are the baffles still in good shape? Seals fitting good and laying flat against the cowl? What do the plugs look like? Any evidence of lean running?

If fuel injected, have you cleaned the injectors? How about the fuel distribution device, I forgot what it is called. A little piece of dirt can affect chts a lot. It would be unusual for three cylinders to see it at the same time.

You mentioned it has been creeping up. Perhaps a gradual buildup in the injectors of some gunk?
 
You may have already mentioned it, but are the baffles still in good shape? Seals fitting good and laying flat against the cowl? What do the plugs look like? Any evidence of lean running?

If fuel injected, have you cleaned the injectors? How about the fuel distribution device, I forgot what it is called. A little piece of dirt can affect chts a lot. It would be unusual for three cylinders to see it at the same time.

You mentioned it has been creeping up. Perhaps a gradual buildup in the injectors of some gunk?

O-320 No change in baffles. Plugs look normal.
 
She flew around on only the lightspeed for 10min and all temps were exactly in line with our normal expectations. Are we just making less power with the mag off, thereby cooler? I would think the lightspeed can support near complete combustion based on its very low mag drop during runup.

In simple terms, a plug ignites the mixture and the flame grow until it reaches a point where maximum pressure exists in the chamber. It takes a bit of time for the flame front to roll across the chamber, so the designer ignites the spark before the point he wants peak pressure (advance). The movement of this point impacts power, heat, detonation potential, etc.

In a dual plug engine, you have something I call relative timing. Each plug fires at opposite ends of the chamber and the fronts meet in the middle (flame front travels approx 1/2 the diameter of the chamber). If you stop igniting one plug, the remaining flame front must travel close to the full diameter to reach max pressure. This will cause the peak pressure to occur late and creates an effective reduction in ignition advance. retarded ignition reduces CHT's and increases EGTs.

This concept also applies to blended timing advance when using different ignitions with different timing. Your low mag drop on the LS ignition is due to it's earlier timing (it is doing a larger share of the work in reaching peak pressure). These advance changes do affect power, but it is often not significant and hard to notice. The movement of heat between the chamber and exhaust is much more noticeable. Optimum peak pressure keeps more heat in the chamber doing work moving the piston. late peaks produce less heat in the chamber, as they are letting more of that heat flow out the exhaust.

Knowing all of this should help you sort out if timing is a factor in your particular case. The fact that reduced timing brings your temps right back in line with expected would point me toward investigating your actual igintion advance. A mag can be tested with simple tools. The lightspeed is a computer and you will need a timing light to confirm what it is actually doing to your advance, either across the board or at any given RPM/MAP combination.

Larry
 
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RPM Drop

I would think the lightspeed can support near complete combustion based on its very low mag drop during runup.

This is a false assumption. The reason the Lightspeed (and most electronic ignitions) have very little drop during run-up is because they advance the timing at low manifold pressure whereas the mags remain fixed at less than optimal timing for run-up power. At high power settings, there is little to no difference in the "completeness" of combustion between a mag and an electronic ignition. Therefore, running on one ignition (Lightspeed) in flight still reduces the effective timing of the engine and will result in lower CHT's.

Skylor
 
Ok, I think we have something. Thanks for the additional nudge to prove the Lightspeed. We got a timing light on it and it's base timing (without the MP connected) is stuck at about 43deg BTDC! It didn't change at all with or without the MP tube connected. Yikes. We dutifully stepped through the troubleshooting flowchart. This isn't going to be a fun conversation with Klaus I bet.

Now we're just on Logistics to find an ignition to get to OSH.
 
Ok, I think we have something. Thanks for the additional nudge to prove the Lightspeed. We got a timing light on it and it's base timing (without the MP connected) is stuck at about 43deg BTDC! It didn't change at all with or without the MP tube connected. Yikes. We dutifully stepped through the troubleshooting flowchart. This isn't going to be a fun conversation with Klaus I bet.

Now we're just on Logistics to find an ignition to get to OSH.

Assuming the Lightspeed is working correctly, I'd guess timing was set on it with the crank at 25deg BTDC instead of TDC as required. If timing was set at TDC, then look at the remote timing control (if one is connected), then the only thing left is to fix or replace the box. If you replace, recommend shifting to one or preferably two pMags.

Carl
Former Lightspeed owner - pulled and replaced with dual pMags.
 
Ok, I think we have something. Thanks for the additional nudge to prove the Lightspeed. We got a timing light on it and it's base timing (without the MP connected) is stuck at about 43deg BTDC! It didn't change at all with or without the MP tube connected. Yikes. We dutifully stepped through the troubleshooting flowchart. This isn't going to be a fun conversation with Klaus I bet.

Now we're just on Logistics to find an ignition to get to OSH.

Glad you found the problem. That's pretty agressive timing for 30" and 2700 RPM. Given that this has been going on for a while, it wouldn't be a bad idea to pull the top plugs and look for any detonation damage on the piston crown.

Larry
 
Ok, I think we have something. Thanks for the additional nudge to prove the Lightspeed. We got a timing light on it and it's base timing (without the MP connected) is stuck at about 43deg BTDC! It didn't change at all with or without the MP tube connected. Yikes. We dutifully stepped through the troubleshooting flowchart. This isn't going to be a fun conversation with Klaus I bet.

Now we're just on Logistics to find an ignition to get to OSH.

You could also throw a mag on in a pinch. I have spare mags (both impulse and non-impulse) and a spare harness you could borrow, including a gear and good plugs. Would be happy to drop it at Fedex tomorrow.

send me a PM if interested and I'll give you my number.

Larry
 
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Glad you found the problem. That's pretty agressive timing for 30" and 2700 RPM. Given that this has been going on for a while, it wouldn't be a bad idea to pull the top plugs and look for any detonation damage on the piston crown.

Larry

Yeah, I agree, pretty scary. I've been in each cylinder with a borescope very recently and will again armed with this new knowledge.

We've also been commiserating with Dr. Horton who had some good ideas for 'hacking' the lightspeed to fix it at 23deg in order to meet our immediate objective :). "See ya' next weekend!"
 
Yeah, I agree, pretty scary. I've been in each cylinder with a borescope very recently and will again armed with this new knowledge.

We've also been commiserating with Dr. Horton who had some good ideas for 'hacking' the lightspeed to fix it at 23deg in order to meet our immediate objective :). "See ya' next weekend!"

Good luck with that, but be careful. until you find cause of the failure, you're kind of flirting with disaster, as you don't know what it will do next. I am not sure that I would be confident that it will stay at 43*, if your thinking of adjusting the pickup or setting up an offset to move that back 18*

One could assume that it is just the MAP sensor failing. However, I don't think you would get 43* at any MAP setting in the lower RPMs (at least it shouldn't be set up that way). That would lead me to think it is more than just a MAP sensor.

Good luck.

Larry
 
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Mag

Just a comment on magneto mounting slippage. If the mag and mounting surface are properly cleaned, a new gasket and lock washer used, and the proper torque of 204 inch pounds used, it is virtually impossible for the mag to rotate on the mounting pad. It is vitally important that the lock washers not be reused. Torque the mag fasteners and then need to move the mag: replace the lock washers. I have seen A&P's reuse lock washers on many occasions. NOT ACCEPTABLE.
 
This has been quite the adventure. Definitely a Lightspeed Plasma II+ failure stuck at approx 43deg timing any way you cut it. A new replacement is installed and behaves exactly as it should. We shot it with the timing light and, yeah, this is the way it should be. A test flight agrees that we have the airplane we know so well back, no matter if it is hot out. CHTs and oil temp are back where they should be.

Borescope: Yeah, there are some areas of some pistons that are a little cleaner than I would like. I can't discern any real pitting, but maybe that is just wishful thinking. Definitely no chunks missing. We had really backed off of run time while we worked through this. Hopefully listening to the machine helped some. It is what it is at this point and we're extremely glad that we found the real smoking gun. Thanks to all for the comments.

We'll fly it some more this week then we'll see ya' at OSH!

(That sure is one ugly failure mode of the Lightspeed!)
 
After a steak dinner, Test flight #2 results just in. "Could not have been any happier." It is good to have a built-in test pilot on staff to accelerate testing.

I'm sorry for the lack of engineering detail, but it is by design. When my CHT is 385 and we absolutely know from the last 9yrs that it should be 355-360, it is way out of whack for us. The important reference is Change. Listen to the machine.
 
(That sure is one ugly failure mode of the Lightspeed!)

Definantly not good!! I have the timing output signal from the Lightspeed Plasma III going to an open input on the EFIS so that the degrees timing is logged in with the datalog file.

This also provides a visual display for troublshooting and managing advance with various fuels.
 
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I have noticed gradual similar CHT increases say 25 to 30 Deg on my O- 320 D2J with a non impulse Slick mag on the left and a LS Plasma II plus on the right . I tried the "Run only on the LS plasma" for about 3 or 4 minutes today at about 80% power and noticed a substantial drop in CHT on all four also in the neighborhood of 30 deg On return to both all the CHT increased back up to the 390 range. Decided to go to mag only and saw a decrease in power . Not sure what thats tell me but the mags got about 350 hours on it and I believe I will check the timing and plugs on both in a couple of days.
 
Definitely a Lightspeed Plasma II+ failure stuck at approx 43deg timing any way you cut it. A new replacement is installed and behaves exactly as it should. We shot it with the timing light and, yeah, this is the way it should be. A test flight agrees that we have the airplane we know so well back, no matter if it is hot out. CHTs and oil temp are back where they should be.

Hi Scott, I've been having the same high CHT issues with my TMX-360. When you say a new replacement is installed, does that mean you replaced the Lightspeed brainbox? ... Bill
 
Hi Scott, I've been having the same high CHT issues with my TMX-360. When you say a new replacement is installed, does that mean you replaced the Lightspeed brainbox? ... Bill

Yes. Simply because it's base timing was obviously messed up. It was stuck at full advance no matter what.

We went through log books last night and were able to determine roughly when this occurred and that we could count the total number of hours flown until resolution on one hand.
 
(That sure is one ugly failure mode of the Lightspeed!)

Yes, and it may explain some past issues with other engines. A high compression engine, running WOT and leaned to best power, will detonate heavily given an ignition failure mode that defaults to 43 degrees.

Most MP sensors are three wire, 5V power, ground, and signal. The typical signal varies from a bit less than one volt at high manifold suction (low MP gauge pressure) to something near 5 volts at low manifold suction (wide open throttle). Low output voltage tells the control system to add advance. Thus it appears an open or high resistance circuit, either on the power side or the output voltage side, could default the system to max advance.

I don't know for sure, but I theorize that current OEM automobile code flags MPS output less than the expected lowest output voltage, turns on the check engine light, and switches operation to a pre-programmed default value. That's certainly what an aircraft system should do.

I'll look into the EDIS system I'm currently flying. Ross, can you comment on the new CPS system? And it would be interesting to hear from Electroair.
 
High CHTs

Thanks Scott, I am envious that you were able to troubleshoot and resolve so quickly. This one has been a real bear for me. ... Bill
 
Yes, and it may explain some past issues with other engines. A high compression engine, running WOT and leaned to best power, will detonate heavily given an ignition failure mode that defaults to 43 degrees.

Most MP sensors are three wire, 5V power, ground, and signal. The typical signal varies from a bit less than one volt at high manifold suction (low MP gauge pressure) to something near 5 volts at low manifold suction (wide open throttle). Low output voltage tells the control system to add advance. Thus it appears an open or high resistance circuit, either on the power side or the output voltage side, could default the system to max advance.

I don't know for sure, but I theorize that current OEM automobile code flags MPS output less than the expected lowest output voltage, turns on the check engine light, and switches operation to a pre-programmed default value. That's certainly what an aircraft system should do.

I'll look into the EDIS system I'm currently flying. Ross, can you comment on the new CPS system? And it would be interesting to hear from Electroair.

With the CPI or EM-5 we can default the extreme ends of the MAP scale (shorted or open failures) to 0 MAP advance so you'd only have the base RPM setting of around 25 degrees total. The CPI uses an integral sensor. We have supplied over 600 of these in EIC, XIC and CPI units over the last 17 years. Zero MAP sensor failures. The CPI has a gauge mode to show current total timing as well.

The EM-5 uses an external MAP sensor and will show an error code in the programmer and turn on the check engine light if there is a open or shorted sensor. We have heard of about 8-10 MAP sensors failures in the last 22 years over many thousands of systems sold. Most of these can be attributed to people not mounting the sensors with the vacuum port down as the instructions state or substituting their own El Cheapo brand of sensor.

I'm not sure why any manufacturer would have 43 degrees programmed in on a Lycoming EI or why it would be designed in such a way to advance if the MAP signal is lost. Scary IMO.
 
Has there been any communication from Klaus on this failure? I would be curious to hear from him. All be it, having had conversations in the past with him, I can just imagine the tone of the conversation.
 
Has there been any communication from Klaus on this failure? I would be curious to hear from him. All be it, having had conversations in the past with him, I can just imagine the tone of the conversation.

No there has not. We're not wasting the brain cells on it right now as I imagine the same conversation as you do :). Something to deal with after OSH.

Ross, thanks for your comment. I was intending on asking you how you deal with this.
 
No there has not. We're not wasting the brain cells on it right now as I imagine the same conversation as you do :). Something to deal with after OSH.

Ross, thanks for your comment. I was intending on asking you how you deal with this.
If you do talk with him please post the results of the conversation.

. . .Calling Klaus I was told I screwed up the wiring. . .
Oh, never mind! I should know better than to ask.
 
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With the CPI or EM-5 we can default the extreme ends of the MAP scale (shorted or open failures) to 0 MAP advance so you'd only have the base RPM setting of around 25 degrees total...

So is that the failure mode: "Hard over" to max or min MAP? If so, then I can see how easy it is to program both ends of the scale out of the CPI. An easy failsafe for an unlikely, but potentially damaging condition.

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.
 
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 did you change out the MP sensor with he box change out? Or find any fault in the original MP sensor?

Considering I had the exact same problem with my dual LightSpeed Plasma II+ install, I'll share what I know. This goes back to 2002 but I suspect the Plasma II+ has not appreciably changed - sorry if my assumption is not correct.

- 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
 
Scott did you change out the MP sensor with he box change out? Or find any fault in the original MP sensor?

Dennis, I know Team Card did not spend time on board level diagnostics, beyond a quick visual inspection.

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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