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Loss of timing
If we are talking about the incident where arcing at the alternator apparently caused this failure, my recollection was that V40 was designed to prevent this type of issue.
However that is why we have dual ignition systems, if one malfunctions you go to the other and land ASAP. When my LSE ignition started to play up I knew straight away and wen to the mag. No damage to the engine at all. Actually I may well fit a a different type of ignition in my next lycoming, with fuel injection, but am a happy PMag customer especially with Bills EIC as you can monitor the mags and see what is going on with them. |
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P-mag wants you to remove the units and do an inspection. The act of removal and replacement is not horrible, but opening up the back of the engine every hundred hours is not fun and definitely increases the risk of dropping hardware into that gaping hole. But the inspection itself is compelling. You are looking to see that all that stuff is still in place. Shaft endplay, magnet alignment? All that stuff is important and let?s face it, fragile. Plenty of warnings to handle this with kid gloves in the P-mag manual. In contrast, the CPI sensor is bolted to the side of the case with a mount stout enough to lift the engine with. If you have an end play or magnet misalignment problem, the crankshaft is broken. So yes, to answer your question ? zero maintenance for CPI. Further, the CPI sensor is potted so it is essentially chemical proof. If you want to wash the engine down with solvent or degreaser, you?re not going to hurt the sensor. Contrast this with P-mag, where the case is open vented. You have to cover the Pmags with plastic or remove them to wash down the engine because the boards will get soaked. And yes, it happens. I had a board replaced because solvent entered the case and ate the board. But the maintenance free aspect is not the primary advantage of CPI. That belongs to the fact that the P-mag curve ? even the most conservative one ? is too aggressive. We have known for years that P-mag equipped engines run warmer and some even exhibit ?CHT issues?. And thanks to the fairly recent flight test efforts an dissection of their curve by several members here, the cause is now clear: Too much advance at high power. In fact, the issue is so well known that even the maker of the third party programmer recommends his product should be used to adjust the problem away. That, or you can mechanically retard the timing (as I?ve done on my -8). But this doesn?t really solve the fundamental issue, it just masks it. True, people are not melting down engines and the issue is manageable by ?spoofing? the standard program, but why not get an ignition that works right out of the box? And on the subject of ignition curves, P-mag doesn?t even offer the LOP switch function of CPI. This is a very useful feature and a compelling discriminator for those that do cross country work. So CPI delivers a safe, cool advance curve for takeoff and climb, as well as a fuel stretching LOP setting and everything in between. The components are robust, proven with decades of use, and maintenance free. |
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Considering that I am somewhat familiar with the maintenance recommendation of PMAG “ the opening up the back of the engine and all that you listed” I will leave that portion out of the discussion since the complexity and risk of it seems to be a matter of opinion. What I like to know, what advance curve is provided by CPI and how much of customization is expected for the end users/customer? Not all of us are either interested or knowledgeable in finding the best curve thru hours and hours of flight testing. With CPI, right out of the box, do I get a default timing that is an improvement over other EIS and what is involved in the switch for LOP (both in terms of installation and usage) Is it just a toggle switch? I appreciate the info. |
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So with CPI, every sale is for an individual engine and client, not a one solution fits all. We ask engine type, CR fuel octane and will enter a custom base map for you if desired, slightly conservative to be safe. No need for you to do any programming if you don't want to. To think that an A or B curve suits every engine and mission out there is simply nonsense. No way it's optimal for all engines, where we commonly have CRs from 7.5 to 10 and even higher in some cases. Data plate timing for IO-390s is a lot less than most other Lycomings, many people run mostly on mogas, some fly low or high, some fly ROP, some LOP. Interesting how many seem to discount the science of flight testing results by Nigel, Dan and Michael here on VAF. In short, we can enter a safe curve for YOUR engine and mission, no need for you to do much if you don't want to. Likewise you have the ability to fine tune (in logical 1 degree increments) if you wish, plus change the amount of LOP advance which is selected on/off with a small toggle switch. So, there is no "standard" advance curve with our products unless you don't give us any details, in which case, we'll generally enter 24 degrees of rpm timing for O-235, 290, 320, 360, 540 engines and 20 degrees on IO-390 engines with zero MAP advance or retard- pretty much standard mag timing. But, this would not be a good idea on a 10 to 1 engine running mogas. |
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Is there some data that compares a fined tuned curve of your system vs. the stock curve, lets say curve A of a PMAG in terms of fuel saving/additional power, etc? I am hoping to see a measureable difference (perhaps fuel burn would be a good measureable indicator). |
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The LOP function is activated by applying system voltage to a discrete pin in the CPI connector. The physical interface for the LOP function is a toggle switch in my case. The LOP function is programmed by scrolling through the CPI windows until you get to a discrete LOP window. You simply toggle up or down to get the additional advance you want (3 degrees in my case). Once set, activation of the LOP switch simply tacks on an additional 3 degrees advance to the existing map. If you’re idling at 20 degrees, then activating the switch will give you 23 (20 + 3). If you’re at the top of climb and the normal RPM and MAP values have you at, say, 32 degrees, then the LOP switch give you 35 (32+3). It’s also noteworthy that this function is deactivated at high MP levels. So if you forget to turn off the switch and do a go around, no problem. I'm glad Ross answered the “as delivered” program because I never used it. I went straight to building my own. A casual glance in the manual shows it to be very conservative at high power though, and testing confirms that’s exactly what is needed. In fact, my testing shows that even Lycoming’s data plate timing value is more than required for takeoff. My program pulls up to 5 degrees off the data plate value in some circumstances. And for the record, I'm stock (8.5) compression. |
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Too much or too little may cause power loss or CHT issues and too much can reduce detonation margins, especially on mogas with high CHTs and IATs. Too little is generally safer than too much. I think Nigel's data is the most complete and Michael's showed us the extremes of WOT/SL vs. LOP/ low MAP up high. I think the OP was really asking if the original software, hardware problems experienced by Pmags were now licked and only interested in actual reliability in delivering sparks in the Pmag offerings of today. You'll get different answers from different people depending on their experiences. This thread has taken a new direction discussing other factors outside reliability. I'm not sure that serves the purpose of the OP's question. There have already been other threads comparing the various EIs available today. |
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This issue is the breadth of the curve. P-mags deliver very good LOP efficiency because they advance far enough to do some good up in that rarified air. Unfortunately, they start advancing so early that down low and rich they make plenty of heat and cylinder pressure, but don't do more work. Plenty of credible flight test results on this site to review for confirmation. In short, a good hot spark can be delivered by any EI, and the engine architecture does the rest when LOP. Rich mixtures are easy to light and there's really no difference what lights it off. But timing is everything. The compelling issue is if the EI can advance far enough to light the LOP mixture, pull it back enough for the best power mixture, and retard enough to protect the engine at the SL, 100% power mixture. Most any EI can deliver on some of these conditions, but CPI does all of them and that's where the "performance advantage" is found. And I do agree that the OP's question has been answered long ago. Maybe the mods can split the "comparison" posts out into a more appropriate thread. My apologies for my role in the OT. |
I thought this was a thread about P-Mags.
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