LifeofReiley
Well Known Member
Bob... ++++ 1 But there are good systems making good head way.
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Its clear in this case that the one manufacturer that chooses to obfuscate this information uses a curve that one has to wonder what in they heck they were thinking.
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The idea of setting the timing one or two degrees after top dead (TDC) center is suggested by Emag for those who run composite propellers so the spark fires after the prop has crested TDC and the spark helps spin the prop. This may be necessary because when below 200 RPM’s the Pmags fire at TDC, not after TDC, and a light prop may not have the inertia to get past the compression stroke and spark plug firing when starting. Metal props don’t seem to have this problem. (For the record, I run the A curve and my TDC is set at zero for my O-360 with a Catto prop.)
...../QUOTE]
Bill R.
I have a question about this part or your post. Brad explained to me when I was setting up my P-mags on a new engine that using no jumper and setting the timing due to my light prop a couple degrees past TDC made the timing essentially the same as running the A curve timed at TDC.
I will be the first to admit that this is all a mystery to me, I am still running with it set the same way since I have had no problems and I have not taken the time to understand what I get from the various timing curves, 170 hour plus.
I just don't get what I gain by messing with the various timing curves so I have left well enough alone, but I certainly don't want to hurt my engine.
Curious if you agree about the timing a little past TDC and it being the same as the A curve with timed at TDC.
Eager to understand.
David, I think I understand pretty much what you are saying and agree that ICP should be the ultimate determinant factor. But there is one thing that you have discussed often that I do not understand, and that is your contention that the actual spark event is often happening way after we think it is in a mechanical system (conventional mags).
When you check timing using a dynamic, inductive timing light, are'nt you seeing the timing of the actual spark event??
I can understand that is there is a lot of mechanical lead/lag in the gear train and mag mechanisms and that there is less in crank sensor fired electronic ignition, but isn't the sum product of all that going to be reflected in the actual current being sent down the wire that is indicated by an inductive timing light??
If the timing light says that the spark event is happening at say 25 degrees BTDC, are you saying that comprehensive engine instrumentation will indicate that it is happening later?
Just trying to understand. Thanks
I can understand that is there is a lot of mechanical lead/lag in the gear train and mag mechanisms and that there is less in crank sensor fired electronic ignition, but isn't the sum product of all that going to be reflected in the actual current being sent down the wire that is indicated by an inductive timing light??
If the timing light says that the spark event is happening at say 25 degrees BTDC, are you saying that comprehensive engine instrumentation will indicate that it is happening later?
What I find most funny in this thread is the willingness to take a chart and assumptions made by someone you don't know as gospel, even after a manufacturer whose product directly controls Pmags attempts to explain how the chart is wrong.
What curve are you referring to? You have never seen or discussed Pmags actual curve, just numbers that are part of an equation that calculates that curve. By the way, that's how modern ignitions outside of lycomings have done it for decades.
Interesting timing curve......just sayin
Please tell us where this came from so we don't get it confused with the Pmag.
I have no idea. Sorry if it caused confusion Brantel. I was only ref. it because of how complex they can be vs how simple they can be. It is NOT a pmag chart
Yep I know I've worked on code to do timing advance calculations in C using a multidimensional array, pin capture and timer interrupt...
Even though it became a bit more clear in this thread later on that the numbers being returned serially were not the real advance numbers due to various rounding errors etc., there is ample evidence from the chart that the timing on a PMag is advancing well before the other established ignition manufacturers have done given a particular mid/high power RPM/MP combination.
The chart isn't the curve. It's ONE variable that the curve takes into consideration. That's all.
They protect it as proprietary so that a bright guy with a homemade box won't take their curve and how they achieve it...put it on the Internet for someone else to put in another box to package and sell for 20% less than Pmags. Easy enough to do if you don't have to do any of the engineering or testing.
I don't want to be contentious either but how do we know this is true? Bill says it is but do we just take his word for it? (Sorry Bill)
My stance is that Bill very well may be correct but if Bill is correct, the guys at EMagAir are deceiving all of their customers with their published marketing and technical documentation as well as the tool that they give us to monitor and configure our Pmags.
There public data is either correct or it is not and if it is not, what good is it?
If you've done what you just said you've done, you know there is no evidence of anything based on that chart. It's part of an equation. It's one variable. That's like saying you can predict HP based on an RPM chart without knowing anything else. I'm not trying to be contentious here, but you are spreading misinformation and people are throwing our things like "Just buy XX instead" based on your misinformation. The chart isn't the curve. It's ONE variable that the curve takes into consideration. That's all.
But we DO know it's working better than a magneto.
Pretty bold statement!
Is there any test data available to substantiate this claim?
No worries Brian! You are doing a good, honest thing with your device and posts....
Bill and I are online friends and have been for a long time... I want to keep it that way.... He has a neat product for the Pmag and deserves a ton of credit for bringing it to market.
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Exactly!...
Do we know exactly what the ignition map of a PMag looks like?
...No
But we DO know it's working better than a magneto.
...
The EICommander does much more than just spit out the raw data as Brian did. The device interprets it and figures out those number's contribution to the timing curve. It also l monitors when the #1 cylinder fires and compares that to the other P-mag and alerts the pilot if there is a significant difference. The data to do that does not come from the streaming data that Brian reported when he initiated this thread. In addition, the EICommander allows you to tune the timing configuration to your needs.If what you are saying holds true then a EI Commander is doing nothing but spitting out values from the equation, just as Brian has done.
And that would make the product Bill sells worthless. I doubt that being the case.
Other products in this category do not hide this "proprietary" information.
Brian's intention is to see if the ignition is causing CHT issues and he shouldn't have to take his engine off and put it on a dyno to verify a EI maufacturer's RPM/MAP curve. Hence why the other manufacturers provide an interface for one to actively see what is going on.
I've been directly involved with 3 PMag installations and all 3 airplanes picked up performance immediately.
Do I think ignition map data is a useful pursuit? You bet! But really, what are we going to DO with that info?
(SNIP)
So perhaps we should keep the end goal in perspective and not freak out 99% of the readers by putting the notion in their head that their engine is going to self destruct the next time they fly. PMags may not be the bleeding edge of ignition timing for every Lycoming ever built, but they are a vast improvement over magnetos. That's one part of their marketing you can believe.
For example, some engines like the IO-390, require timing down around 20* BTC. By simply installing a P-mag and running either the A or B curve, you are doing yourself no favors. You really need to adjust the B curve and dial the timing in as required by your engine manufacture. This can be done via the EICAD program or our EICommander.
EmagAir has said from the beginning that they are not releasing their curve which is common in all manufacturing and aftermarket tunes in the performance world. They aren't deceiving anyone.
They created a tool to let people control their units, not decipher their proprietary info. You are using the wrong tool for the job you're attempting to do. If you want to KNOW the curve, rent a dyno and do some real testing.
A box made on your kitchen table isn't up for the task you are taking on.
EmagAir tells you they won't give you their curve but we are to believe that they validated your numbers as their curve? That just doesn't seem likely to me.
Bill tried nicely to explain to you the errors in your assumptions. You continue to get more and more offended. Now you ask if we are going to take Bill at his word? On this topic...yes I am.
Pretty bold statement!
Is there any test data available to substantiate this claim?
The inconsistencies of the end users experince are a bit puzzling. Although I have very little time on my pmag, the experience of the mag check in the air between my slick and the new pmag was hardly noticeable, 30 RPM drop vs 40 with the slick, every thing else the same. I am running the A curve and auto plug with the pmagBob, you would not be asking this question if you were in my 4 the other day when i switched the mag off and saw no effect on performance just running on EI. Then when I switched the EI off and just ran on the mag there was an instant drop in power and the EGT's were all over the place.
What we know about Mags is that they are about as accurate as a broken watch, set up just to ensure that the engine does not melt under any fuel/mixture/rpm, etc condition.
I grew up working on bikes like Vellocettes, Pre Unit Bonnevilles and the like with mags. Even the Harley has EI these days and is a vast improvement on what went before.
The inconsistencies of the end users experince are a bit puzzling. Although I have very little time on my pmag, the experience of the mag check in the air between my slick and the new pmag was hardly noticeable, 30 RPM drop vs 40 with the slick, every thing else the same. I am running the A curve and auto plug with the pmag
For me it is not about how good or bad the Pmag is. I agree however that it is good. I bought and fly behind one each flight. The original intent of this thread was to see how the timing effects my CHT's. Nobody should run away from the Pmag based on this thread.
... But I'd urge some restraint when reporting your somewhat disturbing findings until they are well understood/vetted. And keep in mind the audience here. There are very few who who really know how to use an accurate ignition map in the first place and most of the rest are going to interpret this debate as PMag = bad.
The inconsistencies of the end users experince are a bit puzzling. Although I have very little time on my pmag, the experience of the mag check in the air between my slick and the new pmag was hardly noticeable, 30 RPM drop vs 40 with the slick, every thing else the same. I am running the A curve and auto plug with the pmag
Thats just it, I am not sure what is so disturbing, my data more or less matches what the manual already says just with more detail. I am not qualified to pass judgement on the numbers I posted and have not said they are out of line. I have stated that my own engine reacts like it could stand to go back to the "A" curve or maybe even less advance than the "A" curve which can be done using EICAD.
The inconsistencies of the end users experince are a bit puzzling. Although I have very little time on my pmag, the experience of the mag check in the air between my slick and the new pmag was hardly noticeable, 30 RPM drop vs 40 with the slick, every thing else the same. I am running the A curve and auto plug with the pmag
If the P-mag's timing curves were as bad as some of the people on this thread would have you believe, there would be a trail of melted Lycones all over the world.
The problem is the "inconsistencies" in the planes the P-mags are installed on.
Some have cooling issues (Heck, I reduced my CHT's by 20*F just by going after my baffles with RTV!), some have different compression ratios, some even have different head designs. (Ever wonder why one IO-360 is rated at 180 HP and another is rated at 200 HP?)
Like any system we install in our planes, it is up to the builder to read and understand the installation and operation of each component. It is impossible for the manufacture to understand how 500 different builders, with 500 different engines, cooled by 500 different baffle installations will operate their device.
The P-mag manual makes it pretty clear how they need to be installed and configured to match your installation. They do not recommend timing that is outside the requirement of any engine manufacture.
They do go out of their way to provide a tool, the EICAD program, to configure the timing to match your engine.
Heck, if you have forced induction, you can dial the timing in to exactly what your requirements are.
If the P-mag's timing curves were as bad as some of the people on this thread would have you believe, there would be a trail of melted Lycones all over the world.
I think the issue is that there are plenty of bright people on this forum who are gearheads at heart. They want to understand the real timing ....
Would an operative question to the ?engine guys? be, ?what ignition map is required to maintain 14 degrees ATDC throughout my operational profile.?
Yes Don, that is exactly the question you should be asking. But first, a question for you....what are you running now? Your signature says you have an IO-390 and dual p-mags. Are you running the A map, the as-delivered B map, or a modified, shifted B-map?
Over the next several weeks I'll characterize my "A" curve performance then venture carefully, cautiously to a modified "A" starting with something like Steve did.
540-K has pretty much the same cylinder head as our 390's. Given 20 BTDC timing, high manifold pressure, and a near-stoich mixture the peak pressure is arriving earlier (about 7 ATDC) than the mid-teens optimum (the 14 or so you mentioned previously). By running the 26 degree A map, your peak pressure under the same conditions is even further from optimum, probably near TDC and very high...not a good thing.
The K-series 540's have a velocity stack intake tube design that's buried in the sump, so even though the cylinders are stock angle-valve the intake is completely different. Not sure its pertinent to this discussion but worth noting.
The K-series 540's have a velocity stack intake tube design that's buried in the sump, so even though the cylinders are stock angle-valve the intake is completely different. Not sure its pertinent to this discussion but worth noting.
Also worth noting is if one is running mogas with a PMag I would be very cognizant about mechanically retarding the timing as others have done here.
That said, is the -K intake tube system really all that much different compared to those used with the 360/390 angle valve horizontal sump?
..hopefully I can dig up a pic of the sump.