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04-14-2017, 02:19 PM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by erich weaver
I retarded the timing on my Pmags across the board. ...Didn't realize it til later, but that change also significantly lowered my in-flight CHTs while not having any noticeable negative effect on speed.
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See what I mean?
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Dan Horton
RV-8 SS
Barrett IO-390
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04-14-2017, 02:31 PM
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Join Date: Oct 2007
Location: Salmon Arm, BC
Posts: 933
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Been reading this thread, and can add another data point. IO-540-D4B5. I have an SDS ignition running the top plugs and a mag timed to 25* running the bottom plugs. Most of my flying is local, ~3000' ASL, 23 squared (55%), LOP at 9.5 - 10.0 gph. The SDS is set at 28* for those numbers, and my advance switch adds 4*.
Today I flew these numbers, and every 5 minutes for 3 cycles I threw the advance switch. Analyzed the resulting data and the only discernable change is adding 4 more degrees advance would lower my EGTs across the board by ~20*. CHT did not change. Could not identify any trends in airspeed - 3000' here is flying the valleys and keeping a constant elevation means airspeed fluctuates quite a bit as you move through rising and falling air currents.
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Mark Olson
1987 RV-4 Sold
2003 Super Decathlon - Sold
F1 EVO Rocket, first flight May 31/14
First in line for the Sonex JSX-2T kit
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04-14-2017, 02:45 PM
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Join Date: Jul 2009
Location: Mojave
Posts: 4,652
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Quote:
Originally Posted by erich weaver
Not very far. The big takeaway from Nigel's article seems to be that the potential gains from timing tweaks are pretty small and as you state, things get a little messy when throwing mixture into the mix...
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Well let's not let the pendulum swing too far with overgeneralizations...
The benefit for playing with advance is far from linear, but it is certainly there. High and lean, the performance benefit is significant. At least I think a change from 198 to 201 knots at the same FF is significant. And as stated, the ability to build in detonation margin when down low and fat with a retarded timing set is also significant.
The big takeaway is what Dan and I and others have been stating for a long time now:
Variable timing is no good by itself; you need the RIGHT timing for the condition. There are no "one size fits all" solutions.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.
Michael Robinson
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Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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04-14-2017, 03:51 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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You guys are funny!
When I was a kid my dad you to laugh at me because I knew that one car was 1/10th of a second quicker to 60 than another. Therefor, he should buy the faster car.
He knew he wasn't racing his car to church on Sunday so that extra speed wouldn't do him a lot of good.
The same thing goes for electronic ignitions.
Yes, the can be tuned better and ideally would be tuned to each individual engine.
However, the P-mags in standard form are working and working well for 99% of the people who install them. Assuming they are installed and timed correctly.
Yes, there are better timing maps and some of the other ignitions out there can be tuned in increments of X RPM's. However, how many people understand the finer points of ignition timing and can time their engines to maximize performance. Not to mention the risk tolerance involved in doing so. Not only do you risk damaging a very expensive engine but possibly risk your life.
The P-mags in standard form are a plug-and-play installation, for the most part.
Once installed you can fly high, low, LOP, ROP, or whatever you want and they will not damage your engine.
The best part is that once installed, timed, and configured properly, they are a never worry about device that keeps your engine humming along happily.
While we are a group of "experimenters", not everyone wants to experiment with their engine but they do want better performance. The P-mags provide that and they provide the backup power redundancy most pilots look for in their system.
The advantages of electronic ignition, coupled with an internal generator, and easy installation are the selling point of the P-mag ignitions.
If the timing curves where so dangerously aggressive, as mentioned in this thread, then there would be melted engines all over the world and that is just not the case. Could the timing curve be better? Yes it could, but it is still a LOT better than a fixed time magneto.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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04-14-2017, 03:57 PM
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Join Date: Jun 2005
Location: Cedar Park, TX
Posts: 3,156
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Oh Bill...  . What was that peak CHT you saw again?
Another shot of coolaid for me please.
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Scott Card
CQ Headset by Card Machine Works
CMW E-Lift
RV-9A N4822C flying 2200+hrs. / Cedar Park, TX
RV8 Building - fuselage / showplanes canopy (Done!)
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04-14-2017, 04:14 PM
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Join Date: Jan 2005
Location: Yorkshire, England
Posts: 2,052
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We have dual P-Mags on our 7.
We rock up, pull it out, it starts 3rd blade cold or hot. Uses $8 NGK plugs and flies really well.
Because we can now analyse the far end of the fart, doesn't make the fart any better or worse 
Why haul a dumb mag and big spark plugs around when you can just enjoy simple, great engineering ?
Bill - the EI Commander went on the 8 to a new owner, he says it it is great !
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"I add a little excitement, a little spice to your lives, and all you do is complain!" - Q
Donated in 2020
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04-14-2017, 04:38 PM
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Join Date: Jan 2005
Location: NC25
Posts: 3,508
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Quote:
Originally Posted by Carl Froehlich
But - they will only sell you an engine with one pMag. If you want a dual pMag set up (like most people) they will sell you an engine with one pMag and nothing in the other mag slot. You then buy the second pMag from Emag.
I assume there will be a credit for not getting the Slick mag - I drop my order for engine and prop later this week so I'll find out.
Carl
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Can you provide a link to where it says only one Pmag. When I read the announcement (cannot find it now), it was a $1,000 upgrade. Delete the price of two Slick Mags and add in two Pmags and $1,000 sounds about right.
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Gary A. Sobek
NC25 RV-6 Flying
3,400+ hours
Where is N157GS
Building RV-8 S/N: 80012
To most people, the sky is the limit.
To those who love aviation, the sky is home.
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04-14-2017, 05:15 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Quote:
Originally Posted by scard
Oh Bill...  . What was that peak CHT you saw again?
Another shot of coolaid for me please.
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Over 500 Scott, but that was with an early version of the P-mag hardware and software and lead us to the development of the EICommander. The issue was a lost timing mark, not a bad timing map. Since then, Emag has updated both the hardware and software. Also, my airplane is not a good example for this group because of the Sam James cowl. I just don't believe they cool as well as a standard Van's cowl. It has take me some time to get everything sorted out, much of which had nothing to do with the P-mag and their timing map.
Since Version 40 came out a few years back, the P-mags have been rock solid.
Granted, having the ability to monitor and tune them is a bonus!
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
Last edited by N941WR : 04-14-2017 at 05:20 PM.
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04-14-2017, 05:16 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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Quote:
Originally Posted by mike newall
We have dual P-Mags on our 7.
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Bill - the EI Commander went on the 8 to a new owner, he says it it is great !
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I'm with you Mike, I wouldn't fly behind a traditional mag.
Let the new owner know that they can contact me, if they have any questions.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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04-14-2017, 05:28 PM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by N941WR
However, how many people understand the finer points of ignition timing and can time their engines to maximize performance.
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I'm sure most assumed the best choice was pre-installed.
Using a set of P-mags and your EI Commander, Nigel demonstrated that the factory settings are too advanced for ROP, all the way up to 16,000 feet.
Facts are facts. You've seen the data. Do you find fault with it?
BTW, this is not a hardware or brand condemnation. It's just a poor choice of factory installed timing values. Any ignition, magneto or EI, would offer the same result given the same timing values. The values can be changed with keystrokes, or as in Nigel's example, with an EI Commander. So it really does come down to acceptance or dispute of the data.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
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