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  #41  
Old 04-14-2017, 05:40 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
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Originally Posted by RV6_flyer View Post
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.
Not specifically documented. You have to call Van's. The extra $1000 gets you one pMag and one slick mag. Don't yet know how much extra one pMag and no slick mag will be. There is no option to get two pMags from Van's.

Carl
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  #42  
Old 04-14-2017, 05:52 PM
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N941WR N941WR is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
Not specifically documented. You have to call Van's. The extra $1000 gets you one pMag and one slick mag. Don't yet know how much extra one pMag and no slick mag will be. There is no option to get two pMags from Van's.

Carl
Why are they charging you an extra $1000 for the P-mag?

Are the price of a P-mag and one Slick close to the same cost? Shouldn't it just be an even trade?
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RV-9 (Yes, it's a dragon tail)
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  #43  
Old 04-14-2017, 05:58 PM
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N941WR N941WR is offline
 
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Originally Posted by DanH View Post
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?

....
I would ask, is the test that Nigel performed is unique to his engine with the higher compression pistons? How about his induction, exhaust, propeller, and fuel delivery?

Will someone with a completely different setup experience the same thing?

Nigel mentioned that his tests were to see the impact timing changes have on performance and not as a definitive test of the P-mag's timing curve.

Someone with a fixed pitched prop might experience different timing variations because their MAP / RPM numbers will be different, meaning the P-mag may select a different timing for each combination.
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  #44  
Old 04-15-2017, 09:27 AM
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DanH DanH is offline
 
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Originally Posted by N941WR View Post
I would ask, is the test that Nigel performed is unique to his engine with the higher compression pistons? How about his induction, exhaust, propeller, and fuel delivery?
Ok, so you're suggesting the existing data might be anomalous, but apparently have no alternate to present.

The good news is that you happen to have an available airframe, engine, and prop which are totally different from Nigel's, equipped with P-mags and an EI Commander, which you know how to use.

There is data available. Here's what Michael Robinson found...with an entirely different airframe and engine, stock compression, and different RPM:

http://www.vansairforce.com/communit...6&postcount=44

Short version:

100% power (0 MSL) 31.1"/2700 no power difference from 20 to 28 degrees
Cruise at best power (8,500 MSL) 23"/2300 best timing 27~28
Cruise at Peak EGT (8,500 MSL) 23"/2300 best timing 30
Cruise at 50 LOP (8,500 MSL) 23"/2300 best timing 33

Parallels Nigel's observations very well, i.e. advancing past 30 or so is entirely non-productive when ROP, in particular at high power settings. All you get is less HP and higher CHT...yet the stock P-mag advance was delivering 35 degrees at 23"

My own observations (which I'll be expanding in due course) are that when running ROP, my 8.9 angle valve motor may prefer even less advance. At 8500 and 65%, there is no detectable speed difference between 23 and 27 degrees, just a CHT increase, and that increase matches Nigel's observation of 2.5F per degree of advance.

Recall that many certified angle valve motors have a choice of 20 or 25 degrees, and Lycoming backed timing down to 20 for a lot of them, including the 390. Maybe it's because they have a dyno, eh?
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Last edited by DanH : 04-15-2017 at 09:56 AM.
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  #45  
Old 04-15-2017, 10:13 AM
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Toobuilder Toobuilder is offline
 
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Originally Posted by N941WR View Post
You guys are funny!

...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...
I would caution the use of hyperbole in the context of a technical discussion. One purpose of "...operating an Experimental airplane..." is education, and I have learned an awful lot about ignition timing in the last couple of years. So has Dan, Nigel, and others. I think we're all trying to present this information so that others can benefit from all the avgas and brain cells we have expended in the collection of this data. I dont think anyone has suggested that the Pmag product has "dangerously agressive" curve in this thread, but it is certainly agressive. And while there are not "melted" engines all over the world, there are scores of threads concerning elevated CHT's among the RV fleet. And while many of them are primarily cooling related, the sub optimal timing curve is certainly a contributor.

As Dan points out, you are in a perfect position to gather and present data - I'd encourage you to do so. Pmag and some of the other ignitions certainly broke new ground, but its time to get on board with developing a new understanding of ignition timing so we can take the next step. Ross' SDS products are the cutting edge today WRT tunability, but I know he'll add new features as soon as they become apparent. In other words, we've come a long way, but there is still plenty of work left to do.
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  #46  
Old 04-15-2017, 12:11 PM
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Larry DeCamp Larry DeCamp is offline
 
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Default Thread Drift !!!

I have 2 P mags on a 150HP 0320 and as expected no problems. I purchased 2 EPI ignitions from Ross for a 8.5:1 0360 but stayed with AFP injection BECAUSE I didn't want to deal with the variety of sensors associated with direct electronic fuel injection ON MY CURRENT PROJECT.

Since then, I read reference to 100LL affects on O2 sensors. At this point I feel justified for not experiencing the cutting edge of performance. So, I hope this stimulates useful dialog... Let the flames begin !
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  #47  
Old 04-15-2017, 03:12 PM
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DanH DanH is offline
 
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Originally Posted by Larry DeCamp View Post
Let the flames begin !
Let's not.

Again, this is not a hardware or vendor condemnation, nor a debate about EI vs magneto, and it surely has nothing to do with fuel delivery. The issue is timing. Any ignition (CDI, EI inductive, or magneto) would net approximately the same result if timed the same for a given operating condition.

The P-mag has been very popular, and I'm sure that's why Vans chose it for the option list. Its advance schedule can be corrected, at least in part, with an EI Commander, as demonstrated by a professional test pilot. Although there is always some percentage of an audience who prefers their belief system over fact, the only real debate left is how much the values might shift with engine configuration change. In the RV world, it mostly means parallel valve vs angle valve.

I wouldn't bet on big differences, as all the av engines are pretty similar in the combustion chamber. Returning to Bill's doubts, here's another example, a turbo Continental on a famous dyno, at 30.4" and 2400. BSFC is 0.565, so it's ROP and pretty close to best power mixture.

Ignition timing is about lighting the mix BTDC so peak pressure arrives at the point of best mechanical advantage, generally accepted as 12 to 15 crankshaft degrees ATDC. This dyno is instrumented to measure that point of peak pressure (theta PP, yellow, upper right) and the actual spark point in degrees BTDC (green, upper left). Here we see spark between 20.1 and 21.7 BTDC resulting in thetaPP between 9.8 and 17.1, the average being 13.6, right where it belongs. More advance would be counter-productive.

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Last edited by DanH : 04-15-2017 at 04:12 PM.
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  #48  
Old 04-15-2017, 03:20 PM
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JonJay JonJay is offline
 
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Quote:
Originally Posted by DanH View Post
Let's not.

Again, this is not a hardware or vendor condemnation, nor a debate about EI vs magneto, and it surely has nothing to do with fuel delivery. The issue is timing. Any ignition (CDI, EI inductive, or magneto) would net approximately the same result if timed the same for a given operating condition.
Actually, it wasn't even that. It was a simple question or observation about Van's offering EI. It then morphed into this discussion, which has been great. Perhaps a change to the Post title might help protect the discussion for future reference.

I know a lot about engines, but each time I think I know a lot about something, this group of folks here makes me feel like I know very little about anything. Great discussion.
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  #49  
Old 04-18-2017, 09:32 AM
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RV6_flyer RV6_flyer is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
Not specifically documented. You have to call Van's. The extra $1000 gets you one pMag and one slick mag. Don't yet know how much extra one pMag and no slick mag will be. There is no option to get two pMags from Van's.

Carl
To save others time here is Copy / Paste of relevant communication with Van's who contacted Lycoming.

..."customers selecting the E-Mag option, this would include replacing the Plain Magneto (on right of the accessory housing) with the E-Mag System. This would include a fully installed & tested unit at the Lycoming factory with all the required spark plugs, adapters and harnesses of the E-Mag EIS." ...

..."Therefore, each cylinder will have one aviation spark plug (for impulse magneto) and one automotive spark plugs (for E-Mag) installed." ...

I did this because I am leaning toward purchasing a New Lycoming engine from Van's for my RV-8 under construction. Have not seen a better value than a new Lycoming from Van's. May be able to pickup at Lycoming factory if I have not built on the airpark lot that I want to buy.
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