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RPM drop Mag and EI LS Plasma III

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Mike Whisky

Joined: 05 Jun 2006
Posts: 336
Location: Switzerland

Posted: Wed Sep 25, 2013 10:50 am Post subject: RPM drop Mag and EI LS Plasma III

Hi,



on todays runup I saw that the RMP drop for the mag (EI off) is about 260 RPM which seems to be quite a lot to me, the drop on the EI (mag off) is only 20 RPM. I am used to see only 100 RPM in the planes I flew. Is this due to the higher RPM that the EI delivers or do I need to look at the timing of the mag. What are others seeing with the same setup?



Thanks

Mike

_________________
RV-10 builder (flying)
#511

Tim Olson

Joined: 25 Jan 2007
Posts: 2872

Posted: Wed Sep 25, 2013 10:57 am Post subject: RPM drop Mag and EI LS Plasma III

I think you'll see a little of everything in replies.  On mine, I've 

seen maybe 20-40rpm,

but I've been in other fine working RV-10's that drop 200+  So I'm not 

sure why

the difference, but certainly you will find variation.



On 9/25/2013 1:50 PM, Mike Whisky wrote:

 	  Quote: 	
		   



 Hi,



 on todays runup I saw that the RMP drop for the mag (EI off) is about 260 RPM which seems to be quite a lot to me, the drop on the EI (mag off) is only 20 RPM. I am used to see only 100 RPM in the planes I flew. Is this due to the higher RPM that the EI delivers or do I need to look at the timing of the mag. What are others seeing with the same setup?



 Thanks

 Mike



 --------

 RV-10 builder (flying, test phase)

 #511





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=409210#409210

recapen(at)earthlink.net
Guest

Posted: Wed Sep 25, 2013 11:25 am Post subject: RPM drop Mag and EI LS Plasma III

I have seen mine different after I adjust the idle mixture...

--

Kelly McMullen

Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ

Posted: Wed Sep 25, 2013 12:07 pm Post subject: RPM drop Mag and EI LS Plasma III

You make a good point. Idle mixture should be set so that rpm rise when pulled to idle cut off is between 25 and 50 rpm, no more. If you see no rise, it is too lean, if more than 50 it is too rich.

If the drop on mag check is smooth, no roughness, then mag is fine, and whether the number is 50 or 200 doesn't really matter. OTOH, if rough, you need to find the cause. Usually fouled plug, but can be mag itself.

 

Best is to check mags at altitude, at the end of your cruise, when you are ready to start down. Just don't turn mag back on if it quits without it. Retard mixture and throttle before turning mag back on to avoid possibility of backfire and damage it can cause. That is why you want to do the check with plenty of altitude, so there is no rush to relight fire if it quits.

 

On Wed, Sep 25, 2013 at 3:24 PM, Ralph E. Capen <recapen(at)earthlink.net (recapen(at)earthlink.net)> wrote:

 [quote]--> RV10-List message posted by: "Ralph E. Capen" <recapen(at)earthlink.net (recapen(at)earthlink.net)>

  

 I have seen mine different after I adjust the idle mixture...

 

 

 --

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD

aarongleixner(at)sbcgloba
Guest

Posted: Wed Sep 25, 2013 3:15 pm Post subject: RPM drop Mag and EI LS Plasma III

Your numbers sound really close to mine.  I had the difference from day 1 with new mag and annual timing checks indicate the mag timing is correct.  Its been 325 hours with no issue.  I would verify the engine does not run really rough on 1 mag, and monitor over time to assure the drop doesn't get larger.  I always figured the EI was either a hotter spark driving more of the combustion, or timed slightly earlier.



Aaron



Sent from my iPad



 	  Quote: 	
		   On Sep 25, 2013, at 2:50 PM, "Mike Whisky" <rv-10(at)wellenzohn.net> wrote:

 

 

 

 Hi,

 

 on todays runup I saw that the RMP drop for the mag (EI off) is about 260 RPM which seems to be quite a lot to me, the drop on the EI (mag off) is only 20 RPM. I am used to see only 100 RPM in the planes I flew. Is this due to the higher RPM that the EI delivers or do I need to look at the timing of the mag. What are others seeing with the same setup?

 

 Thanks

 Mike

 

 --------

 RV-10 builder (flying, test phase)

 #511

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=409210#409210

RVflyHI

Joined: 01 Sep 2010
Posts: 9

Posted: Wed Sep 25, 2013 5:29 pm Post subject: RPM drop Mag and EI LS Plasma III

As a point of reference mine shows 20 when on the plasma III and 150-170 when on the mag. Mine is lean when testing mags on the ground.  I believe it was pelican perch that stated testing mags LOP in cruise is the best way to see problems from the mag.  I always test mine on run-up.  

Sent from my iPhone

On Sep 25, 2013, at 16:15, Aaron <aarongleixner(at)sbcglobal.net> wrote:

 	  Quote: 	

 Your numbers sound really close to mine.  I had the difference from day 1 with new mag and annual timing checks indicate the mag timing is correct.  Its been 325 hours with no issue.  I would verify the engine does not run really rough on 1 mag, and monitor over time to assure the drop doesn't get larger.  I always figured the EI was either a hotter spark driving more of the combustion, or timed slightly earlier.

 Aaron

 Sent from my iPad

> On Sep 25, 2013, at 2:50 PM, "Mike Whisky" <rv-10(at)wellenzohn.net> wrote:

> 

> 

> 

> Hi,

> 

> on todays runup I saw that the RMP drop for the mag (EI off) is about 260 RPM which seems to be quite a lot to me, the drop on the EI (mag off) is only 20 RPM. I am used to see only 100 RPM in the planes I flew. Is this due to the higher RPM that the EI delivers or do I need to look at the timing of the mag. What are others seeing with the same setup?

> 

> Thanks

> Mike

> 

> --------

> RV-10 builder (flying, test phase)

> #511

> 

> 

> 

> 

> Read this topic online here:

> 

> http://forums.matronics.com/viewtopic.php?p=409210#409210

toaster73(at)embarqmail.c
Guest

Posted: Wed Sep 25, 2013 5:49 pm Post subject: RPM drop Mag and EI LS Plasma III

...And the Lycoming operators manual states: 

 

A smooth drop-off past normal specification of 175 RPM is usually a sign of a too lean or too rich mixture.

(3) If RPM drop exceeds 175 RPM slowly lean mixture until RPM peaks. Then retard the throttle to the RPM specified (50-65%) for the magneto check and repeat check. (Paraphrasing now) If the drop off does not exceed 175 RPM and 50 RPM difference with smooth running continue on.

 

-Chris

 

N919AR

 

From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Kelly McMullen

Sent: Wednesday, September 25, 2013 4:07 PM

To: rv10-list(at)matronics.com

Subject: Re: RPM drop Mag and EI LS Plasma III



 

You make a good point. Idle mixture should be set so that rpm rise when pulled to idle cut off is between 25 and 50 rpm, no more. If you see no rise, it is too lean, if more than 50 it is too rich.

If the drop on mag check is smooth, no roughness, then mag is fine, and whether the number is 50 or 200 doesn't really matter. OTOH, if rough, you need to find the cause. Usually fouled plug, but can be mag itself.



Best is to check mags at altitude, at the end of your cruise, when you are ready to start down. Just don't turn mag back on if it quits without it. Retard mixture and throttle before turning mag back on to avoid possibility of backfire and damage it can cause. That is why you want to do the check with plenty of altitude, so there is no rush to relight fire if it quits.



 

On Wed, Sep 25, 2013 at 3:24 PM, Ralph E. Capen <recapen(at)earthlink.net (recapen(at)earthlink.net)> wrote:

--> RV10-List message posted by: "Ralph E. Capen" <recapen(at)earthlink.net (recapen(at)earthlink.net)>



I have seen mine different after I adjust the idle mixture...

--

napolin(at)me.com
Guest

Posted: Thu Sep 26, 2013 2:46 am Post subject: RPM drop Mag and EI LS Plasma III

Hi Mike



I have seen similar numbers to yours on hot and humid days.  I have since started doing the mag check leaned a bit and it has not exceeded 200 rpm drop on the hottest days.  On cool days the drop is under 100rpm.  No engine roughness during mag check or flight.



Niko



Nikolaos Napoli



 	  Quote: 	
		   On Sep 25, 2013, at 2:50 PM, Mike Whisky <rv-10(at)wellenzohn.net> wrote:

 

 

 

 Hi,

 

 on todays runup I saw that the RMP drop for the mag (EI off) is about 260 RPM which seems to be quite a lot to me, the drop on the EI (mag off) is only 20 RPM. I am used to see only 100 RPM in the planes I flew. Is this due to the higher RPM that the EI delivers or do I need to look at the timing of the mag. What are others seeing with the same setup?

 

 Thanks

 Mike

 

 --------

 RV-10 builder (flying, test phase)

 #511

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=409210#409210

flying-nut(at)cfl.rr.com
Guest

Posted: Thu Sep 26, 2013 4:16 am Post subject: RPM drop Mag and EI LS Plasma III

I'm guessing that you're set up a little too rich.  All other parameters 

being the same.

Having said that, being able to read a digital RPM Vs. an analog gauge 

may account for some of the disparity.

Linn

On 9/25/2013 9:44 PM, Nikolaos Napoli wrote:

 	  Quote: 	

 Hi Mike

 I have seen similar numbers to yours on hot and humid days.  I have since started doing the mag check leaned a bit and it has not exceeded 200 rpm drop on the hottest days.  On cool days the drop is under 100rpm.  No engine roughness during mag check or flight.

 Niko

 Nikolaos Napoli

> On Sep 25, 2013, at 2:50 PM, Mike Whisky <rv-10(at)wellenzohn.net> wrote:

>

> 

>

> Hi,

>

> on todays runup I saw that the RMP drop for the mag (EI off) is about 260 RPM which seems to be quite a lot to me, the drop on the EI (mag off) is only 20 RPM. I am used to see only 100 RPM in the planes I flew. Is this due to the higher RPM that the EI delivers or do I need to look at the timing of the mag. What are others seeing with the same setup?

>

> Thanks

> Mike

>

> --------

> RV-10 builder (flying, test phase)

> #511

>

>

> Read this topic online here:

>

> http://forums.matronics.com/viewtopic.php?p=409210#409210

>

>

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Mike Whisky

Joined: 05 Jun 2006
Posts: 336
Location: Switzerland

Posted: Thu Sep 26, 2013 8:13 am Post subject: Re: RPM drop Mag and EI LS Plasma III

Thank you all,

I'll try to lean next time and verify idle mixture once more.

Thanks

Mike

_________________
RV-10 builder (flying)
#511

rv10flyer

Joined: 25 Aug 2009
Posts: 364

Posted: Fri Sep 27, 2013 8:12 am Post subject: Re: RPM drop Mag and EI LS Plasma III

Van's engine, two mags, 200+ drop if I don't lean. I always lean from startup until takeoff about 3/4"-1" out, through run up too.

_________________
Wayne G.

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