Home > VansAirForceForums

-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.

Go Back   VAF Forums > RV Firewall Forward Section > Traditional Aircraft Engines
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Thread Tools Search this Thread Display Modes
Old 01-20-2016, 09:38 PM
Canadian_JOY Canadian_JOY is offline
Join Date: Aug 2007
Location: Ontario, Canada
Posts: 2,370
Default Starting Recommendations: 1 Impulse Mag +1 Pmag

We've recently acquired a 114-series P-Mag (with latest V40 firmware) with the intent of replacing the right hand Slick mag on our O-360-A1F6. The current plan is to retain the left hand impulse-coupled Slick mag.

My question to those with experience with this configuration is, should I continue to plan on starting using only the left impulse coupled mag, or should I simply set both P-lead switches to "ON" and start on both the impulse and P-mag? If experience has proven one method to work better than the other, why is that the case?

Our ignition control consists of toggle switches, so there's no worry about having to figure out how to make a key switch achieve the desired ignition configuration for engine start. P-Mag power is supplied through a separate toggle switch being fed from a separate breaker on the main electrical buss.

Thanks for your well-considered and helpful responses.
Reply With Quote
Old 01-20-2016, 10:29 PM
AltonD's Avatar
AltonD AltonD is offline
Join Date: Sep 2005
Location: Dothan, Alabama
Posts: 1,492

I have plasma iii on right, impulse on left. I can start off either, but it starts better on plasma.
Alton DeWeese
N526RV RV7A Tip Up, IO360 180 W/Hartzel BA prop.
Flying ~950 hours since Aug 2010

Construction Log
?The secret of getting ahead is getting started. The secret of getting started is breaking your complex overwhelming tasks into small manageable tasks, and then starting on the first one.?

?Mark Twain
Reply With Quote
Old 01-20-2016, 11:01 PM
rwarre rwarre is offline
Join Date: Jul 2007
Location: Wray, Co
Posts: 601
Default My 2 cents

I was developing hard starting issues with two mags(especially with engine hot) and also installed one pmag. I always with both the slick mag and pmag on and never have had any issues with starting. I see no advantage of starting on one mag.
Reply With Quote
Old 01-20-2016, 11:25 PM
Scott Hersha Scott Hersha is offline
Join Date: Jan 2005
Location: Cincinnati, OH
Posts: 1,755

Like Alton, I have a slick mag and a plasma III. Similar to your installation I think. I start with both toggles on. No problems after 7 years, 600+ hours, and 600+ engine starts.
RV6/2001 built/sold 2005
RV8 Fastback/2008 built/sold 2015
RV4/bought 2016/sold/2017
RV8/2018 built/Sold(sadly)
RV4/bought 2019 Flying
Cincinnati, OH/KHAO
Reply With Quote
Old 01-21-2016, 06:48 AM
tim2542 tim2542 is offline
Join Date: Aug 2009
Location: Redding,Ca
Posts: 633

I've used the combo you are installing (slick-impulse and Pmag), it doesn't matter if you start on one or the other or both, on my plane any combo works just fine. But I used both all the time since there is no reason not to have all the spark you can get while cranking.
Tim Andres

Last edited by tim2542 : 01-21-2016 at 06:50 AM.
Reply With Quote
Old 01-21-2016, 07:13 AM
Walt's Avatar
Walt Walt is online now
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 5,840

Start on both.
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website:, Email:, Cell: 972-746-5154
Reply With Quote
Old 01-21-2016, 07:16 AM
BillFear BillFear is offline
Join Date: Oct 2007
Location: Sherrills Ford, NC (Lake norman area)
Posts: 432
Default Always use both, starts great

We have an impulse mag and one Pmag. Always leave them both on and she usually starts on first blade, we have a primer system but never use it.

Always have alternator on before start and until after shutdown also.
Bill Fearheiley
Lake Norman, NC (14A)
RV7a N705RP (no longer own)
Contribution in for 2017, money well spent
Reply With Quote
Old 01-21-2016, 07:33 AM
Canadian_JOY Canadian_JOY is offline
Join Date: Aug 2007
Location: Ontario, Canada
Posts: 2,370

Thanks for the great feedback! From a point of logic I couldn't see any reason not to use both the impulse mag and P-Mag for starting and wanted to make sure there wasn't some obscure (or blindingly obvious! ) reason not to. Thanks to your very helpful replies I'll be using both ignition systems at engine start.
Reply With Quote
Old 01-21-2016, 07:45 AM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
Join Date: Jul 2009
Location: Mojave
Posts: 4,737

Personally, I ditched the impulse mag first on the two airplanes I've done. The Pmag renders the need for an impulse coupling obsolete, and you get to ditch the added weight and complexity of the impulse coupling. Win-win-win.

If you're in love with the impulse, start on both.
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
Harmon Rocket II -SDS EFI
1940 Taylorcraft BL-65
1984 L39C
Reply With Quote
Old 01-21-2016, 07:59 AM
RVDan RVDan is offline
Join Date: Jun 2012
Location: Frederick, MD
Posts: 873

I have my left mag with impulse and right replaced with Electroair ignition. I decided to keep the impulse mag.
On a previous airplane, I had Plasma on the left and mag right without impulse. Had to start on the plasma in that case. The problem was if the battery was low the airplane could not be started as the battery voltage sagged to much to run the Plasma ignition. Not a problem at my home base, but when away a major inconvenience. So on my current airplane I kept the impulse, and if I can get the prop over compression with the starter, I can get it started.

With the impulse mag, I start on both.
Dan Morris
Frederick, MD
Hph 304CZ
RV6 built and sold
N199EC RV6A flying
Retired Aerospace Engineer and A&P/IA
Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

All times are GMT -6. The time now is 01:09 PM.

The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.