VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #1  
Old 01-22-2009, 07:37 PM
Bill Wightman's Avatar
Bill Wightman Bill Wightman is offline
 
Join Date: Aug 2005
Location: OKC, OK
Posts: 687
Default P-Lead wire routing question

I'd like to know if any of you have experience running your mag P-leads in the same bundle with other instrument wiring. I'm aware of the voltage spikes (about 170 volts peak) the P-leads carry. The wires I will use are AWG-18, and very well shielded. Shielding will be grounded at the mag end only.

Proposed routing: My RV8 has several firewall forward transducers feeding a VMS-1000C that pass through the firewall in a big bundle together. Wanting to keep the mess to a minimum, I'm considering routing my Slick mag's P-leads through the same firewall grommet, where they'll remain bundled up with the VMS stuff for about 18" or so before diverging to the mag switches. Is this OK? The VMS manual only states not to bundle *ignition* wires with the transducer wiring, but this is a bit vague so I'm poking around for some feedback here.

I'm concerned about possible interference with the VMS transducer wiring if they're bundled together.

Bill
__________________
?The important thing in aeroplanes is that they shall be speedy.?
- Baron Manfred von Richthofen


RV8 under construction
RV4 - Sold

United B777 FO, Chicago
Aero Engineer
RV8
Reply With Quote
  #2  
Old 01-22-2009, 09:01 PM
Frank Smidler Frank Smidler is offline
 
Join Date: Feb 2005
Location: Stoughton, WI
Posts: 473
Default No problem after 2.2 hrs

I ran the p-leads in the same bundle with all my other wires (EGT, CHT, oil pressure, gas pressure, oil temp, alt. field) and no issues after the first 2.2 hrs. The P-leads were shielded. I did run the bus power from the battery through a different hole. Wish I had more hours to report more conclusively.
__________________
Frank Smidler
N96FS, RV-6
Flying 1/11/09
1085 hr
2WI6 Stoughton, WI
Formally of Lafayette, IN

Last edited by Frank Smidler : 01-22-2009 at 09:03 PM. Reason: Adding to my commments
Reply With Quote
  #3  
Old 01-22-2009, 10:45 PM
Greg Arehart's Avatar
Greg Arehart Greg Arehart is offline
 
Join Date: Jul 2007
Location: Delta, CO/Atlin, BC
Posts: 2,391
Default

I don't have a VMS in my instrument group, but have had no issues (of which I am aware) with the Dynon wiring etc. all of which goes through the same hole as the P-leads. P-leads are shielded of course. This after 33 hours.

greg
__________________
Greg Arehart
RV-9B (Big tires) Tipup @AJZ or CYSQ
N 7965A
Reply With Quote
  #4  
Old 01-23-2009, 07:41 AM
David-aviator David-aviator is offline
 
Join Date: Feb 2005
Location: Chesterfield, Missouri
Posts: 4,514
Default

Quote:
Originally Posted by Greg Arehart View Post
I don't have a VMS in my instrument group, but have had no issues (of which I am aware) with the Dynon wiring etc. all of which goes through the same hole as the P-leads. P-leads are shielded of course. This after 33 hours.

greg
My P-leads are grouped with a many other wires coming through the fire wall and so far all is OK - including the radio, it sounds the same as before when there were no P-leads. (I mention this relative to having installed the P-leads with #18 wire to and from the mags with no shielding, I forgot they should be shielded. Again, so far, so good. The radio sounded good once I got the squelch under control.)

New flap motor installed, should be ready to launch again in a day or so.
__________________
RV-12 Build Helper
RV-7A...Sold #70374
The RV-8...Sold #83261
I'm in, dues paid 2019 This place is worth it!
Reply With Quote
  #5  
Old 01-23-2009, 09:06 AM
SteinAir SteinAir is offline
 
Join Date: Feb 2005
Location: Minneapolis
Posts: 2,473
Default

In general if your P-Leads are properly assembled with shielded wire you shouldn't have any problems. That being said, on any RV that we finish, we will always run them separately through their own small grommet. It helps for future maintenance, and just is a bootstrap to ensure the system will be quiet.

Either way I think you'll be fine, but my personal preference would be to run them alone.

Cheers,
Stein
Reply With Quote
  #6  
Old 01-23-2009, 06:18 PM
Bill Wightman's Avatar
Bill Wightman Bill Wightman is offline
 
Join Date: Aug 2005
Location: OKC, OK
Posts: 687
Default Thanks for the answers!

OK, I guess I'm gonna take the easy way out and run them together with the other wires. If I have any problems, I'll separate the P-leads out.

Frank, Greg, David and Stein: thank you for taking the time to help out.
__________________
?The important thing in aeroplanes is that they shall be speedy.?
- Baron Manfred von Richthofen


RV8 under construction
RV4 - Sold

United B777 FO, Chicago
Aero Engineer
RV8
Reply With Quote
  #7  
Old 10-06-2010, 11:29 PM
ge9a ge9a is offline
 
Join Date: Jan 2005
Posts: 167
Default Any more follow-up?

I'm wondering if running senor wires for my AFS (oil press, oil temp, fuel flow, CHT, EGT, etc.) with my left mag P-lead and other misc. 14v power wiring FWF will cause issues. Right ign is LS and P-leads come from VP-200 switch panel.

Also, should I run the wiring from my LS direct crank sensor by itself? Or is this a relatively 'quiet' harness to the LS ignition module? I'd like to run it with my right-side CHT/EGT wires.

I'm thinking the only 'really noisy' wires that run through the firewall are my LS primary ignition wires, which I will run completely separate from everything else. It sure would keep things tighter if I could run everything else as a single bundle through the firewall, then routed where it all needs to go. Is that a really bad idea, all things considered?

Like everybody here, I'd rather avoid issues now than have to change it later! And as always, thanks for any input you may have.
__________________
Greg English
Beaverton, OR
RV-9A QB
Reply With Quote
  #8  
Old 10-07-2010, 01:27 AM
justplanecrazy justplanecrazy is offline
 
Join Date: Mar 2008
Location: Perth, Western Australia
Posts: 30
Default EGT and CHT sensor wires with Spark Leads

Another similar question for my installation. I have seen a few pictures of installations with the CHT and EGT sensor wires bundled with spark plug leads along the end of the cylinders. Is this OK or should it be avoided?

Thanks,

Rob
Reply With Quote
  #9  
Old 10-07-2010, 10:08 AM
az_gila's Avatar
az_gila az_gila is offline
 
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
Post Since thermocouple...

Quote:
Originally Posted by justplanecrazy View Post
Another similar question for my installation. I have seen a few pictures of installations with the CHT and EGT sensor wires bundled with spark plug leads along the end of the cylinders. Is this OK or should it be avoided?

Thanks,

Rob
...outputs are in the millivolt range, and the sparks are in the kilovolt range, I would avoid this. It's a far greater variation than the earlier P-Lead discussion, and there is usually no need to do it...
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
Reply With Quote
  #10  
Old 10-07-2010, 10:37 PM
justplanecrazy justplanecrazy is offline
 
Join Date: Mar 2008
Location: Perth, Western Australia
Posts: 30
Default EGT and CHT wire Routing

Does anyone have any good photos of how they routed and terminated their CHT and EGT's to avoid this scenario?

cheers,

Rob
Reply With Quote
Reply


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 12:17 AM.


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.