blahphish

blahphish

Well Known Member
I'm new to engine side stuff so I have a question regarding tachometer reading. I'm wondering if I should get a tach transducer such as the one vans sells, or should I wire my EMS to the p-leads of the mags to read engine RPM? Here is what I'm working with:

Skyview system
Lycoming 6cyl
2 slick mags but might eventually upgrade to 1 or 2 p-mags

The Skyview installation manual seems to indicate I can use either a dedicated transducer or hook to p-leads but I'm unsure if one is better than the other for my situation.
 
If you do the Vans transducer, it will be independent of what ever ignition system you end up with, no reconfiguring if you change to a Pmag or Lightspeed etc.

If you do use the Vans unit, it is an 8 pulse, but runs at half engine speed.

I have no idea as to the life expectancy of the Vans transducer.

Easiest for sure is to just hook up to the "P" lead.
 
Tachometer from Plead

Brian,
The MGL tachometer ( which I have) does not work well from a P-lead signal. Rainer confirmed that an engine driven signal generator would yield more stable results. I can't say about any other brand of tach/efis, but the MGL unit is programmable to accommodate varying signal outputs per revolution. Ie, I assume an eight pulse or 4 pulse generator could be programmed to work on a six cyl engine.
 
Larry DeCamp said:
Ie, I assume an eight pulse or 4 pulse generator could be programmed to work on a six cyl engine.
Click to expand...

The number of pulses have nothing to do with the number of cylinders, it is something referenced to the rotation of the crankshaft.

But, the drive on the accessory case runs at half engine speed.

I am using Vans pulse generator/tach transducer or whatever you call it on my 540.

The GRT unit is programmable to a wide input in pulse/crank revolution range.
 
P-leads.

Brian, we had a Van's transducer on our -6 and it went maybe 300 hours and broke, so we replaced it.

My buddy had a D-180 in his -4 and used the P-lead pickup....that was 5 years ago and still running strong. Since the P-lead pickup has no moving parts and the transducer does, it's my pick as well.

Best,
 
Thanks for the feedback everyone. I think I'll try to go with the p-lead route and hopefully I can get accurate readings and can buy the AFS hall sensor mentioned by Rob as an ace in the hole if necessary.

One of the posts mentioned using shielded wire. Any merit to this?
 
You should use shielded wires. The P-Lead signal is a high power signal which could interfere other systems like audio. But ground the shield only on one side.
 
I've gone the P-Lead route with the Dynon D-180, GRT EIS, and Garmin G3X (the G3X is connected to P-Mags, the other two to Slicks). All work just great!
 
To echo an earlier response, I also have found the Van's transducer as unreliable. I replaced the first at 50 hours and the second just failed at 350 hours. I just switched to the Flight Data Systems tac using the mag signal at for not much more than the transducer cost from Vans.
 
I've seen the Vans whirlygig break also. MGL sells a tach sensor that screws into the slick's inspection plug hole. No moving parts. No interference signal.
P.S. Have you ever held a P-lead by hand and grounded yourself while the engines running? Doesn't bite as hard as the other side of the coil, but you sure know its working.
 
Ironflight said:
I've gone the P-Lead route with the Dynon D-180, GRT EIS, and Garmin G3X (the G3X is connected to P-Mags, the other two to Slicks). All work just great!
Click to expand...

Paul,
Did you use shielded wire to the D-180? I have the D-120 (EMS). The wire in the harness (from Stein) to pick off the P-lead RPM is not shielded. I'm wondering if I should remove the wire & replace with shielded.:confused:

And...if the wire should be shielded, which end should be grounded?

Maybe I'm over-thinking this stuff. :(

Thanks!
 
TX7A said:
Paul,
Did you use shielded wire to the D-180? I have the D-120 (EMS). The wire in the harness (from Stein) to pick off the P-lead RPM is not shielded. I'm wondering if I should remove the wire & replace with shielded.:confused:

And...if the wire should be shielded, which end should be grounded?

Maybe I'm over-thinking this stuff. :(

Thanks!
Click to expand...

Nope - not shielded (the tach pick-off wire) on either the Dynon airplane or the GRT airplane.
 
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