[koda2]

The Lycoming TCDS lists Slick mags 4371, 4370 as the right mags.
Other sources, including Vans, list 4373, 4370.

The only difference apparently is the lag angle, 25 degrees for the 4373 and 20 for the 4371. Any reason for the discrepancy?

If I go with a single Lightspeed in lieu of the 4370, which would be better?

Dave A.
6A build

 

[AltonD]

My left mag is a impulse coupled mag, 25 degree. For the right, I have a lightspeed plasma III. I have the IO-360-M1B. With this setup, I can start on either (I have individual toggles)

 

[frewjm]

Lightspeed mags

Hi Alton, is there any information about performance increase for your engine with the CDI ignition - Lightspeed Plasma III ? Can this increase be assessed as a % of more HP.

 

[osxuser]

The Lycoming TCDS lists Slick mags 4371, 4370 as the right mags.
Other sources, including Vans, list 4373, 4370.

The only difference apparently is the lag angle, 25 degrees for the 4373 and 20 for the 4371. Any reason for the discrepancy?

If I go with a single Lightspeed in lieu of the 4370, which would be better?

Dave A.
6A build

I'd stick with the 25? lag, I don't think you'll have any reason to run 20?. The more timing, the better the top end power typically, of course this decreases your detonation margin somewhat, but I've not heard of this being a problem on 100LL.

 

[az_gila]

I'd stick with the 25? lag, I don't think you'll have any reason to run 20?. The more timing, the better the top end power typically, of course this decreases your detonation margin somewhat, but I've not heard of this being a problem on 100LL.

Err... I think the lag angle referenced is in the impulse coupler, it has no effect at normal running speeds.

The engine is timed at 25 degrees for both magnetos.

The latest Lycoming data seems to show that either a 4371 or a 4373 is certified for the engine model.

http://www.lycoming.textron.com/support/publications/service-instructions/pdfs/SI1443G.pdf

 

[Caveman]

One data point

The Lycoming TCDS lists Slick mags 4371, 4370 as the right mags.
Other sources, including Vans, list 4373, 4370.

The only difference apparently is the lag angle, 25 degrees for the 4373 and 20 for the 4371. Any reason for the discrepancy?

If I go with a single Lightspeed in lieu of the 4370, which would be better?

Dave A.
6A build

My IO-360 M1B from Mattituck came with

Magneto ? Slick w / impulse coupler
Model# 4371

plus one Lightspeed plasma II

 

[koda2]

Good info

Thanks to everyone with the responses.
Gil, I couldn't find a recent Lyco bulletin earlier. Thanks for the SB.

I suspect I will stay with the 4371, even though it would be slightly more susceptible to a kickback and injury to a Sky-Tec starter.

Dave A.

 

[AltonD]

Hi Alton, is there any information about performance increase for your engine with the CDI ignition - Lightspeed Plasma III ? Can this increase be assessed as a % of more HP.

No data on the HP increase. I do know that I get a 10 RPM drop during a mag check when I turn off the mag. I get 100-150 when I turn off the plasma. The mag plugs are on the bottom. I do my run-up with the mixture pull back. Otherwise the mag plugs load up while I taxi. If I run full rich and then do the mag check after taxi, I get the 150-160 rpm drop. Klaus tells me to ignore the actual number: Does the engine run smoothly on the mag. Answer:yes, go fly.