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Finishing PMag set-up for my RV-8

T

Tom @ N269CP

Well Known Member
We've finished installing one Pmag 114 (v.40) to replace the right Slick magneto in my RV-8, leaving me with one IC Slick on the left and the PMag on the right. So now its time to finish setting timing and other parameters suitable for my airplane and flying conditions. I'm reluctant to test fly it until I have confirmed/finalized settings with EICAD.

Plane Specs:
RV-8 with O-360-A1A (8.5:1) carbureted engine with Hartzell CS prop running on 100LL. Aviation plugs on top, auto plugs on the bottom.
Home airport: Durango, CO (KDRO).
Field elevation: 6,689 Ft.
Typical summer DA: 9,000-10,000 ft
Engine Monitoring Eqpt: EI UBG-16 analyzer and FP-5 fuel flow computer
Baffling is in good shape and blast tubes installed for PMag and Slick.

Installation details:
Advance shift: -1.4º ATC (set manually...~1.5 gear teeth ATC)
Advance curve: "A" (jumper in)
MP restriction orifice: Installed

Questions/Comments:
1. What is the factory default "max RPM" setting for the PMag? Did not see in PMag manual.

2. Before using EICAD, should I first reset PMag timing to TDC (zero advance shift) instead of the current "manually-set" -1.4ºATC?

3. The EICAD serial cable connects to PMag terminals 2 & 3 where the "A" curve jumper normally goes. If I run a permanent serial cable from the PMag back to the cockpit, will I have to install the "A" jumper in the DB9 connector (in the cockpit) in order to use the "A" curve? Or do EICAD-entered settings obviate the need for a jumper?

4. What kind of RPM drop should I expect during run-up at 1700 rpm (leaned) when switching from "both" to the left magneto? Saw some big drops at lower RPM's. I've installed a Flight Data Systems T-30 tach with speed signals coming from both the Slick mag p-lead and PMag 12v tach output.

5. My normal high-DA pre-takeoff runup procedure is to lean for peak RPM at 2000 rpm and then move the mixture lever halfway from there towards full rich for WOT take-off. Once airborne, I then climb to cruise altitude at WOT, 2500 rpm and 120-130 mph IAS. (I normally cruise LOP circa 10k-12k feet at 20" MP and 2200-2300 rpm). I very much wish to avoid CHT's above 400ºF during T.O. and climb. FWIW, I've been told that full power run-ups for leaning (to peak RPM) at high DA should be avoided in the RV-8...not sure if this is just "mythology". Any suggestions?

I'd be grateful for any and all comments/suggestions.

Thanks!

Tom
 
Last edited:
Just a few thoughts. First, 1.5 year teeth is not 1.4 degrees. Assuming you have a 149 tooth ring gear, 1.5 gear teeth would give 3.6 degrees.

I don?t know that the Pmag has a max rpm setting.

If you are using pins 2 and 3 for the serial connection, the jumper would short the serial port. It would be setting the A curve, but then the controller wouldn?t be able to communicate with it. I don?t know enough about the controller to see if it saves its settings to the Pmag or not.

The only way to know what your CHT?s will be is to fly it. What have they been with 2 mags? I would expect a little higher with the Pmag.
 
Bill Rapucci ???

He must be on vacation or in a dead zone. He seems to know this Pmag stuff fairly well. He should be replying soon. And I agree with Jesse that 1.5 teeth is way too much. Did mine 0.5 tooth.
 
Jesse said:
Just a few thoughts. First, 1.5 year teeth is not 1.4 degrees. Assuming you have a 149 tooth ring gear, 1.5 gear teeth would give 3.6 degrees.

I don’t know that the Pmag has a max rpm setting.

If you are using pins 2 and 3 for the serial connection, the jumper would short the serial port. It would be setting the A curve, but then the controller wouldn’t be able to communicate with it. I don’t know enough about the controller to see if it saves its settings to the Pmag or not.

The only way to know what your CHT’s will be is to fly it. What have they been with 2 mags? I would expect a little higher with the Pmag.
Click to expand...

Thank you for clarifying this for me. It appears I made a mistake manually setting the -1.4º advance. I'm presently inclined to reset the timing manually to TDC and make any adjustments from there using the EICAD software. I do not have and do not plan to install EI Commander in my panel as I prefer not to make timing adjustments on an ongoing basis. I'm just planning to connect to a serial port in the cockpit and enter the initial setup adjustments using EICAD software on my laptop.

According to the EICAD software downloaded from EMag, there is a user-adjustable "Max RPM" setting for the PMag. EDIT: I have just discovered that the factory default max speed setting is 3328 rpm.

I've very recently installed a UBG-16 analyzer which provides more accurate EGT/CHT data than the previous single cylinder EGT/CHT gauge with CHT measure under the plug that always read quite a bit cooler (<300ºF). During my most recent climb out I briefly saw CHT's circa 410-420ºF before dropping the nose to increase airspeed, which brought the temperatures below 400ºF. But I did not have time before installing the PMag to verify if staying WOT during T.O. and climb would alleviate the CHT excursion. I plan to modify my T.O./climb/cruise procedure to remain WOT from T.O. forward, as much as feasible.

Kind regards,

Tom
 
Last edited:
Tom,

See my comments below.

Installation details:
Advance shift: -1.4? ATC (set manually...~1.5 gear teeth ATC)
Advance curve: "A" (jumper in)
MP restriction orifice: Installed
--> Don't clock the P-mag, it is best to use the EICAD program or our EIC to reduce the timing by 1.4?.

Questions/Comments:
1. What is the factory default "max RPM" setting for the PMag? Did not see in PMag manual.
--> 3328 is the the factory default rev limiter. With the EIC we drop it down to 3072 (increments of 256). Our thinking is, if you have a prop governor issue, you won't need an overhaul. However, raw fuel will be pumped into the exhaust when the ignition isn't firing and when the ignition comes back online once the RPM drops below the limit, that raw fuel in the exhaust will light off with a bang. (Don't ask how I know.)

2. Before using EICAD, should I first reset PMag timing to TDC (zero advance shift) instead of the current "manually-set" -1.4?ATC?
--> It doesn't matter when you set TDC as the configuration settings don't impact the TDC mark.

3. The EICAD serial cable connects to PMag terminals 2 & 3 where the "A" curve jumper normally goes. If I run a permanent serial cable from the PMag back to the cockpit, will I have to install the "A" jumper in the DB9 connector (in the cockpit) in order to use the "A" curve? Or do EICAD-entered settings obviate the need for a jumper?
--> If you change any settings with the EICommander or EICAD program, you are changing the "B" configuration and you DO NOT want to install the jumper because it will force them to the unmodified "A" configuration.

4. What kind of RPM drop should I expect during run-up at 1700 rpm (leaned) when switching from "both" to the left magneto? Saw some big drops at lower RPM's. I've installed a Flight Data Systems T-30 tach with speed signals coming from both the Slick mag p-lead and PMag 12v tach output.
--> It depends on your engine and installation.

5. My normal high-DA pre-takeoff runup procedure is to lean for peak RPM at 2000 rpm and then move the mixture lever halfway from there towards full rich for WOT take-off. Once airborne, I then climb to cruise altitude at WOT, 2500 rpm and 120-130 mph IAS. (I normally cruise LOP circa 10k-12k feet at 20" MP and 2200-2300 rpm). I very much wish to avoid CHT's above 400?F during T.O. and climb. FWIW, I've been told that full power run-ups for leaning (to peak RPM) at high DA should be avoided in the RV-8...not sure if this is just "mythology". Any suggestions?
--> You are on your own with this question.

PM me your email and phone number. I'll send you my Q&A document, which answers a lot of these questions and call to discuss the above.
 
Jesse said:
Just a few thoughts. First, 1.5 year teeth is not 1.4 degrees. Assuming you have a 149 tooth ring gear, 1.5 gear teeth would give 3.6 degrees.

I don’t know that the Pmag has a max rpm setting.

If you are using pins 2 and 3 for the serial connection, the jumper would short the serial port. It would be setting the A curve, but then the controller wouldn’t be able to communicate with it. I don’t know enough about the controller to see if it saves its settings to the Pmag or not.

The only way to know what your CHT’s will be is to fly it. What have they been with 2 mags? I would expect a little higher with the Pmag.
Click to expand...

Correct with regards to clocking the timing by gear teeth.

See my post above regarding the rev limiter.

When changing the P-mag configuration with either the EICAD program or our EICommander, you do NOT install the jumper. The "A" memory location can not be changed, only the"B" memory location can be edited. When making a change, you want to run off the "B" location/configuration. Thus, leave the jumper off.

Yes, the P-mag retains the changes once they are saved.

Correct again regarding CHT's. The only way to know what the impact will be is to go fly.
 
Tom @ N269CP said:
2. Before using EICAD, should I first reset PMag timing to TDC (zero advance shift) instead of the current "manually-set" -1.4ºATC?

Thanks!

Tom
Click to expand...

Yes, you should set or reset the P-Mag timing to TDC if you currently have it manually retarded. You can then adjust the Adv Shift in the software.
 
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