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emap without manifold pressure

BruceMe

Well Known Member
I'm waiting on plumbing hardware to hookup the manifold pressure for my emag, is it unwise/harmful to fly without manifold for a few flights?

Thanks,

-Bruce
 
As option, some leave the MP connection open to the atmosphere. This is not all that bad assuming your are doing a standard profile for cruise.

In other words:
- Leaving it open to atmospheric pressure will provide the pMag with about the same MP level when running WOT. The normal cruise setting.
- Leaving it open when not running WOT will give you no less advance then what you set your mag to. So the pMag is timed closer to your mag, not a problem for your engine.

So, you may not get all the advance compared to having the MP connection made up, but no more - and no less than what you would set for a standard mag.

Carl
 
Thanks! I figured it, I wanted to ask folks that may have done it. I'll drop it in tomorrow and do some testing.
 
Carl question ?

So Carl, do you know the Pmag advance curve based on RPM without MP connected ? I have been wanting to try E10 pump gas in my 7:1/0320 but fear the aggressive Pmag A curve. I had seen it advance to 37 BTDC when I had the EI Commander installed, which is now removed.
 
As option, some leave the MP connection open to the atmosphere. This is not all that bad assuming your are doing a standard profile for cruise.

In other words:
- Leaving it open to atmospheric pressure will provide the pMag with about the same MP level when running WOT. The normal cruise setting.
- Leaving it open when not running WOT will give you no less advance then what you set your mag to. So the pMag is timed closer to your mag, not a problem for your engine.

So, you may not get all the advance compared to having the MP connection made up, but no more - and no less than what you would set for a standard mag.

Carl

This is not completely accurate. At 8000' the Pmag will see around 21" of Map if connected to engine and servo/carb at WOT. Pmag will also see around 21" of map if ported to the atmosphere at 8000'. I have all confidence that the Pmags table will have an advance of over 32* at this MAP level. Not the same as a mag at 25 or 20.

At sea level, your statement is correct, but it becomes inaccurate once you start climbing and your ATMO pressure drops below around 25" (don't know the Pmag adv table and where it starts advancing off it's base)

This can be somewhat problematic during ROP climbs, where the extra advance is not adding any performance, but is increasing CHTs in a flight regime already struggling with high CHTs. The extra advance only begins to add performance at peak or LOP operations, in most cases (exception being higher alt's). Many setups have no issue with this extra heat in the climb, but some do. It was no issue in my 6, but has been a real issue in my 10 once above 8000'. I have had to come up with a mechanism to keep the advance at 25 throughout the ROP climb to keep my CHTs in check. This issue may be somewhat unique to the 10.

Larry
 
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Ok - I never said the pMag will not advance without a MP connection, I said it will not advance as much. I also said it will not advance more than if connected. Perhaps I could have been more precise.

I did not list all the possible permeations, I just bounded the issue. If the pMag is open to atmosphere it will advance beyond your fixed mag setting with altitude - as you want it to do.

The comment on advance and ROP climb is not applicable to all this. I do caution against reaching for the “timing lever” as the only option for managing CHTs. My experience is for WOT climbs, CHTs are coming down as I’m passing above 7K’ or so as engine power is going down.

I run dual pMags with the jumper in which limits the pMags to a maximum of 9 degrees of advance (so for my current IO-360-M1B this means the most advance will be 34 degrees). Engine Performance is superb across the operating envelope, and far superior to the 400 hours I have flying behind mags (on the RV-10 before the pMag install).

I don’t have any experience with the EI Commander, so have no clue what it (or other similarly add on controllers) do to engine timing. I would not recommend adjusting such a controller to have a maximum timing advance beyond 9 degrees. What I tell other builders is install the pMag as listed in the instructions and fly with jumper in. This is a solid, and I consider conservative approach for 95% of RV pilots.

Carl
 
Ok - I never said the pMag will not advance without a MP connection, I said it will not advance as much. I also said it will not advance more than if connected. Perhaps I could have been more precise.

I did not list all the possible permeations, I just bounded the issue. If the pMag is open to atmosphere it will advance beyond your fixed mag setting with altitude - as you want it to do.

The comment on advance and ROP climb is not applicable to all this. I do caution against reaching for the “timing lever” as the only option for managing CHTs. My experience is for WOT climbs, CHTs are coming down as I’m passing above 7K’ or so as engine power is going down.

I run dual pMags with the jumper in which limits the pMags to a maximum of 9 degrees of advance (so for my current IO-360-M1B this means the most advance will be 34 degrees). Engine Performance is superb across the operating envelope, and far superior to the 400 hours I have flying behind mags (on the RV-10 before the pMag install).

I don’t have any experience with the EI Commander, so have no clue what it (or other similarly add on controllers) do to engine timing. I would not recommend adjusting such a controller to have a maximum timing advance beyond 9 degrees. What I tell other builders is install the pMag as listed in the instructions and fly with jumper in. This is a solid, and I consider conservative approach for 95% of RV pilots.

Carl

Maybe I misunderstood your quote:

"So, you may not get all the advance compared to having the MP connection made up, but no more - and no less than what you would set for a standard mag."

If so, I apologize.

I raised the issue on climb CHT's, as it seems several on here are struggling with that issue even though it is not the norm.

Larry
 
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