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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Re: Blower does work
Date: Sat, 18 Jun 2011 07:54:26 -0400
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Ah, yes, interesting about the filterless values.

I don't think MAP vs rpm is going to tell you anything - unless you have the 
engine loaded properly (with a Prop {:>)).  The reason is that at even very 
low MAP pressure you can obtain very high rpm (without a load).

Now MAP vs throttle opening might be more revealing.  Assuming ambient 
pressure then your MAP pressure is basically going to depend on two factors.
1.  How fast the volume of the intake manifold is being exchanged
2.  Throttle opening.

If volume of intake manifold is only being replaced (sucked down) slowly 
then the MAP will tend toward ambient pressure even through a small throttle 
opening.  If the volume is being replaced rapidly (high rpm) then a small 
throttle opening should result in lower manifold pressure because its not 
being replaced as fast as its being sucked down.

  If the volume is being sucked down rapidly (high rpm) and you have a large 
throttle opening then that should result in greater manifold pressure (WOT?)
But, not certain how you are going to correlate these two relationships with 
your blower.

Keep going, we are all waiting with anticipation!!

Ed
--------------------------------------------------
From: "Ernest Christley" <echristley@nc.rr.com>
Sent: Friday, June 17, 2011 11:45 PM
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: Blower does work

> On 06/17/2011 06:10 PM, Ed Anderson wrote:
>> Hi Ernest,
>>
>> I think Tracy's question might have it roots in the following.
>>
>> First, the manifold pressure really did not change much with rpm.
>> Typically you would see an engine under load go from lets say 12" Hg
>> at idle to 29.8" Hg at WOT which in  your units would be from approx
>> 40KPA to 100 KPA at WOT. Without the blower, it looks like most of the
>> orange was below 60 KPA although I think I see a bit up around 65
>> KPA.  So that would indicate approx 13" Hg at idle to around 19.0 "HG
>> at your highest - hardly what you would expect to see if the engine
>> was loaded and turning those rpm.
>>
>> So that indicates your blower is feeding a small throttle opening and
>> an engine that is not processing too many CFM of through put.  The
>> blower appears to be producing approx 15 KPA above the orange or an
>> increase of approx 4.5 " Hg.  However, the question is with less
>> restriction (WOT) would that pressure profile increase due to higher
>> rpms or drop due to less restriction?
>>
>
> I'll be working on getting more load this weekend, but in the meantime I
> probably should call the previous post a false alarm.
>
> This even I went set out to run a test that would be more methodical
> than the previous "grab whatever is in the logs" method.  I set the
> engine up in three situations:  with the blower charging the intake,
> with the air filter turned around to pull ambient air, and with no air
> filter at all.  I attached a picture showing how I turned the filter
> around. (It should also be apparent why my front rotor is getting
> cheated as far as air supply goes.  The air just goes rushing past it.)
>
> For each configuration, I made a run, trying to hold the throttle at
> every 500 RPM on the way up for 5 seconds (1500rpm, 2000rpm, 2500rpm,
> etc), then did the same on the way back down. I made a datalog for when
> the engine was warming up, with the blower active, with the filter turn
> around, with no filter (filterless), and again with the blower in
> action.  That graph is attached.  Basically, this shows the same MAP for
> every RPM, except for the filterless run, which has the MAP jumping all
> over the place.  I don't know what the deal was with the data I got last
> night, but given the strict control and short time frame under which it
> was taken, I trust this data much more.
>
> Upon further reflection, I think I'm may be looking at the wrong thing.
> Given the constraints of such a light load, the RPM is going to follow
> whatever the MAP is.  Is that a "No duh!" statement?  Looking at the
> graphs, I think what would be more telling is RPM vs throttle opening,
> or MAP vs throttle opening.  What say you all?
>


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