Lancair 320 ram air?

On Thu, 25 Dec 2003 12:15:46 -0600, RR Urban wrote:



that is most curious bob. my aircraft has a brackett foam airfilter
(replaced annually) on the air inlet and none on the carby heat. the
reasoning is that carby heat is only applied when well off the ground
and the risk of contamination is small.

the problem is not bugs imho the problem is grains of sand.

you sure the builder didnt rig it up backwards? Stealth Pilot
+++++++++++++++++++++++

It is neither curious nor backwards.

The few RAM AIR designs I have encountered, ALL do WITHOUT the filter
for max ram effect - even the certified Mooney. However, Mooney does
have a mode that employs a filter when RAM AIR MODE is not desired. In
effect, I do the equivalent with carb heat mode.

FWIW....
Loss through the filter appears to be unacceptable to those engineers
that care to max performance with RAM AIR designs. Perhaps those more
knowledgeable will add their 2 cents???

P.S.
The RAM AIR topic has been addressed here in the past. I'm surprised you
are not somewhat familiar with the topic.


Barnyard BOb --

I'm not sure how much manifold pressure is lost going through a well
designed filter. But, for the sake of argument, if we assume a loss of
0.5" HG manifold pressure, my O-360 power spreadsheet tells me that would
be about a 4 hp loss at a 75% cruise condition at 7500 ft, or about 3% of
the power. A 3% power loss would give about a 1% speed loss. If you want
to compensate for the loss in power by increasing the rpm, you need about
a 150 rpm increase to get the same power you would have had with no air
filter losses.

These numbers are specific to the Lycoming O-360A series engines, but I
would expect similar percent power losses for the same MP loss for any
normally aspirated engine. The power loss would be roughly linear to the
amount of MP loss.

--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

The Mooney I flew would gain 1" using the ram air feature. I don't
know if that is standard or how accurate the gauges are but that is what we
always showed.

Jerry

Kevin Horton wrote:
On Thu, 25 Dec 2003 12:15:46 -0600, RR Urban wrote:



that is most curious bob. my aircraft has a brackett foam airfilter
(replaced annually) on the air inlet and none on the carby heat. the
reasoning is that carby heat is only applied when well off the ground
and the risk of contamination is small.

the problem is not bugs imho the problem is grains of sand.

you sure the builder didnt rig it up backwards? Stealth Pilot

+++++++++++++++++++++++

It is neither curious nor backwards.

The few RAM AIR designs I have encountered, ALL do WITHOUT the filter
for max ram effect - even the certified Mooney. However, Mooney does
have a mode that employs a filter when RAM AIR MODE is not desired. In
effect, I do the equivalent with carb heat mode.

FWIW....
Loss through the filter appears to be unacceptable to those engineers
that care to max performance with RAM AIR designs. Perhaps those more
knowledgeable will add their 2 cents???

P.S.
The RAM AIR topic has been addressed here in the past. I'm surprised you
are not somewhat familiar with the topic.


Barnyard BOb --


I'm not sure how much manifold pressure is lost going through a well
designed filter. But, for the sake of argument, if we assume a loss of
0.5" HG manifold pressure, my O-360 power spreadsheet tells me that would
be about a 4 hp loss at a 75% cruise condition at 7500 ft, or about 3% of
the power. A 3% power loss would give about a 1% speed loss. If you want
to compensate for the loss in power by increasing the rpm, you need about
a 150 rpm increase to get the same power you would have had with no air
filter losses.

These numbers are specific to the Lycoming O-360A series engines, but I
would expect similar percent power losses for the same MP loss for any
normally aspirated engine. The power loss would be roughly linear to the
amount of MP loss.

Jerry Springer wrote:

The Mooney I flew would gain 1" using the ram air feature. I don't
know if that is standard or how accurate the gauges are but that is what we
always showed.

Jerry
+++++++++++++++++++++++++++++++++++

I'm no expert, but that's probably pretty close.

Dunno about accuracy, but my RV-3
displayed somewhat less. For me...
it's all much ado about nothing since it
has little bearing on any practical ETA.

Barnyard BOb --

"RR Urban" wrote in message
...

Jerry Springer wrote:

The Mooney I flew would gain 1" using the ram air feature. I don't
know if that is standard or how accurate the gauges are but that is what we
always showed.

Jerry
+++++++++++++++++++++++++++++++++++

I'm no expert, but that's probably pretty close.

Dunno about accuracy, but my RV-3
displayed somewhat less. For me...
it's all much ado about nothing since it
has little bearing on any practical ETA.

Barnyard BOb --

===========
Every Mooney I have flown has always gained an inch with filter bypassed. I
don't have my manuals or logbook handy, but I recall that the POH indicated
an inch gain. The models were older Mooneys: M20(F?, don't recall) and
M20J.

YMMV.

Michael Pilla

"Michael Pilla" wrote in message
...
[...][flush BYB] ===========
Every Mooney I have flown has always gained an inch with filter bypassed.
I
don't have my manuals or logbook handy, but I recall that the POH
indicated
an inch gain. The models were older Mooneys: M20(F?, don't recall) and
M20J.

YMMV.

Michael Pilla

At altitude no big worry about dust and bugs, I wouldn't think. However, in
Missouri where there's lots of particulates and airborne effluvia and
pestilence, I would always filter the air.

Kevin Hortonwrote:

I'm not sure how much manifold pressure is lost going through a well
designed filter. But, for the sake of argument, if we assume a loss of
0.5" HG manifold pressure, my O-360 power spreadsheet tells me that would
be about a 4 hp loss at a 75% cruise condition at 7500 ft, or about 3% of
the power. A 3% power loss would give about a 1% speed loss. If you want
to compensate for the loss in power by increasing the rpm, you need about
a 150 rpm increase to get the same power you would have had with no air
filter losses.
++++++++++++++++++++++++++++++++++++++++

For the sake of argument, if we assume...
My *RAM AIR* only yields 0.75" HG with NO filter...
it's not difficult to understand why a filter is anathema
to the designed RAM AIR system.


Barnyard BOb --

"RR Urban" wrote

For the sake of argument, if we assume...
My *RAM AIR* only yields 0.75" HG with NO filter...
it's not difficult to understand why a filter is anathema
to the designed RAM AIR system.


Barnyard BOb --

OTOH, you could take the stance that the ram air is there to negate the
effect of having a filter, if you wanted to view the presence of a filter as
a mandatory option.

OTOH, I could be wrong, or mistaken.

Naah ;-)
--
Jim in NC

"Morgans"wrote:

For the sake of argument, if we assume...
My *RAM AIR* only yields 0.75" HG with NO filter...
it's not difficult to understand why a filter is anathema
to the designed RAM AIR system.


Barnyard BOb --

OTOH, you could take the stance that the ram air is there to negate the
effect of having a filter, if you wanted to view the presence of a filter as
a mandatory option.

OTOH, I could be wrong, or mistaken.

Naah ;-)
+++++++++++++++++++++++++++++++++++++++

Ponder this perplexing question, Sir Morgans...

Is the glass half full or half empty?



Barnyard BOb - the half fast curmudgeon

"RR Urban" wrote

Ponder this perplexing question, Sir Morgans...

Is the glass half full or half empty?



Barnyard BOb - the half fast curmudgeon

Tis easy! Neither half full or half empty!

Jim ( pessimism are us ) in NC

On cars,,,of which I had some experience in the decade of the 80's
many cars had very poor positive crankcase ventilation filters.
To my simple mind it always seemed more important to filter the air
going into the crankcase where dust must be removed by the oil filter
as compared to the intake air which spends a VERY short time in the
combustion chamber.
As for me and my airplane we filter the carb heated air and taxi on a
dusty strip with the carb heat ON thus making sure the carb is always
nice and warm and then shortly after applying full throttle on take
off I close the carb heat and I KNOW it will not ice up for a least a
few minutes until I am safely in the air.
Now of course this is all contrary to what I was taught by the flying
club,,,but what do I know.

Ray Toews

On Fri, 26 Dec 2003 22:50:47 -0500, "Morgans"
wrote:


"RR Urban" wrote

Ponder this perplexing question, Sir Morgans...

Is the glass half full or half empty?



Barnyard BOb - the half fast curmudgeon

Tis easy! Neither half full or half empty!

Jim ( pessimism are us ) in NC