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email(at)jaredyates.com
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 Posted: Tue Sep 15, 2015 8:04 pm Post subject: Low Air Pressure Sensor |
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I've found a desire to measure differential air pressure inside the engine cowl for cooling diagnostics. Some folks have used an old airspeed indicator for this role. Is there a better way for someone like me who doesn't have an old airspeed indicator? Perhaps some sensors that I could plug into a computer to record the measurements? Thanks in advance!
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rickofudall
Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA
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| Posted: Wed Sep 16, 2015 3:20 am Post subject: Low Air Pressure Sensor |
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Make a multi-channel manometer out of irrigation tubing. Cheap and easy. I think the Rotary engine site still has info on this.
Rick Girard
On Tue, Sep 15, 2015 at 11:03 PM, Jared Yates <email(at)jaredyates.com (email(at)jaredyates.com)> wrote:
| Quote: | I've found a desire to measure differential air pressure inside the engine cowl for cooling diagnostics. Some folks have used an old airspeed indicator for this role. Is there a better way for someone like me who doesn't have an old airspeed indicator? Perhaps some sensors that I could plug into a computer to record the measurements? Thanks in advance!
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ceengland7(at)gmail.com
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| Posted: Wed Sep 16, 2015 4:28 am Post subject: Low Air Pressure Sensor |
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http://www.digikey.com/product-detail/en/MPX5010DP/MPX5010DP-ND/464054?WT.mc_id=IQ60891383-VQ6-41244574155-VQ16-c&wt.srch=1&wt.medium=cpc&WT.srch=1&WT.medium=cpc
This has been used with a volt meter to do what you're after, but obviously would require a bit of fabrication. Once built, you could feed multiple devices to spare 0-5V inputs in an EFIS or engine monitor. The device(s) and their pressure tubing can remain in the cowl, or where ever they're needed, with only wires coming back to the cockpit.
The water manometer Richard mentioned is a lot simpler to fabricate, but a lot a bit harder to use while in flight.
Charlie
On Tue, Sep 15, 2015 at 11:03 PM, Jared Yates <email(at)jaredyates.com (email(at)jaredyates.com)> wrote:
[quote]I've found a desire to measure differential air pressure inside the engine cowl for cooling diagnostics. Some folks have used an old airspeed indicator for this role. Is there a better way for someone like me who doesn't have an old airspeed indicator? Perhaps some sensors that I could plug into a computer to record the measurements? Thanks in advance!
| Quote: |
ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
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user9253
Joined: 28 Mar 2008
Posts: 1922
Location: Riley TWP Michigan
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| Posted: Wed Sep 16, 2015 4:41 am Post subject: Re: Low Air Pressure Sensor |
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When you consider the cost of a pressure transducer and knowledge and skill required to connect it to a computer, buying an old airspeed indicator is easier and less expensive.
Alternatives are a differential pressure gauge or a homemade manometer. Omega sells transducers and gauges.
http://www.omega.com/pptst/PGL-25.html
A manometer can be made with 3/8" clear plastic tubing. Form it into the shape of a "U" and fill it half full of water. Route the ends of the tubing to the two areas where pressure needs to be compared.
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kjashton(at)vnet.net
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| Posted: Wed Sep 16, 2015 5:10 am Post subject: Low Air Pressure Sensor |
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Jared, Maybe you only need to measure the pressure differential above and blow the cylinders. Lycoming recommends about 5” of water differential, depending on HP. This discussion on the Van’s site gave me the idea for a good manometer arrangement. I used it to run some tests on a Long-ez that were informative.http://www.vansairforce.com/community/showthread.php?p=978583-Kent | Quote: | | On Sep 16, 2015, at 12:03 AM, Jared Yates <email(at)jaredyates.com> wrote:I've found a desire to measure differential air pressure inside the engine cowl for cooling diagnostics. Some folks have used an old airspeed indicator for this role. Is there a better way for someone like me who doesn't have an old airspeed indicator? Perhaps some sensors that I could plug into a computer to record the measurements? Thanks in advance! |
[img]cid:0B686E7A-667D-4931-B5DC-EDB5AB7576F6[/img]
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email(at)jaredyates.com
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| Posted: Wed Sep 16, 2015 5:46 am Post subject: Low Air Pressure Sensor |
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Thanks for the help! In this case I'm wanting to measure the differential before and after the oil cooler, but I'd also like to check above and below the cylinders eventually. I hadn't considered the manometer, but I'll look into that.
On Wed, Sep 16, 2015 at 9:09 AM, Kent or Jackie Ashton <kjashton(at)vnet.net (kjashton(at)vnet.net)> wrote:
| Quote: | Jared, Maybe you only need to measure the pressure differential above and blow the cylinders. Lycoming recommends about 5” of water differential, depending on HP. This discussion on the Van’s site gave me the idea for a good manometer arrangement. I used it to run some tests on a Long-ez that were informative.
http://www.vansairforce.com/community/showthread.php?p=978583
-Kent
| Quote: | On Sep 16, 2015, at 12:03 AM, Jared Yates <email(at)jaredyates.com (email(at)jaredyates.com)> wrote:
I've found a desire to measure differential air pressure inside the engine cowl for cooling diagnostics. Some folks have used an old airspeed indicator for this role. Is there a better way for someone like me who doesn't have an old airspeed indicator? Perhaps some sensors that I could plug into a computer to record the measurements? Thanks in advance! |
[img]cid:0B686E7A-667D-4931-B5DC-EDB5AB7576F6[/img]
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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| Posted: Wed Sep 16, 2015 6:03 am Post subject: Low Air Pressure Sensor |
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Many RVs in hot climates have issues with oil cooling. Solutions have
included larger or more efficient coolers, in a few cases adding a
second cooler. If the cooler is fed from the rear baffle by scat tubing.
the differential will be a bit less than the differential above and
below the cylinders, due to losses in the scat tubing and the drop
through the cooler.
On 9/16/2015 6:09 AM, Kent or Jackie Ashton wrote:
| Quote: | Jared, Maybe you only need to measure the pressure differential above
and blow the cylinders. Lycoming recommends about 5” of water
differential, depending on HP. This discussion on the Van’s site gave
me the idea for a good manometer arrangement. I used it to run some
tests on a Long-ez that were informative.
http://www.vansairforce.com/community/showthread.php?p=978583
-Kent
> On Sep 16, 2015, at 12:03 AM, Jared Yates <email(at)jaredyates.com> wrote:
>
> I've found a desire to measure differential air pressure inside the
> engine cowl for cooling diagnostics. Some folks have used an old
> airspeed indicator for this role. Is there a better way for someone
> like me who doesn't have an old airspeed indicator? Perhaps some
> sensors that I could plug into a computer to record the measurements?
> Thanks in advance!
|
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email(at)jaredyates.com
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| Posted: Wed Sep 16, 2015 6:16 am Post subject: Low Air Pressure Sensor |
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Thanks Kelly, my theory is that my 4-into-1 exhaust system is radiating a lot of heat into the lower part of the engine, but before I build a new exhaust system to test that theory, I'd like to make sure that I'm getting good flow through the cooler. I don't have the airspeed advantage that the RVs have, being just a 100-knot airplane.
On Wed, Sep 16, 2015 at 10:01 AM, Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)> wrote:
[quote]--> AeroElectric-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>
Many RVs in hot climates have issues with oil cooling. Solutions have included larger or more efficient coolers, in a few cases adding a second cooler. If the cooler is fed from the rear baffle by scat tubing. the differential will be a bit less than the differential above and below the cylinders, due to losses in the scat tubing and the drop through the cooler.
On 9/16/2015 6:09 AM, Kent or Jackie Ashton wrote:
| Quote: | Jared, Maybe you only need to measure the pressure differential above and blow the cylinders. Lycoming recommends about 5” of water differential, depending on HP. This discussion on the Van’s site gave me the idea for a good manometer arrangement. I used it to run some tests on a Long-ez that were informative.
http://www.vansairforce.com/community/showthread.php?p=978583
-Kent
| Quote: | On Sep 16, 2015, at 12:03 AM, Jared Yates <email(at)jaredyates.com (email(at)jaredyates.com)> wrote:
I've found a desire to measure differential air pressure inside the engine cowl for cooling diagnostics. Some folks have used an old airspeed indicator for this role. Is there a better way for someone like me who doesn't have an old airspeed indicator? Perhaps some sensors that I could plug into a computer to record the measurements? Thanks in advance!
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ceengland7(at)gmail.com
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| Posted: Wed Sep 16, 2015 6:23 am Post subject: Low Air Pressure Sensor |
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More options, if one measurement at a time is sufficient & you want plug&play:
http://www.ebay.com/sch/i.html?_odkw=pressure+gauge&_osacat=0&_from=R40&_trksid=p2045573.m570.l1311.R10.TR9.TRC6.A0.H0.Xdifferential+pressure.TRS2&_nkw=differential+pressure+meter&_sacat=0
Some are <$40, ready to go.
Charlie
On 9/16/2015 8:45 AM, Jared Yates wrote:
[quote] Thanks for the help! In this case I'm wanting to measure the differential before and after the oil cooler, but I'd also like to check above and below the cylinders eventually. I hadn't considered the manometer, but I'll look into that.
On Wed, Sep 16, 2015 at 9:09 AM, Kent or Jackie Ashton <[url=mailto:kjashton(at)vnet.net]kjashton(at)vnet.net (kjashton(at)vnet.net)[/url]> wrote:
| Quote: | Jared, Maybe you only need to measure the pressure differential above and blow the cylinders. Lycoming recommends about 5” of water differential, depending on HP. This discussion on the Van’s site gave me the idea for a good manometer arrangement. I used it to run some tests on a Long-ez that were informative.
http://www.vansairforce.com/community/showthread.php?p=978583
-Kent
| Quote: | On Sep 16, 2015, at 12:03 AM, Jared Yates <email(at)jaredyates.com (email(at)jaredyates.com)> wrote:
I've found a desire to measure differential air pressure inside the engine cowl for cooling diagnostics. Some folks have used an old airspeed indicator for this role. Is there a better way for someone like me who doesn't have an old airspeed indicator? Perhaps some sensors that I could plug into a computer to record the measurements? Thanks in advance! |
|
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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| Posted: Wed Sep 16, 2015 6:27 am Post subject: Low Air Pressure Sensor |
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Could you put heat shields on top of the exhaust pipes.. while stainless
is best, with enough standoff, even aluminum can work. I kind of doubt
your exhaust would be heating the oil from the pipes. Maybe from
blowby. Location of oil cooler and airflow can be tricky. Mooney got it
wrong on their '60s version M20s, putting cooler low on front of
cowling, which is a low pressure area, and in a max performance climb
the airflow actually reverses. Problem was fixed by moving cooler to
rear of engine baffling.
On 9/16/2015 7:15 AM, Jared Yates wrote:
| Quote: | Thanks Kelly, my theory is that my 4-into-1 exhaust system is
radiating a lot of heat into the lower part of the engine, but before
I build a new exhaust system to test that theory, I'd like to make
sure that I'm getting good flow through the cooler. I don't have the
airspeed advantage that the RVs have, being just a 100-knot airplane.
On Wed, Sep 16, 2015 at 10:01 AM, Kelly McMullen <kellym(at)aviating.com
<mailto:kellym(at)aviating.com>> wrote:
<kellym(at)aviating.com <mailto:kellym(at)aviating.com>>
Many RVs in hot climates have issues with oil cooling. Solutions
have included larger or more efficient coolers, in a few cases
adding a second cooler. If the cooler is fed from the rear baffle
by scat tubing. the differential will be a bit less than the
differential above and below the cylinders, due to losses in the
scat tubing and the drop through the cooler.
On 9/16/2015 6:09 AM, Kent or Jackie Ashton wrote:
Jared, Maybe you only need to measure the pressure
differential above and blow the cylinders. Lycoming
recommends about 5” of water differential, depending on HP.
This discussion on the Van’s site gave me the idea for a good
manometer arrangement. I used it to run some tests on a
Long-ez that were informative.
http://www.vansairforce.com/community/showthread.php?p=978583
-Kent
On Sep 16, 2015, at 12:03 AM, Jared Yates
<email(at)jaredyates.com <mailto:email(at)jaredyates.com>> wrote:
I've found a desire to measure differential air pressure
inside the engine cowl for cooling diagnostics. Some
folks have used an old airspeed indicator for this role.
Is there a better way for someone like me who doesn't have
an old airspeed indicator? Perhaps some sensors that I
could plug into a computer to record the measurements?
Thanks in advance!
===========
-
Electric-List" rel="noreferrer"
target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
===========
FORUMS -
eferrer" target="_blank">http://forums.matronics.com
===========
b Site -
-Matt Dralle, List Admin.
rel="noreferrer" target="_blank">http://www.matronics.com/contribution
===========
http://www.matronics.com/contribution
|
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ceengland7(at)gmail.com
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| Posted: Wed Sep 16, 2015 6:45 am Post subject: Low Air Pressure Sensor |
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You don't need to test it; it *is* radiating a lot of heat.  But heat shields that will protect from radiant heat are relatively easy to make. Also, distance is a big factor (variation on inverse square law). Only areas where the exhaust is within an inch or two of the engine will it likely have any significant effect. Years ago, I played with reflective shielding on the oil pan of my O-320 (RV-4, very tight cowl and close crossover 4x2 exhaust) and it had no noticeable effect on oil temps.
I'll bet you're on the right path, looking for air pressure differential issues. BTW, is the oil cooler mounted so that air can't get trapped in it? Trapped air can have a huge effect on a heat exchanger's efficiency. Got pics?
Charlie
On 9/16/2015 9:15 AM, Jared Yates wrote:
[quote] Thanks Kelly, my theory is that my 4-into-1 exhaust system is radiating a lot of heat into the lower part of the engine, but before I build a new exhaust system to test that theory, I'd like to make sure that I'm getting good flow through the cooler. I don't have the airspeed advantage that the RVs have, being just a 100-knot airplane.
On Wed, Sep 16, 2015 at 10:01 AM, Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: Kelly McMullen <[url=mailto:kellym(at)aviating.com]kellym(at)aviating.com (kellym(at)aviating.com)[/url]>
Many RVs in hot climates have issues with oil cooling. Solutions have included larger or more efficient coolers, in a few cases adding a second cooler. If the cooler is fed from the rear baffle by scat tubing. the differential will be a bit less than the differential above and below the cylinders, due to losses in the scat tubing and the drop through the cooler.
On 9/16/2015 6:09 AM, Kent or Jackie Ashton wrote:
| Quote: | Jared, Maybe you only need to measure the pressure differential above and blow the cylinders. Lycoming recommends about 5” of water differential, depending on HP. This discussion on the Van’s site gave me the idea for a good manometer arrangement. I used it to run some tests on a Long-ez that were informative.
http://www.vansairforce.com/community/showthread.php?p=978583
-Kent
| Quote: | On Sep 16, 2015, at 12:03 AM, Jared Yates <[url=mailto:email(at)jaredyates.com]email(at)jaredyates.com (email(at)jaredyates.com)[/url]> wrote:
I've found a desire to measure differential air pressure inside the engine cowl for cooling diagnostics. Some folks have used an old airspeed indicator for this role. Is there a better way for someone like me who doesn't have an old airspeed indicator? Perhaps some sensors that I could plug into a computer to record the measurements? Thanks in advance!
|
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email(at)jaredyates.com
Guest
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| Posted: Wed Sep 16, 2015 7:08 am Post subject: Low Air Pressure Sensor |
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Here's one of the oil cooler mounted. It's a 9-row cooler in a triangular bracket sold for the RV-10, and the outlet is the higher port:http://bearhawkblue.com/wp-content/uploads/IMG_6711.jpg
Here's one that kind of shows the exhaust situation. It doesn't show well how the left side cylinders cross under the sump and very close to it:
http://bearhawkblue.com/wp-content/uploads/IMG_6712.jpg
I've been running about 140-150 degrees over ambient temp. After flying, the oil cooler body measures pretty close to the indicated oil temp with an infrared thermometer, and I've replaced the vernatherm with no measurable change. I have good reason to believe that the oil is flowing, which is why I'd like to verify that the air is flowing too.
On Wed, Sep 16, 2015 at 10:42 AM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:
[quote] You don't need to test it; it *is* radiating a lot of heat. But heat shields that will protect from radiant heat are relatively easy to make. Also, distance is a big factor (variation on inverse square law). Only areas where the exhaust is within an inch or two of the engine will it likely have any significant effect. Years ago, I played with reflective shielding on the oil pan of my O-320 (RV-4, very tight cowl and close crossover 4x2 exhaust) and it had no noticeable effect on oil temps.
I'll bet you're on the right path, looking for air pressure differential issues. BTW, is the oil cooler mounted so that air can't get trapped in it? Trapped air can have a huge effect on a heat exchanger's efficiency. Got pics?
Charlie
On 9/16/2015 9:15 AM, Jared Yates wrote:
| Quote: | Thanks Kelly, my theory is that my 4-into-1 exhaust system is radiating a lot of heat into the lower part of the engine, but before I build a new exhaust system to test that theory, I'd like to make sure that I'm getting good flow through the cooler. I don't have the airspeed advantage that the RVs have, being just a 100-knot airplane.
On Wed, Sep 16, 2015 at 10:01 AM, Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: Kelly McMullen < (kellym(at)aviating.com)kellym(at)aviating.com (kellym(at)aviating.com)>
Many RVs in hot climates have issues with oil cooling. Solutions have included larger or more efficient coolers, in a few cases adding a second cooler. If the cooler is fed from the rear baffle by scat tubing. the differential will be a bit less than the differential above and below the cylinders, due to losses in the scat tubing and the drop through the cooler.
On 9/16/2015 6:09 AM, Kent or Jackie Ashton wrote:
| Quote: | Jared, Maybe you only need to measure the pressure differential above and blow the cylinders. Lycoming recommends about 5” of water differential, depending on HP. This discussion on the Van’s site gave me the idea for a good manometer arrangement. I used it to run some tests on a Long-ez that were informative.
http://www.vansairforce.com/community/showthread.php?p=978583
-Kent
| Quote: | On Sep 16, 2015, at 12:03 AM, Jared Yates < (email(at)jaredyates.com)email(at)jaredyates.com (email(at)jaredyates.com)> wrote:
I've found a desire to measure differential air pressure inside the engine cowl for cooling diagnostics. Some folks have used an old airspeed indicator for this role. Is there a better way for someone like me who doesn't have an old airspeed indicator? Perhaps some sensors that I could plug into a computer to record the measurements? Thanks in advance!
|
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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| Posted: Wed Sep 16, 2015 7:29 am Post subject: Low Air Pressure Sensor |
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OK. That engine install strongly resembles the RV-10 I have. 
That mount is not the most efficient, due to the need for the air to
make a 90 to enter the cooler and a 90 to exit. Many -10 builders use
an Airflow Performance cooler that is the same size as what Vans
supplies, but has extra row of cooling fins. Some go up to IIRC the 2007
or 2008 size cooler.
The -10 setup runs hot until wheel pants and fairings are installed,
moving cruise from 155 to 165-170 range. I don't know if it is adequate
at 100kt speed for an IO-540.
On 9/16/2015 8:07 AM, Jared Yates wrote:
| Quote: | Here's one of the oil cooler mounted. It's a 9-row cooler in a
triangular bracket sold for the RV-10, and the outlet is the higher port:
http://bearhawkblue.com/wp-content/uploads/IMG_6711.jpg
Here's one that kind of shows the exhaust situation. It doesn't show
well how the left side cylinders cross under the sump and very close
to it:
http://bearhawkblue.com/wp-content/uploads/IMG_6712.jpg
I've been running about 140-150 degrees over ambient temp. After
flying, the oil cooler body measures pretty close to the indicated oil
temp with an infrared thermometer, and I've replaced the vernatherm
with no measurable change. I have good reason to believe that the oil
is flowing, which is why I'd like to verify that the air is flowing too.
On Wed, Sep 16, 2015 at 10:42 AM, Charlie England
<ceengland7(at)gmail.com <mailto:ceengland7(at)gmail.com>> wrote:
You don't need to test it; it *is* radiating a lot of heat.
But heat shields that will protect from radiant heat are
relatively easy to make. Also, distance is a big factor (variation
on inverse square law). Only areas where the exhaust is within an
inch or two of the engine will it likely have any significant
effect. Years ago, I played with reflective shielding on the oil
pan of my O-320 (RV-4, very tight cowl and close crossover 4x2
exhaust) and it had no noticeable effect on oil temps.
I'll bet you're on the right path, looking for air pressure
differential issues. BTW, is the oil cooler mounted so that air
can't get trapped in it? Trapped air can have a huge effect on a
heat exchanger's efficiency. Got pics?
Charlie
On 9/16/2015 9:15 AM, Jared Yates wrote:
> Thanks Kelly, my theory is that my 4-into-1 exhaust system is
> radiating a lot of heat into the lower part of the engine, but
> before I build a new exhaust system to test that theory, I'd like
> to make sure that I'm getting good flow through the cooler. I
> don't have the airspeed advantage that the RVs have, being just a
> 100-knot airplane.
>
> On Wed, Sep 16, 2015 at 10:01 AM, Kelly McMullen
> <kellym(at)aviating.com <mailto:kellym(at)aviating.com>> wrote:
>
>
> <kellym(at)aviating.com <mailto:kellym(at)aviating.com>>
>
> Many RVs in hot climates have issues with oil cooling.
> Solutions have included larger or more efficient coolers, in
> a few cases adding a second cooler. If the cooler is fed from
> the rear baffle by scat tubing. the differential will be a
> bit less than the differential above and below the cylinders,
> due to losses in the scat tubing and the drop through the cooler.
>
> On 9/16/2015 6:09 AM, Kent or Jackie Ashton wrote:
>
> Jared, Maybe you only need to measure the pressure
> differential above and blow the cylinders. Lycoming
> recommends about 5” of water differential, depending on
> HP. This discussion on the Van’s site gave me the idea
> for a good manometer arrangement. I used it to run some
> tests on a Long-ez that were informative.
> http://www.vansairforce.com/community/showthread.php?p=978583
>
> -Kent
>
> On Sep 16, 2015, at 12:03 AM, Jared Yates
> <email(at)jaredyates.com <mailto:email(at)jaredyates.com>>
> wrote:
>
> I've found a desire to measure differential air
> pressure inside the engine cowl for cooling
> diagnostics. Some folks have used an old airspeed
> indicator for this role. Is there a better way for
> someone like me who doesn't have an old airspeed
> indicator? Perhaps some sensors that I could plug
> into a computer to record the measurements? Thanks
> in advance!
*ist"
target="_blank">http://www.matronics.com/Navigator?AeroElectric-Listtp://forums.matronics.com
_blank">http://www.matronics.com/contribution *
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email(at)jaredyates.com
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| Posted: Wed Sep 16, 2015 7:52 am Post subject: Low Air Pressure Sensor |
|
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Thanks Kelly, an inadequate oil cooler size is a likely factor. Mine is only a 360 and not a 540, which is partly why I didn't start with the 13-row cooler in the first place.
[quote][b]
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Wed Sep 16, 2015 10:16 am Post subject: Low Air Pressure Sensor |
|
|
At 11:03 PM 9/15/2015, you wrote:
| Quote: | | I've found a desire to measure differential air pressure inside the engine cowl for cooling diagnostics. Some folks have used an old airspeed indicator for this role. Is there a better way for someone like me who doesn't have an old airspeed indicator? Perhaps some sensors that I could plug into a computer to record the measurements? Thanks in advance! |
The quick-n-dirty way is to acquire a low-differential-
pressure like this
http://tinyurl.com/pujah48
There's a number of ranges for these instruments on
eBay. I've got a couple buried in stuff not yet
unpacked from my move to M.L from Wichita. They
ARE g-loading sensitive to a degree so stright-n-
level measurements will be the most meaningful.
An all electronic solution may present in the
form of sensors like this"
http://tinyurl.com/ps2adq9
Amplified analog outputs that can be readily
observed on a multi-meter. No g-loading sensitivities.
Also, you could use a gage sensor as opposed to a
ported differential device as long as the sensor
itself can be positioned at the lower pressure
environs.
Bob . . . [quote][b]
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dlj04(at)josephson.com
Guest
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| Posted: Wed Sep 16, 2015 11:22 am Post subject: Low Air Pressure Sensor |
|
|
| Quote: |
I've found a desire to measure differential air pressure inside the engine
cowl for cooling diagnostics. Some folks have used an old airspeed
indicator for this role. Is there a better way for someone like me who
doesn't have an old airspeed indicator? Perhaps some sensors that I could
plug into a computer to record the measurements? Thanks in advance!
The simplest is a Magnehelic gauge, search an auction site with
|
'magnehelic differential' and skip the ones where the pointer doesn't
sit at zero in the picture.
There are differential pressure sensors that produce an analog voltage
output if you have logging capability, such as with an inexpensive
logger like a Dataq DI-145. It is more of a project, with the
requirement to set up a quiet regulated power source for the sensor.
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Wed Sep 16, 2015 11:26 am Post subject: Low Air Pressure Sensor |
|
|
| Quote: | An all electronic solution may present in the
form of sensors like this"
http://tinyurl.com/ps2adq9
Amplified analog outputs that can be readily
observed on a multi-meter. No g-loading sensitivities.
Also, you could use a gage sensor as opposed to a
ported differential device as long as the sensor
itself can be positioned at the lower pressure
environs. |
I dug around in the archives to see
the last time I used one of these
critters. ONLY about 13 years ago . . .
http://tinyurl.com/qe4z856
Had to get some data on pitot-heater performance
on a Beechjet. Two of the my DAS channels
recorded pressure altitude and IAS as presented
by a couple of amplified transducers. Got these
nice traces on a 'short hop' to 41000 feet
in the venerable ol' flight test airplane
at RAC . . .
http://tinyurl.com/qe4z856
Bob . . . [quote][b]
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
|
| Posted: Wed Sep 16, 2015 11:54 am Post subject: Low Air Pressure Sensor |
|
|
Not necessarily. Van's supplies the same cooler for both 360 and 540
engines. Most do find the 13 row 2006A cooler needed for the 540.
Airflow systems also supplies a diverter plate to install inside the
mount to ensure not all the air goes through the bottom half of the cooler.
On 9/16/2015 8:50 AM, Jared Yates wrote:
| Quote: | Thanks Kelly, an inadequate oil cooler size is a likely factor. Mine
is only a 360 and not a 540, which is partly why I didn't start with
the 13-row cooler in the first place.
http://www.matronics.com/contribution
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ceengland7(at)gmail.com
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| Posted: Wed Sep 16, 2015 12:55 pm Post subject: Low Air Pressure Sensor |
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|
That SCAT tubing is a prime suspect. It has very high internal skin drag. A friend with an alt. engine in an RV had several inches of manifold pressure loss through about 4' of SCAT (admittedly, smaller diameter, but still....). Most of the RV guys have the cooler mounted on a similar wedge shaped 'adapter', but the side you have facing the firewall is typically the inlet, attached to a hole in the engine baffle where you have your SCAT tube fitting. Your SCAT inlet would be blocked off (no opening). Yes, there are lots of cracked baffles until the baffle gets reinforced. But most do cool adequately.
Probably a minor factor, but the cooler exit in the pic is at 90 degrees to likely flow exiting the cowl. I know that velocity is relatively low there, but little things do add up....
Charlie
On 9/16/2015 10:07 AM, Jared Yates wrote:
[quote] Here's one of the oil cooler mounted. It's a 9-row cooler in a triangular bracket sold for the RV-10, and the outlet is the higher port: http://bearhawkblue.com/wp-content/uploads/IMG_6711.jpg
Here's one that kind of shows the exhaust situation. It doesn't show well how the left side cylinders cross under the sump and very close to it:
http://bearhawkblue.com/wp-content/uploads/IMG_6712.jpg
I've been running about 140-150 degrees over ambient temp. After flying, the oil cooler body measures pretty close to the indicated oil temp with an infrared thermometer, and I've replaced the vernatherm with no measurable change. I have good reason to believe that the oil is flowing, which is why I'd like to verify that the air is flowing too.
On Wed, Sep 16, 2015 at 10:42 AM, Charlie England <ceengland7(at)gmail.com (ceengland7(at)gmail.com)> wrote:
| Quote: | You don't need to test it; it *is* radiating a lot of heat. But heat shields that will protect from radiant heat are relatively easy to make. Also, distance is a big factor (variation on inverse square law). Only areas where the exhaust is within an inch or two of the engine will it likely have any significant effect. Years ago, I played with reflective shielding on the oil pan of my O-320 (RV-4, very tight cowl and close crossover 4x2 exhaust) and it had no noticeable effect on oil temps.
I'll bet you're on the right path, looking for air pressure differential issues. BTW, is the oil cooler mounted so that air can't get trapped in it? Trapped air can have a huge effect on a heat exchanger's efficiency. Got pics?
Charlie
On 9/16/2015 9:15 AM, Jared Yates wrote:
| Quote: | Thanks Kelly, my theory is that my 4-into-1 exhaust system is radiating a lot of heat into the lower part of the engine, but before I build a new exhaust system to test that theory, I'd like to make sure that I'm getting good flow through the cooler. I don't have the airspeed advantage that the RVs have, being just a 100-knot airplane.
On Wed, Sep 16, 2015 at 10:01 AM, Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>
Many RVs in hot climates have issues with oil cooling. Solutions have included larger or more efficient coolers, in a few cases adding a second cooler. If the cooler is fed from the rear baffle by scat tubing. the differential will be a bit less than the differential above and below the cylinders, due to losses in the scat tubing and the drop through the cooler.
On 9/16/2015 6:09 AM, Kent or Jackie Ashton wrote:
| Quote: | Jared, Maybe you only need to measure the pressure differential above and blow the cylinders. Lycoming recommends about 5” of water differential, depending on HP. This discussion on the Van’s site gave me the idea for a good manometer arrangement. I used it to run some tests on a Long-ez that were informative.
http://www.vansairforce.com/community/showthread.php?p=978583
-Kent
| Quote: | On Sep 16, 2015, at 12:03 AM, Jared Yates <[url=mailto:email(at)jaredyates.com]email(at)jaredyates.com (email(at)jaredyates.com)[/url]> wrote:
I've found a desire to measure differential air pressure inside the engine cowl for cooling diagnostics. Some folks have used an old airspeed indicator for this role. Is there a better way for someone like me who doesn't have an old airspeed indicator? Perhaps some sensors that I could plug into a computer to record the measurements? Thanks in advance!
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