[DeTomaso] Rear Window
jderyke at aol.com
jderyke at aol.com
Sat Mar 19 16:48:45 EDT 2016
In the stock configuration, the condenser fan sucks outside air In and blow it forward against the luggage tub, which is contoured to bend the resulting flow down to the pavement, so as to not get a loop circulation that delivers hotter and hotter air into the rear mount condenser,
Please verify/confirmWhich direction does your AC condenser fan "blow"Does it "push out" or "suck in
-----Original Message-----
From: Joseph F. Byrd, Jr. <byrdjf at embarqmail.com>
To: 'Stephen' <steve at snclocks.com>
Cc: detomaso <detomaso at poca.com>
Sent: Sat, Mar 19, 2016 1:33 pm
Subject: Re: [DeTomaso] Rear Window
Please verify/confirmWhich direction does your AC condenser fan "blow"Does it "push out" or "suck in"-----Original Message-----From: DeTomaso [mailto:detomaso-bounces at poca.com] On Behalf Of StephenSent: Saturday, March 19, 2016 14:44 PMTo: jgkrenton at comcast.netCc: detomaso at poca.comSubject: Re: [DeTomaso] Rear WindowGads – thank you all for your input! I’m realizing I will have to put together a synopsis of all the great comments I am getting from the forum. Last night’s tests were “impacted” by a roughly 20 mph wind coming down the Columbia river gorge. This morning the winds have died down, so will most likely get some more runs in tonight before the rains start again (this is the Pacific Northwest). None the less, it is pretty easy to see, from the attached plot, that there is a relationship between air flow through the condenser and how fast the car was going. I’ve corrected for wind speed (hence calling the X axis air speed – as cars speed relative to air with very rough correction). I found that there was not sufficient air-flow through the a/c condenser to spin the computer cooling fan I have strapped to the inside of the condenser fan (see attached for my “southern engineered” setup). But, I knew that, standing still, the a/c fan spun the computer fan enough to generate around 1 volt across the computer fan. So, we made some runs with the a/c fan spinning, starting out with standing still. They showed the impact of speed pretty graphically. Caveats: I know the computer fan was not registering even with the car doing 80 unless the a/c fan was on. So, there is a threshold air flow required to get the computer fan spinning. But, given that blowing at the fan spins it, I’m surprised it didn’t spin when the a/c fan was shut down and car was going 80 mph. Will repeat but get the computer fan spinning with the a/c fan, then shut down the a/c and see if the computer fan keeps spinning when the car is moving. I’ve attached my plot of a/c air flow vs car speed from last night’s runs. Realizing the data is “challenged” by the 20 mph ambient wind, which I am sure was quartering and wandering, heck, not a bad plot. Be interesting to see what I learn with calmer conditions. I’ve also attached a shot of my instrument cluster. Interestingly, the temperature gauge on top of the swirl tank also shows up. Of course, given the airs desire to flow backwards through the a/c condenser, it likely makes some sense to reverse the a/c fan direction. OK – will lose the benefits of a sucker fan in giving better coverage of the coils, and the fan will likely be a little less efficient spinning backwards (OK – fans are nearly flat, not much curvature – maybe not a lot less efficient) but I suspect a significant enhancement in air-flow would be beneficial. Will test this as well. Stephen Nelson From: jgkrenton at comcast.net [mailto:jgkrenton at comcast.net]Sent: Saturday, March 19, 2016 7:58 AMTo: Stephen <steve at snclocks.com>Cc: detomaso at poca.comSubject: Re: [DeTomaso] Rear Window Stephen: It will be interesting to see what Tom Tjaarda has to say. It's my recollection that the deck lid opening is in fact a big air exhaust duct, sort of based on the NACA duct principle. It was designed to help move high pressure air from under the car, up around the engine and out the back. This was intended to help with the cars stability and engine cooling at high speeds while reducing the overall aerodynamic drag of the car. Blocking the opening would impact these functions (as does removing the little side windows). Somewhere around the industry is some information on wind tunnel tests that were done on the Pantera body back in the 70's. I just don't remember where now. I did have the opportunity to be following a friends Pantera who was at 70 or 80 MPH when an air conditioning hose let go and filled the engine compartment with Freon mist (looked like smoke!). I can tell you from that experience that the deck lid opening is very efficient at moving large quantities of air from the engine compartment rapidly and smoothly. Here is some information on NACA ducts which you might find interesting and useful in your explorations. http://ntrs.nasa.gov/archive/nasa/ca...1993093623.pdfhttp://ntrs.nasa.gov/archive/nasa/ca...1993091791.pdfhttp://ntrs.nasa.gov/archive/nasa/ca...1993093645.pdf I also seem to recall that the low pressure area behind the car, and the low pressure in the engine compartment are about equal in that 70 to 80 MPH zone. This means the stock Air Conditioning condenser has no airflow (the pressures are low enough the fan is ineffective) and the condenser can "freeze up" in certain conditions which causes over pressure and is why the hose broke on my friends Pantera. FYI/Your experience may vary.... Jeff/2467 _____ From: "Stephen" <steve at snclocks.com <mailto:steve at snclocks.com> >To: detomaso at poca.com <mailto:detomaso at poca.com>Sent: Friday, March 18, 2016 8:35:52 AMSubject: [DeTomaso] Rear Window I've been pondering for quite a while now the idea of putting a piece of glass in the "window" in the deck lid behind the engine in 5332. This would keep the engine from getting wet every time it rains and would also keep from sucking grit and water off the road when the car is running down the road. Both seem like decent goals. Oh, and it would also make it more difficult for someone to just reach in and remove 5332's dog-bone air cleaner. OK - no one has taken it so far. But, hey, it would be all too easy to remove. Looking at the opening - it sure looks like the original intent was to put in a window. I have sent an e-mail to Tom Tjaarda (attached) asking his thoughts.Hopefully he will respond. In the interim, I put together a set of sensors so I could see what I could learn about conditions in the engine compartment just inches in front of theopening, to the right side of the dog-bone. The attached photo shows theinstrument cluster shot from inside the car. I'm measuring air velocity through the rear window (vane anemometer) Vacuum just in front of the window Rotation of the a/c condenser fan (volt meter connected across the motor, which acts as a generator when the fan turns) Two of the above are fairly straight forward. The vacuum - not so much. When one talks about a vacuum, one is usually talking about a vacuum, relative to ambient atmospheric pressure. So, if a vacuum gauge is hooked up to your intake manifold, it reads the difference in pressure between the atmosphere where the gauge is sitting, and the inside of your manifold, where the hose from the gauge is connected. So, what does one compare to in a moving car? The interior of the car?That is what one would get if one puts a vacuum gauge in the cab and routes the hose to the area in question. But, what does the pressure (or vacuum) inside the car do with the car moving down the road. Open the windows, your ears pop, and the pressure changes. Most of us don't have an external air inlet (at least an intentional one) to the cab except for the windows. My solution is to use a fairly sensitive pressure gauge (a sphygmomanometer- gauge used to read blood pressure. It reads in inches of mercury. FYI, there are roughly 50 inches of mercury per psi). I have connected the gauge with small-diameter plastic tubing to a 200 ml stainless sample bomb. I wrapped the bomb in towels and placed in a cooler to minimize temperature changes. See, the pressure in the bomb will change by roughly .03 psi (1.5 mm Hg) for each 1 degree F change in temperature. I then pressured up the bomb and let it sit overnight to stabilize. It ended up at 280 mm. This is my "zero" at the then current barometric pressure. One has to view the pressure gauge as a delta-pressure device. It shows the difference in pressure between the bomb (high pressure) and the atmosphere around the gauge. So, if the reading on the gauge goes up, the differential is increasing, which means the atmospheric pressure is going down. As in a wee bit of a vacuum around the gauge. Flip side, if the reading on the gauge goes down, well, there is less differential between the 280 mm Hg in the bomb and the atmosphere around the gauge, so the pressure is going up. OK - that is complex. While a gauge that can be read down to around 1 mm hg (0.02 psi) is pretty sensitive, I suspect we are talking pretty minimal vacuum levels.Preliminary testing suggested a reading of 272 mm Hg at 80 mph. The pressure around the gauge went up! Huh. A lot to learn here. I also noted that the volt meter did not show any rotation of the fan on the a/c condenser. Need to make sure the wiring is ok. But, note, the meter reads in mV, and, in my earlier testing, it showed voltage if the fan turned at all. The rubber for the new window shows up today, the window next Wednesday. My plan is to get a decent video and stills of the test instruments at several speeds. Then, when the new window is installed, rerun the test. I suspect the anemometer will still be valuable, since I suspect there will be a lot of turbulence in the air in the engine compartment even with the window in place. Needless to say, having the window in place will complicate putting the deck-lid back in place. Stephen Nelson _______________________________________________ Detomaso Forum Managed by POCAPosted emails must not exceed 1.5 Megabytes DeTomaso mailing list DeTomaso at poca.com <mailto:DeTomaso at poca.com> http://poca.com/mailman/listinfo/detomaso_poca.com To manage your subscription (change email address, unsubscribe, etc.) use the links above. _______________________________________________Detomaso Forum Managed by POCAPosted emails must not exceed 1.5 MegabytesDeTomaso mailing listDeTomaso at poca.comhttp://poca.com/mailman/listinfo/detomaso_poca.comTo manage your subscription (change email address, unsubscribe, etc.) use the links above.
-------------- next part --------------
In the stock configuration, the condenser fan sucks outside air In and
blow it forward against the luggage tub, which is contoured to bend the
resulting flow down to the pavement, so as to not get a loop
circulation that delivers hotter and hotter air into the rear mount
condenser,
Please verify/confirm Which direction does your AC condenser fan
"blow" Does it "push out" or "suck in
-----Original Message-----
From: Joseph F. Byrd, Jr. <byrdjf at embarqmail.com>
To: 'Stephen' <steve at snclocks.com>
Cc: detomaso <detomaso at poca.com>
Sent: Sat, Mar 19, 2016 1:33 pm
Subject: Re: [DeTomaso] Rear Window
Please verify/confirm Which direction does your AC condenser fan "blow"
Does it "push out" or "suck in" -----Original Message----- From:
DeTomaso [[1]mailto:detomaso-bounces at poca.com] On Behalf Of Stephen
Sent: Saturday, March 19, 2016 14:44 PM To: [2]jgkrenton at comcast.net
Cc: [3]detomaso at poca.com Subject: Re: [DeTomaso] Rear Window Gads a
thank you all for your input! Iam realizing I will have to put together
a synopsis of all the great comments I am getting from the forum. Last
nightas tests were aimpacteda by a roughly 20 mph wind coming down the
Columbia river gorge. This morning the winds have died down, so will
most likely get some more runs in tonight before the rains start again
(this is the Pacific Northwest). None the less, it is pretty easy to
see, from the attached plot, that there is a relationship between air
flow through the condenser and how fast the car was going. Iave
corrected for wind speed (hence calling the X axis air speed a as cars
speed relative to air with very rough correction). I found that there
was not sufficient air-flow through the a/c condenser to spin the
computer cooling fan I have strapped to the inside of the condenser fan
(see attached for my asouthern engineereda setup). But, I knew that,
standing still, the a/c fan spun the computer fan enough to generate
around 1 volt across the computer fan. So, we made some runs with the
a/c fan spinning, starting out with standing still. They showed the
impact of speed pretty graphically. Caveats: I know the computer fan
was not registering even with the car doing 80 unless the a/c fan was
on. So, there is a threshold air flow required to get the computer fan
spinning. But, given that blowing at the fan spins it, Iam surprised it
didnat spin when the a/c fan was shut down and car was going 80 mph.
Will repeat but get the computer fan spinning with the a/c fan, then
shut down the a/c and see if the computer fan keeps spinning when the
car is moving. Iave attached my plot of a/c air flow vs car speed from
last nightas runs. Realizing the data is achallengeda by the 20 mph
ambient wind, which I am sure was quartering and wandering, heck, not a
bad plot. Be interesting to see what I learn with calmer conditions.
Iave also attached a shot of my instrument cluster. Interestingly, the
temperature gauge on top of the swirl tank also shows up. Of course,
given the airs desire to flow backwards through the a/c condenser, it
likely makes some sense to reverse the a/c fan direction. OK a will
lose the benefits of a sucker fan in giving better coverage of the
coils, and the fan will likely be a little less efficient spinning
backwards (OK a fans are nearly flat, not much curvature a maybe not a
lot less efficient) but I suspect a significant enhancement in air-flow
would be beneficial. Will test this as well. Stephen Nelson From:
[4]jgkrenton at comcast.net [[5]mailto:jgkrenton at comcast.net] Sent:
Saturday, March 19, 2016 7:58 AM To: Stephen <[6]steve at snclocks.com>
Cc: [7]detomaso at poca.com Subject: Re: [DeTomaso] Rear Window Stephen:
It will be interesting to see what Tom Tjaarda has to say. It's my
recollection that the deck lid opening is in fact a big air exhaust
duct, sort of based on the NACA duct principle. It was designed to help
move high pressure air from under the car, up around the engine and out
the back. This was intended to help with the cars stability and engine
cooling at high speeds while reducing the overall aerodynamic drag of
the car. Blocking the opening would impact these functions (as does
removing the little side windows). Somewhere around the industry is
some information on wind tunnel tests that were done on the Pantera
body back in the 70's. I just don't remember where now. I did have the
opportunity to be following a friends Pantera who was at 70 or 80 MPH
when an air conditioning hose let go and filled the engine compartment
with Freon mist (looked like smoke!). I can tell you from that
experience that the deck lid opening is very efficient at moving large
quantities of air from the engine compartment rapidly and smoothly.
Here is some information on NACA ducts which you might find interesting
and useful in your explorations.
[8]http://ntrs.nasa.gov/archive/nasa/ca...1993093623.pdf
[9]http://ntrs.nasa.gov/archive/nasa/ca...1993091791.pdf
[10]http://ntrs.nasa.gov/archive/nasa/ca...1993093645.pdf I also seem
to recall that the low pressure area behind the car, and the low
pressure in the engine compartment are about equal in that 70 to 80 MPH
zone. This means the stock Air Conditioning condenser has no airflow
(the pressures are low enough the fan is ineffective) and the condenser
can "freeze up" in certain conditions which causes over pressure and is
why the hose broke on my friends Pantera. FYI/Your experience may
vary.... Jeff/2467 _____ From: "Stephen" <[11]steve at snclocks.com
<[12]mailto:steve at snclocks.com> > To: [13]detomaso at poca.com
<[14]mailto:detomaso at poca.com> Sent: Friday, March 18, 2016 8:35:52 AM
Subject: [DeTomaso] Rear Window I've been pondering for quite a while
now the idea of putting a piece of glass in the "window" in the deck
lid behind the engine in 5332. This would keep the engine from getting
wet every time it rains and would also keep from sucking grit and water
off the road when the car is running down the road. Both seem like
decent goals. Oh, and it would also make it more difficult for someone
to just reach in and remove 5332's dog-bone air cleaner. OK - no one
has taken it so far. But, hey, it would be all too easy to remove.
Looking at the opening - it sure looks like the original intent was to
put in a window. I have sent an e-mail to Tom Tjaarda (attached) asking
his thoughts. Hopefully he will respond. In the interim, I put together
a set of sensors so I could see what I could learn about conditions in
the engine compartment just inches in front of the opening, to the
right side of the dog-bone. The attached photo shows the instrument
cluster shot from inside the car. I'm measuring air velocity through
the rear window (vane anemometer) Vacuum just in front of the window
Rotation of the a/c condenser fan (volt meter connected across the
motor, which acts as a generator when the fan turns) Two of the above
are fairly straight forward. The vacuum - not so much. When one talks
about a vacuum, one is usually talking about a vacuum, relative to
ambient atmospheric pressure. So, if a vacuum gauge is hooked up to
your intake manifold, it reads the difference in pressure between the
atmosphere where the gauge is sitting, and the inside of your manifold,
where the hose from the gauge is connected. So, what does one compare
to in a moving car? The interior of the car? That is what one would get
if one puts a vacuum gauge in the cab and routes the hose to the area
in question. But, what does the pressure (or vacuum) inside the car do
with the car moving down the road. Open the windows, your ears pop, and
the pressure changes. Most of us don't have an external air inlet (at
least an intentional one) to the cab except for the windows. My
solution is to use a fairly sensitive pressure gauge (a
sphygmomanometer - gauge used to read blood pressure. It reads in
inches of mercury. FYI, there are roughly 50 inches of mercury per
psi). I have connected the gauge with small-diameter plastic tubing to
a 200 ml stainless sample bomb. I wrapped the bomb in towels and placed
in a cooler to minimize temperature changes. See, the pressure in the
bomb will change by roughly .03 psi (1.5 mm Hg) for each 1 degree F
change in temperature. I then pressured up the bomb and let it sit
overnight to stabilize. It ended up at 280 mm. This is my "zero" at the
then current barometric pressure. One has to view the pressure gauge as
a delta-pressure device. It shows the difference in pressure between
the bomb (high pressure) and the atmosphere around the gauge. So, if
the reading on the gauge goes up, the differential is increasing, which
means the atmospheric pressure is going down. As in a wee bit of a
vacuum around the gauge. Flip side, if the reading on the gauge goes
down, well, there is less differential between the 280 mm Hg in the
bomb and the atmosphere around the gauge, so the pressure is going up.
OK - that is complex. While a gauge that can be read down to around 1
mm hg (0.02 psi) is pretty sensitive, I suspect we are talking pretty
minimal vacuum levels. Preliminary testing suggested a reading of 272
mm Hg at 80 mph. The pressure around the gauge went up! Huh. A lot to
learn here. I also noted that the volt meter did not show any rotation
of the fan on the a/c condenser. Need to make sure the wiring is ok.
But, note, the meter reads in mV, and, in my earlier testing, it showed
voltage if the fan turned at all. The rubber for the new window shows
up today, the window next Wednesday. My plan is to get a decent video
and stills of the test instruments at several speeds. Then, when the
new window is installed, rerun the test. I suspect the anemometer will
still be valuable, since I suspect there will be a lot of turbulence in
the air in the engine compartment even with the window in place.
Needless to say, having the window in place will complicate putting the
deck-lid back in place. Stephen Nelson
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6. mailto:steve at snclocks.com
7. mailto:detomaso at poca.com
8. http://ntrs.nasa.gov/archive/nasa/ca...1993093623.pdf
9. http://ntrs.nasa.gov/archive/nasa/ca...1993091791.pdf
10. http://ntrs.nasa.gov/archive/nasa/ca...1993093645.pdf
11. mailto:steve at snclocks.com
12. mailto:steve at snclocks.com?
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14. mailto:detomaso at poca.com?
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