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The video length? That's why they invented fast forward buttons, progress
sliders, etc.
I haven't measured it, but I'll guess our underhood temps while moving, or
even while idling with our poorly positioned fans running, is not high
enough to boil the fuel. When we stop the engine and the airflow pretty
much stops (except for what escapes through the hood gaps, etc), then the
air temp goes up, to the vicinity of the temp of that big hunk of iron
below the carb. A spacer may reduce the conducted heat, but if the air all
around the carb is hot, the carb temp will go up.
For an experiment I added a drain to the carb vent, and did see fuel coming
out after stopping. This weekend I hope to open the carb and check the
fuel level, etc. I used my IR thermometer to read temps on stuff that was
nearly black, and there were many spots that were initially well over 170,
some even after 15 minutes with the hood open.
My first generation Jetta had large flexible flaps over large holes in the
panel the radiator mounted on. The would apparently open when the car was
in motion, but close when the car stopped, to prevent hot air recirculation=
.
I already thought of using the electric fan many of us have as a "bilge
blower" (like on boats) on hot restarts.
Stu
On Tue, Sep 15, 2015 at 2:48 PM, Tom Witt via Tigers <tigers@autox.team.net=
>
wrote:
> I finally got around to watching this video. It was like watching paint
> dry. It could have been 30 seconds long, not 20 minutes. But anyway (it=
=E2=80=99s
> not Stu=E2=80=99s fault), it did eventually shows the gas boil at a low
> temperature. I=E2=80=99ll just throw these things out there:
>
> 1. No one ever mentions it, but there has to be some cooling effect of
> both from the air being drawn into the carburetor and the evaporation
> effect of the gas (like when you apply rubbing alcohol to your body). Th=
en
> again, without cold air ducting..., maybe not.
>
> 2. A cooling effect likely offsets some of the heat soak while the car is
> in use. However, when the engine is stopped that cooling also ceases.
>
> 3. It would seem best to isolate and insulate the carburetor from the res=
t
> of the engine compartment. This, however would require some type of hood
> scoop (or duct) and and an isolation enclosure under an already crowded
> hood.
>
> 4. I=E2=80=99m wondering if the horn opening block off plates some use (t=
hat work
> at idle/stopped) to prevent recirculation are a detriment at higher speed=
s
> not allowing cooler air to pass through the engine compartment? I=E2=80=
=99ve
> always through a spring loaded door seemed a better concept. Closed at an
> idle/stopped condition, but opened from the flow of air as the car moved
> forward.
>
> 5. If anyone is interested, some of the 280Z=E2=80=99s had a fan and duct=
ing that
> blew air onto the injector rail. The concept would seem somewhat adaptabl=
e
> to blowing cool air on the carburetor after the car shut off. A 555 Timer
> could control the run time after shut-off.
>
> It seems any attempt for correction deviates from a stock appearance. And=
,
> a crowded area under the hood doesn=E2=80=99t leave many options for isol=
ation or
> ducting. Has anyone run without their hood to see it it makes a differenc=
e?
>
> Just some rambling thoughts.
>
> *From:* Stu via Tigers <tigers@autox.team.net>
> *Sent:* Friday, September 11, 2015 5:42 PM
> *To:* Tiger Net <Tigers@autox.team.net>
> *Subject:* [Tigers] Carb Fire Research
>
> I've been doing some research, and found an interesting video:
>
> https://www.youtube.com/watch?v=3Dd7AkcjnCTVU
>
> To summarize, this guy does a good experiment that proves that some
> components of normal gasoline boil at around 170F.
>
> Our engines are usually well above this, so when we stop it's safe to
> assume that the underhood temperatures spike, heating up our carbs, and
> everything else. So there could easily be some boiling in the carb bowl=
.
> And once the 170F components boil off, the temperature rises even more.
> When trying a hot restart, new fuel is introduced to the much hotter carb
> when the pump comes back on, perhaps there could be a few moments of
> additional, perhaps more violent boiling, blowing vapor and fuel out the
> vent.
>
> Last weekend I tried recreating the problem. Similar hot day, drove
> around the same loop, etc. Parked and waited 10 minutes, about the same
> time as before. I had cleaned the top of the carb, so it was obvious tha=
t
> nothing had come out when I opened the hood and looked But listening
> closely, I thought I could hear a faint sizzling sound from somewhere
> within the carb... I did not try a restart, since I hadn't seen this
> video at that point.
>
> Any opinions?
>
> Stu
>
> _______________________________________________
>
> tigers@autox.team.net
>
> Donate: http://www.team.net/donate.html
> Archive: http://www.team.net/archive
> Forums: http://www.team.net/forums
> Unsubscribe:
> http://autox.team.net/mailman/options/tigers/sabre2tgr@gmail.com
>
>
>
>
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<div dir=3D"ltr"><div class=3D"gmail_default" style=3D"font-size:small">The=
video length?=C2=A0 That's why they invented fast forward buttons, pro=
gress sliders, etc.</div><div class=3D"gmail_default" style=3D"font-size:sm=
all"><br></div><div class=3D"gmail_default" style=3D"font-size:small">I hav=
en't measured it, but I'll guess our underhood temps while moving, =
or even while idling with our poorly positioned fans running, is not high e=
nough to boil the fuel.=C2=A0 When we stop the engine and the airflow prett=
y much stops (except for what escapes through the hood gaps, etc), then the=
air temp goes up, to the vicinity of the temp of that big hunk of iron bel=
ow the carb.=C2=A0 A spacer may reduce the conducted heat, but if the air a=
ll around the carb is hot, the carb temp will go up.</div><div class=3D"gma=
il_default" style=3D"font-size:small"><br></div><div class=3D"gmail_default=
" style=3D"font-size:small">For an experiment I added a drain to the carb v=
ent, and did see fuel coming out after stopping.=C2=A0 This weekend I hope =
to open the carb and check the fuel level, etc.=C2=A0 I used my IR thermome=
ter to read temps on stuff that was nearly black, and there were many spots=
that were initially well over 170, some even after 15 minutes with the hoo=
d open.</div><div class=3D"gmail_default" style=3D"font-size:small"><br></d=
iv><div class=3D"gmail_default" style=3D"font-size:small">My first generati=
on Jetta had large flexible flaps over large holes in the panel the radiato=
r mounted on.=C2=A0 The would apparently open when the car was in motion, b=
ut close when the car stopped, to prevent hot air recirculation.</div><div =
class=3D"gmail_default" style=3D"font-size:small"><br></div><div class=3D"g=
mail_default" style=3D"font-size:small">I already thought of using the elec=
tric fan many of us have as a "bilge blower" (like on boats) on h=
ot restarts.</div><div class=3D"gmail_default" style=3D"font-size:small"><b=
r></div><div class=3D"gmail_default" style=3D"font-size:small">Stu</div></d=
iv><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Tue, Sep 15=
, 2015 at 2:48 PM, Tom Witt via Tigers <span dir=3D"ltr"><<a href=3D"mai=
lto:tigers@autox.team.net" target=3D"_blank">tigers@autox.team.net</a>><=
/span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8=
ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir=3D"ltr">
<div dir=3D"ltr">
<div style=3D"FONT-SIZE:12pt;FONT-FAMILY:'Calibri';COLOR:#000000">
<div>I finally got around to watching this video. It was like watching pain=
t=20
dry. It could have been 30 seconds long, not 20 minutes. But anyway (it=E2=
=80=99s not=20
Stu=E2=80=99s fault), it did eventually shows the gas boil at a low tempera=
ture.=C2=A0=20
I=E2=80=99ll just throw these things out there:</div>
<div>=C2=A0</div>
<div>1. No one ever mentions it, but there has to be some cooling effect of=
both=20
from the air being drawn into the carburetor and the evaporation effect of =
the=20
gas (like when you apply rubbing alcohol to your body).=C2=A0 Then again,=
=20
without cold air ducting..., maybe not.</div>
<div>=C2=A0</div>
<div>2. A cooling effect likely offsets some of the heat soak while the car=
is=20
in use. However, when the engine is stopped that cooling also ceases.</div>
<div>=C2=A0</div>
<div>3. It would seem best to isolate and insulate the carburetor from the =
rest=20
of the engine compartment.=C2=A0 This, however would require some type of h=
ood=20
scoop (or duct) and and an isolation enclosure under an already crowded=20
hood.</div>
<div>=C2=A0</div>
<div>4. I=E2=80=99m wondering if the horn opening block off plates some use=
(that work=20
at idle/stopped) to prevent recirculation are a detriment at higher speeds =
not=20
allowing cooler air to pass through the engine compartment?=C2=A0 I=E2=80=
=99ve always=20
through a spring loaded door seemed a better concept. Closed at an idle/sto=
pped=20
condition, but opened from the flow of air as the car moved forward.</div>
<div>=C2=A0</div>
<div>5. If anyone is interested, some of the 280Z=E2=80=99s had a fan and d=
ucting that=20
blew air onto the injector rail. The concept would seem somewhat adaptable =
to=20
blowing cool air on the carburetor after the car shut off. A 555 Timer coul=
d=20
control the run time after shut-off.</div>
<div>=C2=A0</div>
<div>It seems any attempt for correction deviates from a stock appearance. =
And,=20
a crowded area under the hood doesn=E2=80=99t leave many options for isolat=
ion or=20
ducting. Has anyone run without their hood to see it it makes a=20
difference?</div>
<div>=C2=A0</div>
<div>Just some rambling thoughts.</div>
<div style=3D"FONT-SIZE:small;TEXT-DECORATION:none;FONT-FAMILY:"Calibr=
i";FONT-WEIGHT:normal;COLOR:#000000;FONT-STYLE:normal;DISPLAY:inline">
<div style=3D"FONT:10pt tahoma">
<div><font size=3D"3" face=3D"Calibri"></font>=C2=A0</div>
<div style=3D"BACKGROUND:#f5f5f5">
<div><b>From:</b> <a title=3D"tigers@autox.team.net" href=3D"mailto:tigers@=
autox.team.net" target=3D"_blank">Stu via Tigers</a> </div>
<div><b>Sent:</b> Friday, September 11, 2015 5:42 PM</div>
<div><b>To:</b> <a title=3D"Tigers@autox.team.net" href=3D"mailto:Tigers@au=
tox.team.net" target=3D"_blank">Tiger Net</a> </div>
<div><b>Subject:</b> [Tigers] Carb Fire Research</div></div></div>
<div>=C2=A0</div></div>
<div style=3D"FONT-SIZE:small;TEXT-DECORATION:none;FONT-FAMILY:"Calibr=
i";FONT-WEIGHT:normal;COLOR:#000000;FONT-STYLE:normal;DISPLAY:inline">
<div dir=3D"ltr">
<div class=3D"gmail_default" style=3D"FONT-SIZE:small">
<div class=3D"gmail_default" style=3D"FONT-SIZE:x-small;COLOR:rgb(0,0,0)">I=
've been=20
doing some research, and found an interesting video:</div>
<div class=3D"gmail_default" style=3D"FONT-SIZE:x-small;COLOR:rgb(0,0,0)">=
=C2=A0</div>
<div class=3D"gmail_default" style=3D"FONT-SIZE:14px;COLOR:rgb(0,0,0)"><fon=
t size=3D"1"><a href=3D"https://www.youtube.com/watch?v=3Dd7AkcjnCTVU"; targ=
et=3D"_blank">https://www.youtube.com/watch?v=3Dd7AkcjnCTVU</a></font><br><=
/div>
<div class=3D"gmail_default" style=3D"FONT-SIZE:14px;COLOR:rgb(0,0,0)"><fon=
t size=3D"1"><br></font></div>
<div class=3D"gmail_default" style=3D"FONT-SIZE:14px;COLOR:rgb(0,0,0)"><fon=
t size=3D"1">To summarize, this guy does a good experiment that proves that=
some=20
components of normal gasoline boil at around 170F.</font></div>
<div class=3D"gmail_default" style=3D"FONT-SIZE:14px;COLOR:rgb(0,0,0)"><fon=
t size=3D"1"><br></font></div>
<div class=3D"gmail_default" style=3D"FONT-SIZE:14px;COLOR:rgb(0,0,0)"><fon=
t size=3D"1">Our engines are usually well above this, so when we stop it=
9;s safe to=20
assume that the underhood temperatures spike, heating up our carbs, and=20
everything else.=C2=A0 So there could easily be some boiling in the carb=C2=
=A0=20
bowl.=C2=A0 And once the 170F components boil off,=C2=A0 the temperature ri=
ses=20
even more.=C2=A0 When trying a hot restart, new fuel is introduced to the m=
uch=20
hotter carb when the pump comes back on, perhaps there could be a few momen=
ts of=20
additional, perhaps more violent boiling, blowing vapor and fuel out the=20
vent.</font></div>
<div class=3D"gmail_default" style=3D"FONT-SIZE:14px;COLOR:rgb(0,0,0)"><fon=
t size=3D"1"><br></font></div>
<div class=3D"gmail_default" style=3D"FONT-SIZE:14px;COLOR:rgb(0,0,0)"><fon=
t size=3D"1">Last weekend I tried recreating the problem.=C2=A0 Similar hot=
day, drove=20
around the same loop, etc.=C2=A0 Parked and waited 10 minutes, about the sa=
me=20
time as before.=C2=A0 I had cleaned the top of the carb, so it was obvious =
that=20
nothing had come out when I opened the hood and looked=C2=A0 But listening=
=20
closely, I thought I could hear a faint sizzling sound from somewhere withi=
n the=20
carb...=C2=A0=C2=A0 I did not try a restart, since I hadn't seen this v=
ideo at=20
that point.</font></div>
<div class=3D"gmail_default" style=3D"FONT-SIZE:14px;COLOR:rgb(0,0,0)"><fon=
t size=3D"1"><br></font></div>
<div class=3D"gmail_default" style=3D"FONT-SIZE:14px;COLOR:rgb(0,0,0)"><fon=
t size=3D"1">Any opinions?</font></div>
<div class=3D"gmail_default" style=3D"FONT-SIZE:14px;COLOR:rgb(0,0,0)"><fon=
t size=3D"1"><br></font></div>
<div class=3D"gmail_default" style=3D"FONT-SIZE:14px;COLOR:rgb(0,0,0)"><fon=
t size=3D"1">Stu</font></div></div></div></div></div></div></div>
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<br></blockquote></div><br></div>
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