modifying a carb for blow thru turbo
Paul Clausen
32/36 DGV Webers from cortinas and escorts) for use in blow thru turbo
setups?
I understand there is something about sealing the float bowl?
I dont really understand how the jets can work when there is positive
pressure going thru it but I have seen a 350 holley, totally unmodified used
in a dodgy backyard blow-thru setup.
TIA
SubKool_Ntrance
but I'd love to know if anyone can give pointers for a bit more beef.
"Paul Clausen" <paul_c...@dingoblue.net.au> wrote in message
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Brad
the fuel pressure must be increased to overcome boost
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Brad
"Paul Clausen" <paul_c...@dingoblue.net.au> wrote in message
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Bushy
matching manifold.
If yours is older, check the wreckers, should be able to pick up fairly
cheap.
Hope this helps,
Peter
SubKool_Ntrance
litre 250 6 cyl
--
---^SubKool_Ntrance^---
"Curiosity is not a sin"
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"Bushy" <ple...@reply.to.group> wrote in message
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Jason James
"Paul Clausen" <paul_c...@dingoblue.net.au> wrote in message
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Maybe it works on the ventuuri principle that old fashioned perfume pumps
and flysprayers used : fast flowing air passing close to a tube end, causes
suction up the tube ( petrol suckewd up and passed into the air stream).
Have had zero exp on them
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Jason James
John McKenzie
>
> Does anyone here know anything about modifying downdraft carbs (specifically
> 32/36 DGV Webers from cortinas and escorts) for use in blow thru turbo
> setups?
> I understand there is something about sealing the float bowl?
you must plumb boost from before the carb to the fuel bowl.
and also have no other fuel bowl vents (plug them)
very broadly, carbs work as a result of pressure differences.
if the pressure in the fuel bowl is raised as above, then
the carb will still function. the reason the holley works
and I suspect the dgv is the same (I have one outside but
couldnt be bothered looking - i was going to use it on the
turbo corolla, but it wouldnt fit the manifold without major
problems - so I went with a carter bbd.) is that the fuel bowl
vents are above the carb throat, so any carb bonnet you use
to plumb the turbo to the carb will automatically pressurise
the fuel bowl.
It is important you plumb this from before the carb, and not the
manifold, it wont work it you do it the wrong way.
Also, unless you intend to run less than around 4 lbs boost,
you wil nedd to fill the floats with fuel resistant foam.
otherwise the pressure will cause them to collapse. Don't
let someone bullshit you that using a carb box will prevent
this, it wont and anyone with an understanding of physics will
know this.
Additionally, you must use a rising rate fuel pressure regulator.
the fuel pressure must be kept (ideally 7lbs but since I know that the
45 dcoes don't work too well above 4.5lbs, I am guessing the dgvs may
have a similar issue) 4 or so pounds - above boost pressure. as boost
rises, if the fuel pressure doesnt rise with it, no fuel can enter the
fuel bowl.
> I dont really understand how the jets can work when there is positive
> pressure going thru it
there is always pressure going through it, absolute, not atmospheric or
however you want to phrase it. Again, it is a matter of pressure
differential.
Apparently (and there isn't much to go on since it isnt that common)
blow through weber dcoes can run lean under boost. I believe this is a
matter of sorting rather than design flaw. the dhla dellorto is a
similar carb and has been made to work well in this application.
Going out on a limb, it may require some oddball air corrector to
deliver a desirable fuel curve. Since as I understand it, the air
correctors function is to prevent high speed full throttel over richness
in normally aspirated cars, then perhaps playing with it (sealing it
even - I would love some input on this) woud be the answer.
John McKenzie
Paul Clausen
Maybe it would just be easier to stick an SU or a strommy on the front of
the turbo. Not too good for the oil seal tho, as the turbo was meant for an
EFI car.
"John McKenzie" <jm...@alphalink.com.au> wrote in message
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Bushy
anyway compared to it.
Hope that helps,
Peter
SubKool_Ntrance <fuk_...@yahoo.com> wrote in message
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John McKenzie
>
> Cheers for your help.
>
> Maybe it would just be easier to stick an SU or a strommy on the front of
> the turbo. Not too good for the oil seal tho, as the turbo was meant for an
> EFI car.
>
depends on your personal choice both systems have pros and cons.
blow through isnt that hard to sort out. If you werent too worried
about economy and stuff, you could always just drill the
secondary jet out to buggery. Mike (moron) did it and it worked
well. that would fix that. the other mods are a piece of cake.
John McKenzie
Simon Pigot
>
> I dont know about the webber.......I've got an old Stromberg on my cortina
> but I'd love to know if anyone can give pointers for a bit more beef.
>
Go for a 250-2V head. Check out the pics of the one in my TC on:
http://www.gisparks.tas.gov.au/sgi/2502v
I've seen em in the trading post for about $250 with a reco usually needed.
Nice alloy inlet manifold with WW2 Stromberg and extractors. Much better than
the usual solution which is to shove on a horrible holley :-)
Cheers,
Simon
is: djbradii@optushome.com.au Shaun Brady
"Paul Clausen" <paul_c...@dingoblue.net.au> wrote in message
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Shaddow Edge
Blow through and suck through.
Blow through beens the turbo sits before the carby, (etc) and blows through
the carby.
Suck through is where the carby comes first and then the turbo is mounted
behind it and sucks air through the carby.
Shaddow
Shaun Brady > wrote in message ...