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Van: "van mulders marcel" <van.mulders.marcel@telenet.be>
Aan: "Ron KRANTZ" <rkrantz77@comcast.net>
Verzonden: Zaterdag 20 oktober 2018 19:11:29
Onderwerp: Re: [Fot] Weber vs Mikuni
SU's are not only very simple, but also very very clever because it is so well
performing with that few parts. With one metering needle and a variable
venturi, SU's do most things as well as the DCOE Webers with lots of jets,
screws valves and drillings everywhere. Acceleration enrichment, cold start
enrichment : SU's do it all with that one needle and venturi. On the road, even
well tuned Webers need a lot more fuel than SU's. I had a TR6 with SU's for
some years, and when travelling in group with other TR's, the PI and Weber
TR6's had to refuel 3 times when I needed only 2 times (8 litres/100km or 30
miles with a gallon when driving relaxed). But of course,when looking for the
ultimate performance, no carburetor can beat Webers and exchanging the jets etc
is resembling the "mapping" of a modern fuel injected car.
Marcel
Van: "fot" <fot@autox.team.net>
Aan: "Kas Kastner" <kaskastner@gmail.com>, "fot" <fot@autox.team.net>, "fubog1"
<fubog1@aol.com>
Verzonden: Zaterdag 20 oktober 2018 14:28:53
Onderwerp: Re: [Fot] Weber vs Mikuni
I totally agree with Kas that the S.U.'s are the simplest carbs around. But
there are ways to get around the short comings (I call it chasing the weak
link). I use to have the problems Kas noted but found a fix. To keep the engine
running properly at high revs on long straights (RA and MidO) I had to increase
static fuel pressure to 6 psi to maintain 2.5 psi on the straights. Then with
development I needed more air/fuel so I taper bored the throat of the S.U.'s
and opened the .090" jets to .096" so I could still use the large array of .090
needles. Plus a few other things to make it all work together.
Ron Krantz
ReK Racing
On October 19, 2018 at 12:31 PM Kas Kastner via Fot <fot@autox.team.net> wrote:
Lots of times at the higher revs the float bowls of the S.U.'s just run out of
gas and they need an enlargment of the needle and seat.Many times the stock
needle and seat j ust does not have enough capacity to flow the fuel needed for
the much richer needles used and the revvs. The SU's are so simple minded and
easy to work with I'd want to very certain that the was a BIG benifit before
changing to jetted carbs that need a ton of parts of you are going to make use
of the capacity of the units.
If you do not tune for the day and the weather at that time what is the point
in having all that adustment. With the SU a couple flats adjustment up or down
and you are done the hour. Bigger machinery does not mean bigger power or even
more useful power.
BUT, if you are going for the expensive route, get the msot you can get. DCOE
45's are the ticket. Start with a small venturi and work up from there. Yes,
you neeed to buy alterate venturies otherwise you have just wasted your
money.These same carbs were used on the Sebring and Le Mans Spitfire coupes
1147 cc engines and proved 3% more power by tuning. To get the benifit you need
to work at it.
Never be beaten by equipment.
On Fri, Oct 19, 2018 at 9:01 AM fubog1 via Fot < [ mailto:fot@autox.team.net |
fot@autox.team.net ] > wrote:
BQ_BEGIN
Yes HS4 carbs.
Glen
-----Original Message-----
From: van.mulders.marcel < [ mailto:van.mulders.marcel@telenet.be |
van.mulders.marcel@telenet.be ] >
To: fubog1 < [ mailto:fubog1@aol.com | fubog1@aol.com ] >
Cc: fot < [ mailto:fot@autox.team.net | fot@autox.team.net ] >
Sent: Thu, Oct 18, 2018 5:48 pm
Subject: Re: [Fot] Weber vs Mikuni
Glen,
With 1 1/2s carburettors, I suppose you mean HS4? The SU logic is a little
weird. 1" + 1/2" = 6/8" so you would think it are HS6s, but when talking about
HS carburettors, 1 + 1/2 = 1 + 4/8 and they took the 4 to name these carbs
HS4...
Marcel
Van: "fubog1" < [ mailto:fubog1@aol.com | fubog1@aol.com ] >
Aan: "van mulders marcel" < [ mailto:van.mulders.marcel@telenet.be |
van.mulders.marcel@telenet.be ] >, "Mike Harmuth" < [ mailto:ofracer@gmail.com
| ofracer@gmail.com ] >
Cc: "fot" < [ mailto:fot@autox.team.net | fot@autox.team.net ] >
Verzonden: Donderdag 18 oktober 2018 22:39:39
Onderwerp: Re: [Fot] Weber vs Mikuni
Well I won't speculate on the cause, but I doubt that it's the SUs.
My small crank 1300 w/1 1/2s on a eurospec manifold w/Stahls header, "big"
valve head, would buzz easily to 9k, still making power, if I let it.
Normal shift point 7800-8000.
FWIW...
Glen
-----Original Message-----
From: van.mulders.marcel--- via Fot < [ mailto:fot@autox.team.net |
fot@autox.team.net ] >
To: Mike Harmuth < [ mailto:ofracer@gmail.com | ofracer@gmail.com ] >
Cc: fot < [ mailto:fot@autox.team.net | fot@autox.team.net ] >
Sent: Thu, Oct 18, 2018 2:12 pm
Subject: Re: [Fot] Weber vs Mikuni
-"...hitting a wall at that point..." : is it possible this is rather pointing
to the camshaft than to the SU's? If it are the carburettors, maybe the power
would decrease more gradually above 6500 rpm.
-In general one choke per cylinder is better, and 2 Webers 40 DCOE isn't
overkill I think
- what about trying HS6 SU's on your actual manifold?
At what maximum rpm is your engine still reliable?
Marcel
Van: "fot" < [ mailto:fot@autox.team.net | fot@autox.team.net ] >
Aan: "fot" < [ mailto:fot@autox.team.net | fot@autox.team.net ] >
Verzonden: Woensdag 17 oktober 2018 15:49:45
Onderwerp: [Fot] Weber vs Mikuni
I'm looking into switching out my twin HS4s on the 1296 race engine to either
Weber or Mukinis. I know this has been done for years and I'd like to get close
the best set up out of the gate.
I don't think the SUs are up to the task of moving enough air with the new
ported head and Stahl header. I've worked on the SUs and gotten them to finally
deliver a good AFR , 12.6, at 6500 RPM under load but I seem to hit a wall
(figuratively) at that point. I suspect that the openings just aren't big
enough to deliver the mass of air required. (spreadsheet or other flow
calculator link appreciated)
Biggest gate I suspect is the intake valve, 1 3/8" head (~35mm) HS4 is ~38mm at
best.
Recommendations? I've seen all these setups at the track, each with pluses,
minuses and overkill cause it looks cool.
One weber DCOE 40 or 2? what jets, tubes etc for a starting point? Best
manifold?
2 or 4 Mikuni 40? jet size?
thanks
mike
_______________________________________________
[ mailto:fot@autox.team.net | fot@autox.team.net ]
[ http://www.fot-racing.com/ | http://www.fot-racing.com ]
Archive: [ http://www.team.net/pipermail/fot |
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Archive: http://www.team.net/pipermail/fot
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Archive: [ http://www.team.net/pipermail/fot |
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BQ_END
_______________________________________________
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http://www.fot-racing.com
Archive: http://www.team.net/pipermail/fot
--=_6dc99f15-3815-469c-abdc-8aa9d3793ef3
Content-Transfer-Encoding: quoted-printable
<html><body><div style=3D"font-family: Verdana, Arial, Helvetica, sans-seri=
f; font-size: 10pt; color: #000000"><div><br></div><div><br></div><hr id=3D=
"zwchr" data-marker=3D"__DIVIDER__"><div data-marker=3D"__HEADERS__"><b>Van=
: </b>"van mulders marcel" <van.mulders.marcel@telenet.be><br><b>Aan:=
</b>"Ron KRANTZ" <rkrantz77@comcast.net><br><b>Verzonden: </b>Zaterd=
ag 20 oktober 2018 19:11:29<br><b>Onderwerp: </b>Re: [Fot] Weber vs Mikuni<=
br></div><br><div data-marker=3D"__QUOTED_TEXT__"><div style=3D"font-family=
: Verdana, Arial, Helvetica, sans-serif; font-size: 10pt; color: #000000"><=
div>SU's are not only very simple, but also very very clever because =
it is so well performing with that few parts. With one metering needle and =
a variable venturi, SU's do most things as well as the DCOE Webers with lot=
s of jets, screws valves and drillings everywhere. Acceleration enrichment,=
cold start enrichment : SU's do it all with that one needle and venturi. O=
n the road, even well tuned Webers need a lot more fuel than SU's. I had a =
TR6 with SU's for some years, and when travelling in group with other=
TR's, the PI and Weber TR6's had to refuel 3 times when I needed only 2 ti=
mes (8 litres/100km or 30 miles with a gallon when driving relaxed). But of=
course,when looking for the ultimate performance, no carburetor can beat&n=
bsp; Webers and exchanging the jets etc is resembling the "mapping" o=
f a modern fuel injected car.</div><div>Marcel</div><br><hr id=3D"zwchr"><d=
iv><b>Van: </b>"fot" <fot@autox.team.net><br><b>Aan: </b>"Kas Kastner=
" <kaskastner@gmail.com>, "fot" <fot@autox.team.net>, "fubog1" =
<fubog1@aol.com><br><b>Verzonden: </b>Zaterdag 20 oktober 2018 14:28:=
53<br><b>Onderwerp: </b>Re: [Fot] Weber vs Mikuni<br></div><br><div>I total=
ly agree with Kas that the S.U.'s are the simplest carbs around. But there=
are ways to get around the short comings (I call it chasing the weak link)=
. I use to have the problems Kas noted but found a fix. To keep the engin=
e running properly at high revs on long straights (RA and MidO) I had to in=
crease static fuel pressure to 6 psi to maintain 2.5 psi on the straights. =
Then with development I needed more air/fuel so I taper bored the throat o=
f the S.U.'s and opened the .090" jets to .096" so I could still use the la=
rge array of .090 needles. Plus a few other things to make it all work tog=
ether.<br>Ron Krantz<br>ReK Racing<br><br>
<blockquote>
On October 19, 2018 at 12:31 PM Kas Kastner via Fot <fot@autox.team.ne=
t> wrote:
<br>
<br>
<div dir=3D"ltr">
Lots of times at the higher revs the float bowls of the S.U.'s just run o=
ut of gas and they need an enlargment of the needle and seat.Many times the=
stock needle and seat j ust does not have enough capacity to flow the fuel=
needed for the much richer needles used and the revvs. The SU's are so sim=
ple minded and easy to work with I'd want to very certain that the was a BI=
G benifit before changing to jetted carbs that need a ton of parts of you a=
re going to make use of the capacity of the units.
<div>
<br>
</div>
<div>
If you do not tune for the day and the weather at that time what i=
s the point in having all that adustment. With the SU a couple flats adjust=
ment up or down and you are done the hour. Bigger machinery does not mean b=
igger power or even more useful power.
<div>
<br>
</div>
<div>
BUT, if you are going for the expensive route, get the msot you can get=
. DCOE 45's are the ticket. Start with a small venturi and work up fr=
om there. Yes, you neeed to buy alterate venturies otherwise you have=
just wasted your money.These same carbs were used on the Sebring and Le Ma=
ns Spitfire coupes 1147 cc engines and proved 3% more power by tuning=
. To get the benifit you need to work at it.
<br clear=3D"all">
<div>
<div dir=3D"ltr" class=3D"gmail_signature">
<p><strong><span style=3D"color: #000099;">Never be beaten by equipme=
nt.</span></strong></p>
</div>
</div>
<br>
</div>
</div>
</div>
<br>
<div class=3D"gmail_quote">
<div dir=3D"ltr">
On Fri, Oct 19, 2018 at 9:01 AM fubog1 via Fot <
<a href=3D"mailto:fot@autox.team.net"; target=3D"_blank">fot@autox.team.n=
et</a>> wrote:
<br>
</div>
<blockquote class=3D"gmail_quote">
<span style=3D"color: black; font-family: Arial, Helvetica, sans-serif; =
font-size: small;">=20
<div>=20
<span style=3D"font-size: small;">Yes HS4 carbs.</span>
</div>=20
<div>
<span style=3D"font-size: small;">Glen</span>
<br>=20
</div>=20
<div>=20
<br>=20
</div>=20
<div>=20
<br>=20
</div>=20
<div style=3D"font-family: arial,helvetica; font-size: 10pt; color: bla=
ck;">
-----Original Message-----
<br> From: van.mulders.marcel <
<a href=3D"mailto:van.mulders.marcel@telenet.be"; target=3D"_blank">van=
.mulders.marcel@telenet.be</a>>
<br> To: fubog1 <
<a href=3D"mailto:fubog1@aol.com"; target=3D"_blank">fubog1@aol.com</a>=
>
<br> Cc: fot <
<a href=3D"mailto:fot@autox.team.net"; target=3D"_blank">fot@autox.team=
.net</a>>
<br> Sent: Thu, Oct 18, 2018 5:48 pm
<br> Subject: Re: [Fot] Weber vs Mikuni
<br>=20
<br>=20
<div id=3D"m_-3204379643218842764yiv7557179423">=20
<div>=20
<div style=3D"font-family: Verdana,Arial,Helvetica,sans-serif; font-=
size: 10pt; color: #000000;">=20
<div>
Glen,
</div>=20
<div>
With 1 1/2s carburettors, I suppose you mean HS4? The SU logic is =
a little weird. 1" + 1/2" =3D 6/8" so you would think it are HS6s, but when=
talking about HS carburettors, 1 + 1/2 =3D 1 + 4/8 and they took the 4 to =
name these carbs HS4...
</div>=20
<div>
Marcel
</div>=20
<div>
<br clear=3D"none">
</div>=20
<hr id=3D"m_-3204379643218842764yiv7557179423zwchr">=20
<div class=3D"m_-3204379643218842764yiv7557179423yqt0596148954" id=
=3D"m_-3204379643218842764yiv7557179423yqt61649">=20
<div>
<b>Van: </b>"fubog1" <
<a href=3D"mailto:fubog1@aol.com"; target=3D"_blank">fubog1@aol.co=
m</a>>
<br clear=3D"none">
<b>Aan: </b>"van mulders marcel" <
<a href=3D"mailto:van.mulders.marcel@telenet.be"; target=3D"_blank=
">van.mulders.marcel@telenet.be</a>>, "Mike Harmuth" <
<a href=3D"mailto:ofracer@gmail.com"; target=3D"_blank">ofracer@gm=
ail.com</a>>
<br clear=3D"none">
<b>Cc: </b>"fot" <
<a href=3D"mailto:fot@autox.team.net"; target=3D"_blank">fot@autox=
.team.net</a>>
<br clear=3D"none">
<b>Verzonden: </b>Donderdag 18 oktober 2018 22:39:39
<br clear=3D"none">
<b>Onderwerp: </b>Re: [Fot] Weber vs Mikuni
<br clear=3D"none">
</div>=20
<br clear=3D"none">=20
<div>
<span style=3D"color: black; font-family: Arial,Helvetica,sans-se=
rif; font-size: small;"> </span>=20
<div>=20
<span style=3D"font-size: small;">Well I won't speculate on the =
cause, but I doubt that it's the SUs.<br clear=3D"none"> </span>
</div>=20
<div>
<span style=3D"font-size: small;">My small crank 1300 w/1 1/2s o=
n a eurospec manifold w/Stahls header, "big" valve head, would buzz easily =
to 9k, still making power, if I let it.</span>
</div>=20
<div>
<span style=3D"font-size: small;">Normal shift point 7800-8000.<=
/span>
</div>=20
<div>
<span style=3D"font-size: small;">FWIW...<br clear=3D"none"> </s=
pan>
</div>=20
<div>
<span style=3D"font-size: small;">Glen</span>
<br clear=3D"none">=20
</div>=20
<div>=20
<br clear=3D"none">=20
</div>=20
<div>=20
<br clear=3D"none">=20
</div>=20
<div style=3D"font-family: arial,helvetica; font-size: 10pt; colo=
r: black;">
-----Original Message-----
<br clear=3D"none"> From: van.mulders.marcel--- via Fot <
<a href=3D"mailto:fot@autox.team.net"; target=3D"_blank">fot@auto=
x.team.net</a>>
<br clear=3D"none"> To: Mike Harmuth <
<a href=3D"mailto:ofracer@gmail.com"; target=3D"_blank">ofracer@g=
mail.com</a>>
<br clear=3D"none"> Cc: fot <
<a href=3D"mailto:fot@autox.team.net"; target=3D"_blank">fot@auto=
x.team.net</a>>
<br clear=3D"none"> Sent: Thu, Oct 18, 2018 2:12 pm
<br clear=3D"none"> Subject: Re: [Fot] Weber vs Mikuni
<br clear=3D"none">=20
<br clear=3D"none">=20
<div id=3D"m_-3204379643218842764yiv7557179423">=20
<div>=20
<div style=3D"font-family: Verdana,Arial,Helvetica,sans-serif;=
font-size: 10pt; color: #000000;">=20
<div>
-"...hitting a wall at that point..." : is it possible this =
is rather pointing to the camshaft than to the SU's? If it are the carburet=
tors, maybe the power would decrease more gradually above 6500 rpm.
</div>=20
<div>
-In general one choke per cylinder is better, and 2 Webers 4=
0 DCOE isn't overkill I think
</div>=20
<div>
- what about trying HS6 SU's on your actual manifold?
</div>=20
<div>
At what maximum rpm is your engine still reliable?
</div>=20
<div>
Marcel
</div>=20
<div>
<br clear=3D"none">
</div>=20
<hr id=3D"m_-3204379643218842764yiv7557179423zwchr">=20
<div class=3D"m_-3204379643218842764yiv7557179423yqt010505939=
3" id=3D"m_-3204379643218842764yiv7557179423yqt73080">=20
<div>
<b>Van: </b>"fot" <
<a href=3D"mailto:fot@autox.team.net"; target=3D"_blank">fot=
@autox.team.net</a>>
<br clear=3D"none">
<b>Aan: </b>"fot" <
<a href=3D"mailto:fot@autox.team.net"; target=3D"_blank">fot=
@autox.team.net</a>>
<br clear=3D"none">
<b>Verzonden: </b>Woensdag 17 oktober 2018 15:49:45
<br clear=3D"none">
<b>Onderwerp: </b>[Fot] Weber vs Mikuni
<br clear=3D"none">
</div>=20
<br clear=3D"none">=20
<div>=20
<div dir=3D"ltr">=20
<div>
I'm looking into switching out my twin HS4s on the 1296 r=
ace engine to either Weber or Mukinis. I know this has been done for years =
and I'd like to get close the best set up out of the gate.=20
<br clear=3D"none">
</div>=20
<br clear=3D"none">=20
<div>
I don't think the SUs are up to the task of moving enough=
air with the new ported head and Stahl header. I've worked on the SUs and =
gotten them to finally deliver a good AFR , 12.6, at 6500 RPM under load bu=
t I seem to hit a wall (figuratively) at that point. I suspect that the ope=
nings just aren't big enough to deliver the mass of air required. (spreadsh=
eet or other flow calculator link appreciated)
<br clear=3D"none">
</div>=20
<div>
Biggest gate I suspect is the intake valve, 1 3/8" head (=
~35mm) HS4 is ~38mm at best.
<br clear=3D"none">
</div>=20
<br clear=3D"none">=20
<div>
Recommendations? I've seen all these setups at the track,=
each with pluses, minuses and overkill cause it looks cool.=20
<br clear=3D"none">
</div>=20
<br clear=3D"none">=20
<div>
One weber DCOE 40 or 2? what jets, tubes etc for a starti=
ng point? Best manifold?=20
<br clear=3D"none">
</div>=20
<br clear=3D"none">=20
<div>
2 or 4 Mikuni 40? jet size?
</div>=20
<br clear=3D"none">=20
<div>
thanks
</div>=20
<div>
mike
<br clear=3D"none">
</div>=20
</div>=20
<br clear=3D"none">________________________________________=
_______
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</div>=20
<div class=3D"m_-3204379643218842764yiv7557179423yqt0105059393" =
id=3D"m_-3204379643218842764yiv7557179423yqt79273">
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</div>=20
</div>=20
</div> </span>_______________________________________________
<br>=20
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