I still believe that $1500 spent on porting, a cam, a valve job and better
valves would be as efficient if not more so. I think a Solex setup is at
least that in cost if not more.
Mike
----- Original Message -----
From: "Vicki Burrows" <gregnvicki@earthlink.net>
To: "datsunmike" <datsunmike@nyc.rr.com>
Cc: "milton3" <milton3@pobox.com>; "Peter Long" <Peter.Long@ecologic.ca>;
"roadster list" <datsun-roadsters@autox.team.net>
Sent: Tuesday, August 13, 2002 7:03 PM
Subject: Re: horsepower vs. torque
> Well, since we are voicing opinions here, I am in the Mikuni/Weber style
camp.
> You're right that the airflow is the key, but the manifold and carbs for a
> Mikuni/Weber set up appear far more flow efficient. No offense to the SU
cars,
> as SU's are excellent carburetors. However, the Mikuni/Weber set ups are
far
> more tunable and offer many features that an SU simply cannot.
> Greg Burrows (soon with SK's)
>
> datsunmike wrote:
>
> > At more than $100 per HP gained it's awfully expensive.
> >
> > I bet getting a head properly ported and better valves (Manley) a good 3
> > angle valve job and a different cam would enable a SU car to out pull a
> > Solex car providing you get different needles especially for the higher
RPMs
> > where I think the 1600s and 2000s run outta gas. A longer duration cam
would
> > help that too.
> >
> > BTW, a 240 racer at Lime Rock for the SCCA Volvo Vintage races told me
the
> > Mikuni factory was destroyed by fire and the carbs are NLA.
> >
> > Mike
> >
> > ----- Original Message -----
> > From: "milton3" <milton3@pobox.com>
> > To: "Peter Long" <Peter.Long@ecologic.ca>; "roadster list"
> > <datsun-roadsters@autox.team.net>
> > Sent: Monday, August 12, 2002 6:27 PM
> > Subject: Re: horsepower vs. torque
> >
> > > Hey Peter,
> > >
> > > I'm not picking on you for your comments, but voicing a different
opinion
> > > and explanation. There are benefits to both, and I wanna talk about
where
> > > the power is located. I'm going to tie it in to the SU (.5*46mm) v.
Solex
> > > (44mm) discussion from last week since that one didn't sit well enough
to
> > > digest.
> > >
> > > Note: I'm only voicing my own opinions and trying to help folks
> > > understand the difference so they too can voice an opinion.
> > >
> > > On 12 Aug 2002, at 14:51, Peter Long wrote:
> > >
> > > > The rate of acceleration is greater. These are two extreme
> > > > examples to show you that 240 hp is not equal to 240 hp.... peak
> > > > horsepower ratings sell magazines, torque wins races."
> > >
> > > Funny thing though: The BMW Z cars only get to look at S2000 tail
lights.
> > > I've been on track in lapping sessions with both. The S2000s are
faster
> > > around Texas World Speedway's 2.8 mile road course. I've watched them
> > > compete at AutoX's too, and the S2000s take the nod there too.
> > >
> > > Why? Because acceleration from a standstill isn't the only factor
when
> > > winning races. I'm going to suggest that you look at the HP v. RPM
curve
> > > and compare the total area under the curve - matched to the right
driver
> > > the car with the greater total area takes the nod if it is geared
> > > perfectly for the event.
> > >
> > > But, the average driver (like me) needs the power (yes power, not
torque)
> > > at the RPM they are accelerating from. It is easier for a driver like
me
> > > to deal with the power at the top of the RPM range because this fits
with
> > > the idea of press the pedal harder to go faster - it isn't always
> > > convenient or safe to shift in competition.
> > >
> > > Sufficient torque is required to get the car moving and accelerating,
but
> > > it is power that determines how fast the speed (RPM) of the engine can
> > > change. So, yes, a high torque car can break the tires loose with a
gas
> > > pedal application, but that does not imply that it is necessarily
> > > accelerating (changing velocity) quickly.
> > >
> > > That said, it's probably pretty clear that I like a rev happy motor in
a
> > > car. I take the opposite fence on a motorcycle where I go for low
rev'g
> > > torque monsters, but I'm no motorcycle racer either.
> > >
> > > So, SU v. Solex carbs on our Roadsters:
> > >
> > > It was argued that because the SUs are only supplying one cylinder at
a
> > > time, they can be compared with Solex's based on inlet diameter. This
> > > suggested that the SUs 46mm were larger than the Solex's 44mm inlets.
> > >
> > > The problem here comes from two variables not considered. One is
engine
> > > RPM. At 3000 RPMs, each cylinder is firing 1500 times per minute or
25
> > > times per second. That suggests a lot of direction changes for the
> > > airflow in the SUs, slowing the velocity of the air flow on a cylinder
by
> > > cylinder basis. Then, since the SUs feed two cylinders, the air flow
path
> > > is not straight - further slowing the velocity of the intake air.
> > >
> > > So, the Solex's 44mm inlet definately flows a larger volume of air
> > > allowing it to stuff a larger combustible charge in each cylinder than
the
> > > SU's shared 46mm inlet. And, I'm betting the intake duration on the
Solex
> > > Cam reflects this improved ability to charge the cylinders.
> > >
> > > The other difference is the shape of the intake path. The faster flow
> > > through a straigt path (like the Solex) leads better high RPM
performance.
> > > The slower flow through a curved path (like the SUs) leads better low
RPM
> > > performance.
> > >
> > > Personally, I think my SU 2000 is a little anemic above about 4.5k.
And,
> > > since it is easy to tach up a car by downshifting and getting into the
> > > power band when needed - I'd like to move it up into the Solex type
> > > territory. So, just some ramblings. Let me know if there are holes
in
> > > this reasoning, 'cause the investment is significant. The returns
don't
> > > seem cost effective from a 15hp gain perspective - but the change in
the
> > > power curve justifies the expense (that is, if I ever get the $) for m
e.
> > >
> > > Top Down in Houston,
> > > Milton and the BeautyQueen
> > >
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> >
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