I see what you are saying, and agree! Given the choice of bolting on a Solex
set up vs doing some quality port and cam work, I would take the port work (as
long as the machinest really knew what he/she was doing).
Greg
datsunmike wrote:
> 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
> > > >
> > > > /// datsun-roadsters@autox.team.net mailing list
> > > > /// Send admin requests to majordomo@autox.team.net or go to
> > > > /// http://www.team.net/cgi-bin/majorcool
> > > > /// Send list postings to datsun-roadsters@autox.team.net
> > >
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