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 me.
>
> Top Down in Houston,
> Milton and the BeautyQueen
>
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