On Thu, 3 Oct 2002, Walt Philipson wrote:
> I've always had a questions about how much webers help. Do they do a better
> job of metering fuel across the range of rpm and load, there for providing a
> fatter power band? How does this compare to Richard Goodes three ZS set up?
On my soap box again...
Webers in and of themselves don't necessarily help. What they give you is
the ability to tune the available fuel to whatever use you decide. So, if
you want a boulevard cruiser - no problem. You want a screamin' 7000 RPM
TR6 - no problem. Well, no problem as far as the "fuel mapping" is
concerned.
:-)
You can set up a fatter power band, but how you accomplish this is the
"black art" of Weber tuning. For example, most street driving is done on
the idle jets. You obviously utilize the "mains" when you go to wide open
throttle. There is a progression from idle to main jets. Tune this "right"
and you're in fat city. This tuning is done by replacing idle jets,
emulsion tubes, main jets and air correctors as well as accelerator pump
jets and last (but not least) fuel pressure and float height. Everything
is inter-related.
How does it compare to a GoodParts triple Stromberg setup? Well, the total
area of the carb throats on the Webers is probably 30% more than the
triple strombergs. So the potential for more air flow is there for sure.
However, nothing comes without cost. So, what you get for performance on
the idle side of things _may_ effect your power at wide open throttle. As
you can probably imagine - a so-called individual runner intake manifold
will flow okay at low air velocity and it will (hopefully) flow a lot more
at WOT. What happens on a street application is that the airflow is so low
at the carbs that you get "reversion" - the carbs "spit" some unatomized
fuel back out the throats. This is innefficient.
So, while you can tune them for a street application, the amount of
benefit is marginal. If you tune them for racing, the tuning variations
are truely mind-boggling. You get a lot more benefit in the racing
application so the effort is "cost justified"
But, like I've said in the past - the ooohs and aahhhs that you get when
you pop open the bonnet has some value too... so the answer is "it
depends". The one real gotcha is that the $1500 (or whatever) acquisition
cost of the Webers is only the tip of the iceberg... you'll spend (easily)
another $250 to $500 getting the carbs dialed in to your application.
That's equal to several ZS rebuilds!
Sorry for the wishy washy response... Weber DCOE's let you do _anything_.
The key is whether you can "do" good things as opposed to introducing "bad
things". I ran Weber DCOE 40's on the street for a couple of years. Around
town, the mileage was awful (sometimes as low as 15 MPG). However, on the
freeway, at 70 MPH, I averaged about 25 MPG. That's as good if not better
than the stock Zeniths. FWIW, I switched back to the Zeniths and they have
been rock solid the last 5 years (knock wood) and the 20 years or so
before that.
> Walt Philipson
> 74 TR6
regards,
rml
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