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And I think this is a totally reasonable position.
The proper volume of fuel for a given engine load is the
proper volume of fuel and it doesn't matter much how it
gets there, at least if you are comparing the proper amount
to an improper amount (ie improperly tuned DCOE carbs vs
properly tuned SUs).
I think John Parker is operating on the assumption that
there are lots of people out there with cars that are simply
not tuned properly. I'd guess this is the correct assumption.
Few people dyno their cars, and even if they did, fewer are
equiped to properly tune their car given the results of a
dyno run.
Once you've got the proper volume of fuel, then things
like air volume and velocity come into play. That's when
you'll see differences between a single downdraft vs
throttle body injection on a DCOE manifold.
Given proper tuning and my understanding of different people's
objection, I'll propose the following summary:
weber downdraft:
CON: Reduces air velocity with the 90 degree bend.
Hard to tune. Unequal length runners not optimal.
PRO: Fewer carbs to tune. Intake pulses more evenly
distributed to carb throats.
holley on weber downdraft manifold:
CON: Reduces air velocity, unequal length runners.
PRO: easier to tune, intake pulses evenly distributed
SU sidedraft:
CON: SUs are all worn out or expensive to buy new. Hard to tune
perfectly to a non-stock motor. Intake manifold unevenly feeds
pulses to carb throats.
PRO: SUs somewhat inexpensive to refurbish. It is possible to
use volvo's tuning specs on a stock motor and get good tuning.
Better intake air velocity from direct shot into intake port.
Easy to tune to 75% of ideal.
Mikuni on SU manifold:
CON: Expensive(ish). Same manifold effects as SUs.
PRO: Easier to tune than SUs. Achieves almost ideal use of SU
manifold by virtue of carb design.
DCOE type carbs on DCOE manifold:
CON: Absurdly expensive to tune. All the bits expensive as well.
Ideal fitment may require putting a dent in the fender.
PRO: When tuned properly these carbs are nearly perfect. There
is a reason racers and ferrari use them.
Throttle body injection on DCOE manifolds:
CON: Expensive and complex to install
PRO: All the performance advantages of DCOE carbs but easy to tune.
Lynx DCOE manifold:
CON: You need DCOEs, injection, or adapt SU/Mikuni carbs to this
manifold. Unequal length runners.
PRO: Fewer carbs to tune (if using DCOE style carb). maximizes
air velocity.
D-Jet injection / D-Jet manifold:
CON: D-Jet doesn't adapt itself to non-stock motors. Hard bits
complex and expensive to adapt to a carbed car.
PRO: Near ideal on stock motors.
Programmed Injection / D-Jet manifold:
CON: Expensive (in time or money or both) to install even on a D-Jet
equiped car. It still won't have quite the throttle response of a
DCOE style manifold.
PRO: Ideal running performance on all motors.
K-Jet on K-Jet manifold:
CON: Rare. Fuel metering device reduces intake velocity. Old and
expensive if some bits break.
PRO: Adapts to wide variety of motor changes. Very very efficient
and simple design. Some bits are so common they're quite cheap.
This was the stock injection sold by volvo in some markets into the
mid 90s, for good reason.
Chris
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