|
I think the purpose of this carb setup is to allow people who
have non-stock setups to tune their car without going to the
trouble required for a fuel injection setup or a weber setup.
I have a car with an unknown cam, high compression head, dual
valve springs, and other assorted weird stuff. It has a standard
issue fuel injection exhaust manifold and a random distributor.
Needless to say, there is no correct tune for this motor, as
described in a volvo green book. I have twin HS6 carbs on the
car right now and they kinda work (the car runs, at least). I
bet if I put the car on a dyno with an exhaust reader, I'd see
that the car runs rich over some RPM/load ranges and lean over
others. I also bet that if I could adjust the fuel parameters
easily, I'd be able to get quite a bit more power and fuel economy
out of this motor.
SUs have needles, springs, jets, and damper oil all to adjust.
To tune this setup, I'd need several needles, springs, and so on.
I'd make a change, run the car on the dyno, see if it improved
things, and make another change. At a certain point, I'd have to
start modifying my needles to see if I could tune the car further.
The situation is worse with webers. Webers require bunches of
little brass bits that need to be changed in order to adjust
parameters. Want more fuel at medium RPMs at part throttle? Change
this brass tube and now your settings for low RPM full throttle
are all changed too, so you'll have to change another brass bit and
that'll screw something else up. Back in the day, the car maker
would have 20 motors running on dynos with legions of engineers
fiddling with this stuff to find the ideal setup (Economy, power,
emissions, throttle response). No normal private party has the
resources to tune webers to even 70% of ideal, even if you ignore
emissions.
If the mikunis are more adaptable, they'll eliminate this issue.
If your car is stock, you can go with the volvo green book tuning
specifications and get an ideally running car -- volvo already did
the work for you 30 years ago. If you do this, you'll probably have
a car that runs better than 99% of "improved" motors out there.
If you've got a non-stock cam, exhaust, ignition, or so on, you'll
want something that is easy to tune. And, you'll want to rent some
dyno time and use it to tune your car.
chris
|
