[urq] CIS airflow meter limits HP?

[james accordino]

--- JShadzi at aol.com wrote:

And it is VERY easy to over carb a V8.  That happened
all the time, probably still does.  My 371 C.I. SBC
with worked heads and a rad. cam could bearly support
the 750 c.f.m. carb.  Idle and low speed operation was
a joke.

> Interesting to notice, when
> V8 guys upgrade their carb's, the bigger carb's are
> rated by CFM, but for
> some reason, Audi CIS guys never think that theri
> CIS meter (basically a
> carb) will ever become an air restriction, though by
> looking at it, it almost
> gives me an air-flow-heartattack.  Though I've never
> actually done a flow
> bench test on the airflow meter, IME, any car with
> Audi CIS is very tough to
> tune over 250hp (yes, dyno #'s there), though many
> factors start becoming
> restrictive above that number, you are trying to
> flow 300hp of air through an
> airflow meter designed to flow 165.

I think this is right on target.  They can't produce a
bucket for an air cone.  This car was intended for the
general public.  Idle or most certainly off-idle/low
rpm performance would have suffered greatly.

> It stands to reason that the CIS system is limited
> to certain levels of HP.
> Audi/Bosch engineers would be
> poor engineers if they developed a fuel system for a
> 165hp car that was still
> capable of fueling to 300hp.  That kind of
> application would cause very poor
> resolution in the stock application, why overdesign
> a component to the point
> that it would sacrifice the intended application??
>
> The CIS system is precise and flexible, but only to
> a point.  It will run
> well all day long with 12psi boost and about 225hp,
> but once you try pushing
> past that point, every hp is an excersize in
> diminishing returns (IME tuning
> Audis for over 4 years, many of them race cars).
>
> Anyway, the point is mute, show me a CIS Audi that
> can actually dyno more
> than 275hp, and I'll rest my case.
>

I wonder what the maximum CFM of the airflow meter is?
BTW, maximum I EVER got from my SBC was 419hp. Earth
shaking idle at 1400 rpms.  Dog below 4500 rpm, and no
real rip till 55-5700.  No chance of passing
emissions, etc.  That's 8 cylinders and 371 C.I.  250
or more from 2.1 liters for an engine that you expect
to idle, behave at low speeds/temps., and pass
emissions seems like a pipe dream.  To me at least.

Jim Accordino

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