[Diy_efi] CIS EFI via Fuel Pump PWM

[Stephen Webb]

> It works... don't knock it. :-)

Definitely not knocking CIS.  I think it's great.  Works well, is
reliable, and pretty easy to tune.  My point was this:  Why go through any
trouble making an "efi CIS" if what you end up wiht is essentially what
CIS is out of the box.  I guess it's not really the same as CIS (no
airflow plate, basic metering, etc), but I guess I'm missing the
benefit.  Do CIS injectors have some benefit that I'm not aware of?  They
are small, reliable and cheap, but the added size/complexity/cost of some
EFI mods would seem to outweigh those benefits (just use EFI injectors at
that point).  

Don't get me wrong, I'm all for exploring new ideas and methods, but at
some point it seems like a lot of trouble for little benefit.  

> Similar but on a different scale. The K-Jetronic with Lambda
> operates on the control pressure of the fuel distributor IIRC.

I thought I remembered reading that the frequency valve controls the
"differential pressure", which is separate from control pressure?
(I don't claim to be an expert, just a parrot.)


> A large bypass valve can in itself simplify the fuel distributor -
> but if had been that simple and had satisfactory results, Bosch
> would have done it that way, 15 years ago. :-)

:)  True.  Of course 15 years ago maybe the control was just too
expensive?  Also they were building on a solid foundation of K-Jetronic,
without lambda, so their starting point was pretty well determined.  

> It _should_ work to some extent. The consequences of simplification
> may not be worth it. Think of what'll happen if the bypass injector
> gets clogged or fails to open...

Yes.

While on the subject of CIS:

I have read in a few places that the actual CIS airbox / air flap
restricts airflow, and is responsible for up to 20% (?!) loss in airflow.
Does anyone know how true this is?

-Steve


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