K-Jet /PIC hybrid

[Tlsalt at aol.com]

James Montebello wrote:

Only KE-Jet has the mixture adjustment.  Plain K-Jet used a mechanical
box using manifold vacuum to operate a diaphram to adjust mixture,
and a bimetallic strip to vary mixture based on engine temperature.

I'm certainly very interested in what the original poster uses to actuate
the plunger in the fuel distributor.  I glanced at this years ago, and
came away uncertain that I could build a servo-based mechanism that could
be fast and accurate enough.  I never considered the airflow sensor to be
all that "wacky".  It was a very nice design for what it did, and it was
used very successfully on some very powerful engines (Porsche 930 Turbo,
Ferrari 308GTBi), and operated very simply and reliably.  It's primary
failing was a high sensitivity to cam overlap, requiring you to get
power with displacement rather than extreme cam timing and revs.

james montebello

On Mon, 23 Apr 2001,  Brian Michalk wrote:

> How are you planning to actuate fuel flow?  The K-Jet has a mechanical 
> fuel distributor with an electrical mixture adjustment.


You guy are splitting hairs.  I have a pre KE-Jet car (911SC) with "plain" 
K-Jet and a separate electronically controlled closed loop mixture 
adjustment. It uses a little pulsed frequency valve in the control pressure 
line operated by an analog box under the seat.  The most interesting thing 
about K-Jet is Bosch didn't think it would work as well as it did, after 
spending years focusing on timing the injection.  Some said it was a folly.  
There are published internal documents on the debate of how it would work 
that became public only recently.  I think it is a lesson on how tolerant the 
I/C engine really is and why a tube with a few holes in it worked for 100 
years.  The fuel distributor is a non-serviceable part and when it goes bad, 
it is done, and internal corrosion is a problem.  The warm up regulator and 
thermotime switch are other culprits, but they usually last through the first 
ownership, which is about all they need to do. The system stayed in 
production for over 15 years.  The 911's and 930's usually make more power 
when converted to EFI, but there are many other reasons for this muddying the 
water.  Some people have used the V8 model on turbo fours with dual injectors 
with pretty good results.

Paul Saltwick
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