K Jetronic

[C M Smith <cmsmith@domain.elided>]

The K Jetronic was an earlier analog injection system than the L Jetronic. 
It used an inverted cone type air volume meter that was directly connected 
to the fuel distributor center "plunger". As more air was drawn in the 
center plunger was lowered in the fuel distributor allowing more fuel to be 
injected to each cylinder simultaneously. The central characteristic was 
that it was a continuous injection system, as opposed to the timed 
electronic ( but still analog) L Jetronic. Interestingly, engineers 
discovered that the engine could care less whether the fuel was injected to 
the intake port when the intake  valve was open or closed, or even 
continuously, so injection timing was a waste of time except as a way of 
adjusting mixture.

The K Jetronic was a brilliant system, actually more elegant mechanically 
than any carburetter. Its day in the sun came when some guy at Volvo, SAAB 
or Bosch realized that mixture could be fine tuned by playing with the fuel 
pressure through a feedback loop. The initiator of the feedback loop is the 
now ubiquitous O2 sensor (even Formula One engines use these babies) which 
signalled a valve in the line pressure to bleed excess fuel pressure back 
to the fuel tank, leaning or enriching the mixture as the O 2 signal pulses 
varied. The Bosch K Jetronic Lambda Sond system was invented in about 1975 
and first appeared on Volvo and SAAB cars destined for the US and Canada. 
The SAAB 99 engine of 1985 cc was the most powerful 2 litre engine ( 118 hp 
SAE Net) on the NA market at that time essentially because they had first 
dibs at this new system with an engine that could really pump out the power 
( well over 225 hp in naturally aspirated Rally trim with a trick twin cam 
4 valve head, stock block, now capable of over 300 hp in turbo streetable 
form, and about 800 hp in the Pikes Peak 9 3).

More than you needed to know eh?

Cheers

Michael
Michael Smith
Calgary, Alberta
Canada
91 Alfa 164L, White, original owner

--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided