Hope you find my little project amusing......
piper 270/2 cam
mgmetro head with mild porting
mgmetro dizzy with slight curve adjustment
LCB manifold and rc40 two box exhaust system
duplex timing gear
95 ron petrol
Max power 87.5bhp at 5736rpm
Max torque 87.3lb/ft at 4321rpm
Not very highly tuned but the torque curve is like a diesel engine's!
This engine wouldn't pull top gear below 40mph with an HIF carb and now
it can plug along quite contentedly at 15mph! it even starts first time
in the winter with no coughing or spluttering!
Top speed was 125mph before I put the supercharger on.........
Bosch K-Jetronic Overview:
There are many books on the subject and I have gleaned most of the
useful information from them so here are the basics,
The Fuel injection system is pressurized by a high pressure fuel pump
mounted by the tank, fuel then goes through an accumulator (pressure
vessel) which damps out pressure fluctuations and holds a pressure in
the system when the ignition is switched off. The fuel then gets pushed
to the front of the car into a metering unit, this unit is about
150wx300dx200h, the metering unit has a built in pressure regulator
which bleeds off excess fuel back to the tank, make sure this pipe is
8mm inner diameter minimum otherwise the restriction upsets the overall
system pressure (I found out the hard way!) this return has to be
drilled into the highest point of the tank (filler neck is good and
epoxy resin is petrol resistant!)
The metering unit consists of an air filter, feed and return fuel
outlets, 4 injector outlets, a cold start injector outlet, and two
outlets for the warmup regulator (Choke equivalent)
As air enters the metering unit, it is filtered and then goes through a
venturi with a disc in it that floats higher the more air is consumed,
this metering unit works on the mass air flow principle, unlike carbs
which meter fuel according to vacuum and a preset system of jets, when
set up correctly, the unit will always give the correct air fuel ratio
for normal running as it is measuring the weight of the air and not any
vacuum that is being created by the engine.
Idle mixture is adjusted by a small hex screw in the metering unit that
is accessible through a little cap on the top of it, this screw adjusts
the bottom end of the metering range and doesn't make a lot of
difference to the top end(Full throttle), the mid and top end of the
metering range are adjusted by the warmup regulator pressure, this is
where you can adjust your full throttle mixture in the knowledge that
it will be spot on at the midrange as well!
The warm up regulator works the opposite to how you would expect, it
has a bimetallic strip in it that when 12v is applied, it increases the
pressure on the metering arm therefore leaning the fuel mixture, so to
richen the mixture you need to shim it up to lower the pressure(simple
but time consuming, I put a valve on mine so I could adjust the mixture
from inside the car and view it on a lambda sensor display!)
The cold start injector is wired from the starter through a
thermotimeswitch which can be plumbed into the cooling system to sense
the overall temp, when the key is turned the timeswitch lets the cold
start injector run for a short period and then stops to ensure no
flooding if the engine doesn't start first time.
I have to admit that I have never needed the cold start injector in
sunny sussex so have just used it to block the hole in the manifold!
There is also an idle valve that bypasses the throttle butterfly when
the engine is cold, this is fed by the ignition feed that also feeds
the warmup regulator.
The injectors are activated by fuel pressure from the metering unit and
only spray above about 40psi, they are constantly running which is why
the system is sometimes referred to as CIS
Constant Injection System.
I Used the golf manifold but cut off the four runners and had two
runners tig welded on to the outer pair and used an old mini manifold
as a JIG to bolt it to when it was being welded.
I then got four tubes lathed up to accept the injectors and drilled the
manifold diagonally (two in each runner) so that when the injector
tubes were welded in they lined up with the back of the valves roughly,
the injectors just push-fit into the tubes, always get new O-rings for
them as the older ones tend to perish and the new ones are
nitrile(green). Make sure that the injectors don't snag your exhaust
manifold before you get them tigged in (I have used aluminium brazing
rods and they have been fine for 30,000miles
If you have any questions then do ask them, as this is a nice
conversion once set up correctly!!!