Mini (throttle bodies)
question is whether the Canems ECU can run a Mini with motorcycle
throttle bodies. The answer is yes. To prove the point,
the test car (originally fitted with an MPI injection setup)
was converted with throttle bodies from a Kawasaki GPZ1100
and a custom-made inlet manifold.
throttle bodies give the opportunity for a significant power
increase for minimum outlay, due to the abundance of second-hand
motorcylce spares. From the factory, the GPZ1100 was fitted
with four throttle bodies (one per cylinder). Naturally,
the Mini engine only requires two, as pictured below. These
castings were actually 34mm in diameter which provides adequate
airflow for a 998 engine whilst maintaining a crisp throttle
As a first
step, the throttle bodies were respaced to suit an A-series
cylinder head. With an extended throttle linkage this can
easily be achieved (particularly with separate throttle
castings, such as these Mikunis).
a Weber carburettor, it's widely known that a longer inlet
manifold gives better results. Typically, this requires
a bulkhead box to enable physical fitment of the carburettor
itself. One of the advantages of the Canems injection system
is that the ECU maintains balanced air/fuel ratios between
all four cylinders, rather than relying on the 'wet-manifold'
principle of a long and convoluted casting. Thus, the throttle
bodies can be mounted almost straight onto the cylinder
head itself. This makes fitting easier and maximises air
flow through the manifold itself.
car, a manifold was fabricated from mild steel. A simple
jig (pictured above) was employed to ensure accuracy. Fabricated
from scrap metal, the cost of these two inlet manifold stubs
was minimal. Rubber mounting boots help to insulate the
throttle bodies from the heat of the engine itself .
on the car itself, there is more space available than there
is with a single SU carburettor. Naturally, performance
is also vastly improved over such a setup. The car remains
entirely tractable around town, providing good fuel economy.
When required, there is the power (and distinctive Weber-style
bark) available however.
time being, foam filter socks are used - placed onto the
original motorcycle ram pipes. Naturally, a plenum with
cold air feed could be installed as there is plenty of room.
specification of the injection system is as follows:
GPZ1100 throttle bodies (34mm diameter)
MPI Mini fuel-rail and 3 Bar pressure regulator
BMW Cooper S injectors (330cc/min)
time being the car has been tuned on-the-road only, with
data from two lambda sensors. Despite this, there is already
a vast improvement in performance over the previous setup
(ie. factory-fitted MPI injection). The engine is much more
willing to reach higher RPMs, and it seems all of the low
speed torque of the factory setup is maintained.
airflow through the twin throttles means more fuel is required
(at the top-end of the rev range, under load). The injection
timing has also been retarded, due to a greater distance
from injector to cylinder.
without saying that the car will be back on the rolling
road soon and you'll be kept informed of results. From the
feel of the car, we're expecting good results.