| You have to balance the throttle bodies mechanically with both air bypasses closed, else the mechanical balance of the butterflies will be distorted by the air being bled in down stream of them.
Once that's done, then balance the CO as above.
One other thing to bear in mind is measure the CO at the take offs on the down pipes.
The exhausts are linked at the collector so measuring at each can will again distort the readings.
It can be done but you need to monitor changes in CO pretty quickly as your measuring the average of both pots. The gunson will not react quickly enough. The sampling pump isn't big enough.
The theory on correct CO being achieved just by balancing the throttles is a sound one, but in practice won't ring true.
The rear cylinder is running hotter and the inlet tract not as vertical as the front one. Those two elements affect the combustion as well as others, so the rear will run richer on "identical" settings, hence the bleed screws to balance things up. Even on near identical CO readings, the corrected values for CO, O2, CO2 and lambda usually differ between cylinders.
If the highest CO reading you can get is 2.4%, somethings not quite somewhere would be my guess.  |