Balancing throttle bodies

Hi guys,

has anyone got a procedure for balancing the airflow through the throttle bodies?

My car is running pretty rough at part throttle so i took the air box off last night to have a look. The air flow through each throttle body seems to be very different. Im guessing that if i can balance them out it will probably run a lot better. All i need to know is where are the adjustment screws for each body and what the airflow rate should be at idle.



You need an air flow meter and have to adjust them in pairs.

The adjustment screw is on the large pulley between the bodies, if you have a standard K4 ECU then they need to be set at 7 CFM at idle.

Some further info here…

BTW Mike has an Emerald ECU fitted which is why his airflow is lower.

I’ve got a synchrometer coming in the post tomorrow. Its suitable for 30 - 50 mm diameters. Hopefully this will fit.

So are there two screws - one for each pair of bodies??

How come the airflow is lower for the Emerald ECU?

that will be fine.

Actually there is only 1 screw that adjusts the balance between each pair - there is no by-pass adjustment at all for the bodies, bet you will have different readings on each trumpet If you do, you can loosen off the butterfly fixings and snap the linkage shut and retighten them without moving anything else, this sometimes sorts them out.

The Emerald is a user mappable ECU so it doesn’t matter how much air it sucks in at idle the fuel can always be adjusted to be at the correct level (actually it does matter but you get the idea)