Changing throttle body

[Noshest]

Hi, I have a too large single throttle body with poor low rpm control, otherwise perfect tuned, planning on swap to a 65 mm from the 80 mm throttle body.

Its a turbo charged 1.8L engine, basic AFR with flex fuel.

Anyone have knowledge if its minor adjustment in the maps, or a complete re-tune after the operation?

[derOJ]

not a direct answer to your question, but...
did you try all the idle control strategies?

I used to control the idle via the idle valve. But now I figuered out that controlling with ignition is much better.
So I fixed the duty of the idle valve and let the EMU controll the idle via ignition retard/advance
Works very well...

[Noshest]

Yes, have them both, idle is perfect, but when I drive the car in low rpm, its impossible to drive smooth, even the lightest throttle and the the car jumps, its a lightweight car on 700 kg and 300 hp.

[RHD]

if your tuned om MAP only then theoretically the tune will not change much at all. You may have to pull your transients enrichment back a bit.