Yura

closed loop work or no(cos st3)? For example if I will cruise without boost.
I have cos whith L8 ECU and I want to order the st3 chip MSD, but there is a lot of difference in cost and I don't know is this difference propriety or no. I use my car mainly for drive within city(but use it hard), sometimes for drift or drag.
Thanks for any advice.

foreigneRS

there would be absolutely no difference if the non-lambda chip was perfect for your engine and ran at lambda = 1 at those conditions anyway

but there could be a significant improvement if it's not, and it is unlikely to be perfect at all off boost conditions and idle due to component differences and wear that the closed loop takes account of.

it's not just the fuel price that you save either - it's also lengthened service intervals as you wouldn't have to change the oil as regularly, or the spark plugs etc