Multiar produces significant gains in performance, CO2 emissions and torque. However, Fiat will not simply allow the enhanced power outputs to go to market without adjustments to power and torque, probably to maximise economy.
And when Fiat says the Multiair heads can be fitted to current engines, what they mean is current blocks, because the system is complicated and has a highly developed mechanico/electrical system to activate the valves.
The T-jet will continue, as will many current engines, but with the Multiair head fitted. Ditto the new 1.8 which has been launched with direct injection but as yet no Multiair. Within two years all Fiat petrols will be Multiair and all Diesels Multijet2.
The small 1.2 four as used in GPs, 500s and Pandas will be dropped. It will be replaced next year by the sgv 0,9 twin with Multiair, developing between 65 and 105 bhp depending on whether it is turbocharged or not. This engine is smaller and weighs less than the curreent 1.2 four, so will allow good steering lock and a light, nimble handling. And in every iteration it produces less than 100g/km of CO2.
The new engines (not sgv) are supposed to be launched at Frankfurt in September on the Mito and revised GP.
Apparently production of the current engines is already running down and the new Multiairs being cranked up.
I don't think it will make much difference to resale values because a) people are afraid of new technology and b) most people don't know or care what's under their bonnets anyway.