performance better of course la... coz' mivec got high cams mar... but reliability isn't there. 1.6 head is not exact fit onto 4G91... compression will still be lost, and the head cooling will be a serious issue here, coz' the water jackets placement if not mistaken are different... this is the main reason why those 4G62 plonk in 4G91 head will have gasket leak every now and then. If u 4G91 plonk in 4G92/93 head will have the same problem confirm!
Besides that... 4G91 got rev cut at 6.8k for a reason... u can't just hike up the rev cut to 9krpm or 10krpm wihtout doing something with the internals. Confirm this engine will kong out the bearings, of blow a hole thru ur pistons, even the 1.8mivecs (4G93 block) also kong out their bearings, u think 4G91's wan can last ah!?! 4G93 has stronger internals than 4G91 lar brader. Even so, u know how much it'll cost for u to plonk in a mivec head + ecu + rechip ar? My workshop can get a mivec complete engine at 3.5k... might as well drop in straight the mivec engine. At least it will be problem free, you'll have high compression internals, comes with g'box everything lar.
If u use 1.8 wiring + ecu... it will definitely produce a super-potato mivec engine! This is because of the tuning part. Mivec when open liau will be running on a completely different fuel mapping.. in other words can be said that mivecs have 2 different fuel mappings. But 1.8 ECU can only contain one. So u'll have to choose to either be super rich at low end before mivec open (which means power loss + super makan minyak), or super lean after mivec open (which means ur engine will knock and kabooom.. u get the picture).
IF u ask me... i say dun spend on all these funny mods lar. Just go for pnp la.. change what head lar. Pointless... coz it effects your reliability too much.
