Re S4 And S5 Engine
 

I JUST TOOK MY S4 TURBO ENGINE AND TRANY TO FIT IT IN 1ST GEN RX7 BUT NOW I NEED TO BRING MY S4 BACK TO LIFE.I WAS GOING TO BUY S4 J-SPEC ENGINE BUT I HEARED THAT S5 TURBO ENGINES ARE A LOT BETTER. MY ONLY PROBLEM IS IF S5 ENGINE WILL DIRECTLY FIT IN MY 87 TURBO OR WILL I NEED TO DO SOME MODS. I WAS GOING TO GO WITH COSMO BUT I DON'T KNOW IF I AM READY 4 THAT YET. SOMEONE HELP PLEASE!!!!

fit, yes, but there's other problems. wiring/ecu for one thing. try the search under the rear wheel of the featured car in the top right corner of the screen. you'll find plenty of info.
in short, its not plug and play.

THANKS