Hi all, im considering doing either the fuel rail mod on my 1.8 or I have a dual feed rail I can throw on. My question is would I require a re-tuneafter either mod? Im not looking for power gain just reliability of getting fuel to all cylinders. Same injectors will be used.

 

It's been fairly well proven that dual feeding the rail isn't the solution everyone thought it was a few decades ago. General consensus is that cyl. 4 was running hotter than 1-2-3, especially with poorly managed forced induction kits of the era. That being said, no, you shouldn't need a retune with a modified rail or dual feed rail. Log your fuel pressure with a standalone ECU to ensure fuel pressure isn't dropping when at full throttle, near redline, and the highest boost your car will see, if applicable.

 

Would a better option for reliability be a coolant reroute then to mitigate heat in cylinder 4?

 

Yes, that’s exactly the reason for the reroute. The reroute restores the coolant path to the way Mazda originally intended when the B6/BP were installed in FWD cars.