Return fuel line.

[CTScott]

Originally Posted by abstractmethod

My goal is to find out how necessary a return fuel line is for turbo application on a 1nz-fe..

In a perfect system one with a 1:1 regulator would be used. For most typical applications (up to about 8 psi) it isn't essential, and very few of the boosted Yaris owners go that route. With the stock fuel pump one is not required, but with an upgraded fuel pump you may find that the manufacturer says that one is required. With a closed system there are spikes in pressure (that can shorten a pump's life) when the injectors close. With a return system those spikes are significantly reduced, since the regulator is close to the valves (injectors).

So, the question is how much boost are you intending? If you are going to stay in the 8 psi range, then you don't need to upgrade the fuse pump, but if you are going to go above about 12psi, then you will start to run into the limits of the stock pump.