Hi folks. I have a question. I have a dc5 with k24/20 tuned with kpro @260hp. I am still using stock fuel pump and wanted to change to a walbro 255. Will this affect the whole air/fuel ratio or will it be the same? Any input? Thanks

 

It is just a change in fuel volume. It will nor alter your tune at all

 

^As Shodan said. Changing the fuel pump is safe on the stock tune. Changing the injectors (to a larger flow) is not, and will require adjustment.

 

Changing to a higher volume fuel pump will increase the static fuel pressure in a dead-head system, increasing the amount of fuel delivered at the injector. At idle and light throttle loads, this will likely simply show up as larger short-term and long-term fuel trim values and a loss in fuel economy, however, at WOT, the greater fuel volume provided by the big pump will make the car run richer and richer as the duty cycle increases because the stock pump cannot provide maximum pressure under high demand loads. In short, your tune will not be dangerous... but it will not be optimum either.

 

Think again, because it is returnless system, doesn't mean that it's not regulated.

 

I never said it wasn't regulated... what I did say is that just like in a return system, the small bypass orifice for the regulator cannot dispense of the increased volume created by the higher output fuel pump, so the feed pressure increases and thus, the tune requires a bit of clean up.