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Originally Posted by AFBeefcake
I have 1v4 right now.
I plan on staying NA.
Would there be any gain in going to 2v4?
Would adding a walbro fuel pump to ether 1v4 or 2v4 be an a good idear?
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Yes there is a very nice torque gain in going to 2v4. 1v4 with a stock fuel pump and fpr regulator is about the same at wide open throttle as the factory tsb rom is with the fuel pump or fuel pressure regulator. An increase in fuel pressure has the same effect as the 1v4 software for wide open throttle performance, both get rid of the lean condition which causes ignition retard and intermittent hessitation problems. Because they both add extra fuel doing both together causes a power loss at high rpms due to an excessively rich afr. In the case of 1v4 and raising your fuel pressure you do one or the other and 1v4 offers much better part throttle performance, the ability to run 87 octane if desired, and a raised rev limit.
With stage 2v4 however the afr for higher air flow rates has been leaned out in order to let the injectors work for higher air flow rates and allow the fuel pressure to be raised without any performance loss. The 2v4 software should work well with or without the fuel pump and with or without an impreza fpr.