I’m having a debate with a mate and hopefully someone on here can answer my question. I have a baxr6t it has been tuned to roughly 400hp. I blew up the original motor as it overboosted and have since built a new engine with forged internals blah blah. I have fitted a new boost controller/solenoid. But I stupidly removed the old fuel pump which was a walbro 460 and replaced it with a 255. Dumb I know who downgrades. I know I need to get it retuned but my question is will having a smaller pump lean it out and not supply enough fuel? It still has stock injectors and fpr. I’m probably wrong but the walbro 460 wouldn’t be used anywhere near its potential and the 255 would be near its limit but does the different pumps vary the fuel flow rate or is however the ecu is tuned negate how much fuel it requires?

 

if you've still got stock injectors and FPR then downgrading/upgrading the in-tank pump makes little difference... I doubt you've got 400hp at the wheels with stock injectors, too.

I doubt  the 400hp as well was told that when I bought it. 

255 is plenty for 400 horsepower. Remember too that the fuel pressure regulator controls fuel pressure, not the pump, assuming the pump is up to the task. Therefore it shouldn't need a retune after a new pump.

The exception is that a 460 might have been overwhelming the factory FPR at idle so it might have been tuned around higher fuel pressures.

I doubt the pump change will cause you issues, but you can always get the car run up on a dyno for $100 or so to check actual power and AFRs.

Thanks guys that was my argument with him is that I didn't think it would make much difference as it only has stock injectors and fpr. He reckons that because it was tuned with the 460 that by putting in the 255 it would lean out massively at higher rpm now. The car does need a retune as it has a new engine plus a heap more upgrades, but it actually runs really well and I checked the plugs and they have no sign of leaning out. He also said that a 255 is only good for 200kw in a 4 cylinder at most. Think I've won that battle haha!

Yeah nah your mates an idiot.

 

Helpful post is helpful 

Making 440hp with a 255 and stock fpr 🤷‍♂️ 😋

 

I think you'll be okay lol