SAFC: compensating for bigger injectors/pump?

[CyberEye]

Is there a certain percent I should lean out at first to compensate for my 550's and 190lph pump, use that as a baseline and then fine tune from there? Or should I just start at 0 and slowly work my way back untill my fueltrims 0 out

[steve]

For injectors I use the formula % comp = (old injector/new injector) - 1.

So for replacing 450cc injectors with 550cc injectors assuming the same base fuel pressure:
450/550 - 1 = 0.82 - 1 = -0.18 or -18%

Again as long as you fuel pump and fuel pressure regulator are set to the stock base pressure there is no adjustment for them required.

You will then have to make some adjustments to the low end to correct for the difference in deadtime between the old and new injectors. Most upgraded injectors have longer deadtimes than stock so you'll need more fuel than the basic calculations at low injector pulse widths to make up for the fact that the injectors don't open as quickly.

Steve

[keltalon]

Originally Posted by steve

For injectors I use the formula % comp = (old injector/new injector) - 1.

So for replacing 450cc injectors with 550cc injectors assuming the same base fuel pressure:
450/550 - 1 = 0.82 - 1 = -0.18 or -18%

Again as long as you fuel pump and fuel pressure regulator are set to the stock base pressure there is no adjustment for them required.

You will then have to make some adjustments to the low end to correct for the difference in deadtime between the old and new injectors. Most upgraded injectors have longer deadtimes than stock so you'll need more fuel than the basic calculations at low injector pulse widths to make up for the fact that the injectors don't open as quickly.

Steve

what about 390cc to 550s?

[steve]

Originally Posted by keltalon

what about 390cc to 550s?

What about them. I assume you can do the math.

Steve

[otofmyway6]

lol that made me laugh out loud