adding more fuel and the tuning process...

[Syndicate]

going to go 550cc's and an APEX'i safc. now, i assume ill need an upgraded regulator for the fuel pump and the injectors, so how is tuning done with a SAFC and a new FPR? set the FPR to get in the ball park and then fine tune with SAFC? or am i thinking of a rising rate FPR that would give me problems?

thanks

[Syndicate]

ps--is 550 enough for 400 whp? or would 650 be better?

[Van]

Whether or not you need to upgrade to an adjustable fuel pressure regulator depends on what you base fuel pressure is, after your fuel pump upgrade. Seems some people need them, some don't. The pump chosen may have an impact on this.
An AFPR and a s-afc are different things that will net different results.
A S-AFC will tell the ECU what you want it to see for airflow, the ecu then turns on the injectors for that amount of air. With the s-afc, you can either add more air/fuel (+%) or subtract air/fuel (-%) from what the MAS is seeing, in order to yield more power, get better timing advance, less knock sum, compensate for a hacked MAS at idle, delay fuel cut with bigger injectors, etc.

You can make small injectors bigger, up to a point, with more fuel pressure. You'd want a fuel pressure gauge.

I think there is an injector/HP formula over at Extreme Turbo and DSM Performance. It will probably show you a *really* large cc/inj though. 660's would be better than 550's for your stated goal, IMHO. There is a link to their site on the top left side of this page.

[Syndicate]

ok, that makes total sense! thanks!