now is it right that people install a S5 fuel pump into there S4 because it pumps more fuel.

 

please answer i got to know if this is right or something like that.

 

no the injectors and the pressure regulator only allow so much fuel HOWEVER if the S5 pump flows more the upside is it will continue to supply fuel longer then the S4 pump so u wont be "working the fuel pump" on WOT..

 

Actually that's wrong. If the pump had greater capapcity then the injectors and FPR can do nothing to stop more fuel flowing all the time.

In this case though S4 and S5 pumps have the same performance, so there's no point swapping.

 

thats not true the injectors are rated at a certian psi they can only flow the max psi the injector can flow so in this case u will just have higher fuel pressure IF the pump pushed more pressure then the stock s4.. which means the line will hold more pressure but the injectors will not spray any more then they are rated for!

the idea behind a high psi pump is so u dont lean up due to lack of pressure at wot! normally this is only a problem with turbo vehicles!

 

No office, but you really don't know what you're talking about here. Injectors are not rated "for pressure". They will flow a particular volume at a particular pressure (i.e. 550cc/min @ 250kPa) for S4 TII), but if you increase the fuel pressure, the injector will flow more and if you decrease the fuel pressure, the injector will flow less. Simple as that, there's no way around it. When it's open an injector is just a hole for fuel to be pushed through, nothing more.

 

Shouldn't the FPR limit the pressure that the injectors see?

 

yes the fpr regulates everything and btw an injecotrs MAX flow is it if u buy 750cc injectors they MAX and 750 no way to spray more!

 

No, it's only job is to keep a constant pressure differential between the fuel rails and the manifold. It can't compensate for changes in upstream pressure. More pressure in = more pressure out.

 

so I'm guessing either way it wouldn't be a good Idea to change it out would it be just keep it in the garage until my S4 fuel pump goes out right.

 

Unless the pump is giving you problems there's no point in changing it. Unless you've engine is extensively modified there's no need to upgrade it anyway.

 

ok thanks.