With exhaust and intake manifold do i need to tune my car if i got a basic fuel return system? Ill be putting a SC and a bunch of other things on too but in a couple months so im wondering if its safe to run my car with its current mods if i put a FRS on it and get it tuned months later. What would happen?

 

u should be ok. just might not get an optimal air/fuel ratio.

 

I would just wait to install the RFS until you get the supercharger installed.

 

if you install the FRS, but do not hook up a vacuum line to the regulator, and set the fuel pressure to match stock... it will have no effect on the tune at all.

 

Would an FRS give my current DW 550cc injectors the capability to push more fuel for more power, even if its just 20% more?

~Dv8

 

you can increase fuel pressure with a RFS and get more out of the injectors... how much more depends on a few factors. it requires a complete retune of course.

 

Also keep in mind, a Walbro flows significantly less as you increase fuel pressure. And raising 10% fuel pressure does not add 10% more fuel - it is much less than that (the sqrt of the dif).

 

So why is it that the G or Z need such big injectors for not that much HP? Im running 550cc DW and Im at 85% DC at 9.5PSI. Its only making 300ish on a mustang dyno.

A 300zxtt for example is well into the 400's hp on 550cc injectors.

The way I look at it, the FRS should give my 550cc a lot more head room, but your saying no.

Is it because the stock Fuel system is set at 52psi from the factory and thats high to start with?

~Dv8

 

the purpose of the rising rate FPR is to increase fuel pressure as you increase boost.

Static fuel pressure is the fuel pressure that is in the rail relative to the vac/pressure in the manifold. The purpose of a fuel pressure regulator is to give the injectors a relatively constant amount of fuel pressure so that the ECU is easier to program. Here is what I mean; under vacuum, with out a fuel pressure regulator, MORE fuel would be injected than normal since the manifold is "sucking" the fuel into the rail.

To compensate for this, the FPR drops the pressure in the rail so that not as much fuel is available to be injectors. The opposite happens under boost. The pressure in the manifold pushes back on the fuel trying to come out of the injectors. With out a fuel pressure regulator, you would have to keep the injectors open longer, or use bigger injectors, which can make having a smooth idle difficult.

With the FPR installed, when the boost pressure in the manifold increases the regulator increases the pressure in the fuel rail in a linear proportion so that the same relative amount of fuel is injected. AKA, with vac fuel pressure goes down, with boost, fuel pressure goes up..

SO no, a FPR doesnt give more headroom. Like Phunk said, you can bump the pressure as a bandaid, but thats not the proper way to do reduce IDC's

 

Manifold vacuum isn't going to "suck" more fuel out of the injectors.

 

its a good thing vacuum is near 0 at WOT, so you'd never know...

but you agree that boost pushes against the fuel? not sure why you would think that vacuum doesnt pull.

 

Sure, vacuum helps suck the fuel/air mixture into the combustion chamber, but it won't literally suck extra fuel from the injector itself.

Maybe we are talking about two different things.

 

the stock fuel pressure regulator is static, and never changes fuel pressure.

this means that the fuel pressure differential between the rail and engine is higher at idle, and lower under boost.

adding a 1:1 vacuum referenced fuel pressure regulator will, rather then hold a static fuel pressure, hold a static fuel pressure *differential*.

When compared to the factory static pressure regulator, the 1:1 referenced regulator included with the FRS will aid tuning by having a lower differential at idle, meaning less MAF voltage correction or injector pulsewidth reduction is required when using a piggyback. This assists in creating a cleaner smoother idle and cruising tune with piggy backs.

Under boost, it helps by raising the differential, thus getting more out of the injectors once the pressure differential passes the stock pressure minus manifold pressure.

Basically, in easy terms, the FRS is using a 1:1 vacuum assisted regulator to alter the fuel pressure curve to assist you in tuning by giving you dynamic pressure that is more appropriate for the current engine load. under any given engine load, the regulator is aiding your tuning and requiring less dramatic fuel map tuning. It smooths everything out, and gets more out your injectors when you need it, and less when you dont.