what is the point to upgrade fuel pump?

[Vovan]

if not upgrading fuel regulator? as the stock one is still configured for stock pressure. or will the computer increase the pressure itself when needed?

i'm also confused about the following: large pump and increased pressure - this means the mixture is rich, and will be rich untill we reach high boost, so under the 4500 revs the mixture will be very rich? or the ECU will control it and we change only MAX fuel pressure by adjusting fuel regulator?

[dabigbolf]

the way i see it....

Bigger fuel pump is needed when your stock fuel pump isn't pumping enough fuel to the injectors fast enough, which can lead to hesitation when giving it some stick....

So you get a bigger fuel pump which pumps more litres per hour so when your motor does need the fuel your injectors always have it.

You can have a massive fuel pump system, your car is not going to run any richer because of it. Just means your injectors will have enough fuel if need be.

How much fuel actually goes into the motor is all controlled by your ecu. not by the amount of fuel actually getting to your injectors.....

could be wrong, but that seems logical to me, thus a saf-c is used to control your richness or leaness, as stock ecu cant do that when you do the mods such as exhaust, cooler, and then raise boost...

[Lippo]

Your right with the fuel pump issue.Doesnt matter if you have a 1000hp fuel pump,its the ecu that controls the amount of fuel pumped in.

[Brody]

Though a higer pressure will push more through the injectors when they open?

[b2barker]

I could be wrong here but:

1) The ECU controls injector pulse widths and has no knowledge of how much fuel is flowing.

2) A "bigger" pump may just be capable of more flow, with the same pressure. ie. maintaining the same pressure under increased duty cycle.

3) If you have a larger pressure fuel pump you should be regulating the pressure because of 1)

If I am wrong please tell me, it's the only way I'll learn

[browny]

This is my understanding - it may not be correct.

An injector is basically a hole that is open or closed. The rate at which fuel passes through this hole is governed by the pressure differential either side of the hole (ie higher DP = more flow, lower DP = less flow). The amount of fuel entering the engine is controlled by the length of time the injector is open (ie higher Dt = more fuel, lower Dt = less fuel).

The ECU controls the length of time the injector is open and the fuel regulator controls the pressure differential. In a turbo car the regulator raises the fuel pressure with boost so the DP across the injectors is constant. Any excess fuel is returned back to the tank.

A fuel pump has a curve which relates its flow and pressure. Typically as pressure increases flow decreases. An engine will requires a certain max flow at a certain max pressure. The pressure is set by the reg and the pump is designed to meet this duty.

If you start increasing power, the fuel flow and pressure requirement from the engine changes. If the pump cannot meet the flow requirement the fuel pressure drops, less fuel is injected and the engine leans out - which is sometimes fatal.

[Sydneykid]

Hi guys, I quite often see the comment, bigger fuel pump = richer A/F ratios at all RPM's. I have never seen this happen in real life. As Browny has said (very succinctly) increasing the pressure increases the amount of fuel that goes into the engine. Increasing the flow rate of the fuel pump only makes a difference when the old pump could not keep up.

The fuel pressure regulator and the ECU are the real determiners of fuel flow into the engine via the injectors.

[Vovan]

but aren't the stock fuel pump push the max amount of fuel that stock injectors can handle?

[browny]

In a perfect world yes.

I would expect the designers specify components that are oversized to allow for things like wear/fouling etc. How much each item is oversized is a anyones guess.

Also, I suspect the specs of components like injectors are influenced by things like "standard" tooling so they are cheaper for mass production. eg why develop the tooling to make a special injector with a 0.2467mm hole in the end when you have tooling to produce injectors with 0.25mm holes.

[siksII]

What you guys are saying seems perfectly logical, although, (even though sydneykid has said this does not happen in real life, and has a much larger chance at being right than me....) everyone who gets an aftermarket fuel pump says that their car drinks more petrol than before the pump.

My car seems xtra thirsty compared to others as posted in fuel consumption threads, it is basically standard, and i have partly believed its because of the aftermarket fuel pump fitted.... Often even at lower revs(around4500) i see puffs of unburnt fuel come from the exhaust on lift off..

Do you think the increase in consumption is just in our heads(quite possible..). Is it possible for the standard regulator to allow more fuel in due to the aftermarket fuel pump (not sure how the reg works)?

there has been a thread where people have complained about the fuel pump/consumption issue before.

[Sydneykid]

Originally posted by siksII

Often even at lower revs(around4500) i see puffs of unburnt fuel come from the exhaust on lift off..

For that authentic 2 Fast 2 Furious look...... *ricey*

S of S

[JimX]

I installed an 044 pump in. My engine is still leaning out at 215rwkw. The next step is an upgraded regulator and/or injectors.

I got the S-AFC tuned anyway, and my economy is around the same or even a little better (just did a 13.8L/100km almost all around town in traffic).

[JimX]

Originally posted by siksII

My car seems xtra thirsty compared to others as posted in fuel consumption threads, it is basically standard, and i have partly believed its because of the aftermarket fuel pump fitted.... Often even at lower revs(around4500) i see puffs of unburnt fuel come from the exhaust on lift off..

Unburnt fuel between gear changes can happen no matter what. At this point the throttle is closed and no engine will suffer from leaning out with no air going in. Usually it indicates an aftermarket blow off valve, not an aftermarket fuel pump.

[dabigbolf]

my question is, why stick a massive fuel pump on a stock engine.

mods should be done in proportion with each other.

over kill can be good in some areas... like tyre width... (can never have to wide)

But if your engine is still stock, just keep the stock fuel pump, untill you upgrade other stuff aswell.

[Vovan]

this is what i understood... upgrade your fuel pump - the pressure will be the same and engine will get as much fuel as it needs, but once you upgrade your engine - it wil lreuqire more fuel and will automatically increase its flow.. but if you don't have pump, you won't receive more fuel.

[JimX]

Originally posted by dabigbolf

my question is, why stick a massive fuel pump on a stock engine.

Because the stock pump is finished up around 215rwkw, along with the injectors. You can increase the limit slightly by fitting a bigger fuel pump and a rising rate regulator. My car is happy to go through 215rwkw with the current turbo, but the pump and injectors are limiting it.

I only have an 044 only because it was dirt cheap. A 910 or 984 is more than adequate for the kind of power I'm looking for.

[rob77]

I currently upgraded my turbo to a trust td06-20g, my power went from 245hp to 344hp at pretty much the same boost. At this point I am maxing out my fuel pump and injectors, both stock. Tomorrow a bosch 910 is going in and I will be ordering a set of sard 550cc injectors to suit over the next couple of months.

[R31Nismoid]

As people have said... a bigger pump just increses the flow rate.

I've just done a Walbro pump... (RB25DET) and now i've reached the limit of the injectors.

I can either get a different regulator and increase the pressure to get more fuel.

Or upgrade injectors to flow more.

[rob77]

I think its best to just replace the injectors as expensive as it can be wacking in a fuel reg to increase the flow on already max'd out injectors seems pointless... just my 2cents worth. Shame its gonna cost me about $3000 more to get the ecu and injectors in and tuned. *sigh* never ends

[R31Nismoid]

Yeah... should've put that in.

Fuel reg will run over not much after... so i'm gonna do injectors.

550cc is enough for a bit over 300rwkw.