Stage 3 IDC question, Fuel pump alone?

[Davenow]

Will just adding the walbro BY ITSELF bring the IDC's down? Will I need to re tune the fuel map for it?
I hear its a like 1 hour install, plug and play.
If this simple 100$ mod will bring my IDC's down with no additional tuning, I AM IN!

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[Jon [in CT]]

It's conceivable, but unlikely, that a fuel pump alone might reduce maximum IDC. But what are your options if it doesn't? It appears to me your only viable option then would be larger injectors, which would require the larger fuel pump anyway. So what do you have to lose by insalling just the fuel pump now? And please let us know whether it has any effect.

[jbdadog]

It will definately be able to bring your idcs down. As with the extra pressure there will be more fuel per squirt. Tuning it is the fun part. It won't drop them i imagine more then 5% if your luck but it is a good mod to start with(on your way to stage 4). I just finished buying stage 4 because of this problem. I am a p*$$y when it comes to tuning my car so i gave in. Good luck.

[Jon [in CT]]

Originally posted by jbdadog
It will definately be able to bring your idcs down. As with the extra pressure there will be more fuel per squirt.

What?
The job of the stock fuel pressure regulator is to maintain a fuel line pressure that is 3 bar above the intake manifold pressure. when fuel line pressure rises above the 3 bar differential, the FPR opens a return line and sends the excess fuel back to the gas tank. So it seems to me that there are only two scenarios where simply adding a larger fuel pump will produce "more fuel per squirt."
1) the stock fuel pump is unable to pump its rated minimum 130 liters/minute into the fuel line when boost pressure is high, allowing fuel pressure to fall below the 3 bar differential;
2) the fuel pressure regulator or fuel return lines are somehow overwhelmed by the higher flow produced by the aftermarket fuel pump.

[jblaine]

Didn't we go over this already 3 weeks ago? I can't (again) imagine this will do anything worthwhile without an adjustable FPR.

[SysRq]

I suspect that stock fuel pump is not even capable of maintaining 3 bar of differential pressure as you push injectors to the limit... I'd bet money that fuel pressure drops towards the redline. If this is true, then a higher-flowing fuel pump will indeed be beneficial even without an adjustable FPR.

Has anyone measured fuel pressure with stock fuel system?

[Davenow]

I spoke to Mark.
A higher pump will do nothing. He says the Walbro is higher VOLUME not pressure. Also because the factory pressure reg is designed to return the fuel back to the tank past a certain PSI, what I need is a rising rate adjustable fuel pressure reg. It installs in line after the factory reg. About 250 bucks, and will increase the pressure to the injectors.
However he said a really nice RR FPR will end up costing me nearly the same or more than just buying STI injectors.

He also said that really, nothing needs to be done. They have had several cars running around with IDC's in the high 90's and hitting 100% at WOT in places, for YEARS without a single injector failure.

That said I am thinking I will stick with stage 3 while I pay down my CC.
In the meantime I will continue my search for the perfect autoX turbo (spools like or close to stock, but can push 17.5PSI or so easily) Possibly a vf35/29/FP upgrade/ION turbo then get the injectors/pump to go along with it. Maybe next winters project.
I will replace the clutch/flywheel when I do that.

[motoxphil]

Dave,

Here is some info I posted elsewhere:

"If you are concerned with the IDC you can always lean the AFR out as torque drops but you will most likely have to reduce ignition timing. As long as you AFR stays constant and you don't loose control of your fueling, I personally wouldn't worry too much.

2 to 3 degrees less ignition timing will allow you to run around 11:1 but you will have a dramatic increase in egts by doing so.

Take your pick: high egts, lean AFR, and low IDCs or low egts, rich AFR, and high IDCs.

Everything is a give and take."

Thanks,
Phil
TurboXS

[Davenow]

I just did the stage 2 to stage 3 jump yesterday. I still have a bit of fine tuning to do (boost is a TINY bit low, and I am SUPER rich, so I am going to do a LITTLE leaning/logging)
I just wanted to say one thing about stage 3

[Z1 Performance]

SysRQ is eactly right in his statement.

The Walbro/Supra pumps flow considerably more fuel at the same pressure than the stock unit (almost double in fact, given the same voltage to the pump).

Dave - do you have injectors yet? if not, the pump is cheap insurance that your fuel pressure does not drop as revs increase under full boost.

The rising rate regulator is nice, but not necessary at all on most WRX's. The stock regulator does a fine job. The idea is not to give the car more pressure..it is to give it more volume, and keep its pressure linear as revs increase.

Adam