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Old 09-28-2007, 08:50 PM   #1
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Default New greddy install problem

Ok,

So i just took today off and installed the greddy kit.

Everything is installed car is retarded 4*. runs great untill it hits about full boost and it just looses power for a sec, the car does not die. Almost feels like a fuel cut-off, first thing in the morning gonna double check the pressure.

What should the fuel pressure be?

What do you think the problem may be?
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Old 09-28-2007, 09:01 PM   #2
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Assuming that the power comes back after the momentary dip, it probably isn't fuel pressure. Not that there's anything you can do about it given that the Vortech regulator is non-adjustable.

It could be that on the transition into boost the ECU is pulling fuel momentarily because it senses that the mixture has gone rich and yet the ECU has not yet gone into open-loop mode.* Do you have a boost gauge, or is the determination that this occurs at "about full boost" being made by seat-of-pants analysis. I postulate that perhaps this is occurring right at the transition into boost, rather than near the point of maximum boost.

Do some searching on the subject of O2 sensor clamps.

*explenation: Normally, the ECU runs in closed-loop mode, meaning that it adds or trims fuel to maintain a stoichiometric mixture. If the mixture is too rich it trims fuel, if the mixture is too lean it adds fuel. This is done primarily because the catalytic converter requires that the mixture be within a narrow range around 14.7:1 AFR in order to do its job. When the ECU determines (by AFM and RPM) that it is running in a very high load condition however, it ignores the O2 sensor and deliberately runs the engine a bit rich. It is speculated that when the transition into boost happens suddenly and at a low RPM, the ECU has not yet decided to run open-loop (it does not think the load is high enough just yet) and thus tries to trim fuel in response to the rich mixture that the fuel pressure regulator is causing.
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Old 09-28-2007, 10:09 PM   #3
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If you don't figure it out by next weekend, i'll most likely be in fairfax & manassas and could look at it.

I think Joe is on the right track, so I don't have much more to add.
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Old 09-28-2007, 11:06 PM   #4
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Just to clarify...

When it loses power, it is almost like something shuts off and the car completely falls on its face, kinda like a fuel cut, its very voilent, and the car dosent go anywhere untill you let off the gas. As soon as you get back on the gas and the boost starts to come in the same thing happens again.

I am running a boost gauge and it is reading about 4-5 PSI when it happens. All the hose clamps are tight and I am fairly certain there are no boost or vacuum leaks. The car idles perfectlyand is smooth until you get on the gas.
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Old 09-28-2007, 11:26 PM   #5
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Ah- I misinterpreted.

So if you're holding low levels of boost (2-3PSI) it's fine, but as soon as you get up to 4-5PSI it begins to hesitate. And under no circumstances can you get beyond this an operate smoothly at 4-5PSI or above. Yes?

That does sound like fuel. For starters, have you replaced the fuel filter recently? (or ever?) Might also be one of those rare cases where the stock fuel pump can't handle the load.

Sounds like you've got a good handle on where to start troubleshooting. The behavior you describe is definitely not normal.

Also, we're certain that the fuel lines to the FPR are installed properly- the line from the rail goes to the side port of the FPR, and then the line from the center port of the FPR goes to the hardline back to the tank.
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Old 09-29-2007, 01:05 AM   #6
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hook up fuel pressure gauge, duct tape to windshield, drive.....should hit about 80psi and hold there. if not you've got fuel delivery issues. if not you might have spark issues, what plugs are you running? what gap?, newish wires?....stuff, like that. base kit is very basic
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Old 09-29-2007, 01:25 AM   #7
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Fuel lines are hooked up correctly, Ill try changing the fuel filter tomorrow, I have one laying arond here somewhere...

I was thinking about the fuel pump on the way to dinner tonight. I remembered reading something about the stock pump not being able to supply enough fuel.

The reccomended pump is the walbro 190LPH HP correct?

I will also double check plugs tomorrow as well...

wires are fairly new, NGKs


Thanks for all the quick replies.

-Kyle

Last edited by jtpaintballwdp; 09-29-2007 at 01:25 AM. Reason: .
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Old 09-29-2007, 01:39 AM   #8
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Hey kyle, if it is violent bucking I'd check the filter and the sock in the fuel system. The lean tip in issue that Joe describes happens just before full boost, about 3.5k to 4k. It's more of a hesitation and then it gets back down to business and boogies to redline. Rx7 owners bitch about this all the time and it usually ends up being the two filter elements
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Old 09-29-2007, 01:43 AM   #9
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All right, thanks for the input, and the Greddy kit=P
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Old 09-29-2007, 05:49 AM   #10
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jtpaintballwdp -

It's not your Fuel Pump either.
Even though you say fuel lines are corrrect, I'd do some double checkin on it. You did install the FPR that came with the kit?
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Old 09-29-2007, 07:25 AM   #11
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jtpaintballwdp.. take a photo of your engine bay! The guys here are GOLD looking for flaws. Photo Hunt style.
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Old 09-29-2007, 08:43 AM   #12
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Yeh I installed the vortech that came with the greddy kit.

Just woke up, gonna try and figure somethings out.

Ill take a pic while I am out there.
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