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Lean and bog when i hit boost

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dsmdragon

dsmdragon

15+ Year Contributor
135
0
Oct 11, 2006
corvallis, Oregon
Ok I am trying to figure this out and need help. This should probably go on the 420a turbo thread but I think it's a little different topic.

I just Got my turbo kit put on my 420a and it has a vortec 12:1 FMU An FCd at 4.6v and a turbo 4g63 fuel pump on it, and pump rewire. My problem is when I hit 5psi or even around 2 or 3 psi My A/F gauge goes lean and the car feels like it bogs or has nlittle power when in boost. other then that the car runs great and the A/f mix is perfect until then. What could be the problem?
Do I need a 190lph pump
Does the FCD need to be at 4.63v?
or is there something else wrong, like would a boost leak cause this or do I need more then what I have for fuel mod's etc. Let me know:confused:
 
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I would post in the n/t turbo section since I have no damn idea what fcd at 4.63v means. If you dont have a wbo2 then that blinking light you call an af gauge doesnt really work. You may have an issue with fuel pressure rising with boost.
 
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4.63v is what the FCd hooked to the map sensor is supposed to be at on a n/t eclipse that see's boost.
Does the stock Turbo'd cars fuel pump like on the gst/gsx support 7psi on a n/t 420A? and I know the narw. band A/f gauge doesn't help but I'm sure when it just sit's on red lights (which means lean, If you don't understand that either.) isn't a good thing when in boost.... I could careless right now if it just spiked green, at least I know it would have fuel to supply the inj's.
 
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Given you are turboing a n/t car, I would have to say that a wideband a/f gauge is absolutely necessary... and even a logger if they have them for that model.

The narrow is just a light show as everyone will tell ya. They aren't really that accurate. Get a wideband. Trust me, I just came from ignition timing my car about 5 minutes ago. Rather than just seeing a couple blinking lights, its a hell of a lot better to see a digital readout from an independent O2 sensor to give you the precise a/f mixure.
 
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Based on what I can tell from your setup it looks like you would need two things before you go any further, a wide band O2 and some type of EMS (ie...DSM link). Trying to run a turbo without these two essentials is fruitless in my humble opinion!!!

I would also think that you would need larger injectors than stock and a larger fuel pump as well to feed the engine wit that turbo.

How does that turbo you have compare to a 50 trim?

I know that once I jumped up from a stock T28 to a 50 trim, I needed 750 cc injectors, a 255 pump and a AFPR to get enough fuel to handle the new turbo's increase in air volume.
 
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well I know about the A/f gauge. i had it on there from before I turbo'd the car. so no problem there.
As far as I have looked into the problem on this site alot of n/t to turbo guys just run the fmu and fuel pump on stock inj. just not over 8psi. So I just need to know why it's lossing the power when i hit boost and if the stock turbo 1g pump is enough to give me what i need in lhp and psi ratings

the turbo is great. I like the lag it's at 3-3.500 rpm's not to bad. but the 60 trim swap i did, mostly keeps the cfm's through the rpm range better for me. Or so i was lead to believe when looking it up.
 
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Id say if your running a 60 trim then your stock injectors are entirely too small. You can believe that your narrowband o2 sensor is sufficient if you want but everyone here is trying to tell you what works and what is safe and accurate. A wide band will give you a nice stable reading instead of a rough estimate. A rough estimate on a narrowband could be as much of a fluctuation as 11.0-15.0/1 in the green. A 1g fuel pump should be ok for maby 8-10 psi on a 60 trim I would think but dont quote me on that. Get bigger injectors first something between 550cc and 650cc then a wide band. That size injector is assuming your keeping boost at or below 10 psi.
 
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