question about fuel cut

mk3sons

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Sep 23, 2009
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ya i know... "another one..." this one is different though! iv searched believe me. I was wondering what might cause a almost stock 7m to boost past one bar with no fuel cut? all it has is inter cooler hard pipes, blitz bov, Greddy boost gauge, Greddy profec ebc and a 3" Dp with the stock elbo. From what i understand boost cut should be below 12 psi mine is like 16+ just wondering what you guys think about this. thank you!
 

radiod

Supramania Contributor
Dec 13, 2007
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Is your boost gauge messed? Just throwing that out there.

Are you getting any codes at all? A stock fuel system just simply can not support that much boost without grossly leaning out. Something has to be reading wrong or you're got mods you aren't listing or don't know about.
 

mk3sons

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radiod;1528587 said:
Is your boost gauge messed? Just throwing that out there.

Are you getting any codes at all? A stock fuel system just simply can not support that much boost without grossly leaning out. Something has to be reading wrong or you're got mods you aren't listing or don't know about.

hum i don't know how accurate the gauge is but its a Greddy and it says trust super tuning blah blah blah... i just checked codes and go a 34 and a 21 maybe that has something to do with it? oh and the car came with a narrow band a/f guage that i am pretty sure stays in stoich during boosting.
 

ben1984j

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Jan 18, 2009
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Well the code 34 means that you have hit fuel cut at some point (but how long has it been since you cleared your codes)?

Is it possible the previous owner put in a Lexus AFM that you were unaware of?
 

mk3sons

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ben1984j;1528753 said:
Well the code 34 means that you have hit fuel cut at some point (but how long has it been since you cleared your codes)?

Is it possible the previous owner put in a Lexus AFM that you were unaware of?

ya i hit fuel cut ~16. i need to figure out what the difference is then!
 

hvyman

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I would think you have a lex afm but fuel cut varies from car to car. Usually its 14psi below.
 

mk3sons

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camera is dead maybe these will help?

what a nice before and after hehe :)
 

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supradjza80

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Apr 24, 2007
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mk3sons;1529481 said:
This sir is an excellent question! I'm guessing i just follow the hose from my boost gauge to the engine?

Check your accordion pipe (turbo inlet pipe) for leaks or cracks. Since it looks like a stock AFM and ambient temps right now are LOWish your car should probably be FCing before 16psi (again all cars vary though). Mine with the stock afm is between 11-14psi based on the atmosphere with the afm adjustment screw fully backed out, but i have a wideband to monitor afrs after changing the adjustment screw (still pig rich at 10.5 afr from 3500 to redline). My guess is pirate air getting into the system without going through the afm, so accordian pipe and associated PCV/bybass valve lines to the accordian tube should be triple checked for cracks.
 

mk3sons

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supradjza80;1529492 said:
Check your accordion pipe (turbo inlet pipe) for leaks or cracks. Since it looks like a stock AFM and ambient temps right now are LOWish your car should probably be FCing before 16psi (again all cars vary though). Mine with the stock afm is between 11-14psi based on the atmosphere with the afm adjustment screw fully backed out, but i have a wideband to monitor afrs after changing the adjustment screw (still pig rich at 10.5 afr from 3500 to redline). My guess is pirate air getting into the system without going through the afm, so accordian pipe and associated PCV/bybass valve lines to the accordian tube should be triple checked for cracks.

Okay thanks for the info. i recently got a new accordion pipe so i am sure that has no cracks, but i will check the hoses and what not attached to it. also quick question, what is wrong with narrow band gauges? they generally do the same thing right? as long as it doesn't go to lean i should be fine?
 
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hvyman

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Narrow band gauge go off the stock o2 sensor which "corrects" to fast for a gauge and all you will get is lights flashing and is not something to go off of.

A wide band will tell you what your afr's are all the time and is 100x more accurate.
 

mk3sons

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hvyman;1529511 said:
Narrow band gauge go off the stock o2 sensor which "corrects" to fast for a gauge and all you will get is lights flashing and is not something to go off of.

A wide band will tell you what your afr's are all the time and is 100x more accurate.

mine has no flashing lights. i have no idea what your talking about :(
 

hvyman

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So what does you afr gauge read then?

By flashing lights i mean when your cruising all seems good but when your on it your not sure....

If your unsure read up on wide band and narrow band.
 

mk3sons

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hvyman;1529517 said:
So what does you afr gauge read then?

By flashing lights i mean when your cruising all seems good but when your on it your not sure....

If your unsure read up on wide band and narrow band.


okay well... mine does NOT do this http://www.youtube.com/watch?v=pjSlw_7hNrU

mine sits in lean until i do some hard pulls the it goes up to the middle (center of stoich) and it does hang out there no flashing wavy bs like that one