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  #1  
Old 11-22-2006, 10:06 PM
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curly2k3 curly2k3 is offline
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Um yeah, help needed, ALOT

well i finally got to RSmotors to hook up the SAFC and dyno tune with Ron, well as much as i would like to report some bad ass numbers, yeah no. leading up to it all here is a breif backround of the recent.
about a month or so ago now we built a 2.5" catless Y pipe, then a full 3" cat back... we also modified a VW 2.0 AEM intake to work with the SVX with a nice cone filter on the end. all was well at this point minus the car running on the lean side due to lack or map work and maxing out the stock MAF. so i purchased a Apexi SAFC and had every intent to go to town and get it back how it should be. well to make a long story short, the car had been running soild and pulling hard, however today comes and while at RS the car decided to be a typical SVX and it started to act up. heres where the fun starts, we got the car up on the dyno and the thing seemed to run super lean, so Ron hooked up the wideband and we checked it, as we dialed it down we found its starting AFR was 22! wtf? as we do the pull the numbers look horrible, the best run as far as the ratio goes tho, we made a whopping 104 AWHP and 109 AWTQ, simply pathetic. as we start to tune i think something is up because the car is taking its sweet time on every pull... i was concerned then i see the worst thing i could, Ron looks over and shakes his head, oh god i think... we look at the plot and its a pathetic curve, nothing until 3 and after 4.5 it dies off rapidly, and the MAF graph was REALLY messed up, where the power trailed off the MAF map went crazy. needless to say the car is running odd, it used to climb and pull like mad up to redline, now it struggles to reach it. so i get to do more research and try to figure out what exactly is going on, this really sucks, finally thought we would peg this pig but nope...i get to go back again another day to get it all done the right way again. so basically i am back to the start,any ideas on what i can do? or how to fix it?
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  #2  
Old 11-23-2006, 05:28 AM
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michael michael is offline
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Did you toss your stock exhaust & airbox? I tried the catless exhaust and intake mod with no luck. It had a placebo effect for a few days till I realized it was slower. Low end power took a dive and high end stayed the same or got slightly worse.
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Old 11-23-2006, 05:49 AM
ItsPeteReally ItsPeteReally is offline
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WHOA! too many variables!

Let's take this a step at a time.
Quote:
about a month or so ago now we built a 2.5" catless Y pipe, then a full 3" cat back... we also modified a VW 2.0 AEM intake to work with the SVX with a nice cone filter on the end. all was well at this point
Was it? Or did it just seem to be OK?
It might well have been louder, but did it actually perform as well or better than previously?
Quote:
minus the car running on the lean side due to lack or map work and maxing out the stock MAF
So you measured the air/fuel ratio? What was it?
How did you know that the stock MAF was maxing out? Did you measure the output?
Quote:
and the MAF graph was REALLY messed up, where the power trailed off the MAF map went crazy
So we can quite sensibly say that the replacement MAF is not working properly. Why could this be?
Are all the connections clean, firm and tight?
Is the power supply you are feeding to it stable?
Is it correctly sited to measure the airflow, and not sitting in a swirling, eddying mass of turbulence?
Is it broken internally, or has a bad internal connection which is continually making/breaking under the influence of engine vibrations?

There's lots of questions, and only you've got the answers.

Sorry to keep harping on about measuring things, both here and in the sig, but it is really important.
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Old 11-23-2006, 07:52 AM
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Let's take this a step at a time.

Was it? Or did it just seem to be OK?
It might well have been louder, but did it actually perform as well or better than previously?

we measured 0-60's, 60-100 and both were faster than before, and the car at least felt like it pulled much harder, actually would pin you back in the seat once it hit the power band.

So you measured the air/fuel ratio? What was it?

before it registered at 16.2 and now it ranges from 12.1-22(extreme side on idle)

How did you know that the stock MAF was maxing out? Did you measure the output?
only for the fact that its running overly lean at anygiven time, and at WOT it gets really lean, not to mention on the monitor it was only reaching 3.79v when it should be topping out at 5.1v max

So we can quite sensibly say that the replacement MAF is not working properly. Why could this be?
Are all the connections clean, firm and tight? YES

Is the power supply you are feeding to it stable? Checking those, due to the irratic MAF readings at WOT this is what i am thinking.

Is it correctly sited to measure the airflow, and not sitting in a swirling, eddying mass of turbulence? we actually did a flow bench test with smoke and a directed fan and it was flowing extremely smooth

Is it broken internally, or has a bad internal connection which is continually making/breaking under the influence of engine vibrations? thats my other thought here, maybe harmonics are coming into play, reviewing everything we did yestarday my buddy had taken videos and the camera goes out of focus at different pitches, odd...maybe its the key tho. however, its odd even still because the car was doing great until the point it was on the dyno.

talking with Ron again, we might have another idea, Ron suggested that on almost all full NA builds if the timing gets off they tend to have a dead spot then go hard then die, exactly like mine...however he said they still tend to accel. and pull almost as hard, where as mine isnt at all... one thing that really got me discouraged last night too was i noticed that it will not go into a power mode right now, i think there is an underlying problem that needs to be dealt with. anyone know what this could be? my first thought was the IRIS valve, when the MAF started acting up the first time the IRIS wouldnt open either... anyone have an idea on why this might be or what might be faulty in my system right now?
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Old 11-23-2006, 10:16 AM
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Quote:
talking with Ron again, we might have another idea, Ron suggested that on almost all full NA builds if the timing gets off they tend to have a dead spot then go hard then die, exactly like mine...however he said they still tend to accel. and pull almost as hard, where as mine isnt at all...
Don't get distracted, moving deck chairs about on the deck of the Titanic, you know what's wrong, it's the air fuel ratio.

I cant tell you why it's wrong. But it undoubtedly is.

I'm not clear as to how the ratio moved from 16.2 - a little rich, presumably due to the loss of feedback from the λ sensors (O2 sensors), to a variable 12 to 22 ratio later.

Perhaps there's a clue in the fact that the stock MAF wasn't behaving properly before you swapped it out. From what you say, it wasn't maxing out, but giving up in some way at 3.79 volts.

Unfortunately I can't fix this for you, but by concentrating on the measurements, rather than folklore, you do have a chance.
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Old 11-23-2006, 12:14 PM
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well one of the odd things is what the MAF graph looked like, it was sparatic then went absolutly berserk at the end, like + or - the whole scale of the chart almost, we got it corrected with the Apexi and it was still pulling like the timing was off, one thought we had was a phenom almost... we noticed at different pitches with the exhaust the cameras electronics would go into a resonency at certain points, like the electronics in it...our thoughts, as off as they sounded were maybe the placement of the MAF and Wiring to it are having the same effects? almost like a radio interference but yeah... like i said, i have alot of research to do and trial and error to go...i am so confused and concerned at this point its not even funny. i pour my heart and soul into it and when we take a step it pushes us 3 back...this is never ending and its mentally and physically draining for me. honestly, all the help you guys can give me the better. I am planning to re-route and shield the wiring and test the MAF at a local shop.
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Old 11-23-2006, 03:45 PM
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Just 2 steps back.

High Flow "Dual Cone" Filter
Full High Performance "Race" Exhaust

Quote:
about a month or so ago now we built a 2.5" catless Y pipe, then a full 3" cat back... we also modified a VW 2.0 AEM intake to work with the SVX with a nice cone filter
Do you really believe that these mods improved the engines power ?

Harvey.
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Old 11-23-2006, 04:43 PM
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pulled harder... thats my honest opinion...until the dang SVX is running right again we wont know for sure tho, i think when i can find out why it wont go into a power mode and why the sparatic readings we'll be golden
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Old 11-23-2006, 05:18 PM
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It might be a long shot, but was the aftermarket air filter pre-oiled or did you spray it yourself. Either way you may want to clean your MAF element there may be oil on it from the filter.
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Old 11-23-2006, 05:26 PM
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i oiled it, and actually that was one of the first things i looked at too
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