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Discussion Starter · #1 ·
Ok my car was up at EPL for about 3 months now.
We had a phantom issue of the car fluctuating what seemed to be boost.
Replaced a bum wastegate that came loose around the oring. Swapped boost controller, fixed stupid little mistakes that happend when several people work on a car they dont know...
The car has peaks and valleys in the graph that fluctuate between 20-50hp.
The boost gauge still vibrates, but doesnt seem to be boost dependant.
The only observational issue i seem to have is the fuel pressure gauge ramps up with boost, flutters then drops way below desireable pressure and the car goes lean.
There are no boost leaks, ive been over every line 20 times, replaced them several times.
The car has these spikes in the graph @ certain rpm points. If i run 13 psi and make 280whp (which is approximate for the boost) it surges at the same rpm as it would @ 24psi which has been around 370whp. You can take a ruler and watch the graph raise up and down rpm per rpm. There are no codes for the cam position sensor, no codes for the incorrect correlation for cam to crank.
we recently thought i was starving the pump with insufficient fueling from the re engineered fuel tank, or we were cavitating the tank with an overload of pressure, so i shoved a screw driver in the filler neck, ran the car. Same problem. Ripped tonys tank out of his green car, with his bosch pump, same problem. Tried different files, different injectors same problem. Different cam position sensors same problem. MBC's same problem. Tried to log throttle position a/f requested vs actual, of course the cable is not holding connectivity.
Any thoughts feel free lol
 

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Discussion Starter · #2 ·
Re: problems with a phantom issue. (EdsGTI20VT)

the reason i dont feel is boost related is because when i pull the vac/boost test port and set the base pressure to the desired WOT pressure it still drops pressure, and fluctuates like it does normally. The voltage on the pump is constant, nothing to make sense of the issue at all. Both pumps, tanks, setups, same ****.
 

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Re: problems with a phantom issue. (EdsGTI20VT)

If it is the rubber type (rather than the teflon)It is possible to create a "flapper" when installing the ends. This is a piece of the hose lining that gets cut by the fitting and ends up on the inside of the fitting. When the "flapper" is facing into the stream it has a nasty habit of flapping up under certain flow conditions and partially blocking the line.
Certainly worth looking at.
 

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Discussion Starter · #7 ·
Re: problems with a phantom issue. (bobqzzi)

i would say yes but we cut all of those lines out of the equation when we ran aluminum flare tube from the cell on the dyno to the rail directly.
 

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Discussion Starter · #9 ·
Re: problems with a phantom issue. (bobqzzi)

i have not, i opened it to check the diaphram and spring, it looked fine and it seems i put it back together and damaged it. I sent it back to aeromotive for repair. I jsut got it back the other day. I removed the nitrous, rewired any and all damaged connectors, fixed the small pin holes in the manifold, got a fuel cell to lessen the chance of the tank being a problem (hence the fitting thread) and then im going to go back up to tonys next week for round 15 of going at the issue.
 

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Discussion Starter · #10 ·
Re: problems with a phantom issue. (EdsGTI20VT)

i also got a new set of 02's a new coolant temp sensor, and other assorted bs. I was going to log a bunch of stuff but of course my vag cable broke, and wont stay connected. I just got off msn with kevin and he gave me some insight about locking the dyno and watching fuel pressure, timing and injector duty cycle etc. Also logging tb position, so i have more stuff to check, im just getting fairly disappointed.
 

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Discussion Starter · #11 ·
my question is why does the boost gauge vibrate. It has its own dedicated line. Why does fuel pressure go all over the place with 2 entirely differnet setups. Aeromotive said it can fail 2 ways, the fuel pressure wont adjust because of a bad spring, or it pisses fuel out of the test port...which it did the other day when it tore after i put it back together.
 

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Discussion Starter · #13 ·
Re: (bobqzzi)

the problem is that tony put the gauge on his green car and it was 100% smooth. It vibrates about 1psi on the gauge and only really above 19psi. Its not a huge deal just anything i can grasp onto and focus on...
 

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Re: (EdsGTI20VT)

Quote, originally posted by EdsGTI20VT »
the problem is that tony put the gauge on his green car and it was 100% smooth. It vibrates about 1psi on the gauge and only really above 19psi. Its not a huge deal just anything i can grasp onto and focus on...

Same intake manifold, same spot for the tap? It's good to explore every possibility.
 

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Discussion Starter · #15 ·
Re: (bobqzzi)

nope everything is 100% different. thats why im sort of shoving it to the side.
we ran his fuel system 100% except for the rail and fpr. And got the same fuel pressure fluctuation issue.


Modified by EdsGTI20VT at 12:58 AM 8-22-2006
 

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Re: (O2VW1.8T)

I had this problem on my car with the OEM management, never found out what it was though. Boost would fluctuate ~2psi. With the SEM now, I dont get it. Might be computer related to something like the knock sensors or something... I dunno what specifically though.
 

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I know this will sound wierd but its what happened to me.
I had a similar problem.
boost would fluctuate around 3500 everytime, I thought it was because i was runnig closed loop and that is was regulating boost.(so i wasnt too worried)
But then i was street tuning trying to get the egt's right and now it's completely gone after i added more timing.
Funny thing was i wasnt trying to fix it. I think it might have been an issue with the combination of the cams and ignition timing.
 
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