[GriffinRoot]

Alright Passat world i have a real problem, this post is being made after ive exhausted all other searches and sources. I own a 2001 B5 passat 1.8t 5 speed, it used to be a ton of fun, it was decently fasted, it pulled hard, sounded good, and then i went and messed it up. The only thing ive really done is added an intake that it has run for a long time now. About a week ago i decided to try an add a boost controller after my n75 valve thinking it would bring me just a little boost for cheap. After installing it, i plugged in my obd2 scanner/Live data reader and went for a drive, after pulling off of my dirt road i tried to do a pull, it felt like it really built a lot of boost and then my acceleration dropped, i could barely climb, i can hear my turbo spooling like normal but i had no power so i figured oh just a boost leak. After checking, there was no leak, i have since took the controller out, replaced any cut lines, and have reset the ecu several times, its been multiple days now and i dont have a boost leak, i dont have any engine codes, ive done away with the problem causer (boost controller), i used a bicycle hand pump to test my wastegate actuator and it held the right amount. the car climbs from 2000-2800 rpm like normal and pulls well in every gear but anything above and it just feels and sounds like the boost is all being wasted, i can barely hit 90 on the highway, my live data reader shows the TPS and it rarely goes over 20% even when im really standing on it, in previous data logging sesions before this issue i would hit 100% plenty of time but i cant get that now, not sure if my throttle body coincedentally went bad right when i installed the controller or if im still in limp mode, please help im out of ideas and beers.

 

[Steve in Chicago]

I'd do a boost leak test to verify the entire intake path is holding pressure.

 

[GriffinRoot]

Ill pick up what i need tonight hopefully to do a boost leak test but i really dont think it is one because occasionally i can pull a little bit and i still have the normal turbo flutter when i let off throttle (dv is reversed i know) so that tells me boost holds in charge pipes but ill still check.

 

[dammitcam]

bump for boost leak test

 

[ylwagon]

Could be a failed waste gate flapper too. But hearing turbo "flutter"? That seems like compressor surge and is destructive.

 

[GriffinRoot]

ok i have the boost leak tester i made hooked up as we type, i can hear air escaping behind the engine block towards the firewall somewhere, brings a smell of oil, trying to find what it is, i have an AUG engine

Update: i read an article to make sure i was doing this right, it said you should remove the oil cap so you dont build pressure on the cam seals, well after doing that i cant build harldy any pressure, if i replace the cap, pump it up a little with a hand pump, then turn it alot of pressure is released, so im assuming the hissing noise behind the engine is apart of the pcv system, does this mean im free of boost leaks or is there another problem related to this?

 

[PZ]

I would pull and test the DV. If the only air escaping if from the PCV, you have a vacuum leak in the PCV but not a boost leak.

 

[ylwagon]

ok i have the boost leak tester i made hooked up as we type, i can hear air escaping behind the engine block towards the firewall somewhere, brings a smell of oil, trying to find what it is, i have an AUG engine

I believe that the leak test should include only the tract from the turbo's compressor outlet hose, capped off, to the throttle-body hose, also capped off and fitted with an air connector (tire valve). If you leave the throttle hose connected, there will be leakage past the throttle plate, so now the test includes the intake manifold and valves. Any intakes that are at the overlap portion of their cycle with exhaust valves will allow air to go right out the tail pipe.

 

[GriffinRoot]

I fitted a a cap with a tire valve pre turbo, and a cap at the end of the tb hose, and after posting about the oil cap last night, i tried the test after i removed the pcv puck valve, plugged the hole, then filled it with air from the compressor again, i could hear the sound of oil dripping/bubbling in the oil pan but further reading said that this was a common occurance, i continued this and i was able to get the pressure inside the intake system up to 25 lbs and it held very steady maybe the slightest slowest leak as it took a very long time to decompress and i couldnt hear anything. so maybe this supports PZ's idea of the pcv vavuum leak? but would that be the cause of my lack of power?

 

[GriffinRoot]

This is a follow up for anyone that has a similar issue and finds this thread. I found the cause of this problem the other night, my n75 valve was broken and apparently sending the car into limp mode, cutting throttle to 20%, and not throwing codes. Because of this i decided to install the manual boost controller i made as a stand alone unit apposed to in series with the n75 valve as i had it, connecting the tip hose and wastegate hose directly to it and removing the n75 valve. I would never recomend using a MBC without either a boost gauge or a wideband AFR gauge, luckily for me my scantool has a wideband so ive been checking that lately to make sure my engines opperating safely. So far ive noticed much better throttle response over stock, and an even bigger shove in the high rpm range.

 

[PZ]

Was the air leak from the PCV or from the N75?

 

[GriffinRoot]

air leak was from the pcv, n75 was fine, but i re read the write up on boost leak testing in the a4mods forum and they said to remove and plug the pcv hole in tip and then do the test, after i did that i was able to hold a steady 25lbs.