stock boost or boost leak?

[tsigui]

i have a stock 91 tsi m/t the mods so far i have a aftermarket boost gauge, walbro 255, aem fpr, k/n air filter. i have about 4200miles on the rebuild. i dont have any of the emisions hooked up. i did not have the return from the bov to the intake on for the first id say 4000miles. it was running great with it off for the first 3500mi or so and i did my last oil change and took it out and drove it pretty hard but every time id get to 4k rpm the car would almost jolt in a way like it was getting boost in speratic bursts. eventually it got to the point to where i was blowing lots and lots of black smoke out the tail pipe. i just put the return hose from the bov to the intake on about three days ago. no more black smoke and it does not die when i come to a stop. however im only getting about 11psi boost and about 20-21psi on the vaccum. so my question is should i test for a boost leak?
my boost gauge is tapped into the vaccum line that is running my fpr i t'd it and ran the boost gauge off that as well.

all advice and opinions are greatly appriciated!!

 

[scott90gsx420]

Looks like your on the right path. Supporting mods are your best friend. For starters are you using stock injectors. If you aren't and don't have a way to tune for them then put the stock ones back in. If there stock then what is you fuel press. If its above 37 then you need to pull the vac line off nipple on the afpr and plug the nipple with your finger. Adjust the screw untill your at 37 then tighten her down and put the vac line back on. Black smoke is definitely to rich and bucking is usually caused by rich conditions to.

 

[razrman8]

Your boost and vaccum seem pretty close to right. I would do a test anyway, I mean come on. Boost leak testing takes 5 minutes to do.

FYI- Venting to atmosphere causes split seconds of running rich, like in between shifts. Just throwing that out there.

 

[scott90gsx420]

Your boost and vaccum seem pretty close to right. I would do a test anyway, I mean come on. Boost leak testing takes 5 minutes to do.

FYI- Venting to atmosphere causes split seconds of running rich, like in between shifts. Just throwing that out there.

Ya i forgot that part . I ran with vent to atmosphere because i didnt really know better. i couldnt figuer out why everytime i clutched or reved and let it go the car couldnt catch itself and would die. I read a thread and put the recirc. tube back on and no more issues.

 

[tsigui]

so i did the boost leak test and sure enough i have one. its right off the top of the turbo (stock b) where the turbo is flanged to the intercooler piping. the gasket is visibly torn and hanging out. i was told that some high temp silicon or some right stuff the napa brand gasket in a can will work as good as the paper one.

i have stock injectors. the pressure is set at 37.

yes the boost test was very easy.

however today when i started her up to go over to my buddies to do the test. i was blowing blue smoke and it was very rich to the nose. i was told by my other friend who actually sold me the car and basically told me how to put the engine back together. he had said it could be a bad batch of valve sprigs?? or a bad bearing? i have been burning some oil its not a lot but i am burning some. i would say its progressively getting worse but today has been the first day that Ive noticed the blue smoke versus the black.

 

[scott90gsx420]

Well the black smoke is unburnt fuel. Blue smoke is burning oil, which only comes from bad piston rings or bad valvestem seal/burnt valve. A bad bearing will cause a knock. and running rich will simply hinder your performance.
And if you were running really rich it would have washed your rings, and slowly killed them so thats a even better chance its the rings not the valves or seals.

 

[tsigui]

valve stem seals thats what i was shooting for. and that all makes sense. i do thank you sir. and ill let you know what happens when i get some cash and some time to tear into her. thanks again.

 

[scott90gsx420]

Ok man let me know, wish you the best of luck DSM ftw

 

[red_talon]

good luck on your car!

 

[9!'clipseDOHC]

I would do a compression test before tearing anything apart. Also if you are running super rich with the stock fuel injectors my guess would be your o2 sensor is shot and not cycling. Also just because you found one boost leak, doesn't mean that that was your only boost leak. Everytime you fix a leak, you should do another boost leak test. I have fixed so many boost leaks on my dsm that it would blow your mind. You've got to keep checking.