Thread: Go Figure, Building Boost Issues...

Witts end...

Okay, you guys are smarter than I am... There has to be something that I'm missing... here is the rundown. Car was boostin' like a son of a bitch on Saturday and Sunday... Sunday Night boost started to windle down. We fixed it on Monday by checking for leaks and tightening everything up, back to business! then slowly it started to windle down again. There is boost pressure, but it only builds to atmospheric (0psi gauge pressure). It basically drives like a strong n/a car, but when I let off the gas I can hear the turbo spool down every time.

Turbo is a gtir-t28 I bought about a year ago from a member, it was directly from a GTIR and has about 40k miles on it. It's actually in really good condition. Any questions, feel free to ask!

Things I have tried:
1) Boost Controller - I am running a Greddy Profec B (The old school one, I love it). When the car was boosting fine it actually did its job, very well I might add. There was speculation that the diaphram was leaking on it. So i removed it completely from the system. Took the lines off the tee on my compressor housing, and took the line off of the wastegate actuator. I then put a new line directly from the compressor housing tee to the wastegate. Same thing. Not the issue.

2) Wastegate Actuator being stuck open - This was my first notion... I actually was using a forge adjustable actuator, has multiple springs. I've replaced the 10-14lb spring with the 14-18lb spring - same issue, I removed the arm and tightened it to apply more preload, twice - same issue. I removed this actuator and put on the stock GTIR actuator again, added preload twice again - same issue. Lastly, I ran the car with no pressure source line to each wastegate - same issue. It's not the actuator.

3) Large Vacuum/Boost Leaks - I went up to a friends house on Monday and pressure tested. There were a couple of small leaks. I took off my intake piping and actually clamped the compressor directly to the turbo inlet, after popping off the actual tester a couple times, lol... it held 20-23 psi no problems. We basically tightened the bov to the piping, and the top hat on the bov down, and tightened the spring. The car pulled like a beast when we took it out. It held 9lbs w/ th eboost controller off, and i turned it up to 12lb for a second and it did AWESOME. Then I let Brennan drive it and he said it was only holding 7ish pounds... As I was driving home, 4lb, and eventually 0. And now its acting the same exact way it was before I drove over there... Idles fine, but doesn't build boost over atmospheric. I've looked the car up and down, and I can't find any leaks... I will have to pressure test again this weekend.

4) Turbo Being Fubarred or unbolting itself from heat - The turbo has no outrageous shaft play, spins freely, and is not scraping the housing walls anywhere. The wastegate flapper works fine, and all housings are tight. I even went through and tightened all the housing bolts after the first couple of days. I checked all the bolts to the turbine inlet to manifold and they are tight. The exhaust manifold seems to be seated to the head well, I went over and retightened them. The turbo doesn't spit any black, or white, or rainbow colored smoke. I can hear the turbo spool down after any amount of throttle. I'm going to put exhaust on the car so I can hear everything a little better this weekend.

5) Leaking B.O.V. - I am running a Blitz SS blow off valve w/ a recirc fitting recirced post maf. It boggles my mind because it held the boost on the previous pressure test? I don't see why or how this could be the problem, but after ranting and complaining to my friend, its the only thing at this point that makes sense (Good vac, boost leaking somehow). After I got home on Monday and the pressure stopped building, I tightened the spring down as far as it could go and still the same thing. Could the diaphram be stuck open? That might explain why I can't build boost... I will take it off tonight and check it.

Other random Facts:
- The spark plugs look great, BKR7E from NGK. They were what were in the car when I put her down in November 2007.
- Vacuum is good and pulls around 17inHG at idle. Under load in gear letting th eengine slow the car, well past 25inHG
- I set my TPS at .4 close and 4.00v at wot on Tuesday. (I noticed it was around .54v closed and 5.4 or so wot)
- I set my timing at 15 degrees on monday... I guess I could set it again since I reset the TPS, but it shouldn't matter since its done with the TPS unplugged.
- At the moment running a 4bar 370 program w/ a gtir MAF, just like my sentra. Computer is fine. MAF readings work
- Battery was moved to the rear, Voltage is 12.0-12.4v car off no accessories, when running I see 14.1v.
- Everything electrical is verified by Nissan Data Scan
- IACV/AAC is working from what data scan says...
- I'm using ALL t-bolt clamps and fresh couplers from silicone intakes dot com, and everything is tight.

The only thing I can think of at this point is that I sprung another leak somewhere, but it doesn't make sense because my vacuum is all good. What in the hell is going on here? I'm going to see if I can run another pressure test. i really want to get this car on the road again and healthy before I put her down for the winter so I can do my upgrades that are sitting on the shelf

Anything and everything will help... I'm all ears, and I will do anything. Any questions please feel free to post them up. I have exhausted my brain trying to figure this one out. Usually these issues are all stupid simple fixes, but this one is kicking my ass.

Tokes

When the boost guage reads 0 PSI it means that the car is not building boost at all, it means there is no vaccum and no boost. If you put a boost guage on an N/A car it will read 0 PSI at anything past about 1/3 throttle. I would pressure test again and check the wheels on the turbo. As far as the blow off valve goes, just take it off to see what happens. Unbolt the blow off valve from the piping and rig something up to cover the hole in your piping. Making a test run with no blow off valve is not going to break anything, but it will prove if the blow off valve is your problem. You could also do this to fiddle with the BOV; take off the recirculation fitting so that you can stick your finger into the BOV to feel the plunger. Start the car and let it idle. Adjust the BOV while the car is running so you can feel the plunger open up and close when you blip the throttle from idle. Adjust the BOV so it is open only slightly at idle and then shuts immediatly while blipping the throttle. It should be able to be adjusted this way, if it can't maybe there is something up with it. Before you play with it though I would first take it off, plug the hole, and see how the car runs.

Have you checked to make sure you don't have an exhaust leak between the turbo and the mani? If your losing gasses there then it would spool the turbo up to about 0, but it will not build boost. But the car will run normal otherwise and seem to act like an N/A car. This would be much easier to notice if there was an exhaust on the car.

Either that or you are leaking under boost only, but if you tested it fine up to 20psi, then that shouldn't be it really.

Sounds like you keep getting a boost leak, and keep fixing it, and it keeps happening. Make sure your charge pipes are rough (not chrome or anything) and there's no oil in them that seeps between the pipes and the couplers allowing them to slip off. If it's not an exhaust leak pre-turbo, it's a pressure leak post turbo.

If you had an exhaust leak pre-turbo, it would build boost then bleed off a little bit, an exhaust leak big enough to prevent turbo spool would be so big the car would sound like a locomotive.

I second the boost leak. A leak large enough to prevent any boost is BAD FOR THE TURBO. Without pressure on the compressor side, the turbo could very well be over-revved. Center cartridge failure could occur, if you MUST drive it, keep your foot out of it.

Not completely true. It might not build boost at all, no mater how hard he tries to do it if the leak is pre-turbo. He said he had up to 4psi then slowly nothing by the end of the trip, so it could be a leak on either side of the turbo getting worse in some way. And from what I gathered he is running with no exhaust, so he wouldn't notice if this was the case.

'Course, he did say he checked everything twice. Then again, he also checked for boost leaks and this is still happening.

Well, I put the car together... put the exhaust on finally and was able to hear and determine a couple things. The exhaust manifold leaked slightly and I could smell a little exhaust coming from it so I let it heat up completely and tightened the **** out of the bolts. The leak is less prominent if there at all. I ran it again, and still the same outcome (unfortunately). I took the car out to time it up to see if that was my problem, and I could hear the bov open up when I revved the car to get it into timing mode. I will see if I can pressure test again tomorrow or sunday evening to verify that I didn't spring a leak.

I appreciate your input guys... it makes me think.

NJ-Ser - The wheels on the turbo seem fine. I took the piping apart yesterday and spinned them and it spun freely. I will see if I can make a plate and drill some holes in it to make a block off for the bov and see what the car does. I'll try and adjust the bov again and see if it makes a difference but from adjusting it the last three time it didn't change anything. I took it off today and checked to make sure it wasn't stuck open... (it wasn't).

Went over to my friends and pressure tested again! We found a big leak that must have developed from the last spurt of boost at the coupler on the hot side of the intercooler. Fixed that leak and replaced the silicone lines for the fpr/boost controller. Tested the BOV for extreme leaks and found none. Even pressure tested the intake piping for giggles. As we tested we could even watch the wastegate actuator open when it reached about 7lbs. Took the car out - no boost.

Everything has been tried, and the result is no boost pressure... so the only thing that I can conclude is that there is something wrong with the wastegate flapper on the turbo. I will have to take the turbo and manifold off to check that...

Ameen im taking notes on all your troubles so when i get my boost beast down here it will be smooth sailing ...hehe...

Don-the-Magic-Juan,

I'm pretty sure you won't have this boost issue... most of the ones I've had in the past were all solved within 3 minutes, lol. Stop mooching off my boost drama fool!