Does anything stand out in these graphs?

[Braga_Dub]

I have been seeing limp mode somewhat regularly.
My boost gauge indicates 30+psi when I am at or near WOT 9/10 times.

The code it shoots when it goes limp:
Code:
17965 - Charge Pressure Control: Positive Deviation
P1557 - 35-00 - -

The boost came from Measuring Block 11 and the MAF from Measuring Block 003.
Measuring Block 10 showed a constant Mbar of 999.6 and I left that number alone.

Boost gauge was at 30+psi during every run.

All done in 3rd gear, uphill, multiple times, and they all looked the same.
I was unable to get a full w/o MAF run due to laptop battery life though.

Blue line = What car wanted
Red line = What car got

Boost w/ MAF

MAF during that run:

Boost w/o MAF:

MAF during that run:

Mods:
-- VNT17
-- RC4
-- PP520 Injectors
-- OMI Turbo Inlet Pipe
-- PD150 Fuel Cooler
-- PD Lift Pump
-- BoostFactory SMIC
-- BMC/CDA Air Intake
-- PD134 Oil Cooler
-- 2.5" Turboback
-- Boost Valve Boost Controller

 

[FlyTDI Guy]

I hope this is an ALH... You're requesting about 22 psi and your actual is limiting out at 2601 mBar due to internal limitations. Your boost gauge is able to read beyond your MAP sensor so I'd believe it. You need to get to the bottom of your overboost quickly. Your boost valve is apparently doing nothing for you. How was it setup/calibrated? Something's awry with your boost system. That checklist of things to check is pretty well publicized here, I won't repeat it now. I'd be driving lightly if I were you.

Addendum: All the other graphs look as expected except the MAF actual when unhooked. Usually it will default to 550. Jeff must have it jacked up (not in the damaged way).

 

[Braga_Dub]

Yes, ALH. That explains the logs, thanks

The boostvalve was setup years ago by Jeff.

Saturday I took apart the boost controller, cleaned it up, and made sure the hoses were not plugged. Made no difference.
The vacuum lines were replaced not long ago, but the problem had already been there.

I would assume the boostvalve would "kick in" and limit the boost if the N75 stopped caring. Is this true??

When I have time I will unhook the actuator and see if I can wiggle the VNT "lever" around smoothly. I have a "newish" VNT15 laying around to compare it to.

 

[FlyTDI Guy]

It should be doing something, yes... As you are overboosting and not just spiking for a second, the boostvalve is going to be performing a job it really wasn't intended to do. I'm sure your ECU is still not going to be happy. I'd be looking at my actuator and vanes. Pull some vacuum on the actuator and check for function. It should start to move around 3-6 in/hg and stop around 18-22 in/hg. You should also have a spread of around 15-17 in overall travel. Make sure it doesn't leak down either. Check the vanes and make sure they aren't stuck. You can swap the N75 and N18 for testing if you need. Something's awry, you just need to find it...

Edit: to add chart...

When your boost valve is set correctly, your boost should look something like this...

 

[shizzler]

Damn. Yeah what flyguy said. And stop going WOT for extended acceleration runs until you do exactly what he said.

 

[FlyTDI Guy]

Oh yeah, someone recently here solved their boost issues by cleaning out the little black/white one-way check valve. Some rubber from the hoses had sloughed off and gotten stuck in it. A little brake cleaner and air hose worked fine. Check the big hard vacuum line to your booster also. They like to split with time.

Your boost valve is probably stuck or become mal-adjusted somehow. It doesn't seem to be stopping your overboost and it should be trying to fight it anyhow. Don't know if it can actually win in a constant overboost scenario. Take it apart and clean it out. Don't loose the ball or spring. I would set it to pop about 25psi. You can start low (loose) and work your way back up. Take a run and give it the juice and watch your boost gauge. Set too low, you should see it stop your boost and really feel the power difference. Give it another turn or two and try again. You'll eventually get to the point where it will allow your tune to get all the boost it's asking for but very little over or above.

Honesty, find your real problem first... the boost valve only treats the symptoms.

 

[jsrmonster]

Either your turbo's vanes are stuck, or n75 is leaking vacuum when it's supposed to be dumping vent to atmosphere.

Remove the n75 and clean it with carb cleaner and compressed air. Careful not to break off plastic nipples.

Fix this asap or you will waste your turbo. Boostvalve is not a fix for stuck vanes. They usually fail with crap in the seat and underboost, (ie. big vacuum leak during boost request).

Jeff

 

[Jasengine]

I had a similar ish problem with a boost-creep type problem, but when I replaced some vacuum lines the problem was solved.

 

[im570rm]

how many % is the duty cycle @ 4000 rpm (you can see it on 011 also)

 

[Braga_Dub]

Duty Cycle: 94.4%

I pulled out the hoses, squirted the stuff into the N75, check valve, and then used compressed air. Also did the same for the BoostValve, and loosened it a bit. I will see in a bit how it goes.

If the vanes are stuck, is there a possible fix without having to open up the turbo?


Thanks for the help thus far

 

[Braga_Dub]

Alright:

After doing what was said in the previous posts. I was seeing boost that would hit and hold about 28psi. An improvement over the eleventy billion psi I was seeing before.

I then decided to clean things up a little more and got carried away... Some vacuum got "cleaned up" very well, almost too well. During the cleanup, I found a crack in the boostvalve hose. So that will be taken care of in the next few days. Can I just use thick-ish silicone vacuum hose instead of the chunky vacuum hose? I have quite a bit left over.

After that clean up, I started to see it spike at 24-25psi, then hold 21-22psi for a bit, and finally taper to 19psi at high RPM.
Sound about right for RC4?

PS: Do not use carb cleaner to clean some grease on the strut towers. The paint will hate you for it...

 

[FlyTDI Guy]

Ouch on the paint...

I believe, from what I saw in your first post, you are requesting about 2500 mBar or 22 psi. From what you just described, you're MUCH better. The split in the boostvalve hose is important, you'll need to get that fixed pronto. I would leave things for now but when you get the hose fixed, try another partial turn in on the boostvalve and see if you can get it to hold 22 steady throughout. You'll need to set the valve a few pounds above requested so the ball can re-seat and hold when you are at max boost. It should only pop for a second when you spike above its threshold. Regardless, you're in way better shape now... good job (and persistent too).

 

[Jasengine]

Thick-sh walled silicon hose is fine. I have used it for my vacuum hoses without any problems.

 

[Braga_Dub]

This weekend I replaced the hose, cleaned up the bay a little more, tucked some hoses/wires, and tomorrow I'll adjust the BV a little more.

Is it possible that the spring is "old" and just not acting as it should?

 

[Farfromovin]

Springs could act up in boostvalves. I hate valves personally but sometimes are an evil necessity. Do you have a 3 bar map? Is your tune set for a 3 bar? I thought Jeff was dishing out ALH RC4's that were 24 psi and mandated a larger MAP. Could be wrong here though...