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Discussion Starter · #1 ·
i have a 2006 jetta BRM. stock turbo, no tune, has a fresh cam in it. I’ve done the zip tie mod on the turbo to fix low rpm smoke. Since I’ve had it, I’ve noticed on the highway on flat ground, I could hear the turbo spool up faster and then a very slight lunge forward with the car as the turbo went quiet. This would repeat every 5-10 seconds, but only sometimes.

I’ve just recently got set up with VCDS, and I have discovered that the boost while I’m at cruising speed is always above the specified boost. For example, if I’m cruising at 70, specified boost might be 0.4 bar, but I’m seeing the actual boost fluctuate between 0.6 bar all the way up to 1.3 bar. The weird part is, under higher load, such as pulling up a hill, the actual boost matches specified exactly! No issues there, only under medium load. Obviously this is hard on my turbo and my engine, pushing so much boost all the time, especially because most of my miles are highway miles. So, what’s the best solution here.

Do I buy a PD140 without a smart actuator and run it? I’ve read they run fine with a stock tune but just throw a check engine light, is this true? I don’t mind dealing with just a CEL until I can get it tuned.

Do I get a new n75 and see if that fixes the issue?

Do I check wiring and see if there’s an issue there?

I can’t imagine this stock turbo will last too long running those kinds of boost levels so often and for so long.

Thanks for any input!! It’s much appreciated.
 

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Not sure how changing from a 99HP turbo system to a 140HP turbo system is going to settle your concern for over-boosting and harming your engine. BUT
you will have way more fun driving it for sure.
 

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Discussion Starter · #4 ·
Well im not sure, but from my reading, it seems possible that the vnt control ring in the turbo is worn. Im basing this off of the fact that my actuator travels smoothly and my n75 puts out the correct amounts of vacuum, and I still have overboost. I may tighten up my zip tie a bit more to limit the overboost for the short term.

But, I think a new turbo should solve my problem. And ive already been considering a bigger turbo just as an upgrade, so I may buy one. If it doesnt solve my issue, I’ll continue to troubleshoot but then I’ll have a better turbo to add a tune to in the long run.
 

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I agree with where your thinking.
Come to think of it, the intake may have a lot of carbon buildup. This carbon buildup, theoretically, would artificially narrow the intake runners. That narrowing could increase the velocity of charge air and directly increase the RPM of the turbo and you could be in an uncommanded over boost condition.
This heavy carbon build up in the intake would come from oil blow-by via the PCV breather that goes from the valve cover to the intake. If you have ever disconnected the lower intercooler hose and a bunch of oil came out, that’s your sign.
Common mitigation is to install an oil catch can in the PCV line.
 

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i have a 2006 jetta BRM. stock turbo, no tune, has a fresh cam in it. I’ve done the zip tie mod on the turbo to fix low rpm smoke. Since I’ve had it, I’ve noticed on the highway on flat ground, I could hear the turbo spool up faster and then a very slight lunge forward with the car as the turbo went quiet. This would repeat every 5-10 seconds, but only sometimes.

I’ve just recently got set up with VCDS, and I have discovered that the boost while I’m at cruising speed is always above the specified boost. For example, if I’m cruising at 70, specified boost might be 0.4 bar, but I’m seeing the actual boost fluctuate between 0.6 bar all the way up to 1.3 bar. The weird part is, under higher load, such as pulling up a hill, the actual boost matches specified exactly! No issues there, only under medium load. Obviously this is hard on my turbo and my engine, pushing so much boost all the time, especially because most of my miles are highway miles. So, what’s the best solution here.

Do I buy a PD140 without a smart actuator and run it? I’ve read they run fine with a stock tune but just throw a check engine light, is this true? I don’t mind dealing with just a CEL until I can get it tuned. The classic card game uno online is now available in an online version, and a lot of players enjoy it.

Do I get a new n75 and see if that fixes the issue?

Do I check wiring and see if there’s an issue there?

I can’t imagine this stock turbo will last too long running those kinds of boost levels so often and for so long.

Thanks for any input!! It’s much appreciated.
This was a situation that was simple to figure out, but the diagnostic procedure can still be used to other problems that are more complicated. Therefore, I decided to post this information right here. The car was a Jetta TDI from the year 2006. According to the customer, it abruptly lost all of its power and wouldn't go faster than 40-50 mph. About two weeks before this happened, she had some repair done to it, and after that, it had been functioning normally up until that morning. The following code was given to us:
P0234 – 000 – Limit Exceeded (Overboost Condition) – Intermittent 000564 – Boost Pressure Regulation P0234 – 000 – Overboost Condition

The automobile did not have any power when I gave it a quick test drive. I took a graph of the boost while the throttle was completely open. In the graph that follows, the green line represents the amount of boost that is being commanded by the computer, while the yellow line represents the amount of boost that is being measured by the Map sensor. Evidently, this gadget is producing an excessive amount of boost. The fact that I am easing off the throttle is the only explanation for the decrease in boost that I am observing. When the computer detects this, it reduces the amount of gasoline that is being injected into the engine in order to maintain control and prevent the engine from being harmed by excessive boost. This "fuel limit" refers to the noticeable decrease in power that the consumer was experiencing.
 
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