1Z - Where's all my boost?

[markd89]

Hi All,

This is in my 78 Bus, but please think of it as a 97 Passat TDI ;-)

I have a Malone stage 2-ish tune which is good for 17-18 psi of boost. I'm running the stock IP and turbo. I have a somewhat extreme A2W intercooler setup, but that's another story. Everything else is pretty much stock.

Symptoms:

Recently, I have been seeing less boost than I used to. The engine is slower to boost and peak is less than before.

Peak used to be 17-18 psi now 10-ish.

Freeway cruising normal used to be about 10-12 psi, now it's 6 or 7 psi.

If I let off the accelerator at about 70 mph, I used to maintain ~4 psi of boost, now it's zero.

The bus runs pretty well, it's just has symptoms of low boost: less peppy, more smoke, higher EGT.

I checked VCDS and do not see anything jumping out at me...

There are two faults:

00560 Exhaust Gas Recirculation System, 17-10 Control Different Intermittent (I have the EGR vacuum tube disconnected)
01050 Glow Plug Monitoring 35-00 (I have a bad glow plug)

Other VCDS stuff:

03 MAF Spec: 645 Actual: 445 EGR: 19.9%
04 Injection Spec: .9 BTDC Actual: 1.3 BTDC
011 MAP Spec: 1101 Actual: 969
013 Idle Speed Cyl 1 -.38 Cyl 2 -.07 Cyl 3 -.02

Could the MAF be at fault?

I have checked for boost leaks and haven't found any. I have not pressurized the intake as I don't have a compressor right now.

The stock turbo has appx 170K miles on it. I don't hear any noises but I'm not sure I would notice over the noise of the engine.

Any suggestions on what to check and what the problem might be?

All help much appreciated!!

Thanks,
Mark

 

[Digital Corpus]

A bike pump on the actuator to check to crack and opening pressure of the wastegate.
A setup to pressure test your intercooler piping

I know you track your IATs. Have they been rising?

 

[markd89]

A bike pump on the actuator to check to crack and opening pressure of the wastegate.
A setup to pressure test your intercooler piping
I know you track your IATs. Have they been rising?

Thanks, I'm going to go to HF and buy one of the 3 gallon compressors to test the piping. I'll use the bike pump on the actuator. The actuator should be closed without pressure. i.e. if I disconnect it, I should get maximum boost, right?

I also put in an order at McMaster for a bunch of silicone vacuum hose. I'm going to replace all of it. It shouldn't be bad as it was all new 3 years ago, but maybe something has a hole.

IATs are still good and haven't changed as far as I can see. I do see the EGTs being higher. I have an extra water temp sensor that comes off the head and that's higher too.

Thanks for the help. More ideas, LMK!

Mark

 

[JETaah]

Not that this is the problem at hand here but...
It is my understanding that the boost control hose is better if it is the braided stuff that VW uses. It will have less tendency to be spongy, "inflate", and delay boost control signals. Consider brake lines as an example.
On a typical AHU, 1Z application, you have nearly 8 feet of hose in the boost control hose circuit and even a little deflection in the hose can make some difference in the time that it reacts.

 

[Digital Corpus]

The amount of flex for a silicone hose when it has near infinite volume of air at a given pressure if not where near significant enough to be an issue. You're also dealing with a 3 mm ID. At 8 ft, that is ~1.05 in^3 and if it enlarged to 4 mm ID, that'd be ~1.87 in^3. At 16.5 psi, the GT 1544 flows ~5 lbs/min of air. It would fill either volume in less than 1 ms.

On the other hand, the RC filter on the ECU for the boost signal creates at ~150 ms delay before the ECU sees ~85% of the change in signal/pressure.

 

[JETaah]

The amount of flex for a silicone hose when it has near infinite volume of air at a given pressure if not where near significant enough to be an issue. You're also dealing with a 3 mm ID. At 8 ft, that is ~1.05 in^3 and if it enlarged to 4 mm ID, that'd be ~1.87 in^3. At 16.5 psi, the GT 1544 flows ~5 lbs/min of air. It would fill either volume in less than 1 ms.

On the other hand, the RC filter on the ECU for the boost signal creates at ~150 ms delay before the ECU sees ~85% of the change in signal/pressure.

So you are saying that the little bit of sponginess is not going to be detectable.
Can you define some of your terms so I can appreciate what you are comparing?

1.05in^3....is that notation for 1.05 cubic inches?
What is an RC filter?

 

[JETaah]

Is an air box screen still in place?
Any of this possibly going on?

 

[markd89]

Thanks, no airbox anymore just a filter. I checked and didn't see any major clogging. I bought a little compressor from HF yesterday and am going to pressurize the system today and see if I see any leaks.

Thanks again,
Mark

 

[rocketscience]

Is the N75 old? If you had a known good one you could try swapping it. I swapped mine because it was overboosting and going into limp mode and now it sits around 10 psi max. not sure whats going on but I'm assuming I got a bad one.

 

[markd89]

Yes, the N75 is old. From what I know, the default setting of the wastegate is to be closed (maximum boost). I unplugged the vacuum tube (actually pressure tube) from the wastgate and still only get 9 psi. Maybe I have a bad N75 but I don't think that's not the cause of the low boost. I appreciate your ideas though.

News:

I found the vacuum (pressure) tube coming off the turbo was somewhat crunchy. This is a very hot part of the engine. I cut off a bit of the tube and reattached it, with no improvement.

I tried pressurizing the intake. I couldn't properly block off the part of the intake that goes to the top crankcase breather. I was still able to force air through and maintain 8psi from the compressor and I couldn't see any leaks anywhere even with the help of soapy water.

I am ordering some rubber stoppers from McMaster so that I can block the intake at the turbo outlet and test from there. I'm ordering enough stoppers so that I should be able to isolate different parts of the intake.

 

[Digital Corpus]

So you are saying that the little bit of sponginess is not going to be detectable.
Can you define some of your terms so I can appreciate what you are comparing?

1.05in^3....is that notation for 1.05 cubic inches?
What is an RC filter?

The 3 & 4 mm IDs are actual IDs of the hose between the N75 and the actuator.

inches cubed, thus cubic inches, yes.
RC Filter. I want to have a look at a EDC15 to see what is on their. I have a friend who said that with the same tune, the EDC15 spooled their turbo ~1/4s, aka 250 ms, sooner. Methinks this is a result of the RC filter and the PID settings for the N75 though chiefly the RC filter.

Anyhow, back to boost troubleshooting...

Mark, I think you really only need to test if the intake to manifold hold pressure properly. After this, verifying the wastegate is fully closed would be next on my list. How PITA is popping off the downpipe?

 

[1998TDIMonster]

Have you already run your hands along the intercooler piping to see if your hands are oily? That would be a free and easy teat to be sure. I had a similar issue on my 98 jetta and couldnt figure it out for the longest time. One day while working on my car, I accidentally leaned on the intake manifold and found it had some "give" to it. After rocking it back and forth a few times, i found it was loose. Removal of egr cooler and retorquing the intake manifold allen head bolts with a dab of loctite fixed my issue! Whats making me think it might be this is i too had added smoke and lower sustained boost at any speed. Let us know your findings!

 

[markd89]

So, the intake (pre-turbo) is fed by the oil filter as well as by the CCV. I have an inline filter on the CCV and just for the heck of it, I pulled it while the engine was running.

I was surprised to have vacuum there. The CCV tube is small, the air filter path is wide and one would think that most of the air would come through the air filter path and there wouldn't be a vacuum at idle in the CCV. So, this was the clue.

I removed the air filter and drove up the hill near where I live. It was obvious then that the air filter was the problem.

My custom airfilter was fed by a 3" tube. The filter itself has 6" diameter media, but the way the tube worked, most of that air was going into the center 3" of the filter. That center 3" had cleaned most of the air for 30,000 miles. Solution: I removed the tube feeding the filter. Now I have all 6" diameter working for me. I also ran a leafblower vacuum against the dirty end of the filter to try to suck out some of the dirt. Results: easy boosting and sustained boost of 16-18 psi when needed. Wahoo!!

Thanks again for all your help!
Mark

P.S. I still have the silicone vacuum hoses and will install those when I have time as I think they're a nice upgrade. I also have the $59 HF compressor which seems surprisingly decent which I'll keep for future jobs. It's just not big enough to run air tools, but I don't have space for bigger stuff right now.

 

[Digital Corpus]

http://www.amazon.com/dp/B000EPXKAI