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Daily driver mk5 no boost

Jremey

New member
Location
Washington State
Car(s)
2009 gti
So a day or two ago I noticed I wasn't getting any boost. I could put the peddle to the floor and my boost guage runs flat at 0 and I used to peak around 15 psi. It feels and runs just like it did when I would get heat soaked. This was completely unexpected considering I just installed the Forge Twintercooler. I've been doing a bit of research and one of the more common things I'm finding is either the DV or the n75. The diverter valve is less than a year old, upgraded piston version. I'm also running a unitronic k04 with stage 2+ software and (this may sound dumb) I'm not sure if it has an n75 only because I don't remember seeing it when I installed the turbo, but I assume it has to have one and I'm sure I was probably staring right at it. I did have a small coolant leak which coincided with the IC install that I'm assuming occurred because the coolant hose got pulled away from the pump a bit while trying to maneuver the cooling stack to install the IC hoses. So I was thinking maybe I was getting heat soaked from engine temps rising from being low on coolant. However I'm not leaking coolant anymore and I'm full on fluid but I'm still not getting boost. I don't have vagcom to look at readings and for now I'm planning on taking it to a VW tuner shop after the weekend but really wanna try to figure this out before having to fork over my cc for shop diag. Any ideas out there?
 

Perpetuus

Data Encryption
Location
In my garage
So a day or two ago I noticed I wasn't getting any boost. I could put the peddle to the floor and my boost guage runs flat at 0 and I used to peak around 15 psi. It feels and runs just like it did when I would get heat soaked. This was completely unexpected considering I just installed the Forge Twintercooler. I've been doing a bit of research and one of the more common things I'm finding is either the DV or the n75. The diverter valve is less than a year old, upgraded piston version. I'm also running a unitronic k04 with stage 2+ software and (this may sound dumb) I'm not sure if it has an n75 only because I don't remember seeing it when I installed the turbo, but I assume it has to have one and I'm sure I was probably staring right at it. I did have a small coolant leak which coincided with the IC install that I'm assuming occurred because the coolant hose got pulled away from the pump a bit while trying to maneuver the cooling stack to install the IC hoses. So I was thinking maybe I was getting heat soaked from engine temps rising from being low on coolant. However I'm not leaking coolant anymore and I'm full on fluid but I'm still not getting boost. I don't have vagcom to look at readings and for now I'm planning on taking it to a VW tuner shop after the weekend but really wanna try to figure this out before having to fork over my cc for shop diag. Any ideas out there?

Check for a boost leak first. Also check that all your connectors are plugged in snug, particularly the ones that you would have touched or come close to during the Twintercooler install

But yes, N75 exists even on a K04.

I had a Twintercooler before and cannot recommend it especially if you are on a K03. Even with no boost leak, the extra pressure loss from the Twintercooler (an EXTRA intercooler) creates a very annoying lag in throttle response. I sold it the next day.
 

Jremey

New member
Location
Washington State
Car(s)
2009 gti
Check for a boost leak first. Also check that all your connectors are plugged in snug, particularly the ones that you would have touched or come close to during the Twintercooler install

The new connections was actually the first thing I thought of and those are good. The coupler I was given for the driver side originally was not a good fit. The hose kept popping off. The locking tabs were too wide so I had to grind them down to get it to fit and it worked. The twintercooler solved the heat soak issue and I had been running it for a couple weeks. Last time I had leaks with the new IC I could hear the leaks, very distinct high pitch whistle, I don't hear that anymore but I can still check for leaks. I saw someone post a link for DIY leak down check (I think that's what they called it). Anyone got that link still?
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Is there an Autozone nearby for a free code reading? Yours still have the oem PCV? Have you tested that by disconnecting the PCV tube at the intake manifold and blow into it...it should seal and not allow air to pass through the valve. Nothing has suddenly blocked the air inlet? MAF working or been tested? DV has been checked again? N75 tested to be at 25 ohm minimum? Does the N75 have cracks in its plastic body or the ports/nipples? All connections of boost plumbing sealed? Can you smoke test the intake to throttle body for leak detection? Runner flaps still move?,...you can grab the linkage and move it, it should return to the start position when let go. Is the WG actuator rod still connected? As you likely know, there can be many causes to the loss of all boost.

FMIC note; I don't have lag or anything annoying with the Forge FMTwinC...and mine, a K04, is paired with the S3 FMIC. My actual boost meets its target within 700 rpm in a data log beginning from 2k rpm.

Weird your K04 only boosts to 15 psi before. Were you the original installer of the K04 or did you buy the car with the K04 and tune?

You up North in WA? Or close to PDX?
 
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Jremey

New member
Location
Washington State
Car(s)
2009 gti
Is there an Autozone nearby for a free code reading? Yours still have the oem PCV? Have you tested that by disconnecting the PCV tube at the intake manifold and blow into it...it should seal and not allow air to pass through the valve. Nothing has suddenly blocked the air inlet? MAF working or been tested? DV has been checked again? N75 tested to be at 25 ohm minimum? Does the N75 have cracks in its plastic body or the ports/nipples? All connections of boost plumbing sealed? Can you smoke test the intake to throttle body for leak detection? Runner flaps still move?,...you can grab the linkage and move it, it should return to the start position when let go. Is the WG actuator rod still connected? As you likely know, there can be many causes to the loss of all boost.

FMIC note; I don't have lag or anything annoying with the Forge FMTwinC...and mine, a K04, is paired with the S3 FMIC. My actual boost meets its target within 700 rpm in a data log beginning from 2k rpm.

Weird your K04 only boosts to 15 psi before. Were you the original installer of the K04 or did you buy the car with the K04 and tune?

You up North in WA? Or close to PDX?

So per company policy I can neither confirm nor deny that I'm a store manager for AZ lol that being said I'll attach my code printout. I checked the pcv and I felt the check ball move to close when I blew in the hose so all good there. I'll have to check the runner actuator later after the engine cooks off. I am the k04 installer and as far as the 15ish psi goes, I had the exhaust and turbo inlet and outlet pipes ported and polished so I assumed I would get less boost than most since this should allow the turbo to work less for the same results. It really seems like it's something electronic. When I get on the gas it feels like it's requesting boost but not getting it, and it seems as though my gauge is reflecting this because it will spike around 3 psi then it'll fall flat at 0. The IC hoses and connections are solid. I also have the Forge Twintake and it won't make that flutter sound when I have IC leaks. I am in the PNW, I work in Lakewood and live in the Lacey/Olympia area.
My picture is taking forever to upload so here are my codes:
p0171 system too lean (bank1) populated twice
P0507 idle air control system rpm higher than expected
P2279 intake air system lean populated twice
P0243 turbo/supercharger wastegate solenoid A populated twice
P0101 mass or volume air flow circuit range/performance
I assume some of these are due to some of the mods but not sure.
 

Perpetuus

Data Encryption
Location
In my garage
Quick question, if it is the n75, can I get an oem replacement or do I need to get one from a k04 say an a4 or something similar.

You're looking for an OEM replacement. Just make sure to pick the latest revision of the part. Some store like DAP should be able to help you out.
 

Jremey

New member
Location
Washington State
Car(s)
2009 gti
*Update*
I check the manifold runner actuator, it does return after I manually move it. I took out the MAF and cleaned it and had the battery disconnected on the off chance that doing so would reset the computer. Neither procedure worked. I'm looking into getting either vcds or obd11 pro, I'm leaning more towards pro since it's cheaper and it sounds like I can do more with it. With everything I'm reading and considering the codes I have, I'm really starting to think it's the n75 which is super frustrating since the turbo is brand new since December. That being said, tomorrow I'm gonna see if unitronics has any warranty on their products because for an n75 to go bad within a year on a $2500 turbo kit is ridiculous so fingers crossed.
 

Jremey

New member
Location
Washington State
Car(s)
2009 gti
So I think I've gotten it narrowed down. I've got a new wastegate solenoid ordered, will be here on Thursday. I'm trying to test my DV, under 12 volts it stays closed when I push the piston in. So it would be opened not allowing the system to pressurize and create boost. With reverse polarity, the piston is forced out, closing the system allowing boost to build. I haven't been able to find anything on testing these considering most tests are regarding if the diaphragm or seal is bad on the OE style and not the piston style. Does this sound right to anyone?
 

MagicMK

Drag Racing Champion
Location
PA

So, essentially, it is the solenoid thingy. Here's a description from ECS that may be more useful for those skimming the topic:

Product Details
The N75 valve is vital to the health of your turbocharged engine, it controls when and how far to open the wastegate to allow boost pressure to be released.

Diagnosing a broken wastegate frequency control valve can be difficult, but a common symptom is a lack of boost pressure with no boost leak present in the system.

Replace your faulty N75 valve and restore turbocharger performance.

Also, I see Pierburg, the same German manufacturer that made my OE Diverter Valve replacement, makes this part, as well. I found it on FCP Euro for less than $20. For less than $20 and after changing my PCV, breather tube, and DV... it seems like a good idea to replace this as well.

How long did it take you to install?
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Quick question, if it is the n75, can I get an oem replacement or do I need to get one from a k04 say an a4 or something similar.
It's the same part;
06F 906 283 F
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Problem solved. It was the n75. $35 part from work, not even gonna worry about unitronic's warranty.
That's funny ↑...I responded to the post I quoted above in post #14, before getting to your post including you fixed it. Anyhow, apologies...been vacant for a bit. Glad you got it solved. I'll try remembering to check in...keep a note of the codes, clear them, then see which if any return. But likely the N75 had something to do with other codes...some at least.
 
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