N75 Valve - Audi/VW Testing & Install | How it works | 2.0 FSI A4 B7

The basics of the N75 Waste Gate Frequency Control valve: how it works alongside the waste gate actuator, the waste gate itself and the turbo. You’ll be able to see how it should function in an inactive and powered state, where it is on the Audi A4 B7 2.0, and how to test and replace. This info is also generally applicable beyond VAG FSI or TSI vehicles.
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The B7 has an internal waste gate (aka, the valve that releases exhaust air into the exhaust is IN the turbo housing on the exhaust side), oppose to an external waste gate that you might find in custom or big turbo set ups. This valve is moved by a rod that is moved by the waste gate actuator. The actuator stays closed by default from its own spring pressure. But when enough boost builds up, the air pressure is forced upon the actuator, moving the rod, opening the waste gate.
But the N75 valve is in the middle of this system. Sometimes, it does nothing, allowing boost to flow through it and act on the waste gate (actuator, rod, valve). But sometimes it needs to block that pressure in order to keep your turbo from spooling above its operating specs or smooth out your driving experience. In that scenario, it recirculates the boost (from the compressor side, not the exhaust side - it's not exhaust gas) back into the turbo intake. No air exits the system unless it's through the exhaust. All air that's sucked into the intake either gets recirculated by the diverter valve, passes through the engine and exits over the turbo turbine and out the exhaust, or passes through the engine and bypasses the turbine and still heads out the exhaust. But it's all accounted for.
Although there can be various issues leading to low boost, if the N75 is stuck in it's default state where the actuator and rod are constantly forcing the waste gate to stay open, the N75 would be responsible. A torn diaphragm on the older style of diverter valves could have the same effect, though. As would a boost leak, a maladjusted waste gate rod, an actuator not responding at the correct pressures - or an electrical issue leading to either the diverter valve or N75.
Part numbers:
N75 Valve: 06F 906 283 F
Hose from compressor: 06D145718M
Hose to turbo intake: 06F145718R
Hose to waste gate actuator: 06F145718Q

[@bepolonia]

Exactly what I've been looking for. Thanks for much for posting this.

[@WorknB]

You can be proud of your productions . Im a100% more informed on the function of the N75 and its job inside the world of pipes and hoses in a crammed space. Great commentary and well explained . Just what we are all looking for when we think we know , but really we dont. Easy to hit the subscribe button.

[@MatthewTaylor3]

I love the simplicity of how this is explained.

[@W.Khairi]

With this kind of quality work, a subs is a must, Thanks a lot for sharing.

[@user-lv8uu7uh6q]

Great job bro !!! I have learned more in your video than any of the 100's I watched. I tried these test on my son's car and learned how to fix it !!! Thx

[@dudimus3225]

Great job and very detailed explanation.

[@jacobjones435]

Great technical content, information i needed greatly. Thanks

[@monayhussen4376]

Very helpful I broke the air pressure line connecting to the Wastegate actuator on my new turbo and this helped a lot now I’ll just replace it tomorrow, probably best that I put the car in the service position… 😅

[@primodeelux]

Very informative. Just the info I needed to test my N75 valve on ‘06 VW Jetta TDI.

[@mattttiiass1]

Thanks, great video and explanation. Im subscribing from now on!

[@metiu2002]

Świetny film, bardzo mi pomógł!

[@DorkyThorpy]

Very high quality video, well done.

[@robjohnyson]

Awesome, great info!

[@laceezaustralia2596]

Brilliant video mate

[@NotSoHandyCarGuy]

Fantastic video!

[@jacket9067]

Awesome vid!!! Very clear and succinct

[@arankaspar5165]

Fk yeah dude. Priceless. Very little good easy info on this model AND it's engines. Thank you for sharing the knowledge freely as the internet was intended. This is very much appreciated.

[@karthikgopalan9291]

Excellent video, thank you for making it

[@GIXXERUKX]

Excellent explanation, thank you 👍

[@nevertethered6386]

Very helpful and informative video. Thank you.

[@alexis19081]

This was the best explanation ever well done. Thanks a lot. 🎉❤

[@henryzr23]

You are the man, it's a good video, thanks heaps.

[@souar2]

Great explanation! Thanks

[@atomicpunk993]

Very helpful, thanks!

[@jamiegilbert1098]

Really enjoyed that video.even I understood it.😀

[@ricko3k]

Very informative thanks.

[@dego8032]

Good job, upload more videos!

[@peterperacchio528]

Excellent. Thank you

[@CraigMansfield]

Brilliant. Thank you

[@damiqdeshhuqify]

Good video, thanks

[@trachel7458]

Great video

[@literatemonk]

Thanks a million!

[@fezk3746]

thanks a million!

[@carvalhalantonio2282]

Ter un

[@jerry007garcia6]

Thank you for this Video been looking for exactly what u explained to th dot thanks again

[@xnicole19x6]

Great vid, I have an Audi A4 B6 saloon 1.9 tdi, the car works fine in all of the gears, good acceleration, feels powerful, I get a problem when I’m on the motorway gaining speed I hit about 60mph and the car feels like it looses its power, after this happens it crawls up to 70mph, do you have any idea what this could be? Thanks for reading :)

[@andyfalls6039]

Very helpful video, very well done. Thank you! For the Active State Test, beginning at 3:58, I presume you are applying 12 V to the solenoid. Is that correct or is the voltage something else?

[@NeonMechaPR]

Gracias por el video. Ahora se lo q debo hacer

[@marcelocuadrado6955]

The line of metal in the valve came from turbo boost or inlet return?

[@JenLeigh483]

Great video. unfortunatly its not helping with my issue. I have a b7 a4 2.0 that has good boost at first key cycle and will continue until you shut the car off. At 2nd key cycle and beyond it is low boost then it trips a p0299 code. No other code comes up and after car cools next day full boost again.

[@cherokeebriggs510]

Thanks just sucks having to wait for the part in the mail cause no where in my city has any parts for my car

[@darinmccuistion6662]

Excellent video, easy to understand and very descriptive. I have many questions, might I trouble you for answers?

[@FigureItAudi]

Post them up here and get taken to comment section church!

[@miguelleal7364]

Can this method be also used for audi a4 1.8t 🤔

[@brsrkr2012]

Hey, very detailed! Wish there was more people this detailed! Thanks! I have a 08 A4 2.0t B7 has P0299 code for turbo underboost condition, I replaced the diverted valve, and cleared the codes and drove the car and the same code came back, should replace the N75 valve as well or do you this my turbo is no good? Any comments would be appreciated thanks!!

[@FigureItAudi]

Do you have any type of data logging tool? Ideally, you could monitor the requested vs. actual boost while you drive throughout the rev range. It is possible the N75 is to blame, but it could also be something related to the waste gate flap or any part of the actuator that moves it. Or it could be a boost leak anywhere between the turbo and intake manifold. I'd poke around and be sure all the hoses are on tight before digging deeper - and only assume the turbo is to blame after everything else is eliminated (because $$).

[@abdullast3434]

I need a help please. The hose from the N75 to the actuator. Have no eir or vacuum at all?

[@flok1971]

Thank you very much for this video.. The best i've have seen yet.. It explains a lot!

[@FigureItAudi]

You're very welcome, Michael - I hope it helped you out.

[@flok1971]

@@FigureItAudi Yes... only I have a B6 model with a 1.8T 20V engine, and there is a a slight difference in construction. But the working is the same..

[@NugShrub]

As a tech who is only 2yrs in the game and self-taught. This is great info. I've gone from alignments/ suspension, to hanging chains and swapping motors and Trans, to now being the diag guy since I learned how to use a Pico and try and learn every way to prove a part is bad...and still don't know shit lol. I bought a couple problem audis to practice and learn electrical on and videos like this are priceless. Thank you

[@forgottenknowledge8917]

I'm thinking about using a N75 off a more powerful TDI to control my vanes. My Manifold Absolute Pressure is 220kpa in 3rd at WOT. I want more boost, without paying for a tune. I can spin, do a burnout, all the way to 4th with just the mods I've already done.

[@rwvisuals]

I'm going to be doing this in a few days on my 08 gli, any recommendations for installing? I know there's not a lot of room to play with. Just trying to figure out the best approach.

[@FigureItAudi]

I recognize this isn't special advice - more of a reflection on my own recent work - but I've come to really appreciate the investment I make in tools. Picks, mini ratchets, special pliers, mirrors; so much time is saved when you're well equipped to find creative ways to work through tight spaces and with stubborn parts.

[@garethb7741]

Is this on the 2L tdi 170bhp also?? Or just petrol version

[@Dustmaker]

008801 - boost pressure control valve (n249) p2261 - 008 - mechanical malfunction. Is this the valve to replace ? From a 2.0 tfsi BPJ engine

[@Rwecosher]

Nice vid. I'm trying to find info on why my boost pressure won't hold steady. Once it gets up to peak pressure, it's clear that the wastegate opens, dropping the pressure slightly (the needle jolts back down the gauge) then it seems like the wastegate is hunting. It just won't hold steady at peak pressure. I've made a lot of adjustments to the actuator rod length. The spring inside the unit is strong. The N75 clicks away. The pressure builds with throttle opening/revs. Just drops then won't hold at max.

[@FigureItAudi]

It sounds like you're describing a boost leak. Personally, I've vowed to not play with the actuator rod because without seeing inside the turbo to understand how/when/if the wastegate is actually (fully) closing, I don't have the confidence of verifying the results of my work. But let's assume you've got the rod tuned up perfectly. What I also don't know is what expected boost across the entire RPM band is per the N75 maps. It's hard to say what you're experiencing at exact moments is or is not as it should be. Anyways, with the gate closed and engine under load, building boost up until max, it's conceivable this is still possible with a leak. When the wastegate opens, there could be way too much loss for boost anywhere near peak to be maintained. It's the go to answer but: have you checked the DV yet? Revisioned? Upgraded? I put in the Go Fast Bits DV+ on day 1 and have never had an issue.

[@Rwecosher]

@@FigureItAudi hi. Thanks for the reply. DV? I didn't describe one part which is that the boost pressure fluctuates once max boost is achieved and then the slight drop occurs. My translation of that would be that the wastegate opens too much at this max pressure, then the N75/ECU is trying to correct this drop in oressure but there's lag in the system. I have a VE engine with larger nozzles that i've put in a T4. I've replaced the lines (braided), fitted an intercooler with new hoses. At first i shortened the rod to increase the compression in the spring, making it a slower/more damped response from the N75. It was an improvement so i went a bit more but eventually hit limp mode when it couldn't open the wastegate. I backed off slightly then went for a remap. The guys didn't offer great service, unfortunately. I expected they would adjust things accordingly with the increased boost map etc. So i'm a bit stuck now. I may replace the actuator to rule it out but can't be certain of the preload setting etc..

[@FigureItAudi]

I see, yeah, a few somewhat uncontrolled variables there. "DV" is Diverter Valve, the recirculating blow off valve. Many early B7's came with a version of 06F 145 710, which tend to tear their diaphragms and leak boost like crazy. Basically everyone upgrades to 06H 145 710 D but I went for gfb.com.au/products/blow-off-and-diverter-valves/dv-plus/. I don't get to hear fun noises anymore, but I always opt for the reliable performance upgrade. It's easy to check which version you have, if you haven't already. It may be your problem, oppose to some of the other things you've been mentioning.

[@Rwecosher]

@@FigureItAudi Mine's a 96 engine - AHU. Doesn't have anything like a DV. IT'd be worth me checking for leaks though. Cheers

[@agreene638]

If this is faulty will it cause an overboost error??

[@garethnorwood2084]

If this is broken will it make a whoosh noise a bit like a dump valve on a petrol thanks

[@nicholaswallace7773]

I know this is very late but for anyone else, this is usually your diverter valve.

[@pospc2]

Would you put a manual boost controller on the boost source of you wanted to play around with such a thing? I know it's not recommended.

[@FigureItAudi]

I wouldn't but that's just because I think it's not worth the effort or the resulting situation to deal with. Which is, you'll need to ensure more fuel is being adding to compensate for the added air - whether that's confirming the ECU is automatically compensating for you, or through tuning. But at the point you're needing to tune, you may as well just get a credible tune that adjusts boost for you based on altered maps. If you don't tune, some adjustments also might be required to the MAF and/or other systems to acknowledge/ignore the added boost is having on the system. I don't fully understand how a MBC would impact the 2.0 platform. You'd probably also want a boost gauge to keep an eye on the pressure you're creating throughout the rev range under load. Under the right conditions (and having the right knowledge), it could be a fun and cheap way to add some power. Up to you!

[@pospc2]

@@FigureItAudi I have snow stage 2 water meth kit. It's boost reference progressive controller. With digital boost gauge. I am already stage 1 tune. I want to play around with a couple more psi just to do it. I know I would have to keep it 4psi or less over the tune setting and that it takes 5 seconds to trip a over boost and cause limp mode.

[@markmkv940]

Do the wastegate break ?

[@orvillesandy]

If I want to put a boost gauge there which 1 I have to connect the T hose to

[@FigureItAudi]

Search for a boost tap for your particular vehicle before messing around with any of the vacuum lines down near the turbo. You likely should be tapping into the intake manifold for pressure - and it'll be closer to the firewall so you can route lines to a boost gauge in the car.

[@inseCT320i]

I have a diesel volvo 2.0d,very strange case...when i connect the n75 in the wrong way (VAC to turbo,and OUT to vacuum reserv.) the car does not jerk...when i connect the lines in the right way as should be (VAC to vacuum reserv. and OUT to turbo) the car jerck when pressing and releasing the gas pedal...any help perhaps whats happening ?

[@jimmyneutron1889]

Yesterday I had a poke around the engine bay looking for broken connectors, leaks etc. I found that the N75 2-pin electrical connector was broken due to heat, and the previous mechanic held the connection together with a zip tie :( the zip tie crumbled to pieces when I touched it, and the connection to the N75 was broken. I am wondering if it is safe to drive the car around short distances with the electrical connection on the N75 unplugged. The car is showing a CEL and I believe its on limp mode. Can you confirm please, thanks in advance.!

[@jimmyneutron1889]

I have ordered the connector part from VW and will take it there on Monday, it is today Saturday. 2013 VW GOLF TSi 1.4 stock

[@noesb8932]

I have a check engine light code P0299 Turbo UnderBoost Condition you think its the n75 valve or diverter valve or both? Also have 532 voltage supply signal to small.

[@pauldaly3952]

I have same fault codes with underboost with my A4 tdi 20L ultra keeps going into limp mode waa 75 valve at fault?

[@kennethcollier4660]

Question is that same part on a Volkswagen Jetta Mark 7 1.8 turbo

[@FigureItAudi]

If I was in Vegas, I'd say: yes. It's basically a guarantee that a boost control solenoid like this (whether it's referred to as an N75 or not) is fitted to a turbocharged, consumer-level vehicle of the modern age. Even a tuner-build car with an external waste gate is likely to still make use of this type of part.

[@markmkv940]

It I have a ko4 can I buy the same diaphragm wastegate actuator ?

[@markmkv940]

I’m experiencing overboosting intermittently and now more Frequently. My boost gauge is reading heavier than normal boost and my car is responding very poorly under load. I’m thinking the wastegate is stuck shut.

[@jerryreding7369]

I have a 2008 Passat 2.0t with 201,000 that I just purchased a few weeks ago. When I purchased it, the previous owner told me, and I confirmed with my own scanner, that there was a P0299 code (turbo underboost). I went ahead and pulled out and replaced the entire turbo and exhaust manifold assembly. There was oil dripping from the wastegate control module. Now the other code is gone, but I have a P0245 now. I forgot to clean the connector for the wastegate control module when we reassembled. Is it possible that I could simply have a bad connection preventing the module from operating correctly?

[@bgr69]

Heyy, I have Passat 2006 2.0t and its have P1693 code I don’t know exactly but that part have to change, I bought that part but do you know where is this part? I didn’t find the place

[@durindateague1059]

my car has two n75 valves but it goes into limp mode intermittently how can i fix it the n75 valves are located one at the turbo and one at the forge diverter valve, thanks,

[@FigureItAudi]

Keep in mind the 2nd N75 is actually doing the work of the OE diverter valve was doing but it's just being used as a go-between to reference vacuum pressure between the intake manifold and the DV. You could temporarily get rid of the forge setup just to eliminate that mod from your source of issues. Otherwise, as long as all the vacuum lines (3 on each) aren't leaking, then you've got a failed solenoid or it's electrical. I know you didn't ask for this opinion but I would get rid of the forge setup and stick to a mechanical valve that's solely run off the ECU (like the piston DV or the Go Fast Bits DV+, like I have). Just simplify.

[@Chris-lz7sx]

Is it important for the N75 valve to be close to the wastegate? I want to reroute my N75 valve away from the wastegate near the rear upper part of the car for better access. Would this cause a problem with it's function?

[@FigureItAudi]

I welcome anyone else to join in here but I don't think it would cause a *large* issue. The pressurized air still needs to travel to/from the same components in/out of the N75 but it's possible the added length of hose would delay the various functions of the valve. If the lines were always pressurized at a constant, then no, I don't think there would be any effect. But they're not. If you moved it up a foot it could have little change, but up and over to the other side of the bay - that could be bad. It's a neat experiment that you'd have to measure with logging boost request/response timing differentials.

[@Chris-lz7sx]

@@FigureItAudi My exact thoughts. Because there is no constant pressurised air then the travel time may be a problem. I guess I will post this exact same question over to an Audi forum and see what hits I get. Thanks for your kind and quick response.

[@80sGuy.]

It's all Greek to me but it sounds good and I think it's about time to replace mine for preventive maintenance.

[@HowieLop]

So, when diaphragm in waste gate actuator is broken, keeps in close position, letting turbo keep building pressure? in that case, how the engine manage the overboost?

[@FigureItAudi]

By exploding, either the turbine, or hoses, or failure in the cylinder.

[@HowieLop]

@@FigureItAudi very clear

[@adameusaries]

Im wondering if my n75 valve is misbehaving. I keep building boost when accelerating and it only bleeds off when i take my foot off the gas. Is the possible or is it something else

[@FigureItAudi]

Hey Adameus - What you're describing is more or less the definition of what a blow off/diverter valve does, and that foot off gas = no air = no exhaust = no exhaust turbine spinning = no boost. Is there something happening that doesn't feel right, or data you've collected from the car that's pointing to a problem?

[@adameusaries]

@@FigureItAudi my issue is my boost keeps building to be 22 psi and spikes st 25. Heres the in for its an audi b7 a4 2.0. I just had the engine rebuilt so it has 150 miles on it. The n75 valve is hooked up correctly. I have a go fast bits diverter valve and a ko4 turbo. The car has a stock tune on it because of the rebuild. So when i give it full throttle i get max boost. My gauge reads up to 30 psi. Its suppose to taper off at 8psi or so but it doesn't do that at all. It just keeps boosting. I have no check engine light. I checked it for pending codes. I cant figure out why it the n75 valve isnt doing its job.

[@FigureItAudi]

Thanks for the extra details; I misinterpreted your first comment. I welcome anyone else reading this to chime in because I don't run an upgraded turbo but it sounds like you're overboosting and it could be a few things. If the K04 was also rebuilt I assume it's waste gate is operating via the linkage + actuator from the N75 properly - but if it's not, that'll build way too much boost. Otherwise, the stock N75 maps may not be running a duty cycle high enough to modulate the waste gate (again, I'm not tuned so I don't know to what degree most tuners manipulate the N75 maps to compensate for higher boost levels) while you're using a larger turbo on factory settings. It's possible that without an added boost controller, your N75 is working just fine but it can't keep up with the additional air being pumped around. You may also be running lean right now and might want to check the spark plugs for evidence of that.

[@azamcoolem5729]

What error pop up for this error?

[@fencingspecialist948]

Hi if this valve is faulty could it cause a overboosting of the turbo , thanks

[@FigureItAudi]

Yeah it could. If the N75 solenoid stopped activating under power, it wouldn't be able to release boost pressure back into the compressor and even with the waste gate held wide open, the exhaust turbine might reach speeds beyond what it was meant to.

[@fencingspecialist948]

@@FigureItAudi thank you for the reply , I asked others and had the sticky veins answer but after Google and KZbin I came across this video . I will replace the valve and post back the results

[@chaddaugherty3201]

I have an '07 VW EOS diagnosed with a boost pressure control valve mechanical malfunction. Does this mean I have a bad N75 valve?

[@FigureItAudi]

Hi Chad - I'm not familiar with the platform but drawing from my general experience and knowing that people tend to refer to certain parts using a number of names - your answer is: maybe. It could be a boost solenoid like the N75 (probably has a different short hand part code for your Eos), but it may be your cars diverter/blowoff valve in the induction tract, too. Or something as part of the waste gate mechanicals. Honestly, in the average turbocharged, factory spec car, it can't be that many things. Hopefully you can get some more info from what or whomever did that diagnosis and zero in on the faulty part.

[@chaddaugherty3201]

@@FigureItAudi Thanks! Also, your video is very helpful! The part isn't that expensive so I might try to replace it on my own. Any tips on how to get the factory hose clamps off?

[@FigureItAudi]

@@chaddaugherty3201 Getting them off is easy - I usually just jam a pick or screw driver between the ear and slowly work it open till it's loose enough to slide back. But you will destroy the clamp. To get the same style back on, you'll need something like geni.us/pinch-clamp, or switch to a different style clamp. The one's I used are simple to use but not the "best" solution for longevity.

[@Esarjay]

How much does something like this cost at the dealership or a different auto shop, I have the P024500 on a 2015 A4

[@FigureItAudi]

You should definitely call around since one of the largest cost differences may come from labour rates charged - but there's going to be variance in the part cost too. I doubt you'd get out the door for less than $200.

[@jonathandominguez921]

If Both T25 torex screws are missing would that cause my n75 valve to act up?

[@FigureItAudi]

I doubt it :D

[@jonathandominguez921]

@@FigureItAudi thanks for the reply 🤙🏼

[@SoloForever22]

How do you remove the waste gate actuator

[@FigureItAudi]

@VerifieDribbler _ I haven't removed the waste gate personally, but I'll say that once the vacuum hose is disconnected from the actuator, there's only 2 nuts and a clip that holds the rod (that's basically the same part as the actuator unit) to the rest of the waste gate linkage. The important part to keep in mind here is that the rod is specifically adjusted with those nuts to open the waste gate a certain distance. If you plan on removing the actuator, 1. Make sure you mark where the oem adjustment locations are, and 2. Be prepared for the scenario of the parts not going back together in the same way or at all. I recommend reading these threads on Audizine: www.audizine.com/forum/showthread.php/419180-I-m-stumped-amp-boost-issues.-Possible-wastegate-or-related-failure www.audizine.com/forum/showthread.php/420536-Wastegate-Adjustment Thanks for the question

[@dudimus3225]

The arm? I believe that you need to buy a new turbo

[@nick9463]

Prove it!

[@tomrocs]

Hey, have a 2002 Audi A4 Quattro it’s all stock except for a drop in kn filter. It would boost up to 7-8 psi and hold steady sometimes spike at 10psi and drop back to 7ish. I recently got a stage 1 Unitronic tune, it’s suspose to bring me up to 16.5 psi on a stock car. So I was only able to hit 14 psi max and then it would bleed of to around 12. Now it gets less and is only at 10psi and gradually drops as rpm increase?? Do you think I have a bad n75 valve or possibly a bad diverted valve? Any help would be great

[@FigureItAudi]

@tomrocs There might not be a problem at all, actually. Despite how the boost reacted before the tune - and that yes, there can be a number of ways boost could be lost of mismanaged throughout the system - I'm not sure what you're experiencing is out of the norm. There is data log proof that the max PSI some of these tunes cite it achieved earlier on in the RPM range (like, 2500-4000) and tapers off quite a bit on the top end. Although these cars (the 2 liter, on average) are good highway drivers and have some power on tap for mid-high range, they just aren't built for top end power. Do you have access to data logging software? You can compare actual boost vs. requested boost and see if your car is able to meet what the tune has been set for. If there's a marked discrepancy, then you can start trouble shooting something mechanical. Nice sounding 'stang on your channel, BTW.

[@tomrocs]

Figure It Audi thanks for the quick reply!! This is my first Audi, I am a ford guy, had a ton of mustangs carb/fuel injection among other fords.. This Audi is a whole diffrent animal then what I’m use to. Lol!! I do not have data logging software access I’m just going by what the boost gauge is showing me as I drive? I’m figuring it’s something mechanical like failing turbo/wastegate, torn diaphragm in diverted valve or possibly faulty n75 valve

[@FigureItAudi]

@@tomrocs Well, welcome to the club. Your hit list of possible issues there is bang on and there are usually multiple factory revisions and aftermarket upgrades for each of those parts. It's always possible there's a leak somewhere in the piping or a smashed up intercooler, too. It's all stuff you should be looking at within general maintenance, anyways. Internal waste gates are one of those items where it makes a lot of sense why manufacturers utilize them in their turbo design, but as a consumer, it's the worst reason to have to replace an entire turbo or at least a giant pain in the ass to diagnose and attempt to alter. Having a simple, external waste gate from the factory would have been nice.

[@CliffB5A4]

The standard N75 is designed to taper off as revs increase, if you want it to hold a little longer use the N75j wich delays the signal a tiny bit and also gives an increase of about 3psi.

[@boostfitness5613]

You think this is what’s wrong with my mk7.5 gti? Air & fuel keeps fluctuating and hesitates 😫

[@karamkamel3074]

hi I found this channel because I have a P0420 and P0299 on A4 B7. Do you think the N75 could be the culprit? I hear hissing when I shut the car off as well.

[@FigureItAudi]

Hi Karam - I don't think so, but these codes represent some fairly open ended causes. I'll do my best to give you information to go off of, but if you could share some more details, that would help. Like: Has a MIL/Check Engine appeared? What make and model are you driving? Is it modified? Do you have access to a VCDS tool? Are these new codes - cleared and reappeared? Other than the hissing, do you notice a lack of power while driving? Any other symptoms? P0420 Catalyst System; Bank 1: Efficiency Below Threshold P0299 Boost Pressure Regulation: Control Range Not Reached Combined, these codes tell a story and it may be that your catalytic converter isn't working as it should anymore. P0420 would tell us that - in general - there is an efficiency issue in the cat, and P0299 adds that the turbocharger also may not be operating at full capacity, but more likely that there's a boost problem. So, you're not wrong in thinking the N75 *could* have a role here. But to me, the problem seems to be further downstream towards the exhaust. Realistically, the cat could have some problems that is causing the o2 sensors before and after the cat to flag the system efficiency is down. If we assume there is a blockage of sorts, this pressure would also impact the turbo's ability upstream to get rid of exhaust gas as quickly as it needs to. There are many tests to do though related to your MAF, oxygen sensors and boost levels if you can access a diagnostic tool - before replacing the cat. A visual inspection of your N249/Diverter Valve is a quick and easy place to start, too. If it has the diaphragm on it, it could be torn and should be upgraded regardless. Your hissing noise is a stumper, though, especially when the car is off. That would indicate air (or steam) is being vented to atmosphere from somewhere, or potentially being sucked into the car by vacuum. I'm sure that sound dissipates quickly, though? Hope this helps. Share more!

[@karamkamel3074]

@@FigureItAudi hi. the MIL is on for those two codes. the car is very slow to accelerate. I have an 07 A4 Quattro. just bought it a couple of weeks ago and this happened on my second drive. this is my first venture into Audi. No mods that I know of. car doesn't seem to have been taken care of. I don't have access to VCDS. I cleared the codes and they appeared instantly. I've checked the hoses around the turbo. they seem fine. I've checked the diverter valve. it's the new style piston kind. Lack of power is very obvious. I can hear the hissing on the turbo side of the engine when I shut it off. it goes away after a few seconds. Thanks for responding btw. I really appreciate the help.

[@FigureItAudi]

No problem - happy to help and I hope anyone else reading this now or in the future can add to the convo or learn from it. The loss of power makes me think you either have a major boost leak or your car has been put into limp mode from the check engine status. From the sounds of your checks, the only part that could be a problem on the charge side of the turbo is the N75 valve. It could be stuck open and continually recirculating boost back into the turbo. Since your DV is the piston revision and you say you've checked the intercooler hoses coming off the turbo to the passenger SMIC, then SMIC to lower core, then other side of the lower core to the driver SMIC, and SMIC hose into the intake manifold, it only leaves the N75. On the exhaust side, you could be experiencing a bad waste gate valve, though. If it were to be stuck open, a good deal of boost is bypassing the turbine and going straight out the exhaust. Or, it's being caused by a faulty waste gate actuator. It's not impossible you have a large exhaust leak coming off the exhaust manifold or between the cat and turbo, either. How does the car sound at idle? Have you checked for vacuum leaks? The hissing sound is still the most confusing part of your issue. If it's air escaping from somewhere, try to pinpoint it with the soapy water bubble test.

[@karamkamel3074]

@@FigureItAudi Thanks for the reply. I got a new N75 I'm installing tomorrow. I'm also going to find a shop to run a smoke test if that doesn't work. I'll be sure to let you know what happens. thanks again.

[@Xxx23DWIGHT23xxX]

@@karamkamel3074 Hey Karam, any updates on this? Having similar issues.

[@uhealthandwellness6228]

Hello... How do I resolve a boost control solenoid code P0045, P056E?

[@FigureItAudi]

I would do some Googling on those fault codes and learn more about the possible causes. As much as people (myself included) like to think that replacing parts is the solution to most issues, often it isn't. 0045 indicates a bad ground. wiki.ross-tech.com/wiki/index.php/16629/P0245/000581

[@uhealthandwellness6228]

@@FigureItAudi thank you, just that link alone helped out.. Thanks again

[@psuedonym8344]

I'm trying to figure out my 06 B7.. Lately on cold start 🤧 the car begins to have and on and off jerk when accelerating. Whenever the car jerks, during accelerating I can hear the "pssshh " outside my window even though I haven't given off the gas. I can quick change from 1st to 2nd gear [standard] n 3rd ect it would run smoothly until the next time to stop having to gear into first. So its clutch to first then go then jerk(pshh) go, jerk (psshh))...change gears and so on till next stop. It seems up to 4 "psshss" before letting off the pedal from just 1 gear to another not each necessarily followed by a hard jerk If let the car warm up for about 5 minutes there is no issue n car drives fine. In past I have rebuild the turbo with new turbine n gaskets, n change the N75 while in the area. Not OE but can't say the new is more than 1 year old. I may have the original somewhere but I can't say this is the issue or Diverter failure(never replaced but upgraded forge space) since things work or don't work depending on temp of car.

[@FigureItAudi]

I would check the diverter valve first. If it's the older diaphragm style, get rid of it even if it does not appear to have tears in it. Since you're hearing so much atmospheric boost release, I'm guessing that your diverter valve has failed and is constantly letting boost out the spacer. Again, guessing. This doesn't answer why it would only happen when the car is below operating temperature, though.

[@psuedonym8344]

@@FigureItAudi Thank u for the feedback and shot of confidence. I will investigate like it owes me money cause someone's got to pay for it 😆 ..tanks!

[@psuedonym8344]

@@FigureItAudi FYI update. In taking out the diverter, the top screw was completely loose movable hand almost with the hex! N not even taking out the last screw there was enough room for a piston to fall out. Im pretty sure the spacer goes over the piston. I seen some u take piston out n spacer over but the kit has some make shift plunger at end (not this; was valve with piston on ground from fall with no additional add on pieces to go after spacer) hope this is answer already ordering new one. Tanks again

[@FigureItAudi]

Glad you narrowed it down. FWIW, I switched to the GFB DV+ as soon as I got my B7. The K03 is designed to receive recirculated air and the ECU takes that into account, so although adding blow off valves and other things that make fun noises is cool, I traded in the pshhhh noise for peace of mind.

[@psuedonym8344]

@@FigureItAudi Nice I will consider it. Mine came with the forge but thats the one I saw with own plunger after u fit with spring. Ya I'm ok with wanting that peace of mind sometimes im just like "shhhh! Stop pssshhh! U r not faster than the M8 right next to u!" Thanks for tips my man. I will consider it i just wondering if u replace that whole thing when worn or if u can buy individual springs

[@knolez1546]

So, delete the valve for old school turbo tuning? Can I get away with it on an old TDI, you know, like tuning the turbo on an old Honda?

[@FigureItAudi]

Tell me more about old school turbo tuning - because if you remove the boost solenoid on this setup you'd run into some major issues and risk sending the turbo to spooly boi heaven.

[@metallicafn]

turbo is cracked on the hotside by the actuator .. not sure if anyone else noticed

[@FigureItAudi]

Wow, I think you're right...I'll be checking that out soon. Thank you for the heads up! *begins thinking of turbo upgrades...*

[@metallicafn]

@@FigureItAudi time for a disco potato lol

[@daedaebfishin]

The black case in the front of the engine or after the actuator arm towards the back??

[@daedaebfishin]

0:33 or 4:33 ??

[@1RUFC]

They say the N75 valve should be replaced every 50k miles

[@p4cks]

Step One: Remove engine

[@FigureItAudi]

Alternate step one: solicit the help of a gangly pre-teen with skinny forearms to do the work for you.

[@p4cks]

@@FigureItAudi how have you seem my arms?! hahahaha love it

[@consultancy4277]

😂

[@tahamohamad9359]

My car doesn’t have a turbo but it has that...