Misfire issues .

[Nizmo]

No thanx, gonna fix it to go on the other car anyway. Not going back to stock.

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You rockin K04 on that thing!?! Nice.

Who's tune you running?

[Jayz691]

You rockin K04 on that thing!?! Nice.

Who's tune you running?

Yeah, CTS K04 tuned by Motoza for about 2-3 years now. Was stage 1-2 for a few years before that.

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[Nizmo]

Yeah, CTS K04 tuned by Motoza for about 2-3 years now. Was stage 1-2 for a few years before that.

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You thinking of doing any Wideband o2?

Stage 2 APR k04 tune I ran too lean, pulled timing and boost to 15psi until ECU shut off the N75 for overboost. Did the S3 injectors and ran a wideband. 22PSI no spikes. I have the N75 in parallel with Greddy Profec 2. Now APR stage 3 F23L, S3's, Intake Flap Remove File. I need to schedule the dyno my thoughts are 400 crank HP, 360ish HP by butt dyno atm. Faster than my "Mint" v10, keeps up with 2018 s8 plus.

What did you do for your fuel injectors if you dont mind me asking?

[Jayz691]

You thinking of doing any Wideband o2?

Stage 2 APR k04 tune I ran too lean, pulled timing and boost to 15psi until ECU shut off the N75 for overboost. Did the S3 injectors and ran a wideband. 22PSI no spikes. I have the N75 in parallel with Greddy Profec 2. Now APR stage 3 F23L, S3's, Intake Flap Remove File. I need to schedule the dyno my thoughts are 400 crank HP, 360ish HP by butt dyno atm. Faster than my "Mint" v10, keeps up with 2018 s8 plus.

What did you do for your fuel injectors if you dont mind me asking?

Well if you run a stage 1-2 tune with a K04, yeah, it'll overboost and not be right. Need the correct tune for K04, along with proper fueling.
I have genuine s3 injectors, APR 155bar prv, Autotech HPFP internals, R8 LPFP controller, and 200bar rail sensor. Everything was tuned/scaled properly.
Stock block K04 files are usually about 320-330 crank, nowhere near 400.
Ya ever done any logs(MAF/timing), to get an idea? MAF G's usually line up pretty good with whp, but obviously can vary a little cuz of dif timing maps.

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[Nizmo]

Well if you run a stage 1-2 tune with a K04, yeah, it'll overboost and not be right. Need the correct tune for K04, along with proper fueling.
I have genuine s3 injectors, APR 155bar prv, Autotech HPFP internals, R8 LPFP controller, and 200bar rail sensor. Everything was tuned/scaled properly.
Stock block K04 files are usually about 320-330 crank, nowhere near 400.
Ya ever done any logs(MAF/timing), to get an idea? MAF G's usually line up pretty good with whp, but obviously can vary a little cuz of dif timing maps.

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Oh of course! Yea I was just wondering what you were running in context to the valve explosion. No wideband yet or not going that route was what I was wondering because I was lean the whole time.

K03/K04 almost the same, still both small. K04 versions differ of course but base K04 file from APR is considered stg2 to them. Or Stage 2+ to others.

Long story short F23L with supporting mods more than 400 capable. Prob has in it 26 or 27 psi, more fueling options but 450crank hp capable. Of course F23 versions differ as well. K04 I have on the others are 20psi but not capable of more than 350 BHP. F23 could see 400BHP with a manual (with supporting fueling and rods if you want to push her hard.

[Nizmo]

Common community misconception is the parasitic drive-train loss of 25%. Or more in some cases.

This is true with an automatic traditional torque converter car. AWD is even more of a loss. However, the manuals make more BHP than the auto's with the same MAF reading. Without dyno sheets all this is hyperbolae , but safe to say the manuals have a 10% (or less) drive-train loss.

EDIT - To add complexity to this basically physics subject. Not all B7s came with the same wheels. The final reduction ratio is determined by wheel diameter. Lighter larger diameter wheels increase top-speed. The performance loss can be accommodated for increasing overall top-speed. So in a S-Line manual it has 18" OEM wheels. 235/45/18 I believe.

[Jayz691]

Common community misconception is the parasitic drive-train loss of 25%. Or more in some cases.

This is true with an automatic traditional torque converter car. AWD is even more of a loss. However, the manuals make more BHP than the auto's with the same MAF reading. Without dyno sheets all this is hyperbolae , but safe to say the manuals have a 10% (or less) drive-train loss.

EDIT - To add complexity to this basically physics subject. Not all B7s came with the same wheels. The final reduction ratio is determined by wheel diameter. Lighter larger diameter wheels increase top-speed. The performance loss can be accommodated for increasing overall top-speed. So in a S-Line manual it has 18" OEM wheels. 235/45/18 I believe.

Sorry, but disagree with some of this. First, APR K04 file is their stage 3/K04 file, stage 2 is stage 2, not for a K04 setup. If ya do, ya wind up with issues you described(overboost, limp mode, etc).
A K04 is not getting 400hp, no matter what on a b7. Now us longitudinal guys don't have all the options that transverse have, as far as K04 hybrids, TBO GTX hybrids, etc.. even with say a CTS k04X(hybrid), 400 is a stretch.
Yes, drivetrain loss is slightly higher on autos, but that won't affect BHP, only WHP. Places over seas like UK, etc that always quote "BHP" for everything, that's based off of WHP and an equation, just math. Drivetrain loss on manuals is still a bit more than 10%, but either way, it won't change "BHP", and no different using MAF readings, trying to figure out BHP off of it(MAFx1.25).
And we don't know if the valve "exploded", that just one thought..

Ya know the f23L is much dif than f23T, as the F23T is based of the BW k04-064 and modified. An f23L is basically a k03 with a milled comp housing to for a K04 comp wheel(hybrid).

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[Nizmo]

Don’t misunderstand, the ko4 can do 350bhp all day long. The various version of f23s can net you the 400’s with the supporting mods. You’ll throw a rod just as quick as a gtx will.

Bhp is exactly the same as whp.

If you ran lean on 20psi long enough enough it makes sense to melt the valve. Wouldn’t be the first and won’t be the last. This story as old as Audi time.

[Nizmo]

Apr and other have had many files made for this car over the years. Was always stage 1 and ko4. There are too many individual files for each cars tune you couldn’t just lump them all together nowadays. You could have stage 2 with k04 it depends what apr engineers will do per vin per tune. Ota tunes not always the same.

[Jayz691]

Apr and other have had many files made for this car over the years. Was always stage 1 and ko4. There are too many individual files for each cars tune you couldn’t just lump them all together nowadays. You could have stage 2 with k04 it depends what apr engineers will do per vin per tune. Ota tunes not always the same.

APR no longer has stage 2 cuz of the whole emissions nonsense, but when they did, it was a stock turbo file like all the others. Only company I know of that list their K04 file as a version of stage 2 is Uni(2+). Most list it as stage 3/K04. That's why you had issues running "stage 2" with a K04.
Turbo options are much dif/better for transverse cars, since they had an OEM K04 option to build off of. It's a tough task to get 300whp with a K04 setup on the b7.
IDK what ya mean by "BHP and WHP are the same", it's very different.

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[Nizmo]

APR no longer has stage 2 cuz of the whole emissions nonsense, but when they did, it was a stock turbo file like all the others. Only company I know of that list their K04 file as a version of stage 2 is Uni(2+). Most list it as stage 3/K04. That's why you had issues running "stage 2" with a K04.
Turbo options are much dif/better for transverse cars, since they had an OEM K04 option to build off of. It's a tough task to get 300whp with a K04 setup on the b7.
IDK what ya mean by "BHP and WHP are the same", it's very different.

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I was stating that the N75 is inadequate for anything over the ko4. F23 spikes no matter the tune. APR many years ago had Stock tune (stage 1) and the k04 tune, stage 2. 2+ would be anything like cat delete, no cat, stock cat, stock HPFP, flap delete, etc. Any combo of those. Those are individual files added into the tune. No APR tune is really the same, since there are many options. When you use their software there are many lists of files available not just standard OTA tunes.

300BHP on an 2.0t k04. with a manual is almost plug and play. Little needed for that. Some injectors a turbo and a tune. 350BHP Hi flow cat, hi-flow fuel pump, intercooler, get the oil out of the intake tract and get more timing too. Water/Meth is obviously an option as well. Prob is ko4 lacks the capacity to sustain peak pressure, and induces heat into the cylinder at higher rpm. The intercooler cant cool the charge efficiently. 20psi sustained depending on flavor of ko4 vendor is hard to do.

Wheel Horspower, measure on a static dyne, is the same as BHP measured on a dyno. There is no argument. I guess its possible your thinking of "equations" people use to convert Crank HP to BHP/WHP.

[Jayz691]

I was stating that the N75 is inadequate for anything over the ko4. F23 spikes no matter the tune. APR many years ago had Stock tune (stage 1) and the k04 tune, stage 2. 2+ would be anything like cat delete, no cat, stock cat, stock HPFP, flap delete, etc. Any combo of those. Those are individual files added into the tune. No APR tune is really the same, since there are many options. When you use their software there are many lists of files available not just standard OTA tunes.

300BHP on an 2.0t k04. with a manual is almost plug and play. Little needed for that. Some injectors a turbo and a tune. 350BHP Hi flow cat, hi-flow fuel pump, intercooler, get the oil out of the intake tract and get more timing too. Water/Meth is obviously an option as well. Prob is ko4 lacks the capacity to sustain peak pressure, and induces heat into the cylinder at higher rpm. The intercooler cant cool the charge efficiently. 20psi sustained depending on flavor of ko4 vendor is hard to do.

Wheel Horspower, measure on a static dyne, is the same as BHP measured on a dyno. There is no argument. I guess its possible your thinking of "equations" people use to convert Crank HP to BHP/WHP.

No, BHP and WHP are not the same, BHP is crank, whp is well, at the wheels.
Here in the US we use actual WHP more than not, when Dyno testing. In lots of other countries they like to use BHP(crank), even on the Dyno. The Dyno operator will put in their correction/drivetrain loss, etc. So when they do a run, the Dyno reads power at the wheels(rolling road) but displays BHP after said corrections. BHP readings are a calculation, NOT power at the wheels. That's why BHP are easily fudged, all they gotta do is put a higher drivetrain loss and they got higher BHP...
Only accurate way to measure crank HP is on an engine Dyno, which was used more back in the day of building old v8's, with no ECU, etc. Hook it up, run water/fuel/exhaust and throttle.
Far as stages go, stage 2 has always been stock turbo, hense your issues.
Never had an issue with IAT's, CTS FMIC keeps it nice and cool. Usually a few °C over ambient during a pull.

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[Nizmo]

No issues, only the inadequate N75. No issues running APR or anything other than spikes being controlled. Again no issues! lol

Going back to 06 we had only stock and ko4 tunes. Not sure if you know B5's as well but we had stock and ko4 tunes. Nowadays you can have more than that. Over 25 years in Audi, we use BHP and WHP interchangeably as they are the same. There is no replacement for Crank HP measured on test cell. Rolling road measures WHP/BHP. German car, Metric region. Use whatever you prefer I guess but I'll agree to disagree.

Back on topic was weather you were measuring your lambda running 20psi. Lean will melt/explode which seems to be your issue.

I guess the point I was making was that changing the wheel diameter and weight can have an impact on rolling road dyno tests changing WHP/BHP. Smaller diameter will increase acceleration on the same car. The hp and torque figures will be different (however negligible). In this case an automatic would make less BHP/WHP than the exact same car with a manual.

[Jayz691]

No issues, only the inadequate N75. No issues running APR or anything other than spikes being controlled. Again no issues! lol

Going back to 06 we had only stock and ko4 tunes. Not sure if you know B5's as well but we had stock and ko4 tunes. Nowadays you can have more than that. Over 25 years in Audi, we use BHP and WHP interchangeably as they are the same. There is no replacement for Crank HP measured on test cell. Rolling road measures WHP/BHP. German car, Metric region. Use whatever you prefer I guess but I'll agree to disagree.

Back on topic was weather you were measuring your lambda running 20psi. Lean will melt/explode which seems to be your issue.

I guess the point I was making was that changing the wheel diameter and weight can have an impact on rolling road dyno tests changing WHP/BHP. Smaller diameter will increase acceleration on the same car. The hp and torque figures will be different (however negligible). In this case an automatic would make less BHP/WHP than the exact same car with a manual.

Dude, BHP is crank, not the same as WHP. I can't believe this is even a debate, lol. All these euro guys that say "I'm running 400bhp", that would be low 300 on say a mustang Dyno, that gives power at the wheels..
No, it wasn't running lean, more like 22-23psi in summer, but that don't matter.
Yes, an auto will generally make less who on the same car/setup, but a dif equation would be used to find BHP(crank).
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[Nizmo]

BHP is measured at the wheel. Same as WHP. There is no debate.

Crank HP does not include the driveline. BHP does include the driveline. Very simple.

15 psi with heat is enough to pop a valve, so without knowing the lambda it may be up to the ECU which is never properly ratio'd at high boost. Of course the FPR can accommodate 1:1 but the problem is the heat at high boost. Like you said summer 22psi running lean usually all it takes. The real question is if you're going to do any Wideband after this considering the circumstances as I elaborated to many posts ago. That way the heat can be dealt with through timing and boost keeping the engine rich rather than lean. Lots of Eurodyne guys for that reason. Stock k04 should see 20psi max. Must have spiked hard. As. I also said N75 is inadequate at high boost and cannot bleed fast enough.

Still most plausible explanation is a sodium filled valve explosion at high boost and high heat while on a test drive with a tech. Of course 250K didn't help but the heat kills these motors.

Any dynomometer can measure HP, question is weather the dyne was setup correctly with enough preload to actually get "real" road conditions. Anyone can pop on rollers and get a graph.

400HP at the crank is 340ish with drivetrain loss on a standard day.

[Jayz691]

Wow... BHP is the same as crank. Just because some dyno's (mostly European countries) display BHP on a rolling road, don't mean it's the same as WHP... They calculate drivetrain loss and that's entered into the equation.
Saying 20psi is max for a K04 is also silly, lol. It's all adjusted in the file. N75 controls it just fine, with proper duty cycle. My tuning is custom, so when it was tuned, they had to dial back n75 duty so it won't overboost. It varies by turbo/setup as they're not all the same, that's why custom tuning is much better that OTS files like APR, Uni, etc.
Also, you'll have dif boost levels in cold or warm weather, because it's all load based. Cold air is denser, so you'll get less boost in winter, than you will in summer.
Saying 400crank is 340 at the wheels on a standard day is wild, cuz it will vary by drivetrain, etc.
Adding a wideband to monitor afr won't make a difference in the tuning, they go off of Lambda reading.
Sorry, but a lot of this stuff you're saying is pretty wild, and not even understanding that BHP is a calculation of crank, based off of WHP and estimated drivetrain loss, IDK what to say man, lol.

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[Jayz691]

I'll even leave this here, maybe Google/AI can explain it better and get it across to you.

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[Theiceman]

so,,,,,, meanwhile ,,, back at the original problem .......

Still waiting on the machine shop ?? I want to see this bad boy fixed :)

[Nizmo]

BHP is WHP but since Automatic transmissions came to be the default, so much drivetrain loss needs be calculated. AI answers won't change 100 years of automotive history lol.

We do test cell for engine builds and get the crank HP. We call that crank HP not Brake Horsepower. Then after engine install it is dyno'd and the drivetrain loss is the difference between the two. You can calculate vise-versa if all you had was a wheel dyno or engine test stand. Crank HP is crank HP we don't call that Brake Horsepower. BHP is mostly applied to manuals who require little calculation.

Brake horsepower refers to HP at the brake/axle. It is not accommodating for differences in wheel diameter like a mustang dyno will (If properly set-up).

At the end of the day, it is the wheel diameter that determines the final drive ratio.

[Nizmo]

Wow... BHP is the same as crank. Just because some dyno's (mostly European countries) display BHP on a rolling road, don't mean it's the same as WHP... They calculate drivetrain loss and that's entered into the equation.
Saying 20psi is max for a K04 is also silly, lol. It's all adjusted in the file. N75 controls it just fine, with proper duty cycle. My tuning is custom, so when it was tuned, they had to dial back n75 duty so it won't overboost. It varies by turbo/setup as they're not all the same, that's why custom tuning is much better that OTS files like APR, Uni, etc.
Also, you'll have dif boost levels in cold or warm weather, because it's all load based. Cold air is denser, so you'll get less boost in winter, than you will in summer.
Saying 400crank is 340 at the wheels on a standard day is wild, cuz it will vary by drivetrain, etc.
Adding a wideband to monitor afr won't make a difference in the tuning, they go off of Lambda reading.
Sorry, but a lot of this stuff you're saying is pretty wild, and not even understanding that BHP is a calculation of crank, based off of WHP and estimated drivetrain loss, IDK what to say man, lol.

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You got the valve exploded and want to start arguing every point I make. Duty cycle on N75 is maxed about 20psi, you cannot simply lower duty cycle at 20psi, in fact it usually needs gain to keep waste gate closed. ko4 is great turbo but 20psi usually maxed out. 22 psi its screaming. It is known to not hold 20 or 22psi to redline. Im not picking any model number just generalizing between the 30 various versions of k04. Maybe you got something special but most don't.

We offer APR as a dealer, if you want something else it's fine but generally all the same. Custom tuning for a tiny k04 seems pointless especially since it can't keep you from exploding valves. Wideband is not just a gauge to monitor. You have obviously never spend time on a dyno, because its the first thing we hook up.

[Jayz691]

You got the valve exploded and want to start arguing every point I make. Duty cycle on N75 is maxed about 20psi, you cannot simply lower duty cycle at 20psi, in fact it usually needs gain to keep waste gate closed. ko4 is great turbo but 20psi usually maxed out. 22 psi its screaming. It is known to not hold 20 or 22psi to redline. Im not picking any model number just generalizing between the 30 various versions of k04. Maybe you got something special but most don't.

We offer APR as a dealer, if you want something else it's fine but generally all the same. Custom tuning for a tiny k04 seems pointless especially since it can't keep you from exploding valves. Wideband is not just a gauge to monitor. You have obviously never spend time on a dyno, because its the first thing we hook up.

For a Dyno tune, yes. Not for custom flash tuning. The software won't read an outside sensor..
IDK what ya mean by "n75 is maxed at 20psi", my file request about 22psi with max duty % set at 60%.
Having a broken valve on an engine with 260k miles means nothing. Only debating things you're saying, that don't make sense, sorry...
Most people run a little more than 20psi on pretty much any K04 on these cars.

Brake HP is not called that cuz that's what's "at the brakes", lol.
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[Jayz691]

Here, even something for you to read.
https://www.carthrottle.com/features...-whp-explained

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[Nizmo]

If you did not tune the car on a dyno then technically it's OTA. Just seat of the pants stuff if using custom stuff like Eurodyne etc. A/F is critical to monitor to adjust fuel trims. Correction factor for ambient temps and atmospheric pressures can then be adjusted further. We use a standard day as a value 0. Back on topic you should monitor a/f going forward so you can adjust accordingly, rather than hope and pray it's been accommodated for by the rear o2 sensor which is narrow band anyhow. Nowadays A/F gauges have the ability to do much more than just monitor lambda.

ko4 will spike 22/23 sure, k03 will spike 18/19. Most ko4 cannot sustain that, as well as ko3 which usually settles to 15ish psi. N75 is not the best boost controller, it's nice but has its limits. N75 is only for small turbos imo because it cannot regulate correctly past 20psi. Some have better luck than others but fact remains you ditch n75 with larger than 22-23psi and of course when you go big turbo. Big turbo guys know N75 is inferior to 3-port and 4-port boost solenoids.

I would think if you shared that tune with the other a4 same thing will probably happen. The valve is black from an explosion from the inside out. Not a "chip". That is from melting basically.

[Jayz691]

Or from being cracked, and coated in carbon like the rest of the valve.
If you're referring to OTS(off the shelf) that's NOT what it is, it's custom flashing via data logs. For my K04 tune, I went through 5 revisions till it was dialed in. That was 3 years ago, been fine. I even recently(about 6 months ago) had some logs checked by my tuner, after I fixed a few things, just to see if I should adj the file. It was good... If there was a "tune issue" it wouldn't take 3 years to cause an issue, lol.
Of course a K04 won't hold 22psi to redline, that's why it tapers. Had nothing to do with the n75, it just don't flow enough. As rpm climbs, boost tapers and timing adv goes up. The n75 controls boost just fine, lol. Absolutely no need for an EBC on a K04. Plenty of people even use factory n75 setup on full frame setups without issue. It's only to control the WG, not directly control boost. That's why I don't get why you're saying "n75 is no good over 20psi", that makes no sense. Boost map has a set requested boost pressure under certain load, etc. To build boost, n75 duty goes up. When target is met, it drops, then as rpm goes up, so does n75 duty %(generally, on smaller turbos) to try and maintain boost, but it's only holding the WG closed/partially, depending on conditions.
The downstream 02 is a narrow band cuz it's there to monitor cat operation, upstream is used for Lambda readings.

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[Nizmo]

It is well known that the higher the boost the harder the solonoid is working to keep the gate closed. At one point all solenoids can be overcome.

I did not say the k04 cannot hold boost because of the N75. The k04 is small and cannot hold boost itself period. Not the n75s fault.

The N75 is inadequate at holding higher than 20 psi especially non-ko4 cars like f23 etc. F23's and others can and will hold boost all day to redline.

Sure a cracked housing will be releasing exhaust pressure screwing the a/f ratio further. The rear 02 simply isn't accurate as you may think it is. Wideband is just the way to go, especially with "custom tune".

I won't compare dyno tunes with OTA as they are apples and oranges.

Furthermore, when you hit about 21-22 on almost all OTA tunes overboost is hit. When that happens ECU cuts n75 and limp modes the throttle. The car needs be turned off and back on to fix the condition. Some set CEL some don't. When the car hits overboots usually pulls boost on n75 to 15psi (limit) then pulls timing and fuel. If this is what happened during a pull on that "test drive" but your "custom tune" was pulling 23psi and cut fuel bye-bye valve. Happens all the time. Again you aren't the first and won't be the last. Don't melt your engine.

Id suggest a proper OTA tune until you can dyno a custom proper tune.

[Jayz691]

It is well known that the higher the boost the harder the solonoid is working to keep the gate closed. At one point all solenoids can be overcome.

I did not say the k04 cannot hold boost because of the N75. The k04 is small and cannot hold boost itself period. Not the n75s fault.

The N75 is inadequate at holding higher than 20 psi especially non-ko4 cars like f23 etc. F23's and others can and will hold boost all day to redline.

Sure a cracked housing will be releasing exhaust pressure screwing the a/f ratio further. The rear 02 simply isn't accurate as you may think it is. Wideband is just the way to go, especially with "custom tune".

I won't compare dyno tunes with OTA as they are apples and oranges.

Furthermore, when you hit about 21-22 on almost all OTA tunes overboost is hit. When that happens ECU cuts n75 and limp modes the throttle. The car needs be turned off and back on to fix the condition. Some set CEL some don't. When the car hits overboots usually pulls boost on n75 to 15psi (limit) then pulls timing and fuel. If this is what happened during a pull on that "test drive" but your "custom tune" was pulling 23psi and cut fuel bye-bye valve. Happens all the time. Again you aren't the first and won't be the last. Don't melt your engine.

Id suggest a proper OTA tune until you can dyno a custom proper tune.

It's not hitting "overboost" conditions if it's tuned for it.. if the tune request 22psi peak, and it hits 22psi, it's NOT overboosting. You kept saying "the n75 is inadequate above 20psi", but it's not. With rods, people run 24-25psi on a K04 all the time, on stock boost control solenoid.
The rear 02 is a narrowband because it's not really involved in fuel trims, that's what the upstream is for.
And you do know an f23L is basically the same as a K04, right? Just usually with a k03 turbine. Very different on transverse cars(A3/S3/etc), but the b7 is not transverse. Turbos like the JHM K04-R are basically same as the old Frankenturbo f23L.
The car is/does not overboost, go into limp mode(never), or cut fuel. Never, ever had that happen, lol. As I've said before, this setup/tune is 3 years old(ish)... Nothing wrong with it.
I cleaned up the broken valve, and it didn't crack into the sodium filled area. That's inside the stem, and a little in the head of the valve.
May be hard to tell in the pics, but it's only the metal showing.

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[Theiceman]

i would totally keep that thing on my desk forever lol...
how is the repair coming along ?

[Nizmo]

It may look as if it didn't get to the center but the heat is so high it melts/welds the metal. They will all look like that usually.

Valves are pretty strong as they only bend when a piston hits them, so an inside-outwards explosion from inside the valve took out those chunks. If you haven't still found them thats the tell tale. If you find the pieces somewhere that may change diagnosis depending on what those pieces look like and how many of them there are. If 1 big piece is found whole may be an impact chip/stress-fracture. As it stands now this is straight up sodium filled valve explosion. On cyl 1 no less. Which is what all other cylinders are timing based. Cylinder 1 is usually hottest. Send to a metallurgist to get detailed info on whether it was stress fracture/crack or forceful separation if you want to be able prove my diagnosis wrong. Of course I am not saying 100% guarantee that just my opinion. It could be that the valve exploded at higher rpm and when the valve closed it closed on the fragments taking out the valve and seat. The fragments therefore were small enough to get through the open valve or hole in the valve.

A failing oil pump and/or loose worn rod bearings/crank bearings can cause low oil pressure as well. If the valve got too hot from no oil or little oil the seat will get destroyed. Could be an oiling situation undiagnosed. When you get the car back up it will be apparent what else failed and where the metal fragments are left.

I won't cherry pick a turbo. F23 and ko4 not same. Spikes never good no matter tune. Rather 22psi to redline rather than tail-off anyways. Keep a/f consistent throughout no odd maps accommodating for tailing turbo. Besides can't keep boost. Ko4 cool, f23 better, gtx even better but N75 great stock thats about it. Your not going change my opinion on N75 after 25 years on these cars professionally. It's too small to bleed, causes issues at the higher levels and we ditch them or run them parallel with another controller capping the waste gate control port usually. Stock to stage 1 works well as well, however lifespan of N75 is less than to be desired. They go bad consistently too, usually 5 year life-span or so mileage will vary. Well known again on turbo issues N75 issues.

The only reason I ever brought up N75, is because if was spike/overboost on a k04 and a/f went lean on an old tired engine its no surprise damage resulted. We can argue about the N75, but it's dependent on the situation for if the N75 is the best choice or an alternative can be used. Of course some still use N75 and others don't. Can we agree on that at least? I personally like the newer Spec 2 GReddy Profec. 3 Port. Dyno tune it in AND THEN Cap the OEM waste gate control port. Done on at least 30 cars all love it. Turbo noises for days!

I do understand this is your post and your context is YOUR car, but I am generalizing to all B5, B6, B7 most specifically modded ones. When (they) hit overboots it becomes a fail-safe mode. You can tune in the N75 sure, but this is what happens when you rely COMPLETELY on a $50 boost valve IMO. Giving you respect you deserve for all this work and abilities, its not even you're fault its the kids "test drive".

Hope it gets fixed soon, manual swap if was me :)

[Jayz691]

i would totally keep that thing on my desk forever lol...
how is the repair coming along ?

Just waiting to get the head back, machine shop has it(new seat and deck). Hopefully by end of week.
Yeah, I'll prob keep it, lol.

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[Jayz691]

It may look as if it didn't get to the center but the heat is so high it melts/welds the metal. They will all look like that usually.

Valves are pretty strong as they only bend when a piston hits them, so an inside-outwards explosion from inside the valve took out those chunks. If you haven't still found them thats the tell tale. If you find the pieces somewhere that may change diagnosis depending on what those pieces look like and how many of them there are. If 1 big piece is found whole may be an impact chip/stress-fracture. As it stands now this is straight up sodium filled valve explosion. On cyl 1 no less. Which is what all other cylinders are timing based. Cylinder 1 is usually hottest. Send to a metallurgist to get detailed info on whether it was stress fracture/crack or forceful separation if you want to be able prove my diagnosis wrong. Of course I am not saying 100% guarantee that just my opinion. It could be that the valve exploded at higher rpm and when the valve closed it closed on the fragments taking out the valve and seat. The fragments therefore were small enough to get through the open valve or hole in the valve.

A failing oil pump and/or loose worn rod bearings/crank bearings can cause low oil pressure as well. If the valve got too hot from no oil or little oil the seat will get destroyed. Could be an oiling situation undiagnosed. When you get the car back up it will be apparent what else failed and where the metal fragments are left.

I won't cherry pick a turbo. F23 and ko4 not same. Spikes never good no matter tune. Rather 22psi to redline rather than tail-off anyways. Keep a/f consistent throughout no odd maps accommodating for tailing turbo. Besides can't keep boost. Ko4 cool, f23 better, gtx even better but N75 great stock thats about it. Your not going change my opinion on N75 after 25 years on these cars professionally. It's too small to bleed, causes issues at the higher levels and we ditch them or run them parallel with another controller capping the waste gate control port usually. Stock to stage 1 works well as well, however lifespan of N75 is less than to be desired. They go bad consistently too, usually 5 year life-span or so mileage will vary. Well known again on turbo issues N75 issues.

The only reason I ever brought up N75, is because if was spike/overboost on a k04 and a/f went lean on an old tired engine its no surprise damage resulted. We can argue about the N75, but it's dependent on the situation for if the N75 is the best choice or an alternative can be used. Of course some still use N75 and others don't. Can we agree on that at least? I personally like the newer Spec 2 GReddy Profec. 3 Port. Dyno tune it in AND THEN Cap the OEM waste gate control port. Done on at least 30 cars all love it. Turbo noises for days!

I do understand this is your post and your context is YOUR car, but I am generalizing to all B5, B6, B7 most specifically modded ones. When (they) hit overboots it becomes a fail-safe mode. You can tune in the N75 sure, but this is what happens when you rely COMPLETELY on a $50 boost valve IMO. Giving you respect you deserve for all this work and abilities, its not even you're fault its the kids "test drive".

Hope it gets fixed soon, manual swap if was me :)

New TI avant is manual, so that's the new ride. This will be driven while doing some engine work on the avant, then stripped for some performance parts, then sold. 260k miles and showing it's age. Avant is in 10x better shape, and like mentioned, manual.
Oil pressure is solid. Everything has been done. Good pump assembly with WASA freewheel, new piston cooling jets, updated pickup, etc. Went through everything a few years back, and have a gauge. Sits at 18-19psi hot idle, and 60psi @2500 or so.
I am curious of the cause, but not THAT worried about it. Piece is likely gone. Just glad it didn't hang out in the cyl long, 1 little scratch in the piston dish. That's it.
Gonna pull the turbine housing off the turbo for other reasons(crack), maybe I'll find it. But no turbine wheel damage. Maybe it went through the WG like Iceman said, or blew apart like you said. IDK, maybe I'll find out. No cat for it to get caught in, so maybe in the exhaust somewhere, lol.

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[Jayz691]

Well, finally got my head back, Damm it took forever. Guess that's "not being a priority" for ya .
Can finally start putting her back together..

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[Nizmo]

Couple beers, some tunes on a Friday night building an Audi head, nice night in the shop!

[Theiceman]

Well, finally got my head back, Damm it took forever. Guess that's "not being a priority" for ya .
Can finally start putting her back together..

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wow and they didn't reinstall and lap valves ?? that's crazy . it should have come back ready to bolt on.

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[Jayz691]

wow and they didn't reinstall and lap valves ?? that's crazy . it should have come back ready to bolt on.

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Na, just had them press a new seat in, and deck it. Shop wasn't gonna pay for "everything" and didn't feel like fighting over it. Lawyer would cost more than the work, lol. Just wanna get it together and back on the road.
I lapped the valves before I dropped it off. Just had to hit the new valve/seat quick after getting it back.

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[Jayz691]

Head's together.

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[Jayz691]

Getting there.

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[Jayz691]

Almost together. Get a few hours here and there to work on it, and it's been HOT AS HELL, lol.

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[Nizmo]

May I suggest one of those Ego fans! Use it every day, the big one. They now make a smaller one, anyways it mists (pulse or constant).

One of the best investments made, I have to work in some hangars too and it is hotter than the sun in there.

[Jayz691]

May I suggest one of those Ego fans! Use it every day, the big one. They now make a smaller one, anyways it mists (pulse or constant).

One of the best investments made, I have to work in some hangars too and it is hotter than the sun in there.

Could def use a fan for these hot, muggy days, lol. Sux when sweat is dripping on everything you're working on..

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