Fuel Pumps

[Classik]

Cool. l'll be curious to see how you get on, especially with installing the pump in the tank. Take some photos please.

It's going to be done with the guy who recommended the setup, he has done it already And yes, I'll make sure to take photos!

[Weiß-sechs]

You might want to replace the V51 after run pump. It can fail (often without symptoms)

Many apologies for the hijack Classik!

Shopp, will a failed V51 throw an error code on VCDS? I've never heard any pump after switch off even after a "good run" on mine; I do follow the same regime as yourself though with very low revs and a slow cruise for a couple of miles. It'd be nice to know that the V51 is operational...or not.

[Shoppinit]

No, no codes. You just have to listen out for it after you switch the engine off. Can't remember the exact conditions for starting the pump, but it should come on if your engine is fully up to temp when you switch it off.

[Shoppinit]

viewtopic.php?f=2&t=82737

[Classik]

Many apologies for the hijack Classik!

No probs

[Weiß-sechs]

viewtopic.php?f=2&t=82737

Cheers.
That's a blast from the past....only 9 and a bit years old lol
Seems that there's no real easy way to check it out then, especially with my dodgy hearing...I'll see if one of the kids fancies getting a warm ear

[Classik]

As I'll have the intake manifold removed for dirt cleaning and non return valves / jet pump replacement, I'm considering changing the injectors as well.

Following recommandations from an other rs6 forum, I'm considering those : https://treperformance.com/i-23899501-g ... ors-4.html
Do you think they would fit out of the box (form factor, connectors)? BTW what's the name of the oem injectors connectors?
Thanks!

[Shoppinit]

What’s the story?

[Classik]

Hi Shopp,

Thank you vm for the continued interest, but nothing to share atm. But... I'll have some news very shortly as I'll get the car back from my mechanic no later than the day after tomorrow! Needless to say I'll make sure to report here

[Classik]

So I just got the car back from my mechanic and now I have new non-return valves, jet pump, manifold seals and injectors seals. The old jet pump was very loosely attached to its hoses and immediately broke when unmounted, a return valve was not functioning properly, and the manifold seals paint was seriously pealing (photos will come shortly). Of course all accessible pipes and hoses in this area have been cleaned / controlled in the process.

In short the car feels much better (smoother idle, better acceleration) but... the MAFs discrepancies are still there.

[Shoppinit]

FFS. It's getting ridiculous!

Remind me, because a lot of water has gone under this bridge:

- Did you clean the PCV system out completely?
- Did you replace the PCV valves?
- Did you put the old wastegates back on?
- Did you check the N75 pipes for leaks?

Can you do a pressure test on the wastegates? Make sure they both start to open at the same pressure? Should be about 0.5 bar. I mean the whole wastegate, not just the actuator.

Can you check that both wastegates open freely without sticking?

How much discrepancy are we talking about now? Can you do a new log and post it up in csv format? Log the following:

- A half throttle 3rd gear (or 4th if not impracticable) run from 1500 to 6000 rpm
- A full throttle run as above
- A constant speed run at 2600-2700 rpm

Log groups 002, 117 and 118. Or the MAFs, N75 duty cycle and boost (specified and achieved) if you log items individually. In turbo mode.

Once you've eliminated the leaks, PCV, N75, N249, DV and all the other vac systems, there's not much left other than turbo imbalance or exhaust obstruction to explain this.

I wonder if there's a way of checking the pressure from the individual turbos. You could check one turbo at the N75, but the other one would be more problematic. Not sure if there's anywhere you can attached a pressure gauge easily. There might be a blanking plate / plug. Or I guess you could check the pressure at the N75 and compare it to the total pressure at the inlet manifold. I'm not convinced that it's as simple as Total pressure = Pressure1 + Pressure2 but might give some indications.

I'm wondering if a boost side leak could cause this issue. Seems unlikely. Plus you're on Wagners, aren't you?

[Classik]

FFS. It's getting ridiculous!
can't agree more facepalm..
Remind me, because a lot of water has gone under this bridge:

- Did you clean the PCV system out completely? yes
- Did you replace the PCV valves? yes
- Did you put the old wastegates back on? not yet, will do shortly
- Did you check the N75 pipes for leaks? yes

Can you do a pressure test on the wastegates? Make sure they both start to open at the same pressure? Should be about 0.5 bar. I mean the whole wastegate, not just the actuator. yes I suppose I can control whether they are calibrated the same on both sides

Can you check that both wastegates open freely without sticking? will check

How much discrepancy are we talking about now? seems worse than ever Couldn't find the time for a proper test but at idle it was like 2,5g/s left bank versus 4,5g/s right bank..

Can you do a new log and post it up in csv format? sure, will do Log the following:

- A half throttle 3rd gear (or 4th if not impracticable) run from 1500 to 6000 rpm
- A full throttle run as above
- A constant speed run at 2600-2700 rpm

Log groups 002, 117 and 118. Or the MAFs, N75 duty cycle and boost (specified and achieved) if you log items individually. In turbo mode.

Once you've eliminated the leaks, PCV, N75, N249, DV and all the other vac systems, there's not much left other than turbo imbalance or exhaust obstruction to explain this. yes I ve also reach the same conclusion about turbos

I wonder if there's a way of checking the pressure from the individual turbos. You could check one turbo at the N75, but the other one would be more problematic. Not sure if there's anywhere you can attached a pressure gauge easily. There might be a blanking plate / plug. Or I guess you could check the pressure at the N75 and compare it to the total pressure at the inlet manifold. I'm not convinced that it's as simple as Total pressure = Pressure1 + Pressure2 but might give some indications.

I'm wondering if a boost side leak could cause this issue. Seems unlikely. Plus you're on Wagners, aren't you? yes I am equipped with Waggies

Thanks Shoppinit! Actually I kind of reached the same conclusion about the turbos, but still have hope it could be a easier fix..

[Shoppinit]

It still “feels” like an air leak. Could there be something really improbable like a split inlet pipe or something?

Maybe you could put a borescope down where the MAFs go to check for cracks.

A long while ago I mentioned the tubes that go from the inlet to the turbo compressor side. Did you ever check them?

[Shoppinit]

Might be time to make that smoke leak detector kit.

Or get some of the leak detector spray from Audi.

[Classik]

Yeah, time to find that guy/girl from St Denis..

Regarding the other suggestions you've made:
- split inlet pipe / cracked turbo tube : I suppose the curvature is small enough to allow my 30€ borescope to go down inside through the air inlets, good point.
- coming back to a previous question you've asked : yes I did check all pipes surrounding the N75, but not up to the turbos. I hope this can be done without having the engine out..
- As far as the blocked exhaust scenario is concerned, could that explain the discrepancies knowing that the air coming from both turbos is mutualised at the entrance of the manifold?
- Those wastegates you are referring to are part 36 below, right? Maybe it's just lazyness, but wouldn't it be enough just to swap left and right and see how it goes? And BTW, where are the dump valves on our cars? Directly attached to the turbos?

Can't thank you enough for your help!