Audi C5: Allroad boost leak causing overboost???
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- Опубліковано 30 гру 2017
- Thomas
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Video showing VCDS "label file editing" to follow next week... sorry about the wait.
Hi. did you ever make the VCDS "label file editing" video?
@@Kolpus Sorry... I can't find it in the 1600 videos I have. Some label files can no longer be edited (can not click on it to open). When you have VCDS attached to your car and the label file is "clickable"... click on the label file and then simply scroll through the file until you get to what you want to edit / change.
That was awesome.
Even though the PIDs fooled you you still worked through it. I appreciate the effort you took to explain and diagram it for us. Sweet diagnosis. Thanks!
Thank you for watching!
I can see where having the label PIDs reversed could get you into trouble. Good explanation Thomas of pointing it out along with why the boost pressure is high when there is a leak. Makes sense to me :)
I should have tried a Snap-On scanner... oh, my bad... it probably wouldn't have had any PIDs! =)
This is a great video. I am having this exact same problem with my allroad. Gives me some ideas of things to check next.
Thank you for watching!
Makes sense. The boost is leaking so it's not giving the engine what it wants or what sees so it tries to give it more and that hole is not a constant so sometimes the boost is too much.
Real good color schematic. Nice.
Good video Pal. Happy New Year.
Thank you!
Happy New Year to you & yours!
Marty you should make some vids on automotive related stuff . Your quite good at it .
My garage is my stone covered driveway and while I've done a lot of repairs in it I think it's a little too cold out there right now.
My mother in law has a garage but it's not always available.
Interesting diagnostic Thomas. Your explanation made sense to me.
It was a bit of a weird one... next time it won't be for me!
I know I said so already, but... Happy New Year & all the best to you & yours!!!!
(2018, it's official now) =)
Thomas EXOVCDS Thanks my friend.
I'm having the same issue my self on my 05 2.7 allroad. I just tested my n75 and wastegate lines. They were fine. My tune is for 18psi, but I'm surging upto 25psi in wot. I'm about to smoke test my engine on 15psi to see if I can find any leaks.
Great video Thomas!
Thank you... hope it made sense!
Happy New Year & all the best to you & yours!!!!
Same to you and your family and it made a lot of sense!
Liked the old family video's to!
Thank you... I don't get a lot of diagnostics, so I need to trust myself more. Feedback is helping me gain confidence. Really appreciate you watching my stuff!
Thomas trust in yourselfe, if you are fixing cars for so long, and you have your own youtube channel with more than 20.000 people having faith in you, you're doing something right.
And even if you make a mistake, you don't get thrown of the planet.
Thanks Dan!
I have the luxury of not posting my mistakes! =)
I was under the impression the boost pressure readings you see in VCDS were from the MAP sensor in that boot, and the pressure lines that go to the N75 to power the wastegates were the ones connected to the compressor housings of the turbos. If that's the case, the wastegates would get decent stable pressure that would always be more than what the MAP sensor sees. I'm interested in your thoughts.
Although the N75 receives pressure directly from the compressor housings... any large boost leak (such as the torn hose in this video) won't allow boost pressure to push against the wastegate actuators quickly enough to open them. Boost will take the path of least resistance (torn boot)... somehow though, the MAP sensor was able to read boost that was higher than specified at times, probably during the time the split in the boot was opening up or closing.
Good stuff BTW. I Have to watch more of this stuff.
Thank you... here's a good channel I found recently:
ua-cam.com/channels/R73yN7vT7-P541g2qlfRrg.html
Makes sense great analysis
Thank you... feedback / confirmation of my suspicion might help me get more confident!
Happy New Year & all the best to you & yours!
This is very interesting, did you have an over boost code? It seems like it was under boost then after the fix values were good. Maf-map readings would help in this case right?
It was overboosting (as shown by the yellow graph) even though there was a leak. I'm not sure if VCDS would have allowed advanced measuring blocks on that Allroad... to select specific PIDs. Fuel trims might have also been good to datalog. Next time! ;-)
a question I have to change head gaskets and valves for that I have to remove the springs or the valves come out without removing the springs my car is Audi 1999 a6 quattro 2.8
The valves are held in place with springs... you need a spring compressor. You can download service manuals from here:
erwin.audiusa.com/erwin/showHome.do
You can buy the tools that you need from here:
audi.snapon.com/OnlineCatalog.aspx
every throttle body boot tears in that place causing that over boost its make up air added and the n75 cant calculate it
Thank u sir
Thank you for watching!
Good work
Thank you and thank you for watching!
Your workbench with all the pits in it is freaking me out. In 2018 im wishing that top is replaced . How many time did you miss and hit that work top - wow :)
25 years of cockroach hunting!
Looks well used and isn't a museum piece or coffee table = Good mechanic/ technician......and cockroach hunter.....
I used to have a bench like that (this one is the bay next to me)... here's a look back in time:
ua-cam.com/video/34LYdtZWUB8/v-deo.html
Interesting! Always annoying when you have trust issues with scan tool data... Doesn't the N75 take boost pressure right after the turbo's? Up there the boost should be good. I dont know the twin turbo setup from audi that well. Otherwise your explanation sounds very logical. Best wishes Thomas
Yeah... each turbo sends boost from the snail housing to the N75. This was a weird one and since this was the first time my coworker and I ran into this (on one of these engines)... we focused too much on the overboost part. Air rushing out of my E34 turbo wastegate didn't help either... the sound on this Allroad was similar, so that kept me focused on the overboost rather than a boost leak. When I smoke tested the N75 boost hoses, that's when I found the intake leak at the throttle body hose. I know what I'm checking first next time! LOL
Thomas EXOVCDS haha pretty funny :) I had an engine die once when i leaned on the air filter housing only to find it had a massive rip in the intake hose beneath. Right before i was going to grab a smoke machine
I have an MK4 1.8t Golf that is getting this code and goes into limp mode. Boost leak tested, smoke tested, new N75E (N75J previously), new MAP, new MAF, new diverter valve, new turbo/wastegate, all factory hoses replaced and still limp mode and P1557. The car has a mail order tune from GIAC. I searched online and found some individuals with GIAC tune who had this problem due to the tune, but I called GIAC and I was told that it is definitely the N75J valve that is causing the problem. I replaced it with the recommended N75 and the problem continues. Is there anyway to verify that the tune is/is not the problem? I've taken it to a VW specialist with VAGCOM, but he could not figure out what caused the positive deviation code. Any direction would be appreciated.
Is the N75 installed correctly? Does the wastegate move when pressure is applied?
Yes, longest nipple going into the turbo inlet pipe. I will need verify if the wastegate is moving with pressure. I will let you know soon. Thanks
OK
Electrical tape will fix that right up. I think your explanation makes sense 🤓
Will give it a go on the next one!
Thank you!
I guess the leak required more turbo boost...for a given rpm, vehicle speed, load, etc the pcm didn’t see what it is mapped to see. Therefore an overboost condition is present.
I think 🤔 😂
Something along that line.
hahaha thats every tbs on all 2.7t audi normal tear is lower section over boost reading but no real boost
Yeah, that's what I learned that day.
Your brain hurts?, mine is overboosting lol :-D.
I know nothing about this system, but when feedbacks dont agree with reality and the leak is a bit random, im not supprised the computer made the wrong adjustment, and made things worse.
I did say i know nothing lol.
I'm still thinking about this one and I know it will keep me on my toes when dealing with similar issues!