hello all im a newby and need some good advice on low boost levels. much appreciated!

mtaylors3

Registered User
I have recently bought an audi s3 8l 2001.

I bought it with a f*cked engine and turbo so I've spent alot of money on a low milage amk engine and recon turbo. got a good mechanic to fit it all and it runs sweet. But when I picked it up it only boosts to about 5 psi and I think standard they run at 7

I had it remapped at the weekend thinking this would solve it.... it didnt still getting 5psi. Theres no boost leaks on it its been tested. When I bought the car the guy said he had the n75 valve bypassed I think to give it more boost.

Can someone please help as my bank is empty naw, dont want to take it somewhere and get charged a fortune. thanks all!
 
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s3dave

TFSI Hybrid
Supporter
You need to get the N75 plumbed back in as standard and go from there, what sort of map did you get on it?
 

Dani_B19

Audi-sports own special child.
Who the hell remapped it? Dont tell me they actualy turned around, charged you and said rght its remapped and let you go, any mapped would know straight away somethings wrong if the cars only making 5psi, thats actautor pressure, also theys cars make around 11/12psi as standard.
 

mtaylors3

Registered User
it was a mobile remapper. but before it only boost up to 5psi. i thought the remap would sort it. im new to audi turbos so not clued up. where does n75 plumb to?
 

Benjiman46

R-Tech Terrorist
AMKs run between 11 and 12 as standard as Danny says... Does it feel rapid for about a second and then die down to 5 psi or does it only boost to 5? When you unplug the N75 it'll only boost to 5psi, and if a monkey's messed around with it and tried bypassing the n75 (stupid idea) then it will only run on the actuator pressure. The n75 controlls the closing of the actuator, so bypassing it will leave it stuck open, letting all those exhaust gasses that spool up the turbine go to waste, hence it only boosts to 5psi. You should be able to fix it with a properly set up n75 valve (provided it's still there) if not you'll need a new one. Oh and don't fall into the chav-trap of buying one of those "modified/uprated" n75 valves, it'll only knacker your engine over time.

Don't even get me started on the chimp that mapped your car...
 

<tuffty/>

Badger 5 Edition...Its all about the flow...
Staff member
Moderator
Have you scanned for fault codes yet? be the first place to start... 5-7psi is actuator pressure so its either in limp mode or its plumbed up wrong...

<tuffty/>
 

mtaylors3

Registered User
yes the valve is still there. its the one with two small pipes on it. no on the guage it just goes to 5 psi and no higher.
 

s3dave

TFSI Hybrid
Supporter
it was a mobile remapper. but before it only boost up to 5psi. i thought the remap would sort it. im new to audi turbos so not clued up


Here is how it should plumb in, have you got a pic of your setup and then we can probably help better....

 

mtaylors3

Registered User
P1160377.jpg P1160378.jpg

this valve i take is the n75. this was just sat near coilpacks when i bought it. so i told the mechanic just to set it up same as how it all was before it came out.
 

s3dave

TFSI Hybrid
Supporter
Thats your n249 Valve, it looks like it has been by passed, so should be ok,, it is a lot smaller than that, go further back and to your right, by the intake..

The top thin hose directly in the middle of your pic should lead you to it..
 

dre_S3

Registered User
No mate that's not your n75 valve thats your n249, the valve you want is by the tip and looks like the one above and should have a hose connected to it that goes down to the turbo
 

s33nyboy12

Registered User
Please please please please tell us who remapped it? The good news is, your in the right place to get clued up about Audi turbos!

There is some good n75 threads on here just use the search bar at top. Also 5 psi really? My van runs more than that , as said above standard is about 11 psi and remapped should be in region of 20psi + @ peak boost iirc

Sean
 

mtaylors3

Registered User
P1160387.jpg P1160381.jpg

right fellas, this is all i can see. the pipe from the actuator and all yellow pipes lead to these sections pictured. so im taking that the n75 has been removed unless im looking in the wrong place. can you help me from these pics?
 

mtaylors3

Registered User
haha a guy on the internet. his website is redhotremaps.co.uk. when he turned up i thought he was abit of a novice because he had all these wire on a extension lead just taped up together, just didnt look the part but i thought this coul solve it. it does feel faster and has a higher rev range just oviously they is somethig wrong in my pipe work and dont have a clue what to do. the only turbo iv has is a 220 rover haha
 

mtaylors3

Registered User
just looked that is the n75 with the gold plate. so would there be any other reason for low boost
 

<tuffty/>

Badger 5 Edition...Its all about the flow...
Staff member
Moderator
Not really... fault codes? and its a J valve... generic map + J valve is not going to help you I suspect... J valve promotes spiky boost and the ECU will go into limp mode in std tune... J valves can be mapped around by custom mappers so this is not an issue but on a generic map I doubt its the case and could well be throwing the ECU into limp mode... anyway... get the car scanned for fault codes first... there is a link in my sig to a thread that will help you identify what the codes mean and then post them up... this will help diagnose the problem you are having..

Sorry to say but anything could be wrong with your car especially as its now running a no name generic map... and how did you have it leak tested? smoke test?

One last thing... PLEASE PLEASE PLEASE make the effort to use english in your posts... by english I mean capitals where required, punctuation and paragraphs.. I appreciate posting from a mobile (guessing thats what you are doing)... it just makes it much easier to read...

<tuffty/>
 

mtaylors3

Registered User
I used a boost leak tester that goes on your intake and blow air threw. So that part with the gold plate is not the n75?
What do you mean by J valve.
sorry to be a pain!
 

Benjiman46

R-Tech Terrorist
View attachment 10015

right fellas, this is all i can see. the pipe from the actuator and all yellow pipes lead to these sections pictured. so im taking that the n75 has been removed unless im looking in the wrong place. can you help me from these pics?

Right pal, you're looking right at it there... The plug underneath... Make sure that's connected/no wires hanging out. If they are ok, try things in kind of this order: spray a bit of WD40 in the plug just to make sure it's clean and contacting well, make sure your n75 is plumbed up correctly... </tuffty> is your man to ask about that, he's always pulling drawings from places haha, then once you know it's plumbed up right, check pipes for splits/leaks leading to the n75, if there are none, try and borrow an n75 valve to make sure yours isn't fubar. If it's still got problems then the only thing I can think of is the actuator is stuck open on your turbo... Not quite sure why it would be, but I'd be asking questions at the place I got the lump and spinny bit installed. Did you source your own turbo? Are they a preputable company?

Ben
 

Dani_B19

Audi-sports own special child.
Hold on, to me it looks like the J valve is the wrong way around, if so the car will make actuator pressure wont it, when i had trouble with mine (i fitted it wrong) the car went mental, you can fit it so the car will boost to crazy levels then hit limp mode, fit it so the valve wont work and just make actautor pressure or fit it right and itll run right.

Maybe its me looking at it wrog but it looks plumb in wrong! Thoughts?
 

<tuffty/>

Badger 5 Edition...Its all about the flow...
Staff member
Moderator
I used a boost leak tester that goes on your intake and blow air threw. So that part with the gold plate is not the n75?
What do you mean by J valve.
sorry to be a pain!

The N75 'J' valve is a valve that people used to use to get a boost spike out of as its a lazier valve to the std 'F' valve fitted to the S3... its a pikey mod to get a bit more boost as the turbo spools which worked ok on early 1.8t's like thee A3 with AGU engine codes as the ECU were less fussy... the more up to date ECU's used in the later A3/S3 (like yours) don't like positive boost deviation from the boost request it sets which can happen under under certain circumstances... this combined with any other potential issue you may have will end up putting your ECU into limp mode pretty much all the time..

With custom mapping this is not an issue (as long as the mapper knows what he is doing of course and there are quite a few that don't) but as your car has an unknown generic map on it then all bets are off...

It looks plumbed in ok from the pics but there could be other things that cause the issues you are experiencing which at this point is due to the unknown history of your setup... you say you have a recon turbo but it could be the actuator is set incorrectly causing issues... you say you have had a leak test but can you confirm exactly what you had tested and how? it makes a difference... you also MUST read out any fault codes you might have as these will help to diagnose the problem you are having... I would almost put money on a 17705 being in there and possibly a 17608 code...

Read this http://www.audi-sport.net/vb/a3-s3-...portant-when-posting-asking-help-updated.html then get the car scanned for faults and repost...

<tuffty/>
 

<tuffty/>

Badger 5 Edition...Its all about the flow...
Staff member
Moderator
Hold on, to me it looks like the J valve is the wrong way around, if so the car will make actuator pressure wont it, when i had trouble with mine (i fitted it wrong) the car went mental, you can fit it so the car will boost to crazy levels then hit limp mode, fit it so the valve wont work and just make actautor pressure or fit it right and itll run right.

Maybe its me looking at it wrog but it looks plumb in wrong! Thoughts?

N75J are kinda the opposite of a std valve... EDIT... As Dave has confirmed below your spidey sense was spot on Dani... :icon_thumright:

n75j.jpg


...and side by side
N7506.jpg


<tuffty/>
 
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s3dave

TFSI Hybrid
Supporter
Lol this is confusing but it is plumbed in wrong!!

Opposite the intake should go to wastgate...... yours is going to the charge pressure going by your pics....
The pipe with the red tie wrap should be opposite your yellow pipe, then put the other in the bottom...VOILA
 

<tuffty/>

Badger 5 Edition...Its all about the flow...
Staff member
Moderator
Lol this is confusing but it is plumbed in wrong!!

Opposite the intake should go to wastgate...... yours is going to the charge pressure going by your pics....
The pipe with the red tie wrap should be opposite your yellow pipe, then put the other in the bottom...VOILA

Good spot...

<tuffty/>
 

Dani_B19

Audi-sports own special child.
Thought so :). Its ok Dave and Tuffty, we know that old age starts to break down your vision :) haha.
 

mtaylors3

Registered User
Thanks very much lads. Swaped them pipes and god its fast!!! You all have been very helpful. Im glad i joined audi sport. But my boost gauge has stopped working naw. Too cold outside to look thow.
Thank you all again!!!
 

s3dave

TFSI Hybrid
Supporter
Nice ...you have probably just knocked the boost gauge pipe off, (Look for a T piece) ) but make sure you get it sorted sooner rather than later esp if it is plumbed into your FPR (fuel pressure regulator)...:icon_thumright:
 

s33nyboy12

Registered User
Yeh , don't leave that boost gauge just hanging or unconnected create a nice new leak for you and a new fault code if you do get it scanned!

Dani b19= hawk eyes, I had to look 3 times then came the ; " oh yeah!" Lol
 

Dani_B19

Audi-sports own special child.
The only thing id be worries about mate is the pikey remap your car now has, you need to get boost, timing and afr logs up, he surely cant have remapped the car properly if it wasnt running right.


Haha, 2 pints of guniess before hand helped :).
 

mtaylors3

Registered User
Ill sort it tomorow just took it for a drive after i swapped them then parked it it. But soon as i put my foot down after swapping them it was just instant smile on face!!
 

Benjiman46

R-Tech Terrorist
Nice ...you have probably just knocked the boost gauge pipe off, (Look for a T piece) ) but make sure you get it sorted sooner rather than later esp if it is plumbed into your FPR (fuel pressure regulator)...:icon_thumright:

+1!!! Don't drive it if your boost gauge is plummed into the FPR and not working... you'll be running lean as f**k and with it being mapped you'll end up with some nice holes down the side of your pistons ;)

Ben

EDIT: Even not mapped it's still a bad idea btw... :p
 

s33nyboy12

Registered User
Good stuff, least your smiling now! Be a good idea to get it scanned though and reset then a rescan after a short drive. Search people with vcds in your area on the forum section.
 

<tuffty/>

Badger 5 Edition...Its all about the flow...
Staff member
Moderator

mtaylors3

Registered User
Everything plumbed up fine naw. But still on the boost gauge its only showing 5psi. But its oviously not that as i can tell its boosting alot more naw
 
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