s3 8l little to no boost

[goodwoods3]

New here but not new to messing around with cars.

recently purchased a goodwood green s3 on a Wim and soon realised something wasn't quite right with the boost side of things

tried all the basics
smoke check
boost leaks all of those sorted
n75 maf all seem to be functioning correctly
vagcom no faults, expected and delivered boost is falling short by about 300mbar it just doesn't feel right really flat.

any one had similar problems or could suggest anything ?

any help would be appreciated

 

[AGB-S3]

High mileage ? could be the Turbo has seen better days
especially if you can hear it running up.

Take it over to Bill at Badger 5

 

[goodwoods3]

130k, I can’t hear it spool when driving, had the intake pipe off today and the turbo spins freely by hand with little to no play

I know bills the man for these 1.8t’s, and a visit to him would always be on the cards just wanted to get it running better before potential upgrades

 

[Ian W]

I was having issue with boost and it was down to a failing fuel pump, I swapped it out for a sytec one and it was night and day.

It was taking a few goes to start as well.

 

[goodwoods3]

not something I have considered tbh worth checking fuel pressure then I reckon, however it starts and runs lovely other than early any boost

 

[thegoal007]

goodwood green s3...probably my most favourite colour on the S3 ever since my first encounter with one.
Apparently not a popular one by all accounts, but come sale time for one of those it would ceertainly poke my interest

 

[goodwoods3]

My favourite colour for a car also, I have a mk2 golf and a Porsche in green also.

probably the reason why my brother sent it to me when he saw it on eBay this will be even better once it’s got boost and I done a few little mods I have planed just want it get it mechanically right first

 

[OsterForever]

Both K03 and K04 turbos are prone to cracking, which leads to lower efficiency because the exhaust gasses are leaking out of the turbo (you probably won't smell it, I didn't on 3 different cracked turbos in 3 different 1.8T cars). Less exhaust gasses = less spinny action on the turbo wheel. Unfortunately in my experience those cracks aren't easy to spot from the outside so usually diagnosis consists of at least dropping the downpipe (you can usually see some cracks from the exhaust exit side), but ideally you'd take the entire turbo out and check it out.

The fuel pump could also be the problem, as when it's old and can't supply the correct amount of fuel, your ECU will try to compensate by opening the injectors longer and longer, but at some point it'll run out of room for correction and will put you into a soft limp mode, which lowers the boost a lot, but doesn't throw a check engine light, and probably won't throw any codes into the computer either. However in that case it happens suddenly and at high RPM, rather than across the entire RPM range (unless the fuel pump REALLY can't push any fuel but you'd probably see other issues in that case as well and wouldn't be able to get anywhere close to redline under load). I had that issue on my 1.8T Octavia (R.I.P.) where it put me into soft limp mode around 5500 rpm because the injectors were max'd out due to a worn fuel pump.

Anyway, nice looking S3, I always liked the dark green Audi's, my dad had an A6 2.4 V6 in similar (if not the same) colour and I loved that one (although never got to drive it sadly)

 

[goodwoods3]

Appreciate your reply this gives me something else to check, I have got a downpipe and miltek to put on. but wanted to wait unit I had it all running right before it started resto/modding.

guess I’ll have to finish the mk2 golf that’s stuck on my ramp first, wish I’d never started