Audi TT - Loss of boost Remap help please!!

Hi all,

I'll not pretend that I know much about the VW/Audi 1.8t but I'm trying to learn slowly.

Last week I had my Mk1 180 remapped by a local bloke, supposedly to 211bhp but it hasn't been dyno tested so it's purely a guess. All was well and I was enjoying the obviously increased performance but today I got in and had very little boost. Torque app on android seemed to suggest boost but it just wasn't happening.

Just tinkering around as I do and I pulled the little vacuum hose off that goes in to the top of the diverter valve. Suddenly I seemed to have my boost back. I didn't drive far like this as I didn't know what the effect might be but it definitely seemed to help.

I don't know what this indicates as I don't know enough about the operation of the diverter valve. The last turbo charged car I had was a Fiat Uno Turbo in about 1990 and it had a mentally huge dump valve (fitted by a previous owner) !

I know what the diverter valve does per se but I can't quite get straight in my head why removing the vacuum would make boost come back. The vac hose has a negative pressure on it at idle which I presume (?) then becomes positive pressure when under boost, closing the gate to allow the full pressure to the turbo.

Is there other stuff that I should be looking at instead ?

Any advice or pointers appreciated.

Thanks,

malty

Right, after chasing this fault around for ages I think I have got to the bottom of it. It only happens at stone cold idle but stays on for the rest of the journey.

Apparently there is a generic problem in the 1.8t standard map to do with leak detection during cold start. If you Google 17705 and FVPDKLDUS you will find out loads of info about it.

It's normally not a problem but a remap can cause it to show up because of the tweaks made during a remap. My remapper has said he will look at it but he's away for three weeks.

I would like to get it sorted before then if I can and have read that I can read and flash my map using some generic mvvs lead from eBay then just alter what needs to be altered and flash it back.

I'm comfortable with the reading and flashing etc I just need to know how to change what I need to change.

Apparently I need to change the threshold for FVPDKLDUS within the ecu either higher or to all zeroes. Does anyone know how to do that?
Idiots guide required as I'm now treating thus as a learning exercise.

Thanks,

Malty

Any remaps I have had done are always on a rolling rd, these drive up to your house mappers cant see what they have done or any outputs as no rolling rd.
It's worth the extra few quid to have a rolling rd remap.
Glad you got to the bottom of it.

I'm happy with the performance from my remap I just need this fault gone!

Wanted to post about my success story with this.


I read around the Internet for a few days and came across nefariousmotorsports.com
Which is a diy tuning forum. It is really daunting when you first start reading but after introducing myself, giving all the correct info about my car etc and reading their various tutorials, I was able to read off the flash on my ECU and post it up.


Within about an hour someone had taken the time to fix the file for me and put it in the right format to flash it back.

I checked the file over as best I could, checked that the checksum had been updated (car won't start if the checksum is incorrect) and ordered one of the recommended cables for flashing (a whole £7 on eBay).

I picked up a cheap windows laptop for £45 locally to run just the flashing software as I want to play a bit more after everything is sorted and loaded everything up.

Connected up the car to a battery charger to stop the ecu running out of power, connected the laptop to the mains and made sure it's battery was full too and loaded my fixed file into nefmoto's own (free) flasher and after doing several comms tests, proceeded to write.

9 mins later it had completed. I disconnected and turned the key. The car satisfyingly ran perfectly. I cleared the faults and they stayed cleared this time. Very happy days.

Bit of a heart in your mouth moment, when you went to turn it over for the first time?

A bit, yes :-)