Random Boost Pressure drop, Advice needed

[Ares1]

Hey guys,

Need some help and advice on this one.

Occasionally when driving (normally after 5-10mins) the boost pressure drops right off. I ran a diagnostic and saw that the ECU was requesting boost but only receiving <0.2bar instead off 1.5. Obviously big powerless.

Ive replaced the N75 valve, regreased piston and checked diaphragm on Dump valve and checked intake temps when driving, they seem fine staying at 40'c ish.

Ive checked the obvious places with soap spray to look for any boost leaks but all seems air tight.

Note - when i turn off ignition and start up again its fine for another 5-10mins (some sort of acutator or relay problem?)

Any help on this would be greatly appreciated! cheers

Mk1 Cupra 1.8T (180)
AUQ Engine
Forge DV
K&N Induction kit
Milltek Cat Back Exhaust
Custom Re mapp Stage 2

224bhp, 270ft/lb

 

[Gaz7]

Do you have a boost gauge installed ? It's possible you're over boosting and dropping the car into limp mode.

 

[Ares1]

No i dont, Is there a way to bypass the Ecu trigger? Will overboosting damage the turbo etc?

 

[Bigjohn84]

Do you have a boost gauge installed ? It's possible you're over boosting and dropping the car into limp mode.

Why would she be over boosting tho GAZ, do you think it's the map

 

[Gaz7]

I don't know if there is a way to bypass the ECU trigger, and well.. It depends on what you're over boosting to, every turbo has its reccomended limits. As for what the monitored deviation between requested and actual would have to be to send it into limp mode, I don't know. It was just something for consideration. Because if you're requesting 1.5 bar, and getting a lot more , there has to be a reason, be it mechanical or otherwise. Can you do some logs again whilst boost hasn't been dropped ?

 

[Gaz7]

This is all just a possibility.. May be something totally different...

 

[Bigjohn84]

Have you changed anything before this problem started?

 

[Ares1]

Cheers Gaz, 1.5bar boost (about 21psi?) isnt a huge amount of boost through a k03s turbo, The diagnostic showed it requested 1.5bar but actual was 0.2 so something is limiting the boost.

The ecu going into limp mode is defiantly a possible cause i reckon.

I havnt changed anything since the mapp. I reckon the problem was here before the mapp just not as noticeable as it is now with the big increase in boost

 

[Gaz7]

It'd be nice to see a log of actual vs requested boost during the time that you haven't dropped boost.

 

[Ares1]

Yeah I need to get a Vag com reader, this was noticed on a diagnostic run with the Re mapp company, they suggested it could be the N75 valve, but replacing this didnt solve anything