VW Mk4 1.8t Boost Flutter Issue FINALLY SOLVED

[@DumitrescuG.Cristian-sb3lp]

I wonder if you are going for top speed in it if it holds boost. Got the same issue but it is noticeable after 120 mph not that I am driving like that every day but still...😂

[@CliffjumperCars]

The interesting thing about how boost & timing works in the 1.8t (at least with a factory ECU controlling boost, even if you have an aftermarket tune) is that it is both rpm and temperature dependent. It will spike to max boost briefly at a lower rpm, the drop off to its nominal boost level, then perhaps climb or lower slightly depending on how the intercooler temps are doing. If it's cold out and your IC doesn't get heat soaked, you may see close to top boost across the whole rpm spectrum. If it's warmer out and your IC does get too toasty, the ECU will trigger the N75 valve to bleed off boost, and the ECU will also pull timing. In our case I've noticed that max boost is about 25psi, nominal is around 22psi, and if it's warm out we'll only see 15psi. If the IC heatsoaks, it pulls the boost all the way back to 7psi.

[@DumitrescuG.Cristian-sb3lp]

@CliffjumperCars Thanks for the reply. It has a stage 1 tune, done properly I would say. And it makes the same as in your case, goes to 20 psi, levels to 15 drops below and goes back to 15 intermittently. But I am going to cancel some vacuum lines, and SAE is already gone. I am also pretty sure that I may have a leak. N75 valve I will change anyway because it doesn't cost a fortune.

[@DumitrescuG.Cristian-sb3lp]

@CliffjumperCars Engine is a 1.8t AUQ btw