Just trying to determine whether this is turbo or n75 related, or other…
car is audi b5 1.8t, k03, giac
By about 4k i’m at full boost @ ~16psi, after which it starts tapering down… by 6k i’m around 13psi.
Now, say i’m at about 2.5k in 4th gear just cruising, i floor it, and right before 4k when i am nearing peak boost, the engine stutters a few times, the boost fluctuates ~1-2psi during the stutters, and it lasts until about 5k, then continues to pull smoothly. This only occurs when accellerating from a roll like that, and not at all when accellerating hard from a stop and going through the gears.
Also, very occasionally, while driving normal, i will start max boosting around 6-10 psi. This will go away simply by turning off and re-starting the car, restoring 16psi max.
My turbine does have some shaft play, and i’m looking to replace that in the near future (k04). But some have mentioned this could be the work of the n75 not controlling the boost properly, explaining the occasional limp mode…
I just replaced all of the vac lines, two of which were dry rotted completely This issue started after doing that, but prior i obviously wasn’t boosting properly at all.
Temporarily replace the N75 with an MBC to see if it the N75 is working. The recirculation valves are know to fail too, ripped diaphragms leak boost. These would be my first two places to check.
well, i don’t have a MBC available to me as of now, but i did get my hands on a new stock DV, so i swapped it in. After and hour of driving, i noticed no difference. so that isn’t the culprit.
if your hitting 5psi max your in limp mode… which mean you are spiking and ‘overboosting’
in my 1.8t when i had it, n75 race helped surging issues and i ran a forge DV. if your tapering, it could be heat soak on those small IC. I had an issue with the stock IC before i went to FMIC. For a cheaper fix rather than a fmic, to new piping (silicone and remove that small ass pancake piping) to the ic and see if that helps.
It’s only gone in to limp mode twice in about 8 hours of driving. haha i’ve been doing a lot of driving…
The main problem is the surging at full boost/WOT. i’ve got a new-ish n75j on the way, we’ll see what happens after i get that. Seems like the n75 could be the culprit for the overboost and the surging
while i wait on the n75j, i’m going to pick up a new set of plugs. They aren’t toooooo old, but why not…
Although i would assume if they were bad there would be more issues such as rough idle or hard starts and the such, but none of those apply
I would replace the DV with a Forge 007.
Also the N75 Race valve is going to give you more problems then you want with this car. At the most I would run the N75J like your doing. Just make sure you put it in the correct way. It’s reversed from how the stock one goes in.
I just found a leak in my check valve but my issues are way different then yours. lol
This issue started after doing that, but prior i obviously wasn’t boosting properly at all.