Greddy bov issues after FMIC

[Toni]

So after installing the FMIC i can't adjust the greddy bov to a spot where it won't go into a nice little "blowing off loop". So basically if I'm in part throttle I can get the bov to open and then if I keep the throttle where it is it continually blow off over and over and it slowely fads in pressure everytime it does. It will stop if I let off throttle or go back on gas. The worst case scenario for this is highway driving in 5th with cruise on because it rarely just lets off the throttle, it eases on/off.

Any ideas?

[i3igpete]

pressure surging. ray fixed it with a balance tube, I fixed it by going with larger turbos and thicker core.

[Chris@Rvengeperformance]

yep,classic case for a balance tube. Adding a little timing at <6 PSI and 2000-3000 RPM can help

[Toni]

Hmm, I have heard of that balance tube however I thought that was when going very large difference in compressor/turbine that had caused the situation. I'll do some reading up on it.

[Chris@Rvengeperformance]

what turbos do you have?

[i3igpete]

yup it's because all of our turbo upgrades are mismatched to help spool up. thats why going td05 fixes the issue, it doesn't build boost at low loads.

from what I've found, going to a 4" core helps by increasing the volume and the resonance doesn't happen anymore.

[DocWalt]

You might be able to get away with a little bit more timing at low pressures like Gump said, or use the balance tube. The turbos are essentially too efficient at that throttle position and surge, and that can be affected by timing, which is why that can work. The balance tube balances out the flow a little before it crams into the intercooler, and will solve it.

On MIVEC engines, you can make nearly any turbo surge by tweaking the timing incorrectly and making it spool too early.

edit: Pete just posted and said it much simpler than I did.

[Drweldin]

Balance tubes don't always work. I found best cure(for me) was a dual core. You could also try removing the small spring from the Greddy and/or using the second "push" port that most cap or leave open....

[Toni]

Well I have td04H 15g turbos, I guess that is enough of a mismatch to cause this issue. I still have some extra sensors for when I was going to test pressure drop at various points on the dsm smic but never got around to actually doing it. Maybe I'll do some logs and see what it's really doing.

[Woz]

whats your spring pressure off your bov?