What are the proper boost measurements for your volvo?
- Warm Idle: 18 inches of mercury vacuum
- Cold Idle: 16 inches of mercury vacuum
- WOT (Wide Open Throttle) 2,000 RPM: ~5 PSI boost
- WOT 3,000 RPM: ~15 PSI boost
- 75mph @ 3,000 RMP: ~10 inches of mercury vacuum
- Between Shifts: 0 (atmospheric) due to the bypass vale venting manifold pressure to keep the turbo spooled
MVS Forum Member nobbie_nz asks:
Hi guys, all the way from New Zealand 🙂 Have just hooked up a temporary boost gauge on my new 950R 1996 AUTO and I have made some interesting findings.
After hooking up an Autometer boost gauge my vacuum at idle is around 15-17, during deceleration (no throttle) i get 20. Do you guys still think I have a vacuum leak? or do these numbers sound normal?
Now heres the interesting part…SOMETIMES for some reason I only get 8psi of boost, then other times I get 11psi??? During the shift from one gear to another the boost spikes to around 15-17psi (auto box) – please note this is BETWEEN shifts when the boost spikes.
The other thing that happened was that in 2nd gear at wide open throttle boost is at 11psi and then when the car changes to third the boost drops to only 8psi and feels quite sluggish.
Any ideas on what might be the problem here….I did some research on the site and read a little about wastegates?? but not sure if the wastegate would be the problem??
feedback and thoughts really appreciated 🙂
MVS Forum Member MadeInJapan replied:
Everything sounds fairly normal unless your ECU has been chipped. Other than that, I hope you meant 850 and not 950.
MVS Forum Member nobbie_nz added:
Right, i think im a little thick lol…having never owned a turbo car…something just dawned on me.
If the car downshifts to a lower RPM then the boost will start lower and then rise. IF the car downshifts to higher RPMs then the boost will be higher.
So…when changing from 3rd to 4th (auto) I would assume its normal for the boost to drop from 11psi to 6psi when it goes from high revs 3rd to lower revs 4th. The boost would then rise with the revs as the car gets faster.
Have I just solved my weird problem? or is this not normal 😉