AdmiralSenn
New member
- Joined
- Jan 2, 2007
- Location
- Vero Beach
1991 740, B230FT, 16vT with Garrett T3. I did not build this car and I am fairly new to turbocharging, so please bear with me.
Lately my car has had some trouble with power. It drives almost exactly like a naturally aspirated 740. The compressor is spinning up, it's generating boost (currently at 10 psi) but there's only a teensy little bit of acceleration that dies off almost before you feel it. Prior to a few weeks ago it was just as quick as I could ask it to be.
After some searching and pondering, my first thought is that I have a boost leak somewhere so I put together a tester and hooked it up. The hoses hold pressure up to about 20 psi, and I couldn't find any leaks by sound or feel anywhere.
Unfortunately there was also a loud POP, which it turns out is from a Bosch valve, item # 0280142105. This seems to be a Saab overpressure valve, which seems to have taken the place of the external CBV that the T3 in the car came with. It was venting to atmosphere, so I guess it's sort of a BOV given the way it's plumbed.
In fact, the more I look at it the more I wonder if it was even hooked up to the correct port at all. The car has always had a strange noise off boost that sounded like really quiet compressor surge, but the previous owner said that it wasn't when I test drove it. This thing has some sort of vacuum diaphragm but pressure from that side wouldn't open up the valve at all as far as I can tell.
Is this a common modification? <strike>I don't remember ever seeing a reference to this being used on a Volvo before.</strike> It looks like I have an oddly numbered variant, I just found a bunch of threads describing very similar parts with final digits off by one or two. Can anyone who's used one of these tell/show me how it should be plumbed?
And since it apparently held pressure until today, what else should I be looking at to find my boost problem?
For now I guess I'll push the MBC down to zero pounds and drive it like I'm scared of it.
Thanks!
Lately my car has had some trouble with power. It drives almost exactly like a naturally aspirated 740. The compressor is spinning up, it's generating boost (currently at 10 psi) but there's only a teensy little bit of acceleration that dies off almost before you feel it. Prior to a few weeks ago it was just as quick as I could ask it to be.
After some searching and pondering, my first thought is that I have a boost leak somewhere so I put together a tester and hooked it up. The hoses hold pressure up to about 20 psi, and I couldn't find any leaks by sound or feel anywhere.
Unfortunately there was also a loud POP, which it turns out is from a Bosch valve, item # 0280142105. This seems to be a Saab overpressure valve, which seems to have taken the place of the external CBV that the T3 in the car came with. It was venting to atmosphere, so I guess it's sort of a BOV given the way it's plumbed.
In fact, the more I look at it the more I wonder if it was even hooked up to the correct port at all. The car has always had a strange noise off boost that sounded like really quiet compressor surge, but the previous owner said that it wasn't when I test drove it. This thing has some sort of vacuum diaphragm but pressure from that side wouldn't open up the valve at all as far as I can tell.
Is this a common modification? <strike>I don't remember ever seeing a reference to this being used on a Volvo before.</strike> It looks like I have an oddly numbered variant, I just found a bunch of threads describing very similar parts with final digits off by one or two. Can anyone who's used one of these tell/show me how it should be plumbed?
And since it apparently held pressure until today, what else should I be looking at to find my boost problem?
For now I guess I'll push the MBC down to zero pounds and drive it like I'm scared of it.
Thanks!
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