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NO BOOST (Out of ideas)

2K views 51 replies 6 participants last post by  mercdude 
#1 ·
Im out of ideas and I would like to hear your ideas about what to do next, the car is t5 2006 fwd aut so far:

1) New tcv.
2) New sparks.
3) New FPS.
4) New checkvalve.

I have only 6 psi boost peak. On all gears.

I reseted the ecm with the plus and negative terminals of battery and tried to drive. I saw my boost raised to 8.5-9.5 psi (like it should be). Next time i started the car the boost returned to 6 psi. Very strange.

My vacum readings are 25 when going downhill (no gas). I noticed when i press the gas pedal the boost comes up for example to 7 psi and dropsoff to 6. It also occur in vacum from -13 to -16 for example.

Please help me, there is no cel or codes when i checked it on vida.
 
#35 ·
If you really think it ought to have more boost - AND you've confirmed no boost leaks - then I'd crank up the wastegate pre-load a turn or 2. Sounds like a weak spring. If you crank it up too far, it will hit overboost, throw codes, and shut down all the fun. So don't go crazy with it.
 
#39 · (Edited)
There's forge, viva (which may sell forge, I'm not sure), and elevate (which sells turbosmart). They all have slightly different designs. Out of the bunch only turbosmart claims any performance increase. From my experience, I'd say they're right. But I think it has less to do with any 'special' design turbosmart has built into the unit. I'd say that they have improved the quality. The turbosmart unit has 1) a stiffer (better) spring, and 2) a better diaphram. Outside of that, the configuration is basically the same as stock - a rubber diaphram with a spring. You can customize the spring strength (say, switch out the stock spring for 10lbs), if so desired, but I have been warned that anything over the 7lbs will cause overboosting and some nastiness.
 
#40 ·
Before you go wastegate actuator replacement, have you tried replacing the CBV? Turbosmart makes a performance replacement for that as well, but in your (non-tuned) case, I'd just stick with a stock replacement. The CBV is basically another spring/diaphram setup that purges excess boost pressure when the wastegate closes (to protect the turbo turbines). If that diaphram is shot or spring weak, it will be causing leaks.
 
#41 ·
Great info, right now Im not sure what to do. Cbv or wastegate? How do i check them? vacuum leak tester to the nipples?? what are the parameters they should hold?
 
#43 ·
CBV first - it's like $20 for a stock replacement part. Volvo does not make an OEM wastegate actuator replacement so if yours is shot you must buy aftermarket: forge, turbosmart, etc. That's a lot more of a pain than the CBV. Again, try that first. Not sure how to test though.
 
#48 · (Edited)
That's no more compact than the turbosmart unit, which (btw), wasn't that bad to install. Just some patience and long wobble allen sockets will do the trick. I think I ended up having to tape one of the bolts onto the socket in order to get it started but no need to "bend the oil line" or anything like that. Just slip it in under the oil line and then fish the allen bolts through. Make sure you orient the CBV correctly when installing (ask me how I know that). Also, you can get the turbosmart unit on ebay for less than the forge unit, around $130 I'd say.

Just thinking about it, I think I have my old CBV and I know that one is in good shape. PM me if you want it.

Actually, with a side by side comparison, the forge cbv does look about 1/8" less tall. Huh.
 
#49 ·
That's no more compact than the turbosmart unit, which (btw), wasn't that bad to install. Just some patience and long wobble allen sockets will do the trick. I think I ended up having to tape one of the bolts onto the socket in order to get it started but no need to "bend the oil line" or anything like that. Just slip it in under the oil line and then fish the allen bolts through. Make sure you orient the CBV correctly when installing (ask me how I know that). Also, you can get the turbosmart unit on ebay for less than the forge unit, around $130 I'd say.

Just thinking about it, I think I have my old CBV and I know that one is in good shape. PM me if you want it.
I've had both and the install is the same, but I didn't have to bend any pipes out of the way to get the Forge unit in.
 
#51 ·
It was just the regular one and not sure if there's an updated part. It's the main reason why I went with the Forge so I wouldn't have the same issue (also, different springs to choose from).

I think the oil lines may have gone through a revision at some point, but it could just be a placebo. The same lines in my C30 seemed to give more room than in the S40 :confused:
 
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