[Voldsom Volvo]

So I was checking the gap on my spark plugs today and noticed this hose which isn't attached to anything at the end (highlighted in red).

I did however find what seems to be a connection at the back of the area highlighted in yellow.

Is it supposed to be connected or is it some kind of pressure outlet or sensor hose?

Thanks!

 

[Evolv0]

what the hell... thay hose "red" should deff be connected to the little fitting on your intake manifold "yellow" .. you should connect that .... you havent notices any performance issues?

 

[ion]

Bypass valve hose. I'm thinking someone had a boost gauge installed (see this thread: http://forums.swedespeed.com/showthread.php?76769). Then just yanked it out before selling the car, not caring enough to fix the hose.

Since it's already cut, you could just buy and install a boost gauge. I think reconnecting the line should increase your engine's efficiency.

 

[Voldsom Volvo]

Thanks guys!

Yes I figured it should be connected, so that's actually what I did while waiting for help from SS.

I am 99.9% sure that the previous owner did not have a boost gauge installed as it used to be a company car which needs to be fully stock spec. There are no evidence (i.e. small holes or the like) of a gauge having been installed either.

I think I or a mechanic might have disconnected the hose by accident in the past when fiddling around in the engine compartment.

I just connected it to the plastic fitting on the bottomside of the intake manifold cover. It fits fairly snug - so is this how it should be fitted or is it supposed to have a small clamp on it as well?

I have not noticed any performance issues at all in terms of acceleration or pick up. I have however experienced a little bit worse gas mileage at certain speed ranges. And this happened just after I changed my spark plugs (OEM) and I was thinking it was because of plugs. Perhaps this will be fixed now. Chances are I accidentally pulled the hose when removing the engine cover for the spark plug job.

Now that the hose is back on I immediately noticed one thing though. When accelerating slowly from stand still, once the revs reach 1900 RPM there is a nice subtle whistle up to around 2500 RPM. Is this sound turbo or intake related? Either way, it sounds cool and now that I think about it, I remember hearing this in the past as well

EDIT: So if I understand this right, the hose is connected to the bypass valve and relieves the pressure from the turbo as necessary - yes? The pressure is then routed to the intake manifold and reused? If so, I guess it should not cause major issues if the pressure is just let out into open air (as has been the case, before I connected the hose again)?

 

[TG]

Thanks guys!

Yes I figured it should be connected, so that's actually what I did while waiting for help from SS.

I am 99.9% sure that the previous owner did not have a boost gauge installed as it used to be a company car which needs to be fully stock spec. There are no evidence (i.e. small holes or the like) of a gauge having been installed either.

I think I or a mechanic might have disconnected the hose by accident in the past when fiddling around in the engine compartment.

I just connected it to the plastic fitting on the bottomside of the intake manifold cover. It fits fairly snug - so is this how it should be fitted or is it supposed to have a small clamp on it as well?

I have not noticed any performance issues at all in terms of acceleration or pick up. I have however experienced a little bit worse gas mileage at certain speed ranges. And this happened just after I changed my spark plugs (OEM) and I was thinking it was because of plugs. Perhaps this will be fixed now. Chances are I accidentally pulled the hose when removing the engine cover for the spark plug job.

Now that the hose is back on I immediately noticed one thing though. When accelerating slowly from stand still, once the revs reach 1900 RPM there is a nice subtle whistle up to around 2500 RPM. Is this sound turbo or intake related? Either way, it sounds cool and now that I think about it, I remember hearing this in the past as well

EDIT: So if I understand this right, the hose is connected to the bypass valve and relieves the pressure from the turbo as necessary - yes? The pressure is then routed to the intake manifold and reused? If so, I guess it should not cause major issues if the pressure is just let out into open air as has been the case, before I connected the hose again?

The worse part would have been dirt debris getting in there I guess... Good you caught it.

edit:
thx tmtalpey. I love this forum. You learn something everyday

 

[tmtalpey]

That is the line to the CBV (compressor bypass valve), which is used to hold the valve closed to build boost, and to open the valve when boost is not needed. The "subtle whistle" you hear is your car actually boosting, now that the boost isn't being dumped in a circle!

With the fitting off, you were also blowing air out of the manifold instead of into the cylinders. Were you getting terrible gas mileage? I predict it will perk up, too.

 

[Voldsom Volvo]

That is the line to the CBV (compressor bypass valve), which is used to hold the valve closed to build boost, and to open the valve when boost is not needed. The "subtle whistle" you hear is your car actually boosting, now that the boost isn't being dumped in a circle!

With the fitting off, you were also blowing air out of the manifold instead of into the cylinders. Were you getting terrible gas mileage? I predict it will perk up, too.

Thanks! Well as mentioned the gas mileage was a bit off at certain speeds, but it was definitely not terrible. Perhaps off by 10% at certain speeds and on par at other speeds - so maybe around 5% worse on average. But with these gas prices, every little bit helps!

But strange that it did not affect performance in a noticeable way