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08 Sol GXP; Black
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Discussion Starter · #1 ·
I Replaced a busted intake hose/nipple today and found what looks like a missing vacumm line cap. Maybe I busted it off when I vacuumed out a mouse nest from under the engine cover.
Can someone tell me what this is and if I’m missing something?

Also with the silicone intake from DDM, the nipple is longer than the OE plastic one; Any solutions for reducing the length of the braided vent line or nipple?
 

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It appears to me that you can shorten the steel tube that is inserted into the silicone.
 

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That my friend is not supposed to be capped. There is supposed to be a line that runs from where that cap was over to the front of the turbo. I would need a picture of the front of the turbo to be able to tell you what to do. IDK if you still have the factory turbo in your vehicle.

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If you look at the image above you can see a white circular thing on the upper left that is off white in color and has 3 bolts in it. There is a hose that is supposed to run from the nipple in the middle of that off white cover to where that cap was. You are also supposed to have another one of those black electrinic looking things attached to the front of the turbo
 

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I can see the off whgite cap has a hose coming off of it in your second photo. IDK where that hose is connected. The vacuum lines are not connected properly in your vehicle I can tell you that much
 

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Here is a picture of how it is supposed to be connected.

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You need to get rid of that wye and connect the ends of the hoses to where the arrows are pointing
 

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Did you do this or was it like this when you bought it?? The reason I ask is the car must have a tune on it and the error code for the bypass valve must have been disabled because with the way the hoses are connected your check engine light should be on.

for some reason people did this kind of a change to the vacuum lines believing that in some way it made the engine create more HP. It does not do anything like that. The bypass valve is what takes the boost after the turbo and puts it into the intake before the turbo when you let off the accelerator. The turbo doesn't have brakes so it keep on building pressure when there is no longer a need for it. That pressure has to go somewhere. On older vehicles it would be blow off to atmosphere and it was a BOV (Blow Off Valve) that did that. On modern vehicles that use MAF (Mass Air Flow) sensors you can't take air that has been measured and just blow it off to atmosphere. So they came up with the BPV (ByPass Valve (aka recirculating valve)) to handle the excess pressure after the turbo. The BPV is a better system because the pressure doesn't just disappear like with the BOV so the turbo isn't starting off at 0 PSI if you decide to accelerate again. It is starting off where you were. This is a HUGE benefit if you vehicle is a manual transmission where you have to let off the accelerator when you shift the vehicle. The cars ECM controls how much to open that bypass valve and what has basically been done with that wye is the control by the ECM has been removed. This is not ideal as there are minor adjustments the ECM will be making to keep the pressure where it needs to be for how open the throttle plate is.
 

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Discussion Starter · #9 ·
I bought it like this. Its a manual, aftermarket exhaust; I suspect with some kind of tune.. Out of the corner of my eye I swear that on occasion i see the check engine light flicker, like it is forced off.

Thank you. I appreciate your advice and will reconnect the vacuum lines. A Tube cutter should work to shorten the turbo intake nipple.

Was it also common for people to fill the rear end with epoxy or some other filler to stiffen it?
 

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2008 Pontiac Solstice GXP - Mysterious (with unkown origin blue sparkle in rear bumper cover paint)
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Well maybe he has an aftermaket BOV on the charge tubes? I remeber that was a “thing” on some of the Dejon aftermarket charge popes want it?
Is there a picture of the hot side charge tube?
 

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No there is no aftermarket BOV. and even if there was you would still have the hoses connected to the solenoid properly.

No reconnecting the lines will not effect the tune at all.

The trunk pan is made from fiber reinforces plastic so maybe that is what you are seeing? It's not metal. It should be blackish in color. I have not heard of doing anything with an epoxy in the trunk. It wouldn't do a whole hell of a lot unless it was 2" thick and it would probably end up cracking is it was actually secured to the frame rails properly. Heavy as well. Would have to see it to know what you are dealing with as far as that goes.

What does you boost gauge read when you have the accelerator pushed to the floor at 5000 to 6000 RPMs?? If there is no tune it will read 14-15 PSI at sea level and at high altitude 6000+ feet it will read closer to 18 PSI. If you have a tine those number will be 4 to 8 PSI higher depending on the tune. I do not believe you have the GMPP tune because your TMAP sensor in the pipe that connects to the throttle body has 2 bolts/screws holding it in. the upgraded ones that come with the GMPP tune has only one bolt. The GMPP tune was a tune that GM offered for the vehicle that would increase the HP to 290. It is an EPA and CARB compliant tune so if you live in California you would not have an issue passing emissions there with it.

The boost reading is an easy way to tell if a tune has been done.
 

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You also need to get a clamp on that coupling that the tube is connected to, the one you are going to shorten.
 

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No there is no aftermarket BOV. and even if there was you would still have the hoses connected to the solenoid
I beg to differ KG. This was actually a “thing” on the forum back in the day. Although i was mistaken as it was on the cold side charge pipe.
Not saying this is what the OP has, just that the odd hose routing warrants at least a check before dismissing.

 

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Good link down memory lane. Funny enough, I have that exact kit in the link. Never did figure out how the hot side connected.


OP, here’s an additional pic of the stock vacuum lines:

 

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Good link down memory lane. Funny enough, I have that exact kit in the link. Never did figure out how the hot side connected.


OP, here’s an additional pic of the stock vacuum lines:

So you have the BOV on the cold side charge pipe? Isnt there a vacuum line that runs to it?
 

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I beg to differ KG. This was actually a “thing” on the forum back in the day. Although i was mistaken as it was on the cold side charge pipe.

Oh I agree with you about the BOV and people doing it in the past. Those people also had tuning issues because of the engine spiking rich when they let off the accelerator and then spiking lean when getting back into. Like when shifting the car. the ECM could be tuned to handle some of the loss of air but not all of it. That is how the dual port valves came about, they blow off 50% of the air and the other 50% recirculates.

I was saying that the OP does not have a BOV because you could see the recirc valve hooked up.

any kind of an actuator or a valve really needs to be attached to the vacuum or pressure source via it's own dedicated line.... what I mean by that would be having a BOV vacuum line wye'd off of the wastegate vacuum line. That would be a NO NO. the reason being is a high potential of there not being enough vacuum/pressure available in the line for both devices. Always dedicated lines to the source.

The setup in the link that has been provided by @Super Serg helps to correct a lot of the tuning issues surrounding the loss of air from the BOV. It does this by relocating the MAF so it is close to the throttle body. There is still going to be a loss of air but it will be a whole lot less. Good idea but it introduces a whole new set of tuning issues like you cannot simply move the OE MAF sensor because it will not read correctly. So a different MAF sensor needs to be used and it needs to be added to the tune correctly.

The reason why you do not see the use of BOVs today is because it never worked correctly no matter where you put the BOV.. BOV's work best on engines that do not have a MAF and rely only on MAP sensors. The loss of air that has been measured makes it a royal pain to tune correctly. You pretty much have to have the MAF clamped right onto the throttle body and unfortunately you cannot do that because of the turbulence in the air caused by the throttle plate messing up the MAF reading. So it has to be placed 12-18 inches away from the throttle body and the amount of air that gets lost between the MAF and the throttle plate still causes tuning hiccups.

Not saying it cannot be done. It can be, it takes a whole lot of effort by a really good tuner. In the end tho there is no benefit of doing it.
 
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Discussion Starter · #20 ·
KG, The metal tube is glued into the red intake hose so it seems that connection is good. Can add a clamp for good measure though. The metal tube as received has no ridge like the OE hose for the black plastic end of the vent hose to bite over/onto.
Have not checked boost lately, the first few days I was running around i know I saw boost up to 18 psi on the dash display; not sure at what rpm.
 
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