Boost gauge not reading boost

Motoracer110

Well-Known Member
My build used a crate motor turbo and I finally got a boost gauge to see what going on. I feel like my car is quick but not turbo quick. This is my first turbo car so very noob when it comes to components.
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this is where I tied into and no matter how fast I floor the pedal my boost gauge reads 0 just wondering if I’m connecting at the right location


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this is where the hose comes from on the turbo

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this hose came off the t sensor and went to nothing so I plugged it for a test
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also wondering if this brass t is supposed to connect anywhere?
Any help would be greatly appreciated or photos of your setup
 

JBINTX

Goblin Guru
The boost gauge in the Cobalt is electric? You using an aftermarket?
Most of the time the boost gauge reads a vacuum. Only under hard accel does it go positive.

The taped off hole next to the MAF near your filter goes to back of valve cover:

The brass port in your last pic goes to the sensor that sits on top of the intake manifold.
 

Motoracer110

Well-Known Member
Wow thank u jbntx! This helps a ton I’ll connect more things then take more photos to make sure I did it correctly. The donor did not have an electronic gauge only one reading vacuum, but that was in the old motor with a mess of wire and tubes so I had a tough time getting it all where I thought on the new motor.
 

Motoracer110

Well-Known Member
Ok got some pictures to make sure we are talking about the same thing
I used black tape to temporarily cover up the hole port on my intake. The breather on the top of engine I used a separate dedicated air intake with its own mini filter
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so the brass spout in below photo is supposed to go into the sensor with the blue cap?
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Ark :D

Goblin Guru
The tube that you have outfitted with a breather, I have (with a check valve on it) running to the brass fitting on the MAF tube.

The elbow in your second pic, I have running to a .... doohickey underneath the turbo intercooler, not to the sensor in the third pic.

Pretty sure the sensor in the third pic has to do with evap, and is therefore not used in the Goblin. Mine isn't vacuum-capped.
 

JBINTX

Goblin Guru
I don't think you want that breather filter on that line. That line which comes from the 90 degree fitting on the back side of the valve cover needs to run all the way to that brass fitting in the intake tube next to the MAF sensor - closest to the intake air filter. You do not want atmosphere, you want vacuum.

That blue cap is on the EVAP solenoid. If you are in a state that will not require emissions inspections, you can delete the entire solenoid and bolt on a sealed plate. If your state requires emissions testing, I am not sure what others have done???

The middle pic above brass fitting goes to the vacuum sensor mounted on top of the intake plenum

IMG_8456.jpg
 

Motoracer110

Well-Known Member
I don't think you want that breather filter on that line. That line which comes from the 90 degree fitting on the back side of the valve cover needs to run all the way to that brass fitting in the intake tube next to the MAF sensor - closest to the intake air filter. You do not want atmosphere, you want vacuum.

That blue cap is on the EVAP solenoid. If you are in a state that will not require emissions inspections, you can delete the entire solenoid and bolt on a sealed plate. If your state requires emissions testing, I am not sure what others have done???

The middle pic above brass fitting goes to the vacuum sensor mounted on top of the intake plenum

View attachment 15203
thank u it’s hard to take a picture of the sensor with the 3 hoses going into it because of the cooler so I have the same sensor from my donor that I rested on top in exact orientation for reference still a little confused where that brass 90 goes.

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1- is an open hose going to nothing (is that where I plug into that Brass 90?)
2-goes back to the turbo and that’s where I spliced my vacuum gauge into and not reading a vacuum ( is that correct?)
3- is a very short connection going into the manifold which is odd why this line is so long from my donor engine and looks like that’s where the old boost gauge hooks up?

thank u both for helping me through this. The number picture will help he a lot
 

JBINTX

Goblin Guru
You can mount the sensor on the side of the intake. See pic below.

1- plug into that Brass 90 on the intake tube - your pic above that is open
2-goes back to the turbo
3- goes down to the vacuum reservoir under the intake manifold. Black plastic pillow shaped canister.

That sensor above is a charging solenoid. It should have an electrical connector to it. I assume you have that but just not shown in the pic?

What year is your donor? I am still lost on the mechanical boost gauge.

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Motoracer110

Well-Known Member
You can mount the sensor on the side of the intake. See pic below.

1- plug into that Brass 90 on the intake tube - your pic above that is open
2-goes back to the turbo
3- goes down to the vacuum reservoir under the intake manifold. Black plastic pillow shaped canister.

That sensor above is a charging solenoid. It should have an electrical connector to it. I assume you have that but just not shown in the pic?

What year is your donor? I am still lost on the mechanical boost gauge.

View attachment 15208
wow! Just connected the #1 hose to the brass 90 and I now read boost!!!! Thank u for the help I have been trying to wrap my head around this for months couldn’t figure it out. I bet my car will drive better The sensor being used is plugged in just so hard to take photos underneath.
The donor was a 2009 ss turbo but what I thought was a blown head gasket was actually a cracked cylinder sleeve so I purchased a brand new crate motor came with turbo I also had to get a new engine wire harness from gm because the old one was mangled.
this is where I spliced in the boost gauge on hose number 2
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held the back of the gauge up to it to show the brass plug that the 6ft hose plugs into.
Time to mount the gauge on the steering wheel and lights to power can’t wait.
 

Motoracer110

Well-Known Member
Just took out for a spin feels like I’m getting 30+ more hp, so much faster. Boost maxing at 7
Huge thanks again

Now I can work on a hinge to make taking the hood off and back on easier
 

Motoracer110

Well-Known Member
You should have more than 7 PSI. A stock TC puts out around 18.
I read on many sites around 12ish stock is normal. Unfortunately I’m at a huge disadvantage located a mile above sea level the air is much thinner and psi will be less how much less I’m not sure. I will stick a manual boost controller on the car but will wait for the dyno before I mess with that

Edit. Haha just did more searching and other sites stating 18 which makes me happy..next will be dyno and tune for sure
 
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Briann1177

Goblin Guru
18 may have been a bit high, but it's definitely more than 12. My MAP pressures get up to ~30 PSI which if you subtract 14.7 PSI that puts it around 15 PSI. Basically twice the amount of air is getting crammed down.

Even at Denver's altitude which looks to be about 18% less than sea level, I think the turbo should be able to get close to 12 PSI. I really don't know, but 7 doesn't sound right. Check your engine codes. There are codes that will disable the boost. 5 PSI is about the most you'll get running waste gate spring pressure only.
 

Motoracer110

Well-Known Member
Do you think that since the vacuum line was not correct that the car might have locked out and stayed locked out?

Will disconnecting the battery then reconnect get rid of certain codes?
 

Tinkles

Well-Known Member
Turbo theory 101. As you climb in altitude and air density decreases there is less resistance on the turbo so it will spin faster. So it should flow the same about of air and make the same PSI irregardless of what altitude you are at. Turbo cars should not loose power with altitude. That is the theory, now practical application could show a rise or fall in pressure.
 

Motoracer110

Well-Known Member
Turbo theory 101. As you climb in altitude and air density decreases there is less resistance on the turbo so it will spin faster. So it should flow the same about of air and make the same PSI irregardless of what altitude you are at. Turbo cars should not loose power with altitude. That is the theory, now practical application could show a rise or fall in pressure.
Thank u, I think I know the problem. The map sensor below the throttle body is missing its plug I need to figure out the pins that plug into the computer and run new wires to the map. I think that’s why it’s in error mode and under boosting. I’ll make a new post and see if anyone knows what pins go to that map sensor
 
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