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Boost gauge readings

G

Goose57

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Location
Eureka Mo.
Hi all I have a new GM 8 turbo on my new Optimizer. I can’t remember what my boost gauge readings were on my old stock one that came on the truck. I’m not sure this one’s working properly. When under a load going up hill no trailer I floor it and it jumps up then immediately drops to zero before getting back out of it.Before I had a turbo master on the old turbo and can’t remember it doing that. Thanks.

 
Doesn't sound like you're putting much of load on the motor to bring on any sustained boost. Also, the motor is new, stronger and that can manifest itself in many ways to include change in 'normal' boost readings and that goes for the turbo.

What happens on a downshift and a little more sustained throttle?

As for alleviating concerns about the gauge, I'd start with the sender and how well it's sealed before condemning the gauge itself. My Isspro set up was a little wonky and I was able to sort it out with a new sender vs. replacing the whole set up (years later I swapped over to autometer, had an issue with the EGT sender and, again, new sender sorted it out).

If you still have the old turbo you could always swap it in but, I'd still focus on the gauge set up.
 
it all depends on how the boost controller is setup. are you still using the turbo master or are you allowing the PCM to control boost? check all vacuum lines from the pump to the solenoid and from the solenoid to the turbo. with the engine idling you should not be able to move the rod from the actuator on the turbo by hand.

if still running the turbo master, forget all I said above and check the plastic tubing connections. I learned rather quickly the tinyest leak on the tubing will make a mess of things. also if the compression nut is over tightened it will collapse the tubing too.

verify turbo hose clamps are tight as well as the upper intake gasket is sealing too.
 
one other thing is if you are running the factory setup with the solenoid. you can test the solenoid's function with the GMTDscan as well as look at the live data comparing it to what the gauge is showing. the PCM takes a difference between the sensor on the intake and the one mounted to the firewall. in GMTDscan set the solenoid to 100% and you should be able to easily move the rod on the actuator at idle, 0% and it should be stiff where you cannot move it by hand. on my 95 it took me a while to realize the solenoid vacuum lines were backwards!
 
Thanks guys for all the help. I’ll double check the hose routing. I’m not running the turbo master. New stock set up. I do remember seeing the turbo vacuum pot open and closing when disconnecting vacuum. I do believe I have the vacuum lines on right.
I’m using a Tech2 scanner. Will it give me live data on the turbo system? I do remember seeing 14% on the scanner screen something about the turbo. But it was at idle only. I did use vacuum line to feed the boost gauge because I didn’t like the look of the thin white plastic tubing. It’s new vacuum line could it be sucking closed? The reference voltage checked out on the 2 vacuum sensors the one on the firewall didn’t have vacuum at idle. I’ll have to look into that. If the tech2 will give me data I’ll take a drive w/ the scanner on board.
 
You should be able to do the waste gate solenoid duty cycle test on the tech 2 as well. Remember while idling you should not be able to move the turbo actuator rod, if you run the test on the tech 2, once it’s open to about 50% or greater you should then be able to move that rod on the turbo.

By default the pcm is programmed to not allow very much boost without pulling a load. I can’t recall what I saw on mine before modifying it’s programming, but if you can find a decent grade incline like a steep on-ramp to the freeway, use that for testing to see what boost pressures you get from the gauge and from the live data on the tech 2. remember to feed her the onions under acceleration too!
 
On My 2000 K3500 unless the pickup was under load or accelerating there would be no boost on the boost pressure gauge.
Dragging along a load or under heavy acceleration it would climb to about 12 PSI and that was about maximum.
Normal on the highway usually around two to three pounds at about 70 MPH.
 
Sounds like normal stock operation to me. There's a reason why the turbo master came out. On mine the PCM would pull the boost just when you'd need it.
 
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