On a stock GST/GSX, what determines boost cut off?

[civic619]

Hello
I have a 95 Gst equipped with a 14B turbo. When I Had my T25, my boost would cut off at 13psi. I do not have MBC, all else stock except turbo.

Since I replaced it with a 14B and replaced all the vaccum lines with fresh new ones, My boost cuts off at 9-10lbs now.

My question is, are the accuators different from the t25 to the 14B? Does the 14B tend to respond sooner than the T25.. Therefore causing my car to boost up to 9-10lbs???

Or is there something wrong???
If there is, what could i look at?

Thanks!!!

 

[truwarrior]

Maybe you have a boost leak. Check your intake pipes for leaks. I think airflow determines fuel cut. If the ecu sees to much air it will cut.

 

[turboholic]

Originally posted by civic619
Since I replaced it with a 14B and replaced all the vaccum lines with fresh new ones, My boost cuts off at 9-10lbs now.

My question is, are the accuators different from the t25 to the 14B? Does the 14B tend to respond sooner than the T25.. Therefore causing my car to boost up to 9-10lbs???

-Do you mean the max boost only goes to 9-10 psi on the 14B, did you check the waste gate and the area around it for leak prior of installing the turbo? the OEM waste gate actuator on the 14B is set at (internal spring) ~10.5 psi, you can either make a adjustable waste gate arm or install an boost controller.

 

[civic619]

maxes out at 10 lbs...I thought the two actuators are the same.... thanks!!!as for the leaks, i havent pressure tested it yet.. today hopefully.. thanks!

 

[TimG]

Just restrict the amount of pressure that the wastegate actuator sees and you'll get more boost. Just make sure you don't screw around with the BOV vacuum line. To restrict, a MBC is ideal but I've seen people put small bits of metal in the vacuum lines to the wastegate actuator. I highly suggest getting a MBC.

 

[turboholic]

Originally posted by TimG
Just restrict the amount of pressure that the wastegate actuator sees and you'll get more boost. To restrict, a MBC is ideal but I've seen people put small bits of metal in the vacuum lines to the wastegate actuator.

-Orifice.

 

[steve]

If you replaced all the vaccum lines, I guess that means you also replaced the lines between the turbo outlet nipple/BSC/WGA.

There was a metal restrictor orifice in the original hose to slow how quickly the pressure source fills the hose and allow the BSC to bleed off some of the pressure in the line to the WGA and raise the boost pressure.

Without the restrictor the BCS can't vent enough air to drop the pressure in the line to the WGA.

Steve

 

[civic619]

I dont see any Metal Restrictor on the Original hose.. it looks like a plain and simple vaccum hose...