SR Won't Boost Over 6psi - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

bigjacsoc · 02-05-2011, 11:29 PM

I had a manual boost controller for a while and I was able to get the boost up to 8-9psi but wouldn't go any lower or higher no matter how much I changed the MBC. I even took the MBC out and ran it stock and only hit 6psi.

I figured my MBC crapped out and just got a GReddy Profec B Spec II all hooked up correctly and at 0% it boosts to 5.9 and at 20%, 35%, and 40% it hit 6.2psi which is a negligible difference.

WTF? Any answers? Anyone had this problem before?

bigjacsoc · 02-05-2011, 11:31 PM

I had a manual boost controller for a while and I was able to get the boost up to 8-9psi but wouldn't go any lower or higher no matter how much I changed the MBC. I even took the MBC out and ran it stock and only hit 6psi.

I figured my MBC crapped out and just got a GReddy Profec B Spec II all hooked up correctly and at 0% it boosts to 5.9 and at 20%, 35%, and 40% it hit 6.2psi which is a negligible difference.

WTF? Any answers? Anyone had this problem before?

ultimateirving · 02-05-2011, 11:48 PM

get a new wastegate actuator the springs wear out after time, had similar trouble. put a new WGA on and it works like a dream. seeif that works.

bigjacsoc · 02-06-2011, 12:28 AM

I figured this is what could be doing it. Does anyone know if I vacuum leak would do it? I mean there was no difference between 0% and 40% in boost. I have pressure checked all vacuum lines and coupler, only thing that could be causing a leak is something stupid like a bad gasket, or something with the stock recirculating BOV and SMIC.

bigjacsoc · 02-06-2011, 02:22 PM

Bump why is this message not long enough?

JayZeeSILVIA · 02-07-2011, 07:22 PM

sounds like a bad wastegate spring

bigjacsoc · 02-18-2011, 02:19 PM

Bump. Any other ideas?

Kingtal0n · 02-18-2011, 06:41 PM

Quote:

Originally Posted by bigjacsoc

Bump. Any other ideas?

boost comes from the turbine being spun quick enough to spin the compressor quick enough to accelerate air enough to generate a "backpressure" as air molecules compress against each other as they try to cram into the cylinder/intake/plumbing/intercooler/turbo outlet.

So boost problems can occur for many reasons:
A damaged turbine
A damaged compressor
A boost leak
A bad actuator / poor wastegate signal

the boost leak problem also "occurs" when the compressor runs out of "breath". So for instance, asking why your t-25 cannot hold 15psi of boost at 7000rpm is not a "boost leak" problem (where it is out of compressor actually).

So from easy -> hard check the actuator, check the vacuum routing and boost controller lines, then check boost leaks, then examine the compressor wheel, and finally... the turbine.

*Vatche* · 02-18-2011, 07:28 PM

was your car working fine before all of this. you might have your vacuum for the actuator incorrectly setup

02-05-2011, 11:29 PM	#1
bigjacsoc Zilvia Member Join Date: Feb 2008 Location: Woodstock, GA Age: 30 Posts: 166 Trader Rating: (0) Feedback Score: 0 reviews	SR Won't Boost Over 6psi I had a manual boost controller for a while and I was able to get the boost up to 8-9psi but wouldn't go any lower or higher no matter how much I changed the MBC. I even took the MBC out and ran it stock and only hit 6psi. I figured my MBC crapped out and just got a GReddy Profec B Spec II all hooked up correctly and at 0% it boosts to 5.9 and at 20%, 35%, and 40% it hit 6.2psi which is a negligible difference. WTF? Any answers? Anyone had this problem before?

02-07-2011, 07:22 PM	#6
JayZeeSILVIA Join Date: Feb 2011 Location: Florida Age: 31 Posts: 9 Trader Rating: (0) Feedback Score: 0 reviews	sounds like a bad wastegate spring __________________ SKUNKWORKZ BUILT

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02-05-2011, 11:31 PM	#2
bigjacsoc Zilvia Member Join Date: Feb 2008 Location: Woodstock, GA Age: 30 Posts: 166 Trader Rating: (0) Feedback Score: 0 reviews	I had a manual boost controller for a while and I was able to get the boost up to 8-9psi but wouldn't go any lower or higher no matter how much I changed the MBC. I even took the MBC out and ran it stock and only hit 6psi. I figured my MBC crapped out and just got a GReddy Profec B Spec II all hooked up correctly and at 0% it boosts to 5.9 and at 20%, 35%, and 40% it hit 6.2psi which is a negligible difference. WTF? Any answers? Anyone had this problem before?

02-05-2011, 11:48 PM	#3
ultimateirving Zilvia FREAK! Join Date: Nov 2010 Location: arizona Age: 33 Posts: 1,519 Trader Rating: (1) Feedback Score: 1 reviews	get a new wastegate actuator the springs wear out after time, had similar trouble. put a new WGA on and it works like a dream. seeif that works.

02-06-2011, 12:28 AM	#4
bigjacsoc Zilvia Member Join Date: Feb 2008 Location: Woodstock, GA Age: 30 Posts: 166 Trader Rating: (0) Feedback Score: 0 reviews	I figured this is what could be doing it. Does anyone know if I vacuum leak would do it? I mean there was no difference between 0% and 40% in boost. I have pressure checked all vacuum lines and coupler, only thing that could be causing a leak is something stupid like a bad gasket, or something with the stock recirculating BOV and SMIC.

02-06-2011, 02:22 PM	#5
bigjacsoc Zilvia Member Join Date: Feb 2008 Location: Woodstock, GA Age: 30 Posts: 166 Trader Rating: (0) Feedback Score: 0 reviews	Bump why is this message not long enough?

02-18-2011, 02:19 PM	#7
bigjacsoc Zilvia Member Join Date: Feb 2008 Location: Woodstock, GA Age: 30 Posts: 166 Trader Rating: (0) Feedback Score: 0 reviews	Bump. Any other ideas?