Boost falling off - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Silvia_Drift · 06-17-2010, 07:18 PM

Hey guys. I'm having trouble with setting my boost. I want to set it for 19 psi but the boost is always falling off at high rpms. It usually falls off around 6600rpm and higher.

I have a HKS adjustable wastegate actuator so I tried bypassing the boost controller and adjusting it through the wastegate and the boost drop off was even worse.

I also tried playing with the gain and set gain values (Greddy Profec Spec 2) but that didn't do much.

I also fixed all of the boost leaks and while this improved response, the boost still falls off.

Could this be that the actuator is not good enough for the higher boost setting?

My setup:

Redtop SR
GT2871R .64
BC Step 3 cams
Greddy Profec Spec 2

s13silvia123 · 06-17-2010, 09:30 PM

get your motor tune

bb4_96 · 06-18-2010, 08:18 AM

what do you mean by falls off. be more specific.

jspaeth · 06-18-2010, 10:17 AM

I had this problem, and it turned out to be a slice in an intercooler coupler causing a boost leak, but my fuel/spark were just fine bc I am on MAP sensor.

Check for boost leaks

Silvia_Drift · 06-18-2010, 10:17 AM

Quote:

Originally Posted by bb4_96

what do you mean by falls off. be more specific.

The boost will hold steady at 19psi until I get to about 6600rpm. From then on all the way to the 8000rpm limiter, boost falls off to about 15psi before I hit the limiter.

jspaeth · 06-18-2010, 12:50 PM

Quote:

Originally Posted by Silvia_Drift

The boost will hold steady at 19psi until I get to about 6600rpm. From then on all the way to the 8000rpm limiter, boost falls off to about 15psi before I hit the limiter.

There are a few things:

1) Boost leak (i had this and it only caused boost drop off at high RPM)
2) Wastegate flapper can't stay shut enough to hold boost

Silvia_Drift · 06-20-2010, 09:45 PM

Quote:

Originally Posted by jspaeth

There are a few things:

1) Boost leak (i had this and it only caused boost drop off at high RPM)
2) Wastegate flapper can't stay shut enough to hold boost

Checked for boost leaks. The whole system is mint with no leaks.

If the wastegate flapper can't stay shut, that would be a problem with the actuator correct? I don't think the actual flapper mechanism could be bad because it is a brand new GT2871R .64.

Carbomb · 06-20-2010, 10:18 PM

get a external gate. and never worry bout it again!
my buddy had this issue...then he went ext

06-17-2010, 07:18 PM	#1
Silvia_Drift Zilvia Member Join Date: Dec 2004 Location: Canada Posts: 159 Trader Rating: (1) Feedback Score: 1 reviews	Boost falling off Hey guys. I'm having trouble with setting my boost. I want to set it for 19 psi but the boost is always falling off at high rpms. It usually falls off around 6600rpm and higher. I have a HKS adjustable wastegate actuator so I tried bypassing the boost controller and adjusting it through the wastegate and the boost drop off was even worse. I also tried playing with the gain and set gain values (Greddy Profec Spec 2) but that didn't do much. I also fixed all of the boost leaks and while this improved response, the boost still falls off. Could this be that the actuator is not good enough for the higher boost setting? My setup: Redtop SR GT2871R .64 BC Step 3 cams Greddy Profec Spec 2

06-17-2010, 09:30 PM	#2
s13silvia123 Post Whore! Join Date: May 2006 Location: where waldo is Age: 43 Posts: 3,267 Trader Rating: (16) Feedback Score: 16 reviews	get your motor tune __________________ 18g and 20g turbo users click on me http://zilvia.net/f/tech-talk/261219-18g-20g-turbo-users.html

06-18-2010, 10:17 AM	#4
jspaeth Nissanaholic! Join Date: Mar 2006 Location: Philadelphia suburbs Age: 40 Posts: 2,347 Trader Rating: (7) Rides Gallery: jspaeth Feedback Score: 7 reviews	I had this problem, and it turned out to be a slice in an intercooler coupler causing a boost leak, but my fuel/spark were just fine bc I am on MAP sensor. Check for boost leaks __________________ Daily driven

06-18-2010, 08:18 AM	#3
bb4_96 Zilvia Addict Join Date: Jan 2006 Location: Under my car Posts: 785 Trader Rating: (4) Feedback Score: 4 reviews	what do you mean by falls off. be more specific.

06-20-2010, 10:18 PM	#8
Carbomb Zilvia Junkie Join Date: Apr 2009 Location: USA Age: 37 Posts: 318 Trader Rating: (6) Feedback Score: 6 reviews	get a external gate. and never worry bout it again! my buddy had this issue...then he went ext