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

kernel · 09-20-2007, 05:10 AM

When i want to raise the boost to 12 psi...it dosent hold it.

I have the following setting:

SET: 40%
GAIN: 22%
SET START: 10.0 psi
Warning: 14.0 psi and set to 0%

I have changed my stock bov to a HKS SSQV 2007, I have unplug the stock boost solenoid.

My engine is a complet stock S13 Blacktop with a blitz LM FMIC and blitz nur spec cat-back.

Is my actuator too soft to hold that kind of pressure ? My friend had a t25 on his redtop and he was boostin over stock boost no problem..

I have tried a brand new solenoid from another Greddy profec-b spec 2 boost controller and it do the same thing..

I also tried alot of setting and nothing work fine, it always spike to 12 psi then fall down back to 7 psi..then raise again to 10-12 psi. Its a big spike moving.

I had no problem boosting with this boost controller on my other red top.

what should I check next?

Thanks.

jrmiller84 · 09-20-2007, 07:16 AM

The Profec-B isn't easy to get right.

You just have to play with it for a while. I took mine out on a country road and did some pulls, adjusting each time.

This is an Ok description of how to tune it, it helped me a little.

My rule of thumb so far has been if the boost spikes, turn down the gain, if the boost drops off, turn up the gain. But keep in mind your SET value. If you turn the gain up, the boost goes up, turn it down, the boost goes down. There's a very fine line and you have to get as close to it as possible.

Also if you search around you will notice people mentioning that it seems to operate differently in different temperatures. This is completely true. In the daytime my boost is usually pretty good. At night time when it's cool, it likes to fall off every once and a while. Just keep that in mind.

kernel · 09-20-2007, 05:53 PM

Thanks for the link, its helped me to clarify few things...but my real problem is I was able to boost and hold it perfectly at 12 / 18 psi on my Red Top, it had more mods with stock actuator on a GT28R.

I have used the setting that come from a thread on this boards where it say which kind of setting the stock T25 use and it really don't work with me...even I can't get the boost to be hold at 12 psi. I have tried ALOT of setting and spent almost 1h on that doing pull on 3rd, 4th and 5th gear.

Could my actuator be bad and can't hold the 12 psi but at 7 psi is perfect ?

I'm able to get to 12 psi but its fall down to 7 psi right after it reached it with ANY settings, i went from 0-100% on GAIN and 0-100% on SET with SET GAIN @ 10 psi to get 12 psi (i always let a 2 psi difference between the SET GAIN and PSI wanted, response was nice).

I know how the profec b 2 work and how it can be a pain to set it right but like I said, I have tried many differents setting and nothing can get it right.

I hope to get this fixed, thanks.

09-20-2007, 05:10 AM	#1
kernel Zilvia Addict Join Date: Jan 2005 Location: Canada Age: 40 Posts: 934 Trader Rating: (28) Feedback Score: 28 reviews	Boost problems When i want to raise the boost to 12 psi...it dosent hold it. I have the following setting: SET: 40% GAIN: 22% SET START: 10.0 psi Warning: 14.0 psi and set to 0% I have changed my stock bov to a HKS SSQV 2007, I have unplug the stock boost solenoid. My engine is a complet stock S13 Blacktop with a blitz LM FMIC and blitz nur spec cat-back. Is my actuator too soft to hold that kind of pressure ? My friend had a t25 on his redtop and he was boostin over stock boost no problem.. I have tried a brand new solenoid from another Greddy profec-b spec 2 boost controller and it do the same thing.. I also tried alot of setting and nothing work fine, it always spike to 12 psi then fall down back to 7 psi..then raise again to 10-12 psi. Its a big spike moving. I had no problem boosting with this boost controller on my other red top. what should I check next? Thanks.

09-20-2007, 07:16 AM	#2
jrmiller84 Zilvia FREAK! Join Date: Jul 2006 Location: Gainesville, FL Age: 40 Posts: 1,021 Trader Rating: (2) Rides Gallery: jrmiller84 Feedback Score: 2 reviews	The Profec-B isn't easy to get right. You just have to play with it for a while. I took mine out on a country road and did some pulls, adjusting each time. This is an Ok description of how to tune it, it helped me a little. My rule of thumb so far has been if the boost spikes, turn down the gain, if the boost drops off, turn up the gain. But keep in mind your SET value. If you turn the gain up, the boost goes up, turn it down, the boost goes down. There's a very fine line and you have to get as close to it as possible. Also if you search around you will notice people mentioning that it seems to operate differently in different temperatures. This is completely true. In the daytime my boost is usually pretty good. At night time when it's cool, it likes to fall off every once and a while. Just keep that in mind. __________________ BitDestroyer.com

09-20-2007, 05:53 PM	#3
kernel Zilvia Addict Join Date: Jan 2005 Location: Canada Age: 40 Posts: 934 Trader Rating: (28) Feedback Score: 28 reviews	Thanks for the link, its helped me to clarify few things...but my real problem is I was able to boost and hold it perfectly at 12 / 18 psi on my Red Top, it had more mods with stock actuator on a GT28R. I have used the setting that come from a thread on this boards where it say which kind of setting the stock T25 use and it really don't work with me...even I can't get the boost to be hold at 12 psi. I have tried ALOT of setting and spent almost 1h on that doing pull on 3rd, 4th and 5th gear. Could my actuator be bad and can't hold the 12 psi but at 7 psi is perfect ? I'm able to get to 12 psi but its fall down to 7 psi right after it reached it with ANY settings, i went from 0-100% on GAIN and 0-100% on SET with SET GAIN @ 10 psi to get 12 psi (i always let a 2 psi difference between the SET GAIN and PSI wanted, response was nice). I know how the profec b 2 work and how it can be a pain to set it right but like I said, I have tried many differents setting and nothing can get it right. I hope to get this fixed, thanks.