boost spike issues, i think

[primalfear600]

i have 1997 gsx, very lightly modded. turbo back exhaust 2.5 inch down pipe to a 3in catless. it has a K&N cone filter on the stock intake tube and a greddy profec boost controller. i have an autometer boost and air fuel ratio. the A/f gauge is run off the stock o2 sensor.

alright that out of the way here is my question. at low rpm in a high gear if a give it a good amount of throttle the boost will sometimes spike to 15psi and the car seems to almost bog, not so much slow down but it definatly doesn't go much faster. also the A/F gauge pegs on rich... i know that gauge is very inaccurate and i really shouldn't use it at all but i figured i would at least see what it was reading. the car normally runs at 11.5 psi (i just bought the car and i don't know what else has been down maintence, so i dont want to push her until i get some new parts in the motor).

please help, thanks in advance.

 

[JayRolla]

That is a spike and most likely its knocking and pulling timing, so thats the bog. Shortening the vaccuum lines inbetween the wastegate and boost source(where the profec is hooked up) greatly decreases boost spike. the shorter the vaccuum hose the better.

 

[No_Skillz]

Does the needle go up hit 15psi and immediately drop down to 11.5? If it slowly comes down as you're winding out the gear then it's more like boost leaks or your turbo simply can't hold to redline.

Do you have an aftermarket BOV? I'm assuming you do since the stock plastic one definitely will not hold to 15.

How are the vacuum lines for your boost controller hooked up?

If what you are describing is in fact spike, I'm suspecting that one of your vacuum lines going to the boost controller is tapped off of your BOV-Intake Manifold line. If that's the case, remove it and tap it off of your compressor housing instead.

 

[primalfear600]

i asked my professor at my school today, he also said it was most likly knocking and pulling timing. so, to solve the boost spike i should shorten the lines, but what should i do about the knocking? could it be a spark problem?

 

[No_Skillz]

I fthe AF is pegging on rich and it's installed correctly, I doubt you are knocking. Knock is a symptom of predetonation, which is either from running lean or improper spark.

Even with a perfect intake system with no leaks whatsoever, 15psi is not enough to make our stock fuel and ecu system run lean and knock.

If you would like to make sure for yourself, use a logger.

 

[primalfear600]

well its only running off a narrow band o2 its not very accurate... but ike i was saying, it could be a spark problem... like if the wrong plugs were installed?

 

[JayRolla]

Wait a min no_skillz. I know for sure you can detonate by running to rich, its not just a lean condition that causes it.

 

[No_Skillz]

I understand your concern about the AF guage not being accurate since it is not a wideband. However, it doesn't need to be all that accurate to peg rich to tell you that you might be running a little rich. That combined with the fact that you most likely have substantial boost leaks leads me to believe that your car should not be knocking at 15psi.


It could be a spark problem, it could be a timing problem, it could be alot of things.
Lets take this a couple steps back. Please take the time to read my first post and answer my questions so we can get somewhere with a diagnosis.

Edit: Jay, I have no experience with knock on rich conditions. Please give us more info.

 

[JayRolla]

Well where I had the experience is my buddy was getting knock in higher rpms. We added 2-3% fuel with the SAFC in those rpms. It made the knock worse. We then pulled out 5-6% of fuel just to see what would happen and the knock was gone. So wouldnt that be knock from running to rich. Im not that good at tuning but thats what happened.

 

[No_Skillz]

That's interesting and definitely something to think about. But lets wait for the original poster to answer some of the basic questions. Hopefull it's a basic solution and we won't have to move on to that next level.

 

[blkwidow]

Yes there is such a thing as knocking from being too rich. You'd have be really really rich though and it varries from diffrent set ups.

 

[primalfear600]

alright, the seliniod box is in front of the airfilter, the vaccum lines run down from there to the wastegate.

i have a 1st gen BOV

the boost shoots up to 15 psi and sticks for a bit but i usually let off the gas at that point because i don't feel as though thecar should be boosting that high yet...i have it running between 11.5 and 12.

 

[No_Skillz]

There should be two lines to the solenoid. One you described as going to the wastegate. Where does the other one go?

Have you tried turning down your boost? Sometimes the electronic boost controller just isn't set up right. Nothing beats a simple MBC. If I had a fancy unit like the Greddy, I would consider selling it for some extra change and going the MBC route.

 

[primalfear600]

well, its dark out now.... ill let ya know tommorrow morning, however my car also feels a little sluggish on the highway for what it has for mods...

 

[No_Skillz]

After we figure out your MBC problem tomorrow, you should go ahead and do a BLT.

 

[97redgsx]

hey, im the original poster, i was using a friends SN since i didn't have one yet, i just bought my car....

so about the boost leek test...i heard it can be done with a bike pump or something, what exactally would you suggest?

 

[No_Skillz]

I suggest using an compressor. They can be had pretty cheap at pep boys. A bike pump MIGHT work but chances are when you start out you have alot of leaks and it will not have the output for you to see where the leaks are at.

Check out http://www.vfaq.com and look around for boost leak test.

 

[97redgsx]

it appears as though the seond vaccum line goes just below the turbo....