Hi all can any1 wif any experience help me wif this? My intake air reverts back to the turbine when i'm boosting around 0.3 - 0.4 bar at constant low throttle. It produces a psshh psshhh pshhh sound and it's definitely the air getting pushed back out of the intake filter.

Ok, my first bet is tat my BOV isn't working. But on a 2nd thought. If i'm holding constant low throttle at 0.3 - 0.4 bar should the air all be charging into the engine? Why is there a turbulance or backflow? My boost gauge fluctuates rapidly between 0.2 - 0.4 bar when this happens.. Someone pls enlighten me before my turbo is blown.. Help is very much appreciated!!

 

Sounds to me like your bov.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JuiCe57 &raquo;</TD></TR><TR><TD CLASS="quote">Hi all can any1 wif any experience help me wif this? My intake air reverts back to the turbine when i'm boosting around 0.3 - 0.4 bar at constant low throttle. It produces a psshh psshhh pshhh sound and it's definitely the air getting pushed back out of the intake filter.</TD></TR></TABLE>

Compressor surge can occur when the throttle slams shut and the air goes back at the compressor fan from the BOV not being too effective. HOWEVER compressor surge can also occur when there is too much pressure but not enough airflow in the charge piping. In the second case of compressor surge the sound can be described as a "snake-like" sound or a "che-che-che" sound. This sound is a result of the oscillating air in the piping. That is how Maximum Boost by Corky Bell describes this type of compressor surge (too much boost, not enough airflow).

 

My problem sounds like the 2nd case of compressor surge.. Any reasons as to why this is happening? Why isn't there enuf airflow in my charge piping?

 

Dude it's definitely not my BOV. Cos my ears were right beside it when we tested it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JuiCe57 &raquo;</TD></TR><TR><TD CLASS="quote">My problem sounds like the 2nd case of compressor surge.. Any reasons as to why this is happening? Why isn't there enuf airflow in my charge piping?</TD></TR></TABLE>

It's probably doing it beause you are only giving it a little bit of throttle.

 

So am I right to say that most turbo setups will encounter such cases? as in light throttle will result in the 'snake' sounds? I took it a step further just now and boosted to 0.4 bar wif slightly more throttle (I'm runnin in the motor so I can't boost high) I heard the snake sound and shortly after that my BOV. Any comments? Thanks for yr help so far.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BlueShadow &raquo;</TD></TR><TR><TD CLASS="quote">

Compressor surge can occur when the throttle slams shut and the air goes back at the compressor fan from the BOV not being too effective. HOWEVER compressor surge can also occur when there is too much pressure but not enough airflow in the charge piping. In the second case of compressor surge the sound can be described as a "snake-like" sound or a "che-che-che" sound. This sound is a result of the oscillating air in the piping. That is how Maximum Boost by Corky Bell describes this type of compressor surge (too much boost, not enough airflow).</TD></TR></TABLE>

my friends s15 swapped 240 sounds like pigeons. it is weird. it is when he is spooling but only about half throttle. smaller turbos do this because they wick up quick.

 

Yeah you're rite.. It does sound quite like pigeons. I just wonder if all this is damaging the turbine. Wat turbo is he using? I'm using t04b/t3.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JuiCe57 &raquo;</TD></TR><TR><TD CLASS="quote">Dude it's definitely not my BOV. Cos my ears were right beside it when we tested it.</TD></TR></TABLE>

Sounds like an undersized turbo (okay, a 'responsive' turbo ), if you can build 3-6psi with someone's ear in the engine bay. Give us more info, such as motor info, rpm you're hearing this, and the turbo size (so we can find the compressor map). With the rpm & displacement you can find the spot on the map which shows areas where surge can occur. The reason why the BOV isn't opening is because it's set to open upon manifold vacuum. The manifold is seeing pressure, but the tbody isn't allowing enough air through it.

Think of blowing through a straw. When you close the hole a bit, air might escape between your lips if you keep forcing air through it. Dumb explaination, but it works.

 

I'm using a T04B/T3. It's not that small.. I'm built boost with someone's ear in my engine bay becos I was on the dyno rollers with load. Ok, I'm running B18c wif about 8.9 CR. My BOV is 2nd hand which is why i suspect it's not working..

Regarding yr straw blowing theory.. I believe you're saying my blowoff doesn't work cos my manifold is seeing pressure? The 'snake' sound is apparently there every time i lift off the throttle.. And when i lift my foot off, the manifold does see vacuum... as seen in my boost controller.

I went a step further today, I went on high throttle and held it and now my boost cuts off at 0.4 bar.. Sad.. It's like fluctuating between 0.2 to 0.4 rapidly.. Apparently the boost goes a little higher on lower gears.. I managed a 0.6 on my 2nd gear but can never get more than 0.4 on my 4th and 5th. Any comments?