compressor surge?

[Nick2gGST]

So in my case, I recirculated the bov setup using a 1g bov supplied by fabian, thanks mang. Had to buy a longer vacuum hose (might not be stiff enough) for the top of the bov to the IM... sooo now, when I start my car it always flutters at almost any rpm above like 1.5 i hear tstststsss, sooo I opened the hood with the car running listened, I could hear it mostly from the k&n filter. So my first step was to un-circulate the bov and listen directly to that to see if the tstststs was just flutter...but nope, i revved it up again and it was still coming from the k&n filter...I'm sure with the air coming back through the filter the wrong way (if that's what it's doing) it's probably not good for my stock mafs. My only few thoughts are...
1. bov is too stiff? it is crushed.
2. the vaccum line from the nipple of the bov to the IM is not stiff enough so it may be collapsing?

I'm not sure if my vented bov made this sound or not because the bov itself fluttered too.

If it is my turbo itself, why would it do that? If I replace the turbo can I replace it with a 16g without any mods? just literally bolt on the turbo itself and go?

 

[brassc2007]

usually this is because the air cannot get out of the blow off valve and has no where else but to go back through the turbo check your blow of valve

 

[95fwdtsi18psi]

Pull the intake tube off of the compressor housing and check for play, check that BOV out too.

 

[Nick2gGST]

How would I go about checking the bov?> It's your typical crushed recirc 1g bov. How easy should it be to open and close the valve by hand? I do hear some air coming out of it. Could it have anything to do with the vacuum hose like if its not stiff enough? It doesn't seem to suck shut.

 

[Nick2gGST]

Ok just checked, there's absolutely no shaft play at all in fact the turbo looks brand effing new inside.. Again I have a long vacuum hose i got at the parts store they cut off of a spool for a couple bucks. Could that have something to do with it? Which nipple on the IM does that end hook up to?

 

[Rob10_99]

ROFl, that noise is exactly what that means... thats funny...

 

[Nick2gGST]

????

 

[Nick2gGST]

I should also mention that the bov was crushed all the way to the vacuum port. AND my Idle screw thats goes into the throttle body is like all caulked up and turned all the way to the left it seems, but it idles at maybe 600 to be exact, I cant friggen turn it in either direction.

 

[the_mork]

Push up on from the bottom on the bov so that it opens then put your finger over the vacuum hole. When you release the bottom it should drop some but not all the way to be seated. You can also check it with a vacuum pump and gauge to see how much vacuum is required to open it.

 

[Nick2gGST]

It's pretty hard to push it open with my thumb and I'm a strong guy. I don't have a vacuum pump like that, wouldn't know where to use one being such a broke guy?

 

[95fwdtsi18psi]

It's the BOV, shouldn't be the vacuum line. All the way to the left you say? Do you have any logging capabilities, I'm surprised it's idling like it is where the BISS is seated..

 

[VETTE_50_TH]

Alright, this is what happens when you crush a BOV. You will get BOV flutter and low boost, anywhere from 0-5 psi. Run the car above that and see what happens. Its typical. And at such low boost, it will not hurt anything. TRUST ME. My friends talon does it, my friends evo does it, and they all have crushed valves.

James

 

[frankozz]

Is it like a whistle type of sound coming from the filter? My gst did that when I upgraded to a 1g crushed bov.

 

[Nick2gGST]

so vette your saying compressor surge is ok? I'm running 15psi not 5...and its not a whistle, it sounds like air coming back through the turbo via through the air filter even when i vent the 1g the sound still comes from the filter. its like t-t-t-t-t...kinda hard to type the sound of compressor surge. I don't have a mbc i can't just turn it down.

 

[VETTE_50_TH]

Compressor surge and BOV flutter is two different things. VERY DIFFERENT. Fluttering is when the bov cant open long enough to let "boost" out. Compressor surge is this.

YouTube - True Compressor Surge

This is fluttering.

YouTube - Greddy type rs bov flutter

Does it flutter at all boost pressures? Vacuum, 0, positive boost?

James

 

[Nick2gGST]

I coulda sworn that the first video was actually boost creep....Like stated above under wot its 15psi, under idle its 19-20 -vac.

Your not understanding what I'm saying...if the bov was not recirculated..Which i tried, The sound STILL comes from the intake filter as if from the turbo, With it being un-circulated if it was the bov i would hear it coming from the bov and not the intake filter at all. It does come out of the bov too but only a tiny bit. Please try to think about what I'm trying to say.

 

[Nick2gGST]

This is kinda what it sounds like...it's almost dead on:
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/LZUbo_mNDZM&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/LZUbo_mNDZM&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>


Maybe even wastegate flutter?:
<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/jEUWEsqoWz8&hl=en&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/jEUWEsqoWz8&hl=en&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

 

[VETTE_50_TH]

I understand completely what your saying. But the fact of the matter is, your running a t25 at somewhat stockish boost pressure, it shouldnt be surging, EVER. Remove the 1g crushed bov, and run a stock 1g bov. Hell, if you dont have your hands on one, ill send you one. I have a spare.

James

 

[VETTE_50_TH]

Thats second video you posted is what synapse calls flutterdump. All that is, is a bov not opening quick enough. So you lift off the throttle, and the TB closes, and compressed air should be relieved with the bov, but the bov doesnt open quick enough, so its stopped and causes the turbo the flutter. Then the bov finally opens.

The first video is more than likely caused by the bov spring being too tight. Or in your case, too crushed. Same idea.

James

 

[Nick2gGST]

Yeah I don't have a stocker 1g, also Fabian is sending me a second one its a knock off of a greddy type s, but he is doing some sort of mode on it that makes it stiffer as well, idk why. Yeah I'd love your uncrushed one but I literally am broke..haha.

 

[Fabian]

I'm the one he got the 1g crushed BOV from. I took that bov from my car that NEVER fluttered and just sent it to him. I dont understand why a bov wouldnt flutter on my car but it does on his? I never said the mod I did to the type-s makes it stiffer dude, what I did was the common single spring mod that's it.

 

[VETTE_50_TH]

A greddy type s will more than likely do the same thing. 35 shipped when you want it.

James

 

[VETTE_50_TH]

Could you just take a video and lay to rest what we think it is. That would help.

James

 

[Nick2gGST]

I don't have any source for a video camera. It sounds exactly like the 240sx in the video, exactly. Sorry fabian I thought you said that the mod will make it louder by making it stiffer, my mistake, what is the single spring mod? Should the valve inside the bov be closed all the way at idle? Fabian I'm not attacking you, I'm not trying to say it's the bov I'm trying to figure out why it's doing this. It didn't do it before the bov but that could just be a coincidence. Hopefully It'll be fixed when I get that other one from you. Thanks vette but If I buy a stock one for 35 bucks I think I'll go a town over this kid has a evo8 bov for 20 bucks.

 

[the_mork]

Yes, most bovs should be slightly open at idle and close as the intake system becomes pressurized.