Weird noise after accelerator is released.

[rlngtngku]

not sure what section to post this in, so i apologize if its in the wrong one.

After watching those Advan Neova AD07 promo videos posted in the pictures and video section of this forum, it inspired me to ask the question that i have wanted to have answered for some time now:

What the hell is that weird noise that occurs after the drivers release the accelerator? It's not really a noise that i can explain with text but if i had to i would call it a rubbing between 2 surfaces done a bunch of times really fast and then stops when the accelerator is depressed again.

Hope someone can help me out,

http://members.shaw.ca/contactfreds/weird_sound.wav

^-- wav of the sound im talking about.

[Ripper]

blow off valve?

[bmw325e30]

lol

EDIT: The noise is only found on cars that are turbocharged.

Yeah, I think Ripper's right, if it's the same vid I'm thinking of.

[MarshallMX5]

Sounds like just the transmission whining. All cars do it, you can just hear it better on race cars with stripped interiors.

[Munch]

its the bov dude, not the transmission. theres just certain kindsa bov's that make that sound i guess. they all sound a bit different.

[Ghost of Duluth]

Depends on where you are. If you are at Honda night, it's the sound of screeching tires as they screw up and hit things or could be the sound of gears grinding as they miss shifts bout 63% of the time.

Oops, you mean in the Advan video.....BOV. Blow off Valve. Mine make a whooshing sound much like getting punched in the stomach. Lately they have been quite though, deadly quite.......I HATE ROTARIES!!!!.

[scirocco]

isn't he talking about the wastegate? It is activated and makes that sound of metal clashing together rabidly for about a second when the throttle is released so you don't get 40 pounds of boost being rammed into your engine with your foot off the gas.

[markeese180sx]

but 40 pounds of boost is super safe...

[Parry]

No, the waste gate slamms open when max boost is reached to keep 40 pounds of boost from getting jammed into the motor.

You can hear one open usually, although it's easier on a car venting the waste gate to atmosphere instead of back into the exhaust. You'll know when it opens, all of a sudden everything will get about twice as loud lol.

The blow off valve, BOV, is set up to vent the pressure between the turbo and the throttle body. When you have the turbo fully spooled and then snap the throttle body shut, a whole bunch of high pressure air is caught in the intake tubing. If you don't vent it, the turbo can "stall" itself, grinding to a hault becasue it's still spinning and has no place to push all the air it's trying to move. This is both prohibitive of good spool times and bad for your turbo.

The sound you are hearing is the chirping of a "tight" BOV. "EEK-EEK-EEK-EEK-EEK". Depending on how you adjust it, they tend to do that or like Ghost said make a "whoooosh".

blow off valve




and one installed, see how it is between the turbo and the throttle body...

[LOVMUFN]

There aren't to much spots where you can hear the BOV in any of the videos on that post... If it is the part I think it is (near the beggining of the first one where the silver s15 does a few dougnuts) it is exhaust popping with a big straight through muffler. A little excess fuel goes out the exhaust and is ignited by high temps in exhaust and, if you put in a certain resonatating piece in a test pipe and have a straight through turbo type muffler it sounds a little like someone dragging a sack of potatoes on assphault when a car that is highly tuned to the point where the timing is overlapping to get more fresh air/fuel in the cyl or it is just simply not burning all the fuel. Similar to a fireball poping out of the exhaust but it is like a lot of little ones. On some cars a fireball sound like a rubbing noise as well, it just happens in a single go.

[scirocco]

HAHAHA i accidentally forgot what I was typing. I know how it all works. I meant to say that it could be the wastegate because I had troubles with that after I turbo'd my hachigo. In my experience, the BOV doesn't make this sound, it was just a malfunctioning wastegate. I then explained the BOV by accident

[rlngtngku]

hm lots of info on this post, im going to try and rip a sound file of this and then we can al know what the hell im talking about :P

EDIT : I ripped a .wav of the sound, here's the link.

http://members.shaw.ca/contactfreds/weird_sound.wav

[scirocco]

I was just about to do that! Well, anyways I'm gonna take a guess. That sound is Keiichi Tsuchiya drifting the Kei Office S14. Am I right?

[rlngtngku]

Originally posted by scirocco
I was just about to do that! Well, anyways I'm gonna take a guess. That sound is Keiichi Tsuchiya drifting the Kei Office S14. Am I right?

not sure i just went through the vid and quickyl ripped the first one i heard. More importantly id like to know what that sound is.

Is it th BOV or the Wastegate or is it something else?

[Munch]

im pretty positive thats the BOV man. its just makes a different sound then the 'woosh' that comes from a lotta bov's.