It just doesn't sound right.

[Frank B]

I just performed the infamous air box mod removing all but the lip on the bottom half of the air box on my 89 gl-10. This is the second time I have done this, first was on an 86 turbo I had. I remember the rumble and whistle, but there is also a loud whoosh or gurgle of air when I shift. Is that normal, I can't recall that on the 86.

[rallyruss]

I just performed the infamous air box mod removing all but the lip on the bottom half of the air box on my 89 gl-10. This is the second time I have done this, first was on an 86 turbo I had. I remember the rumble and whistle, but there is also a loud whoosh or gurgle of air when I shift. Is that normal, I can't recall that on the 86.

 

the noise you hear is the boost pressure that is stuck in the intake when the throttle plate closes while the turbo is still spinning. hence the need for a bypass valve. I dont feel the air box chop does any good it just lets the motor suck in hot air that blew thru the radiator to get there. but if you like the noise it makes then have fun.

 

this is how I hooked up a Bosch bypass on the RX. the silly little cone filter came with the car. not my fault.

[4WDFrenzy]

If it is the whoosh sound that I think you are talking about, it is normal. Does it sound kinda like a sound clip from a Jason movie? If so, Russ is right. But, installing a BPV or BOV will not stop it from making this sound. Every turbo car that I have ever worked on(that had uprated performance parts, especially on the intake side) has made this noise, BPV or not. It won't hurt anything and nothing is trying to destroy itself, so I wouldn't worry too much. Unless it sounds like someone threw a handful of pebbles into the turbos inlet(which is an indicator of bearing failure and compressor shaft alignment problems), then you have cause to worry.

 

The gurgling sound you are hearing is actually the air back building in the piping and hitting the compressor wheel as the turbo spools down and causing backspin. It is a very common sound on cars that have small turbos(like ours) because the turbos are very quick to spool, especially when not running a BPV to relieve the pressure. If you are still running stock boost, the turbo will last for a good long while. But if you are overboosting(and I use this term loosely), it will not last very long and will ultimately lead to bearing and compressor shaft alignment failure from the added forces.

 

Patrick

[[HTi]Johnson]

Hello.

I heard that the sound you are hearing is the turbo back spooling. This is caused by the turbo spooling then the throttle plate closing all the pressure causes the trubo to try to spin backwards...but the exhaust is pushing the turbine one way and the boost is pushing against it. Which seems to be a bad thing.

As soon as you install a Blow off valve (BOV) or bypass valve (BPV)(both are the same), which are commonly found on intercoolers, it will allow the air to 'Bypass' the throttle body and go back into the intake.

[rallyruss]

if no bypass is used the wear on the turbo is slightly increased. the sound changes some when you install the bypass. It will not "shutter" so much but just "whoosh" hope that makes sense.

If you plan on increasing flow or boost I recomend the Bypass valve. your car will thank you. It also lets the turbo keep spinning between shifts. thats a good thing for quick spool up after a shift.

[baccaruda]

I think it's nothing. I have heard that on both of my turbowagons after chopping their airboxes.

Remember that when you do this mod, you are bypassing the muffler snorkus in the fender, which reduces the sound of the air being drawn in by minimizing the aperture by which it gets to the filter. It also has a convoluted path inside the snorkus, resulting in a longer path to travel to get to the filter aperture, which means that it's another thing that slows down that delicious cold air your turbo craves.

That sound would happen anyway (perhaps on a smaller scale as the airflow IS increased with this mod) but it would have to reverberate all the way out of the snorkus and out of the fender, and would be greatly muffled. That sound is the air cavitating inside the intake as the air entering the intake meets air that suddenly stopped its progress.

 

You still might want to get a BPV though, because any turbo car, no matter what you do to the intake, could use a BPV. It might affect The Noise but that doesn't mean that the noise is a problem.

[Frank B]

Thanks.

I plan on getting a BPV installed. I thought about it and it makes perfect sense that the air would have no where to go, but chopping the airbox isn't going to make the backspin forces on the turbo any worse, it was there the entire time, I just couldn't hear it.

I did the mod because I had been messing with the car all day trying to chase down the famous EA82T stumble, but nothing I did made a difference. So, I was determined to do SOMETHING to that car and see a result....out came the sawsall!!!

I have a nice blue K&N(goodwrench performance) cone filter to install in the fender well(Skip), just haven't done it yet.