I don't how to describe this but I'll do my best.
I seem to get a noise coming from the engine bay about 5 out of ten times I go WOT.
The first time I heard it was only at part throttle as soon as boost was coming in. The noise at that point remined me of high pitched air flutter.
Better yet imagine holding a candy bar wrapper out the window going 150mph!!.Or draggin a thin tin pan on the highway going really fast?
It's so feaking hard to expalin. My two buddies were driving beside me and are also at a total loss as to what it could be.
I thought maybe it could be belt slip since I have a RR 2.8 non slip upper ( grooves in it ) and a 4# lower. I seen no real belt dust or anything to make me think that? NOt to metion it does not seem to loose boost.
It will make the noise the entire time once it starts untill you let off and then go WOT again and Then I wont do it. It seems to be gettng more and more frequent once it started.

So I'll sum it up: It will make the nosie only while in Boost either air flutter @ part throttle or the super air flutter @ WOT.

Do you you think since the 2.8 upper is the grove kind that that could be causing that type of nosie if it was just barley slipping and dragging the belt ( Gates ) across that type of surface?
I'm going to install my GatorBack belt I have lying arround and see if it still does it then. That my only guess.
If it helps I did just install a MonsterBox and TD convertor but this does not sound like it's trans related.

EDIT: I found a ton of belt dust under and on the sides of the blower snout, also all over the front of the blower face.
I took off the gates and put on a Gatorback and took it for 30min romping and I could not get it make the noise again. I'm still not sure that what I was hearing was belt slip...It sounded to violent?


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I have expierenced the same problem myself on more than one occasion. First time was at the track when iceing down my intake. Water dripped down on to one of the coil packs and made its way down into the plug well. Second time was intake tube became loose and was alowing unmetered air into the intake ie after the MAF. Good luck isolating the problem. These have been my expierences in the past, maybe it will help.

 

Sounds like detonation to me.Be cautious ,espesially on wot.Do you have a fuel pressure guage?

 

If it sounds like a fluttering sound then its like my problem above. If its detention then ignore the post above. Your looking at a total different problem.

 

I have a Wideband and A/F is nice and rich so knock is not the issue. I had knock in the past so I know what it sounds like.
Maybe a better way to explain the sound is sandpaper and metal...I don't know?
Took it out again and I think I heard it once.

 

I'm almost 100% sure now that's it's belt slip. I decided pull off the gatorback and put back on the gates belt that was making all the noise.
After I pulled off the Gator I noticed that all the nubs were chewed up and 50% worn down.....Keep in mind this is only after 50 miles of driving and 15-25 romps on the gas!!
So here I am again with Gates belt. I take it out for a ride and the first time I lay into it the GOD AWUL belt shredder noise is back.
Now it makes sense. Since the gates is smooth and slipping across the slotted surface of the non slip it's giving me the sandpaper "belt shredding" sound.
The gator belt has "nubs" there for changing the sound and instead of slipping at high speeds it's just sawing off the little nubs.
I'll install the stock upper in the next day or two and decide what to do in terms of more power. I hope I have this figured out?

EDIT: I saw a 1psi increase while the gator back was installed. That's just one more reason to suspect belt slip right?

 

What lenght belt are you running and have you removed the tensioner's stop so you can run a shorter belt that applies more tension?

Charles

 

Here is my combo:
4# lower
RR non slip 2.8 upper
Twin 100mm metco idlers
68" Gates belt / 68" Gatorback

The Gates is the noisy one. But the Gator back failed fast with no obvious nosie.
It has to be the upper. They way the grooves are back cut it must be shedding the belt. When I first installed the 68" gates it was real tight..almost could not get it on. Now it has a PLEANTY on slack in it to install and remove it. Makes sense..Belt was tight ( No noise ), Belt now is not so tight and makes the "super shredder" noise.
I wonder if take the tab off and run a 67.5" belt if that will cure it?

 

I had the same problem when i had my magnum powers. It had the 2.7 upper. I added a metco aux idler and it elminated the problem. BTW i run a 67" belt with a 4lb lower, 2.85 upper and a metco aux idler with a 90mm pulley and another 90mm where the other idler goes.

 

I hear the Gatorback is not really compatible with the RR pulley because they get tore up as you experienced. Sounds to me you need a new Gates belt.

Charles

 

You know what really sucks? I only have 500 miles on the gates belt!!
You could allways send me one of you tensioners Charles is you feel really bad for me...LOL

 

Since the 68 belt would just fit I assume you have not removed the idler stop. If that is true the least expensive next step would be to remove the stop and run a 67 belt. After that an aux idler, you know my preference. If you go that way Sal or JDM are great guys who can take care of that purchase.

Charles

 

Removed the idler stop today, installed a new 67" Gates belt and it did it again!!
The stock upper is going on Thursday and I'll see if it happens still then.
I did not noticed this untill after my Transmission install. I can't imagin it being a trans related noise.
It seems to make the noise the most during a kick down from 3rd to 2nd. That's also when the blower takes a hard hit in RPMs also.

 

Have you checked everything with your TB? Maybe there is a leak somewhere and air is fluttering out. I would start the motor and put my hand around it or put a small bit of soap and water around it to make sure it's sealing correctly.

I thought I remembered you having a SBTB, but maybe I'm wrong.

 

Udate: I'll make it short. During my trans install my buddy must have installed the inspection plate on backwards. It pushing/hitting the tq convertor bolts under hard loads.
I figured that it did not start making the noise untill after the trans install so I went back over all the stuff that was easy to check. That's how I discovered it.