Just had an Alta cold air intake installed on my '06 MCSa - loved the supercharge whine! But after about 3 weeks the intake developed a high-pitched whistle which I'm sure is coming from the throttle body. It is annoying at times, as the car sounds somewhat like a teakettle. Has anybody else noted this with the Alta intake? The MiniMadness intake I put on my 02 MCS did not make this noise. Is there some kind of fix, short of placing some kind of partition behind the intake? And why did it take 2 weeks for the noise to start? I'm confused...

 

https://www.northamericanmotoring.co...ht=cai+whistle

 

Here is how I got rid of the whistle (Annoying noise at low throttle.) Which is air passing over the TB.

I am putting my Alta Hose back on this weekend and I painted the insulation so there isn't so much bling Pictures are available in my signature (Before paiting the insulation)

So here are some of the things I tried.

1. Put back on the stock hose.
2. Put back on the back wall piece.
3. Insulated the air box.

Result was no whistle, no alta sc whine and the car seem to be starving for air.

I then took the back wall piece off and insulated the back wall.

Result was a very faint whistle(When radio is off and you listen for it) and tha alta SC whine is back.

I am pretty happy with the way the car is now and may look at putting the Alta hose back on.

Another Thread
https://www.northamericanmotoring.co...alta+cai+sound

 

The whistle you are hearing is perfectly normal as mentioned above.

 

It may be normal but unacceptable by some.

 

I've had min installed for over 20k miles and find that with time its not so loud...or is it my hearing is going in my young head

 

If its unnacceptable, leave it stock.

Thats like installing a Stage 5 iron disk clutch and complaining of not being able to feather the clutch from a stoplight.

 

the uni filter that comes with the DDMWorkds air box does not make the whisle sound. it's much longer.

 

Not sure that is the same situation. It is just a annoying little noise so your right if you can't live with it you can go back to stock, fix it or try a different CAI.

 

The source of this whistle has been greatly debated. I too was sure that it was a result of air passing over the TB (at partial/light throttle). A funny thing happened though, when I installed a Detroit Tuned bypass valve (DTBV) the whistle completely disappeared! So in my experience, the whistle was coming from the bypass valve. It could be that it was just starting to open or that it wasn't sealing completely when closed.

So, if you want to get rid of the whistle but not the performance or SC sound that comes with the Alta CAI, I recommend that you install a DTBV. As an added bonus, I love the sharper boost response that you get.

 

I have a 2005 MCS auto with the Alta intake.

I got rid of the whine by rerouting the vaccuum lines - the "VGS" mod. That basically closes the bypass valve sooner.

 

I may try the VGS mod or install a Detroit Tuned bypass valve. How complicated is it to do the VGS or install a DTBV? I will have to do some research on both of those.

Thanks for bringing up some great alternatives.

 

The VGS mod is easy - just a couple of bucks worth of vacuum tubing and a T connector. There are extensive threads on it here on NAM. I've found it easier to just take the intercooler off to get to things, but that's just me.

I haven't done a bypass valve myself.

 

The VGS mod is simple, but some people have not had good results and end up undoing it. The DTBV is much more involved, but not difficult.

 

Since my initial post on this subject, I've tried various things to get rid of the whistle. I finally replaced the Alta foam filter with a K&N RU-4870 and stuffed some 2" X 2" foam strips behind the airbox, against the firewall, leaving enough space for cold air to flow in through the windshield vents. I also put some foam around the rim of the box to make a better seal with the underside of the bonnet. The whistle is so soft now I can only hear it with the window down, and I can't really appreciate any drop-off in performance. If I get really energetic I might try the vacuum bypass later on...

 

I just purchased a Detroit Tuned Bypass valve and hopefully I will get it installed this week. I will let you know if it takes care of the issue.

 

If it really works, I'd like to know where to get it, how to install it, etc...

 

Detroit Tuned for $125 and it includes the instructions. See the NAM vendor directory.

 

I was told by Waylen that, if it doesn't whistle, it's not working. Evidently, the whistling sound is inherent to the intake.

 

Some are pleasant and some are annoying. M7-AGS is pleasant and alta's is annoying. I am speaking from passed experience.

 

I have mcsa too. Just installed Alta CAI today and the whistle sounds gets pretty annoying for the first 30 mins drive but now I seems to get used to it.

I am thinking about doing VGS to eliminate it but Can someone tells me whats the pros and cons of that. I know that the whistle sound may dissappear but I really dont want to give up the SC whine.

 

I just reinstalled the firewall and poked a few holes in it to increase airflow. Its MUCH quieter. Still a little of the whistle, but you really have to listen for it. You loose a little of the hiss, but you still have the sucking and whine.

 

Got it. thx. Just got done filling the alta box gap using my home water pipe insulation. As for the whistle, i am beginning to get used to it. If i cant take it anymore then maybe I will installed the firewall the way you did.
BTW how big is the diameter and how many holes did you make?

 

I can take a pic if you need, but I just made about 7-8 holes about 2" in diameter.

 

My M7 intake has no whistle, just supercharger whine when accelerating.