before he welded the flowmaster super44 on, we tryed a magnaflow, and a 50 series flowmaster....and it still has that drum noise....he said the stock cat is making it do that

 

Fordmann1399,

Is this "Drumming" sound at low RPMs say around 1200rpms or so in 3rd or Overdrive?

If it is both my truck and my dads truck make a drumming noise at around that rpm under load and both of us have custom exhaust and high flow cats.

 

That's the "flutter" I beileve.

I'm looking forward to modifying the y-pipe. But maybe not

I wonder, if you went underneath and measured the two down pipes to there they connect at the "Y", if the two lengths are the same, or are they different?

 

Would anyone like to hear what flutter sounds like? I can make a video/sound clip. I can almost do it on command and have a perfect place to film it.

When leaving my "subdivision" I have a mile long hill that goes up to about 1300 feet elevation from 300ft. So there is a good throttle load and I average around 2100rpm in 2nd gear going up. There are embankments on either size that reflect the sound back perfect. I can do it tomorrow if it would interest anyone.

 

Ken, PLEASE DO! I can host it if you can't find a place to put it.

 

i only drove the truck 15 miles or so...i think it is at 2500-3000 rpms

 

How does it sound now with the magnaflow cat?


biz

 

didnt get truck back yet..i'll let you know soon

 

It is probably resonance or drone then.

 

I'd like to hear it as well.

 

Monsta - any luck recording the flutter sound? If you're having trouble posting the video/audio, try Youtube. Easy to put stuff on there and then post a link here.

 

I should be able to do it today.

I'll probably use YouTube or supermotors.net to host the video. Although I can post it as an attachment here. Thing is I gotta clean my truck a little bit before I go an take video inside it.

 

I have the ford racing shorty headers(borla), stans y-pipe, and gibson cat back single side exhaust. Headers make that exhaust flutter loud in the cab from 1500 rpm upto 2500. Past 2500 rpms it is all exhaust and engine noise. When I first put the headers on I came to this site looking for anybody that noticed differences between the stock exhaust manifolds and switching to headers and the noise I was hearing, sounded like a bad exhaust leak. Everybody scarred me by telling me to Change The PLUGS. After $300.00 noise was still there. So I took it down to the local performance shop to have them reinstall the headers (i originally did it in the garage) thinking that maybe I I had the gaskets not installed correctly. Another $250 for labor and still the same noise. Came to the conclusion these headers just create alot of noise in the cab. Not very noticable on the ouside or as noticeable with the windows down but windows up and radio down you'd think you were sitting in a diesel (not really) but the ticking noise is very noticeable in the cab.

 

As much as I hate to say it, something about stainless causes resonation problems. I'm one of those guys that always puts exhaust on everything, and most any custom stainless exhaust has developed some annoying resonation at a certain RPM. Usually that RPM ends up being your cruise RPM in some murphy's law way.
The mazda rotary engine can be really bad for resonation. Thick mild steel exhaust(like 1/8" wall close to the motor) was the fix for these.

 

I highly doubt the material is the culprit. The makeup of 409 stainless and std aluminized steel are very similar and the only difference is a couple percent of alloying elements. There is not a change in density.

The key is the Thickness as you said. The thicker the wall, the less annoying resonance and flutter can escape through the walls.