mongrull006

wow, this is probably the 1st complaint i have heard about drone from borlas. the only time i really notice any drone is when i am in the 1700 rpm range. and even then it is not bad at all, as a matter of fact i hardly listen to the radio any more and i ride around with the windows down most of the time so that i can listen to my car.

Ty

CrazyAl

OK, what little drone you get with JUST the borlas is nothing worth mentioning, at least in my opinion. It is only in a very narrow RPM range, and even then it's not particularly noteworthy, at least in my opinion.

Now then, if you put an off-road pipe on there it's a whole different ball game. We're talking LOUD. That's the point of view that I'm coming from.

drf

True, the RPM range is VERY narrow - right about 2K or so.

My best bet is to learn to drive around it.

It is very deafining when you hit the "sweet spot" and stay there for an extended time.

Looks like they'res a learning curve in this for me.

Thanks for the insight.

callahan

I have the Borla S-type mufflers. The drone doesn't bother me too much. However, sometimes when idling, I get a loud vibration sound from the rear of the car. No metal to metal contact that I can tell. I'm guessing the frequency of the mufflers is causing the vibration that is causing the noise. Any suggestion as to how to eliminate this noise.

CrazyAl

Yes, this has happened to several of us (including me). Here is what happens: One of the hanger rods for your mufflers is too close to the body of your car. As the exhaust heats up, the pipes expand a little--enough for the rod to rattle against the body. The most common culprit is the rearmost rod on the left (driver's side) muffler. Cut a little bit off of this rod and you'll be good to go!

BradInFl

Crazy al and others, Do you think that adding the Magnaflow X pipe with high flow cats to Borla/Steeda axle- backs will decrease or increase drone? Anyone have experience with this?

CrazyAl

INCREASE, no doubt about it.

The stock cats do a decent job of muffling the exhaust. When you put in high-flow cats (or even worse: an offroad pipe) then you are reducing some of that muffling, and make the exhaust (drone included) louder.

Resonators will still get rid of the drone though.

MikeVistaBlue06

Ok, let me describe how this stuff works. Do you have a bell that you can ring easily such as one of those used at a hotel desk or one on a handle that you ring? If so ring it and listen to it. Then chew a piece of bubble gum and when it is good and pliable, stick it to the bell and ring it again. You should hear a helluva difference, in fact the bell should not ring.

This stuff acts as a shock absorber that dampens the vibration in the metal.

They have a demonstration of this setup in some places they sell dynomat (which is way to damn expensive IMHO). They have 2 bells one w/o dynamat and one with a small piece stuck to it. This is a very effective demo.

To do such a test, you are going to need something in sheets, and something sticky.

Here is what I recommend:

Tap on your car, especially on the outsides of hte rear quarterpanels, the insides of the rear quarter panels, remove the spare tire and tap around that. It will ring. Get yourself a couple of sheets of the dampening material and put it where you hear it ring. You will notice a difference, and should inside the car.

I did just about everything I could on mine to deaden the sound and it is much, much more enjoyable to the ears now as you drive. All I hear is a little rumble from the exhaust (stock), the whirr of my Saleen SC, and my stereo!

I wrote up a detailed section on my soundproofing that you should be able to find with the search. If not, holler back and I'll try to dig it up for ya!

Hope this helps.

Mike

BradInFl

The resonators are just hard for me to do because I don't want to cut in to a brand new X- pipe with high flow cats. I noted that you used the Borla race mufflers as resonators. How would these decrease drone if they are what are causing the drone in the first place. By the way, you provide great information to this forum. Thanks

CrazyAl

There is very little difference between a resonator and a muffler. A "resonator" is just a fancy name for a small muffler.

The "Drone" works like this:

You can think of your exhaust system as a pair of pipes. Any pipe has a natural resonant frequency, which is determined by the diameter and length of the pipe. The drone occurs when the engine happens to be emitting exhaust at the same frequency as the pipe's natural resonant frequency. At that "magic number", which is about 1700-1800 RPM on our cars, the exhaust gets louder (droning).

The factory Ford mufflers have a special internal design which cancels out this resonance. Aftermarket mufflers don't have that. So the problem isn't that "Borla mufflers make drone". The PIPE is responsible for the drone, and while the OEM mufflers cancel it out, most aftermarket ones (Borlas included) do not. In fact, if you were to take off the Borla muffler (no mufflers at all) the drone would get worse.

When you add a resonator into the middle of the pipe, you change its resonant frequency. Specifically, you change the exhaust from "one pipe" on each side of the car to two pipes that happened to be coupled together. These "two pipes" have different resonant frequnecies. This has a couple of effects:

1) Instead of one really bad resonant peak you have two, but they are much smaller (quieter).

2) You change the frequnecy of those peaks so that they occur at frequencies which the engine doesn't excite.

...this diminishes the drone significantly. It doesn't get rid of it 100%, but it makes it a lot quieter. All the resonator does is alter the resonant characteristics of the pipe.


By the way, leave your X-pipe alone. The resonators are installed in the overaxle tubes, which is the straight section of pipe AFTER the X-pipe, but before the tubing bends over the axle.