Diesel350

yep, there some mathematical formula to figure that out.

Diesel350

It will make a difference in making road noise quieter and knocking out panel vibrations but it won't do anything for drone because of the frequency the drone is at. I used dynomat in the trunk and the entire floor boards. Remeber that you can't really block a 133hz frequency range because it is a natural resonance frequency. Just think about an LS460 for example that is heavily insulated with dynomat material. If you straight pipe your exhaust system on that car and don't do it right you'll get pretty bad drone and all the insulation in the world won't cancel out the resonance coming into the cabin area. The best way to address this is muffler design/resonators.

I once had an HKS system on another car and that exhaust system had some pretty large Hemholtz chambers on it and the exhaust system was fairly loud but there was zero drone.

BLKLBL

I'm going to cut the rubber weight off the stock catback and clamp it to the Borla today/tomorrow just for ****s and giggles.
I've already recorded lots of db readings on my iphone with the Borla catback + stock catted manifolds, so documenting any change should be easy.

Update: no need to cut it off, only need a 12mm wrench to un-bolt it from the factory muffler. Will clamp it to the borla and test tomorrow (wife took the car to work today)

Diesel350

For the 1,800 to 2,200 RPM range the frequency range is typically between 133 - 138hz for cars

mahcah

iTrader: (3)

oh I'm doing this today!

Eedo123

Appreciate all the responses so far, and the initiative to find solutions. I think that I will keep the headers and have the stock exhaust re-installed and that should take of the drone, am I correct in thinking this? I will lose power but with the tune I am getting soon, it should be near the same power hopefully.

mahcah

iTrader: (3)

Strapped the rubber on the driver side. Seems to help a little. I think it would help if it was welded to the driver muffler.

BLKLBL

Thanks for the update, I'll slap mine on and report back tomorrow morning

MileHIFcar

So it does help with the drone a little bit?

eternallx

Placebo? Or maybe if you strap/weld a couple of them?

Diesel93

Unbolted the weights from the stock exhaust tonight and would like to try the same. If it worked could you please provide pictures of where you clamped?

mahcah

iTrader: (3)

Like mentioned, it seemed to help. I think welding to the driver side muffler would work but there's only one way to find out

BLKLBL

Strapped the factory weight to the driver side pipe, close to the muffler.
no difference in db readings, no difference in drone. May have smoothed out the vibration in the exhaust pipes a little bit. My console buzzes on cold starts, but didn't do it this time

caymandive

iTrader: (2)

My Borla exhaust and Header setup doesn't drone. Very pleased with it!

virulosity

I made a discovery today regarding this. I had done the intake mod where you disconnect the servo valve and cap the end so that the flap opens all the time instead of at 4,000rpm. This sounded great with the stock exhaust. I just installed a full borla and was surprised how loud it was relative to what people had said on the forums. It also had a very loud drone between 1500-2000rpm. I figured I would switch the intake back to stock to try and quiet the car back down as it was too loud for my taste. To my astonishment, the car has no drone now, and is significantly quieter. I am wondering if the droning is actually the intake making the exhaust sound louder, and that is why toyota put the flapper valve in. People with aftermarket intakes might try going back to stock, its much easier than messing with your exhaust.