by algirdas » Mon 18.08.2008, 05:07
Dear All:
This problem is so simple and even simpler to fix, that I am writing this with a red face. The problem I am talking about is the screeching noise that comes out of a 2.25 inch PECO exhaust that has the exhaust pipe coming out of the muffler and inside the decorative chrome tip. In LEC parlance, the exhaust is an "uncircumcised" one. The whistle manifests itself when the car is at higher revs and on boost. So this is how it goes:
The Problem: See above.
The Epiphany: Floating in full scuba gear in 90 degree F water in a crater 6,000 above sea level. I glance over to my right and take a real close look at my bright orange surface signaling device also known as a "whistle". And the answer came to me.
The Analysis: First, look at the end of the muffler and notice the 12 and 6 o'clock positions. That is where the inside pipe is closest to the muffler tip. The exhaust gases come out of the inside pipe and over the sharp edge of the exhaust tip and that is where the whistle forms.
The Proof/The Fix: Start with the exhaust pipe COLD. Not hot. Not warm. Not cool. COLD. Take a clean rag and soak it with lacquer thinner. Clean the inside of the exhaust tip thoroughly. Not the inside exhaust pipe, but the inside of the muffler tip (the chrome piece).
The fix is to create a smooth transition for gases to get over the lip of the muffler tip. The way the muffler tip rolls back in and leaves that sharp exposed edge is what is creating the whistle. I took a piece of insulating tape and put it on the bottom and top inside of the muffler tip and extended it up over the edge to the muffler tip. Now there is a smooth ramp for the gases as they exit the exhaust pipe up over the edge of the muffler tip. Do this at the 6 and 12 o'clock positions and no more screech.
I have had the tape on my car for a couple of weeks. No more screech. PECO exhaust and Alan's chip-no screech under any circumstances with the tape.
The tape I am talking about looks like really thick aluminum foil with adhesive on one side. Here in the states, we use it on vents and chimneys for gas hot water heater and gas furnace flues. It is NOT duct tape.
Put it on and put it on sloppy. The little ripples in the tape will generate a little bit more turbulence. Sloppy or neat, the whistle will be gone. In a couple weeks of driving, the tape has started to carbon up and you can't really notice it.
Sincerely,
Algirdas
Noli illegitemi carborundum.
