Subaru Enthusiasts Car Club of the Sierras - View Single Post

Dean · 2006-02-21, 10:40 PM

Yes, this belongs in technical.

At Laguna Seca, they have mandated sound limits since stupid people bought property nearby without noticing there was a world renound race track nearby. But I digress.

A normal day is 92db if I recall correctly. Last time I was there, I ran 94db with my silencer in and had to short shift up the hill between turn 5 and 6. No fun.

I tried to put the Megan Racing rear section on my BPM exhaust and it had the junction in the Right place, but the flanges were off by 15 degrees.

So a stop at Home depot, and I was prepared... The theory, based on other's previous results is to point the exhaust up, and away from the sound booth. I think the up helps most as it significantly reduces the reflected sound off the road surface.

Picked up a 4" aluminum Dryer vent, 4" galvanized duct caps, a 4" galvanized adjustable elbow, hose clamps, Misc. long bolts and washers to attach stuff to my silencer, etc.

The first attempt was the 4" dryer vent flipped over so the sound went mostly up, and a little left. This actually worked great for about a run group and a half with my sound readings at 87db flat out... Unfortunately, the flange that held the tube to the flush wall plate which was just a 1/8" of folded aluminum couldn't hold the heat and pressure, and the whole part that would be on the outside of the house fell off in turn 4, and I got the meatball.

I tried a simple angled plate of aluminum attached to a bolt going through the center of my silencer, but that folded in half like a taco before I even made it to the sound check location, and set my personal best of 98.4db as I recall.

By now it was the end of day 1. Found an OSH, and got another dryer vent that looked to be spot welded in the critical joint. Didn't notice until the next day it was only 3"... Still , made it fit, and it lasted 2 or three run groups.

So, the next choice was to make the adjustable elbow work. It is much stiffer material, but the sliding joints that allow it to be most any angle from 0 to 90 degrees aren't that strong. so, had to make the 4" pipe fit my 3.5" exhaust without deflecting the first sliding joint to bad.

Much crimping, cussing, banging, etc. later, it was ready. And it worked great. No loss of integrity, and the metal now has a nice patina. I set my low volume record with it at 84db. A full 14db reduction. In retrospect, I should have angled it a little less so I didn't get soot on the bumper.

For the future, I will pick up a 3.5" mandrel bent piece of stainless flared to fit over my tip and clear the bumper. I'll try it without the Silencer in as well.

You might be able to get away with a simple 45 degree angled tip turned up instead of down, but this look is so much more ghetto...

2006-02-21, 10:40 PM	#1
Dean Señor Cheap Bastarde Real Name: Dean Join Date: May 2003 Location: $99 Tire Store Posts: 9,294 Car: $.04 STI Class: Fast,Cheap & Reliable=STI Deal, did somebody say Deal? Oh, Dean, yeah that's me.	Laguna Seca Exhaust diverter. Yes, this belongs in technical. At Laguna Seca, they have mandated sound limits since stupid people bought property nearby without noticing there was a world renound race track nearby. But I digress. A normal day is 92db if I recall correctly. Last time I was there, I ran 94db with my silencer in and had to short shift up the hill between turn 5 and 6. No fun. I tried to put the Megan Racing rear section on my BPM exhaust and it had the junction in the Right place, but the flanges were off by 15 degrees. So a stop at Home depot, and I was prepared... The theory, based on other's previous results is to point the exhaust up, and away from the sound booth. I think the up helps most as it significantly reduces the reflected sound off the road surface. Picked up a 4" aluminum Dryer vent, 4" galvanized duct caps, a 4" galvanized adjustable elbow, hose clamps, Misc. long bolts and washers to attach stuff to my silencer, etc. The first attempt was the 4" dryer vent flipped over so the sound went mostly up, and a little left. This actually worked great for about a run group and a half with my sound readings at 87db flat out... Unfortunately, the flange that held the tube to the flush wall plate which was just a 1/8" of folded aluminum couldn't hold the heat and pressure, and the whole part that would be on the outside of the house fell off in turn 4, and I got the meatball. I tried a simple angled plate of aluminum attached to a bolt going through the center of my silencer, but that folded in half like a taco before I even made it to the sound check location, and set my personal best of 98.4db as I recall. By now it was the end of day 1. Found an OSH, and got another dryer vent that looked to be spot welded in the critical joint. Didn't notice until the next day it was only 3"... Still , made it fit, and it lasted 2 or three run groups. So, the next choice was to make the adjustable elbow work. It is much stiffer material, but the sliding joints that allow it to be most any angle from 0 to 90 degrees aren't that strong. so, had to make the 4" pipe fit my 3.5" exhaust without deflecting the first sliding joint to bad. Much crimping, cussing, banging, etc. later, it was ready. And it worked great. No loss of integrity, and the metal now has a nice patina. I set my low volume record with it at 84db. A full 14db reduction. In retrospect, I should have angled it a little less so I didn't get soot on the bumper. For the future, I will pick up a 3.5" mandrel bent piece of stainless flared to fit over my tip and clear the bumper. I'll try it without the Silencer in as well. You might be able to get away with a simple 45 degree angled tip turned up instead of down, but this look is so much more ghetto... Attached Thumbnails Attached Images __________________ I am a Commodore PET --- Now get off my lawn you kids... Last edited by Dean; 2006-02-22 at 07:37 AM.