exhaust opinions

D

Doc Bro

New member
Out the side or out back? I realize there are pros/cons to both but I'm interested in hearing the discussion to ensue. Thanks Rob
 
It would depend upon where the sound station's are at. If you choose the wrong side, your in trouble. Out the back is the "safest" but will also weigh the most.

I run a glass pack (Cherry bomb style) with a 45 degree down pipe that ends right before the rear axle on my VW. I've never been hit for sound before, it's light weight, and easy to replace.



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Tim Linerud
San Francisco Region SCCA
#95 GP Wabbit
http://linerud.myvnc.com/racing/index.html

racer_tim @ yahoo dot com
 
Out the side away from sound control. Lighter, shorter, cheap, and you can still use the turn down tip for sound control too if you need.

Plus, if you do it right looks really cool and that will make you go faster, as I am sure you know.

Ron

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Ron Earp
NC Region
Ford Lightning Tow Beast
RF GT40 Replica
Jensen-Healey ITS
1/2 a 260Z ITS - Zero
 
Use a 45 under the car just past the driver and point toward the rr wheel. Exit under the car also dampens the sound. I run a 2 1/2" system with a 12" race muffler and sound usually runs 88-90db.
 
As per the GCR, the exhaust must exit behind the driver and away from the car. If you terminate the exhaust underneath the car, I think you need to point it down (away from the car).

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Wayne Burstein
WDC Region, ITS #10, Datsun 240Z
www.mountainmotorsports.net
 
That is correct, but a side exit can still fit that - mine is about a foot behind my body. It points away from the car.

Ron

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Ron Earp
NC Region
Ford Lightning Tow Beast
RF GT40 Replica
Jensen-Healey ITS
1/2 a 260Z ITS - Zero
 
Originally posted by chuck baader:
I run a 2 1/2" system with a 12" race muffler and sound usually runs 88-90db.
Click to expand...

Chuck,
Wow, my street car (e30) is louder than that. Maybe I should chop off the last 3 feet of pipe on it.
smile.gif


Jim
 
If you want to watch weight--keep it short and terminate it underneath the car.

If weight is not a concern, take it to the back.

Cheers.
 
Originally posted by wburstein:
As per the GCR, the exhaust must exit behind the driver and away from the car. If you terminate the exhaust underneath the car, I think you need to point it down (away from the car).
Click to expand...

It's interesting that the main part of the GCR states that the exhaust must terminate behind a point equidistant between the front and rear hubs, but the ITCS states it must exit "behind the driver". If it exits at a point that is behind the driver's feet, does that qualify? Is that technically "behind the driver"? Or does it have to be COMPLETELY behind the driver, i.e. behind the rearmost point of the driver in a sitting position (most likely a vertical drawn at the back of the shoulders or head)?

Another case of the GCR saying one thing and the ITCS saying another...

MC



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Mark Coffin
#14 GP BSI Racing/Action Digital/Airborn Coatings/Krispy Kreme VW Scirocco
http://pages.prodigy.net/Scirocco14gp
 
I think that the correct answer is "it depends"(a lawyerly answer as I call it) since some cars need the longer run for backpressure or tuning. Testing is the only way to really answer the question and a dyno may tell you something different than the stop watch. With all that said, I would try to go the shortest possible route.
 
Consider "behind the driver" to be behind the driver's head. Exiting under the car actually attenuates quite a bit of sound even though it sounds louder in the car. Chuck

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Chuck Baader
#36 ITA E30 BMW
Alabama Region Divisional Registrar
 
I ran the one on my old Rabbit GTI out the side. It 45'd in front of the shifter, and exited just behind the B-pillar. Also had a 45 'bologna slice' so that it would sort of point to the ground. I also remember reading that the angled end helped w/ the reflected pulse (Pulsar racing or the Hacker bros., don't remember which). Ran a 2.25" system w/ no muffler, and used ot pull 98-99 db at Summit Point. The system that came w/ the Prod car goes straight back, and turns down in the middle of the car. Seemed to work, and was also 98-99 db at Summit, but it'll get changed when the car gets converted to FI.

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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608
 
Originally posted by racer14itc:
Another case of the GCR saying one thing and the ITCS saying another...
Click to expand...

Just remember in cases like that, the ITCS wins over the GCR.

As for the "what does behind the driver mean" question, I always took it to mean behind (back oast) the most rearward part of any driver of the car (if you have a movable seat)... But hey, that's just *my* interpretation.



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Matt Green
"Ain't nothin' improved about Improved Touring..."
 
I run mine under the car and it stops just behind me, then has a 45 turndown that can be rotated to make small changes on sound readings.

I found it was pulling in exhaust pretty bad. Found it by using one of those stick on carbon monixode detectors from an airplane. Watch out if you dump under the car.

Jeff
 
I think you should see what the car weighs before you decide...if you need to add ballast, the exhaust will be the lowest point on the car that you can add weight to. You have more tuning options with the added benefit of weight more or less where you want it...just a theory......

Evan Darling
ITA Integra

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Evan Darling
ITA Integra
 
I now always say the back not side (used to be the opposite).
About a yr or 2 ago, I knocked an exhaust hanger loose on curbing. As I was heading to the pits, b/c of the force (being a bend rather than straight) it ripped the header in half & out of the car, had the exhaust exited out the back rather than to the side (bend vs straight), it wouldn't have had the force to do that.
 
We opted to dump under the car to avoid the clearance problem of trying to get the 3 inch pipe under the rocker panel, or bend the thing over the moving solid axle. I had a local muffler shop contour the pipe to the irregularities of the floor pan, tucking it partially into the driveshaft space, and dumped it before the rear axle with a 45 degree turn-down.

We never ripped it off, and never had a violation for noise level. We always had the option of putting a moveable tip onto the end, and turning the tip away from the sound equipment...never had to do that.

Good luck.

Good racing.

Bill
 
Oops....bad memory...car was 98-99dba at Roebling last week. Chuck

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Chuck Baader
#36 ITA E30 BMW
Alabama Region Divisional Registrar
 
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