View Full Version : Custom exhaust questions
07-28-2004, 05:12 PM
Looking to finally get involved with Sprints next year (perhaps Touring the following year!) and I need to determine what restrictions I need to consider prior to completing my exhaust. All I currently have is a 4-1 header on a b series honda motor. I'm not sure if the benefits of running a test pipe outweight the resulting noise vs. a hi-flow cat.
I guess most importantly is what is the max. dB level allowed at SMP or MIR? What about dumping behind the driver, under the car? Do you use more than one resonator and no muffler? Are there any other things I need to consider?
Any insight in terms of what works best for you is appreciated.
Section 15 in Race Regs (2004) talks about exhast. It also talks about how the exhaust should exit. Recomended sound level for 2004 is 103 db, note the word recomended. All rules and regs are posted on the CASC site here (http://www.casc.on.ca/bulletins.php)
Copied from 2004 race regs:
15.1 Catalytic converters shall be removed.
15.2 The exhaust pipe shall not exit in the fuel filler area.
15.3 Exhaust systems shall be directed away from the body and shall terminate at or aft of the equi-distant point
between front and rear hubs."
"29. SOUND LEVELS
The recommended acceptable level is 103 dba."
07-29-2004, 08:26 AM
In previous years I was using most of a Brospeed exhaust system on the Jetta (2.0l 8V). Made a new one, 2.5" pipe, and one Dynomax Bullet Racing "muffler" to use the term loosely, you can fit anything 2.5" OD through the sucker just by dropping it through if you get my meaning. Most folks run fairly non-restrictive systems, or no muffler/resonator at all. I used to have my system exit in the OE location, now it dumps just in front of the rear tire on the passenger side. I would suggest a passenger side dump, as if you dump on the driver's side, it is a little harsh at SMP. MIR isn't too bad with the passenger side - well at least for the driver. Earplugs are a must in the car regardless, mainly because of the other much louder cars (read Mazdas, some of the other big V8s and the big pickup truck) that are on the track with us...
07-29-2004, 09:01 AM
Hey, some Mazda's are quiet!! Mine is very quiet as I run a 3" pipe through a 3" inlet/ outlet Borla at the very back of the car where exhaust energy is a ton lower. This provides a ton of muffling effect. At idle the car is like a street car. Under load it is quieter than most other race cars. This is good as I hate the sound of a full load rotary as much as anybody.
My suggestion is that you try to get the car as quiet as possible without loosing a ton of power. This will help a bunch as the quiet exhaust will allow you to run the car in civilized society without annoying the nieghbours too much.
Also, it is important to remember that you will like to retain some hearing later on in life and you should try to keep it as quiet as possible.
07-29-2004, 10:45 AM
I'll agree with your "Some Mazdas are quiet"... many are not. They are by and large, some of the worst noise dB offenders at the track, along with some of the best sounding cars... Jim Holtom's Corvette for instance is one of the best sounding cars out there - but oh my, a tad loud when at full song. There are a few cars out there when passing me still are silly loud even with the earplugs... I'm not sure what happened in Ontario Region, but we were about to implement tougher noise regulations, and now it seems to only be 'recommended' and nothing really ever came of it. SCCA has noise rules, I'm not sure why Canada can't implement them.
At one point in time, I thought that the clubs were to post the sound levels of competitors, etc? What ever happened to that? Is there currently any monitoring of sound levels, and if so, are the dB levels of all competitors available?
I know where the 103 comes from, that's the SCCA GCR limit (Section 15) - they are VERY particular about how to measure it, setting/choosing a site at a track, etc. They try to do it scientificially, from what I've seen. They are very strict about it, and the competitors all seem to be in line with it. I've even seen people lose a title at the Nationals because of 1dB... that's life.
Why has this sort of policy not been properly implemented in Ontario (let alone Canada - oh, ya - I keep forgetting... no National rulebook - silly me ;) )
07-30-2004, 06:49 AM
In B.C. they have to be below 98 db to race at Mission, their only track. I have seen some cars fail due to tire squeel. A number of cars that we would consider quiet can't race and have to travel to Seattle (3hrs) or Portland (7hrs).
I would support a move to 103 db everywhere before we are forced to by our neighbours.
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