I was thinking of getting a Toda header for the GSR, but was wondering what to use for the rest of the exhaust. Are mufflers required to pass the DB tests?

 

NASA (or SCCA, EMRA, etc) does not set the sound requirements - the tracks do At any rate you will need some sort of muffler to pass sound.

 

You will need some kind of a muffler. I run 2 dynamax 2.5" straight through race mufflers and was at 94-99db at RA last weekend. 103db is the limit at most tracks in the SE.

Plus an open header makes less power on most setups.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">NASA (or SCCA, EMRA, etc) does not set the sound requirements - the tracks do At any rate you will need some sort of muffler to pass sound.</TD></TR></TABLE>

GCR 12.1 would suggest SCCA does - Kershaw's sound limit e.g. is 106 dB according to a member of their staff. But agreed, you'll either need a lot of bends or some muffling type device (not sure if a Cat alone would be enough ??).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by phat-S &raquo;</TD></TR><TR><TD CLASS="quote"> (not sure if a Cat alone would be enough ??).</TD></TR></TABLE>

Yea .. the cat cuts the noise down by a lot. With the cat my car never blew above 90db.

 

header cat and and a turndown are good enough for my car, until it gets a trailer.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">NASA (or SCCA, EMRA, etc) does not set the sound requirements - the tracks do At any rate you will need some sort of muffler to pass sound.</TD></TR></TABLE>

Not entirely true, RJ, at least out here on the West Coast.

For instance, Willow Springs and California Speedway do not have sound restrictions themselves, so when running w/ NASA or TCRA, anything goes (bring earplugs).

SCCA National office (GCR section 12.1) mandates a 103dB limit at every event, National or Regional, which overrides individual track limitations if they are higher, unless the track's limit is lower, such as Laguna Seca or Infineon.

The question was about NASA, though, so you are correct in saying that the track determines the sound level, as I don't belive NASA has any regulation regarding a maximum.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by phat-S &raquo;</TD></TR><TR><TD CLASS="quote">not sure if a Cat alone would be enough ??).</TD></TR></TABLE>

Cats on racecars are a bad idea. Too much potential for fire in the fdry seasons. Can't count the number of brsuh fires the SRX-7s used to start at Summit Point. SSB/SSC wasn't such an issue, as they were at stock ride height.

 

ehh...ive ran on track open header before at vir twice now...nobody said anything...

but my exhaust welds did break so i didn't really have a choice

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by paRRRker &raquo;</TD></TR><TR><TD CLASS="quote">ehh...ive ran on track open header before at vir twice now...nobody said anything...

but my exhaust welds did break so i didn't really have a choice </TD></TR></TABLE>

Dammit.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">

Dammit.


</TD></TR></TABLE>

u remember now...haha...W0W that crap was loud

 

fwiw, the noise could sometimes drive the racer nuts. FWIW, driver's comfort could be more important than have that extra hp. of course if the racer could handle it, it could drive your competitors nuts. lol.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ghettoracer &raquo;</TD></TR><TR><TD CLASS="quote">fwiw, the noise could sometimes drive the racer nuts. FWIW, driver's comfort could be more important than have that extra hp.</TD></TR></TABLE>

Its also a safety issue. If the other drivers can hear you, its just another way they know you are there.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">Its also a safety issue. If the other drivers can hear you, its just another way they know you are there.</TD></TR></TABLE>

Except the inverse is true. If your car is loud enough for others to hear as you approach, your car is also loud enough to mask other cars as they approach you.

Keep the car quite. There is no reason to have an overly loud car. All a loud car does is annoy the neighbors - which is an increasingly common issue for tracks nationwide.

Well thought out mufflers and exhausts will not cost you power. Even my old RX-7 never broke 100db.

 

Agree w/ CM - I don't see ANY added safety value with a louder exhaust. If anything, a louder intake would have a bigger benefit to what you (.rj) are talking about. Once someone's next to you or ahead, I can't imagine sound is playing any role. PLUS, really loud exhaust turns your gutted car into a bell, not only to the sound meter but to you inside the car. I don't like to run my car w/out my headset on (even if the radios aren't in) just to knock down the sound. I don't want the ringing, the light headaches I associated w/ it and certainly see NOTHING positive about LT hearing loss.

Although our limits are 103 dB, my goal is to be below 100 (well below would be nice). We use two in line muffler setup with a downturn (not to the side). If there is a 1hp loss on that for the number of dBs it lowers it, I can live w/ that. Been bounced for sound once (tired single muffler setup), don't want that to ever happen again.

CM, my comment on the Cats is not that I recommend using it as a sound deadening device but some series require it IIRC and are open from the Cat back - in that case, I think you might be knocking down enough sound w/ the Cat alone ... ??

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by phat-S &raquo;</TD></TR><TR><TD CLASS="quote">CM, my comment on the Cats is not that I recommend using it as a sound deadening device but some series require it IIRC and are open from the Cat back - in that case, I think you might be knocking down enough sound w/ the Cat alone ... ?? </TD></TR></TABLE>

That would be true - my RX-7 w/ cat but no muffler made the 103db limit measured Summit Point. But, it was deafening. If I did it again, I'd add a muffler.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">

Its also a safety issue. If the other drivers can hear you, its just another way they know you are there.</TD></TR></TABLE>

yeah kinda contradicting

 

I agree that some amount of short straight through race muffler is needed to pass most sound limits. Also stick with larger bore tubing like 2.5 inch as smaller bore like 2.0 inch is louder and higher pitched (like a tuba vs. a trumpet).

My fastest race lap at Mid-Ohio was driving with an open header after I was run off track while leading and ripped the system off behind the header and had to pit to remove dragging parts. I don't know how I didn't get run down my Sound Control, maybe they took pity on me or liked my charge back from 16th to 2nd in about 8 laps. It was very fast, unbelievably loud and I drove clouded by the red mist.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Crack Monkey &raquo;</TD></TR><TR><TD CLASS="quote">Can't count the number of brsuh fires the SRX-7s used to start at Summit Point.</TD></TR></TABLE>
I saw an SRX7 land atop a tire wall at Sears Point and the exhaust caught the entire thing on fire and they could not put it out. The entire car and tire wall were an unsavable inferno that seemed to burn forever.

 

Data from the DL-1 suggests strongly that the Golf makes measurably less power without the muffler (Magnaflow all-metal street thing) than without it. I had a two-piece system built that allowed me to remove the back section and bolt on a turndown, and on the same day without the muff, the acceleration data from Oak Tree to Roller Coaster at VIR was significantly worse.

It was no problem meeting the sound limit without it, though...

K

 

Actually having some sort of muffler can help you. You may loose some peak HP but you tend to gain torque.

The only cars I know of that aren't hurt by open exhaust and will still pass 101-103db sound limits are some of the low HP cars (ITB, ITC, H4/H5). Even with a relatively stock b16 set-up in the Del Sol it was over 103db at Road Atlanta straight-piped with a DC Sports header.

Our current set-up is a 2.5" straight pipe with a turn-down, and it's got two Dynomax flow-through mufflers. Depending on the weather, the car runs 99-102db no matter what engine we've got in it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Raceworks &raquo;</TD></TR><TR><TD CLASS="quote">Actually having some sort of muffler can help you. You may loose some peak HP but you tend to gain torque.
</TD></TR></TABLE>

its called back pressure