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355 Challenge w/stock exhaust for Laguna?

Discussion in 'Technical Q&A' started by rob lay, May 24, 2004.

  1. rob lay

    rob lay Administrator
    Staff Member Admin Social Subscribed Miami 2018 Owner

    Dec 1, 2000
    50,835
    Southlake, TX
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    Rob Lay
    I'm nervous about the 103 db sound requirement for Laguna Seca. Anyone know what a Challenge with Challenge exhaust comes in at on the sound meter at LS? I do have a stock 355 exhaust and wonder if it would be an OK bolt on and off just for the LS event? Would the Challenge ECU have probs? Anything else?

    Thanks,
    rob
     
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  3. rexrcr

    rexrcr Formula 3

    Nov 27, 2002
    1,572
    Kalamazoo, MI
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    Rob Schermerhorn
    Depends on weather. I can say that we blew over 105 dB on a humid 80 degF day running SCCA Touring 1 and changed to the "quiet" muffler. Dropped to 92 dBA same day.

    This was not at Laguna, but Blackhawk Farms. Every other track, no issues what so ever with sound for the remainder of the season.

    Bring both if you have them. You can also try fabricating extensions which direct the exhaust toward the inside of the track. Might be good for one dB drop in sound pressure.


    Rob
     
  4. rob lay

    rob lay Administrator
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    Dec 1, 2000
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    Rob, is the stock exhaust a direct bolt on as far as you know? Nothing else needs to be done or fabricated?
     
  5. fatbillybob

    fatbillybob F1 World Champ
    Consultant Owner

    Aug 10, 2002
    19,033
    socal
    You will be black flaged with a challenge exhaust. Go stock and don't even bring the challenge exhaust. However, if LS sees it in their hearts to let the Ferraris slide maybe you will be o.k. but you will be over 103db. I have a sound meter and I fail on the 348 at idle! The 103 db is 50 ft form the track and they have a roving meter too so you can't just let up at turn 5. If you want I can send you my meter and you can prove it to yourself.
     
  6. Diablo

    Diablo Formula Junior

    Just a question to ROB...

    Are you refering to the stock exhaust or the challenge quiet exhaust??

    The stock factory exhaust is quieter than the challenge quiet that we run at Lime rock park.

    Good luck to you.
     
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  8. 4i2fly

    4i2fly Formula 3

    Apr 16, 2004
    1,330
    SF, Bay Area
    LS's sound limit is at 92db between turn 5 & 6. Most people with laud note short shift in that turn to avoid the db meter tripping. Last time I was there a 360C got black flagged mid afternnon for tripping the meter.
     
  9. 360C

    360C F1 World Champ
    Lifetime Rossa Owner

    You will definitely NOT pass with the "loud" challenge exhaust. The normal challenge exhaust will be ok. I used it on my 355 Challenge at tracks where sound is a big issue (some circuits 85db) and never got thrown off in 2 years.
    As far as I recall, all 3 exhaust types (including road) are bolt on, although I only ever used the "standard" challenge exhaust.
     
  10. Gary(SF)

    Gary(SF) F1 Rookie

    Oct 13, 2003
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    Gary B.
    Matt -

    Laguna approved the higher limit for the National event this year. Noise limits vary depending on the event, they have a certain number of days per year they can go higher. I'm kind of surprised they "spent" some of their high-limit days for a Ferrari club event, but I'm glad they did.

    Gary
     
  11. rob lay

    rob lay Administrator
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    Dec 1, 2000
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    The other exhaust I got is just a plain stock unit. I really wish I could run the regular exhaust, but I don't want to spend my week off the track.

    How much will it impact HP?
     
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  13. Aircon

    Aircon Eight Time F1 World Champ

    Jun 23, 2003
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    The dyno tests I've seen done showed no measurable change in HP between a standard exhaust, a challenge exhaust and with/without the bypass valve.
     
  14. Dave

    Dave F1 Rookie

    Apr 15, 2001
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    David Jones
    Rob, pick-up an inexpensive SPL meter from Radio Shack...
    Always a good tool to have!
     
  15. Dr_ferrari

    Dr_ferrari Formula 3
    Professional Ferrari Technician Consultant

    Nov 2, 2003
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    Jim McGee
    Rob,

    The stock 355 muffler should be just fine for the laguna track. We used the stock units for the challenge there and at lime rock with no issues.

    The stock exhaust will not cause any problems with the ecu or overall running of the engine.

    I would also make sure with the stock exhaust, that you have installed the original "intact" catyl. converters. This will ensure compliance with the db meter.

    best regards, Jim
     
  16. davey_jones

    davey_jones Formula Junior

    Sep 28, 2002
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    wherever it's sunny
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    Dave
    If there are different versions of the challenge exhaust, how do you tell which one you have?
     

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