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Thread: to "lighten" the muffler

  1. #1
    Junior Member
    Join Date
    Nov 2003

    Question to "lighten" the muffler

    Hi out there,
    i have a technical Question an i hope i will find the right words for it...

    I have a old muffler, which has seen some better times. So i decides to make some test, how to get a better sound out of it.

    But before i do this, it is essential for me to know, if a 911-Motor lost some engine power or torque, when there is more less backpressure from the exhaust stream???

    Does anybody know this?

    Best regards
    1972 T targa vipergreen in very bad condition (what should i do with it?)
    1972 T Coupe in restoration (i'll do many work on it)
    1978 SC Targa in good condition and a lil bit more hp's than the original 180 (al lil bit to new for me, but a great driver)

  2. #2
    Hi Winnie...if you have an MFI car, some of us (Chuck Miller & I both) have experienced "flat spots" in the power curve with mufflers modified for "sport". We're both of the opinion that it's hard to beat a stock muffler for power delivered. Of course, if it sounds louder, it has to be faster, right?
    Paul D. Early S Registry #8 - Cyclops Minister of West Coast Affairs
    "Now, to put a water-cooled engine in the rear and to have the radiator in the front, that's not very intelligent." -Ferry Porsche (PANO, Oct. 1973)

  3. #3


    So FAR...nothing SPORT about ANY sport mufflers I've ever used...
    Bahia Red '72 911S
    Meerblau PTS 2019 Speedster
    GP Silver, 2018 GT2RS WP....the BEAST
    Daytona Gray 2021 RS6 Avant....BEAST #2...Best daily EVER

    ES #333

    GONE...MANY, many great ones....

  4. #4
    Moderator Chuck Miller's Avatar
    Join Date
    Oct 2002
    Reseda, CA.
    As said before...
    I've tried it twice, for enough money to make me order a-double-of-what-ever-you're-drink'n

    It seems to work fine for a carbureted car in either street or race tune...

    But for the MFI cars in street tune...
    I have found you lose bottom end and transition to gain a little top end... To overcome the lag in low end and transition, I've found you have to diddle the pump enough to lose smooth idle...

    It seems that all the MFI cars that have been successful with sport mufflers have been in race tune where smooth idle and fuel consumption were not an issue... (BTW- I just ran a full tank of gas at a VERY spirited pace, not on the track but spirited all the same, and I got 10.3 MPH...
    (so what the hell am I talk'n about )

    Having a pretty good 'seat-of-the-pants' dyno, I've realized that some of these REALLY fast and LOUD MFI cars have turned out to be kind-a fast and REALLY LOUD cars

    The funny thing is, if someone came up with 'the Magic Sport Muffler' or the 'Magic Tune' to run a sport muffler w/MFI on the street, I'd probably have my wallet out again....

    A lot of people don't realize that the REALLY LOUD and COOL sound on MFI cars from their induction... (while your in the car it's MUCH louder then any exhaust) ... in fact, a lot of factory literature refer to the MFI air cleaner as a silencer or muffler.
    ... just drive your car around the block without it!

    I know the ITG system is close... but... I want something that I can just remove my stocker and put on (without allteration) that would give me back some of THAT sound and not take anything away from the performance.... I would have my wallet open AGAIN...

    Hey Milt, now THAT'S a cottage industry idea you could work on...
    Chuck Miller
    Creative Advisor/Message Board Moderator - Early 911S Registry #109
    R Gruppe #88

    TYP901 #62
    '73S cpe #1099 - Matched # 2.7/9.5 RS spec rebuild
    '67 Malibu 327 spt cpe - Period 350 Rebuild

    98 Chevy S-10 Utility
    15 GTI Commuter

  5. #5
    I would love to be able to do mufflers. If I could buy the two halves stamped, I would experiment with the innards until getting the factory back pressure AND the better sound. I

  6. #6
    I installed an Abarth muffler on my '73 S coupe w/mfi. I noticed more power (not alot) throughout the rev range. I mentioned this to a friend who also has one on his '72 E. He also noticed the power increase. It has a nice rumble, and is about 25% louder than stock.
    I also built 3 sport mufflers, all a little different. One for the street, slightly louder than the Abarth. The second one was for track/street. The third one for the RSR race car. On the third one I cut 2' out of the length and got it down to 11 lbs. vs 26 for a stock muffler.
    I started experimenting around with muffler baffles to reduce the noise of the louder sport mufflers. It seems to me by varying the baffle size and packing you could dial in some back pressure.
    At some point I will put the street sport muffler back on the '73 and compare it to the Abarth.
    '73 S coupe
    '73 targa w3.2
    '74 RSR clone w2.8 twinplug
    '68 v.w. crewcab w2.4 & 5 speed

  7. #7
    A lengthy thread over on Pelican...but keep reading. I found the comment on "non factory sport mufflers" interesting...besides, the subject car is quite a hot rod! Here's the link:
    Paul D. Early S Registry #8 - Cyclops Minister of West Coast Affairs
    "Now, to put a water-cooled engine in the rear and to have the radiator in the front, that's not very intelligent." -Ferry Porsche (PANO, Oct. 1973)

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