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Thread: 2.7 with stock leistritz vs Dansk sport

  1. #31
    Senior Member swisscheese's Avatar
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    Quote Originally Posted by Tom F. View Post
    Has anyone taken apart the different brands of mufflers to explore what makes them vary in performance? I'd like to see some photos.
    Performing open heart surgery on a Bischoff 3/73:
    Name:  Bischoff JM Tuning 110122 (5).jpg
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    (more info and photos in this thread: https://www.early911sregistry.org/fo...light=Bischoff )

    as in the infamous modification drawing:

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    Last edited by swisscheese; 01-15-2022 at 03:43 AM.
    911S 1973
    Early 911S Registry #176

  2. #32
    Quote Originally Posted by swisscheese View Post
    Robert, did you perform this test with the Bischoff and the 2.7RS?
    Hello.
    No not yet. I had pull the engine and slip in three other engines for seat and tuning. I’ll do the back to back test on the 2.7 in about a week and will post the results.

    Back in march 2021 I did a back to back on a 2.4S with 9.5/1
    The leistritz made 203.5@6741 and the bischoff pulled 206.2@6724 and added just under 2lbs extra torque.
    [SIGPIC][/SIGPIC]Robert D. Groß

  3. #33
    The biggest difference I see in compared to a Dansk are the perforated holes and style in the out pipe.
    Regards. Robert
    [SIGPIC][/SIGPIC]Robert D. Groß

  4. #34
    Quote Originally Posted by swisscheese View Post
    Performing open heart surgery on a Bischoff 3/73:
    Name:  Bischoff JM Tuning 110122 (5).jpg
Views: 132
Size:  98.7 KB

    (more info and photos in this thread: https://www.early911sregistry.org/fo...light=Bischoff )

    as in the infamous modification drawing:

    Name:  911 muffler modified.jpg
Views: 128
Size:  66.9 KB

    Doing the dual outlet mod is not worth the effort of roughly 2 additional peak Hp on an S cam engine (but it does free up a bit of drop off power at the upper end.. but it still useless unless you have the means to tune and mod the mfi pump for the added fuel needed. Carbs would be easier too tune for max but are no comparisons to what the mfi can yield overall.
    Unless your motor is spinning up past the 8000rpm zone it’s not worth the work put in and the excessive sound on the street assuming your car is not for the track !
    Regards.
    [SIGPIC][/SIGPIC]Robert D. Groß

  5. #35
    Senior Member swisscheese's Avatar
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    thnx Robert, just added the graphic for reference (I wasn't particularly planning on going to track, nor going to dual outlet). I have a high-compression 2.7RS MFI engine (with correct 2.7RS space cam) and have an Eisenmann exhaust, which, as I understood, is a derivative of the Leistritz/Bischoff examples. The Bischoff was/is date-matching the rest of the car, so took the effort of surgery. Haven't driven yet, nor on dyno, so have no clue re. HP loss/gain. Will hopefully find out this year! Thanks for the informative thread, look forward to the 2.7RS measurement. Tom
    911S 1973
    Early 911S Registry #176

  6. #36
    Hi Tom.
    The best thing you can do for that engine is put a 2mm bigger butterflys and use mag stacks opened up to 40-46.
    With a 9.5/1 it’ll touch 250hp and well over 210lbs torque.
    The low compression motor I’m running has 39mm butterfly’s , mag stacks opened 39/46, 89 octane.
    233hp and 199lbs torque.
    Don’t alter the 36mm dimension below the butterfly and into the port.
    Find a dyno shop with mfi knowledge that can tune it.
    Best, Robert
    [SIGPIC][/SIGPIC]Robert D. Groß

  7. #37
    Senior Member swisscheese's Avatar
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    Quote Originally Posted by glaverbel911 View Post
    Hi Tom.
    The best thing you can do for that engine is put a 2mm bigger butterflys and use mag stacks opened up to 40-46.
    With a 9.5/1 it’ll touch 250hp and well over 210lbs torque.
    The low compression motor I’m running has 39mm butterfly’s , mag stacks opened 39/46, 89 octane.
    233hp and 199lbs torque.
    Don’t alter the 36mm dimension below the butterfly and into the port.
    Find a dyno shop with mfi knowledge that can tune it.
    Best, Robert

    thanks for the advice Robert! I used all parts of my 2.4 S engine, except the '74 cases, Mahle 2.7 cylinders+Wahl pistons and altered MFI pump. "2mm bigger butterflys and use mag stacks opened up to 40-46", are those modified/custom parts, or standard parts from other models? thnx, Tom
    911S 1973
    Early 911S Registry #176

  8. #38
    Quote Originally Posted by swisscheese View Post
    thanks for the advice Robert! I used all parts of my 2.4 S engine, except the '74 cases, Mahle 2.7 cylinders+Wahl pistons and altered MFI pump. "2mm bigger butterflys and use mag stacks opened up to 40-46", are those modified/custom parts, or standard parts from other models? thnx, Tom
    Hi Tom. It’s purely custom.
    Eurometrics can supply and modify throttle bodies. I don’t know who is doing it in Europe.
    I do it in-house as well and or can also just supply the butterfly’s if you can’t find anything and or just the taper machining.
    Best to find a clapped out cheap 2.2T setup and do the modifications. Leave the S bits alone.
    Also, the plastic 72-73 stacks are too thin, That’s why I recommend the mag plus the mag with trumpets combined are taller.
    Regards, Robert

  9. #39
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    Quote Originally Posted by glaverbel911 View Post
    Hi Steve .
    My 74‘ Carrera 0012 was built before model year production began. The muffler tip was still hand massaged to fit the new G style body work on the first few examples. It’s a dual layer type. Probably a low grade stainless and the part number probably a bit unique along with it. Performance is still all the same.

    Bischoff and leistritz were mixed throughout the years. Not just in 72-73. my 70S still has its 69‘ coded Leistritz/single layer. The performance of the bischoff usually betters the leistritz by an extra 1 or two pony’s . I did not have a chance to too run the bischoff in the 2.7 just before the holidays

    I’ve never seen a muffler with 911/X.
    My early three pipe rallye muffler had the part number purposely welded over but still has a 911/1 Code.
    My 69‘ 911S factory built M-List race car came with a megaphone rallye muffler. It’s coded 901/22

    Regards, Robert
    It seems like bischoff overstamped their abbreviated number for a while presumably for those getting the different tailpipe for impact bumper but still using stocks the main part so likely the same. There is an overstamp of the other number that I referred to as “911/x”. In both my cases the “x” is 1 but here is 3 ( overstamp). Seems like 911/“x” is some sort of version number denoting some change maybe pipe shape but not clear what it denotes? These are not my exhaust silencers just came across this 574 example on www so can’t tell if outer wrap is stainless or regular steel.

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    Steve

  10. #40
    [QUOTE=911MRP;1116361]It seems like bischoff overstamped their abbreviated number for a while presumably for those getting the different tailpipe for impact bumper but still using stocks the main part so likely the same. There is an overstamp of the other number that I referred to as “911/x”. In both my cases the “x” is 1 but here is 3 ( overstamp). Seems like 911/“x” is some sort of version number denoting some change maybe pipe shape but not clear what it denotes? These are not my exhaust silencers just came across this 574 example on www so can’t tell if outer wrap is stainless or regular steel.


    I have one of these Bischoff 911/3 (9/74) California emissions mufflers with the extra air tube currently on a 69’ 911E engine that I just finished tuning.
    I did a back to back test with my usual Leistritz test muffler.
    This motor is running original 80mm mahles 9.1/1.
    All I’ve done was valve tweaking and seat geometry and retained stock ports dimensions.

    Both mufflers produced the exact same power of 170hp@6950.
    Attached Images Attached Images  
    [SIGPIC][/SIGPIC]Robert D. Groß

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