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Thread: 3000rpm @ 70mph...what can be done to lower that first figure?

  1. #26
    Join Date
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    Tim @ BMW of Dallas
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    98 Z3 2.8
    My 3.46 diff in the roadster can be a bit exhausting on the freeway... Over 4k RPM @ 90mph. Sheesh. A 6-speed swap will happen one of these days.
    98 Z3 2.8 Roadster - GC, Vorshlag, AKG, ARC-8.
    99 Z3 2.8 Coupe - TCK, GC, Revshift, Kosei.
    97 Cosmos M3/4/5 - GT3582R, Broken.
    13 Smart Fortwo - DD/beater.



  2. #27
    Join Date
    Aug 2011
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    St. Charles, IL
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    1997 BMW Z3
    Where do you get a diff?

    Paul

  3. #28
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    Dec 2014
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    2001 Z3 3.0 Coupe
    Quote Originally Posted by Watch Carefully View Post
    It's not an exhaust drone that bothers me--I probably should have described it differently--nor am I concerned about stressing the motor.
    Rather, I'm at the point (age 50, a veteran of 1000s of loud musical performances, although many with ear plugs) where a long highway drive is such a strain on my senses that my head hums and or my ears ring afterward, if I don't stuff them with cotton. Surprisingly, this practice sees me arrive at my destination feeling less worn out.
    Would some sound deadening perhaps better meet your goals?
    2001 Z3 3.0 Coupe--Sterling Gray/Sunroof Delete/5MT

  4. #29
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    Redding Calif
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    1999 Z3 2.5L 5sp
    Quote Originally Posted by ptimko View Post
    Where do you get a diff?

    Paul
    Junkyard, eBay, members of this forum... they're pretty common.

  5. #30
    Join Date
    Aug 2015
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    Denver, CO
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    798
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    1999 Z3M, 1999 2.8 Coupe
    Yeah, the guy I bought my 2.8 Coupe from found me a 3.46 in a couple days. 42k miles on it no less! It replaced the 4.10 that was in there, but he let me keep that too. I hear those are gold to the E30 M3 crowd, but right now it's just collecting dust in the garage.
    Nathan in Denver

    1999 M Roadster, VFE V3 S/C, Randy Forbes Reinforced, Hardtop, H&R/Bilstein, Apex PS-7
    1999 Z3 2.8 Coupe, 1 of 2, Manual Swapped, M Suspension & Brakes, M54B30 Manifold, Style 68's

  6. #31
    Join Date
    Nov 2005
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    Finland
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    Z3 Coupe individual
    Quote Originally Posted by Randy Forbes View Post
    While it's customary to think that 4th gear is 1:1 and 5th is an overdrive ratio, that's not the case with the 5-speed in the 2.8, 3.0 & 3.2 Z3/Ms; 5th gear is 1:1__or direct drive (so I'm still puzzled that most dyno operators insist on using 4th...).
    I dont know BMW 5 speed manual where fifth was not 1:1. Imho it always is and makes most sense like that. In most six speeds the fifth remains 1:1 and then 6 is over.

    Going to keep stock 3.15 rear end and add 6 speed some day.

    Problem with almost all noise insulation is weight. Cheap noise insulation usually is not made for cars and such will suck water into it over time and then it really starts to weight, and corrode metal, and start electric gremlins etc...
    Last edited by Remotion; 11-15-2017 at 08:04 PM.


  7. #32
    Join Date
    Oct 2012
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    Louisville, KY
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    Quote Originally Posted by Remotion View Post
    ... Problem with almost all noise insulation is weight. Cheap noise insulation usually is not made for cars and such will suck water into it over time... and corrode metal, and start electric gremlins etc...
    Yes, cars should only use Dynamat-type insulation, which is a sheet of lead backed with sticky butyl. It is expensive, heavy, difficult to install even in the easy places, and mainly designed for sound originating inside the car (trunk sound systems). And it does nothing for the sound coming through a Z3 roadster's thin canvas top and minimal window sealing.
    Last edited by Vintage42; 11-15-2017 at 08:33 PM.
    BMW MOA 696, BMW CCA 1405

  8. #33
    Join Date
    Dec 2014
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    2001 Z3 3.0 Coupe
    I agree that this is the wrong car if you're looking for a quiet highway cruiser.

    However....the OP looks to have a hardtop in his avatar image, so I was suggesting sound deadening with the possibility that it would bring the noise to a more reasonable level even though there are trade offs.

    OP....what tires are you running? They might be a big source of noise as well.
    2001 Z3 3.0 Coupe--Sterling Gray/Sunroof Delete/5MT

  9. #34
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    May 2002
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    Quote Originally Posted by Remotion View Post
    I dont know BMW 5 speed manual where fifth was not 1:1. Imho it always is and makes most sense like that. In most six speeds the fifth remains 1:1 and then 6 is over.

    Going to keep stock 3.15 rear end and add 6 speed some day.

    Problem with almost all noise insulation is weight. Cheap noise insulation usually is not made for cars and such will suck water into it over time and then it really starts to weight, and corrode metal, and start electric gremlins etc...
    Numerous other manufacturers ADD a fifth (5th) ratio to an existing design to accomplish an overdriven final drive ratio.

    My in depth experience with BMWs__really taking them apart__began with a '99 M Rdstr, but I have spent some five decades (>50 yrs) playing with cars from just about everywhere, so while BMWs subcontractors may have started with a clean sheet of paper for their gearboxes, not all manufacturers do the same. I stand by my original statement.

  10. #35
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    Feb 2016
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    tempe, az
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    1998 Z3M, 1994 325i,
    Quote Originally Posted by Remotion View Post

    Problem with almost all noise insulation is weight. Cheap noise insulation usually is not made for cars and such will suck water into it over time and then it really starts to weight, and corrode metal, and start electric gremlins etc...
    I live in AZ where we are spoiled. We have no water issues. Still, I think cheap insulation would work well inside the car, where there shouldn't be any water. It's probably not as good as dynamat, but it's cheap, almost no weight to it, and very easy to install. As an experiment, cut a piece to fit the well behind the seats where the top lays down. Drive the car. You will hear an immediate difference.

  11. #36
    Join Date
    Jul 2016
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    Vanderbijlpark, ZA
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    '99 Z3 2.8 Roadster
    Quote Originally Posted by BimmerBreaker View Post
    Just realized OP asked how to lower the first figure. Never said second figure had to be the same

    Try 60mph and your cruising rpm will go down too
    How DARE you beat me to it?
    1999 BMW Z3 2.8 Roadster - show project
    1970 VW 411L Auto - show/restoration project (sold)
    1982 BMW 518i E12/8 - stolen
    1987 Mazda 323 1.5 SL - daily driver, backup show car

  12. #37
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    Feb 2017
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    Suburbadelphia, PA
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    Quote Originally Posted by kornfeld View Post
    I agree that this is the wrong car if you're looking for a quiet highway cruiser.

    However....the OP looks to have a hardtop in his avatar image, so I was suggesting sound deadening with the possibility that it would bring the noise to a more reasonable level even though there are trade offs.

    OP....what tires are you running? They might be a big source of noise as well.
    Summer are staggered 17s with 225/45 and 245/40. Winter are stock 16s with 225s, I believe.

    I do have the hardtop, which helps, but it is rarely on the car. I will try some simple insulation, and maybe my decibel meter app will indicate some improvement.
    Cheers,
    Brad

  13. #38
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    Quote Originally Posted by Watch Carefully View Post
    Summer are staggered 17s with 225/45 and 245/40. Winter are stock 16s with 225s, I believe.

    I do have the hardtop, which helps, but it is rarely on the car. I will try some simple insulation, and maybe my decibel meter app will indicate some improvement.
    Cheers,
    Brad

    I meant specifically which brand and model of tire....some tires are known for being very loud while cruising, while others aren't.
    2001 Z3 3.0 Coupe--Sterling Gray/Sunroof Delete/5MT

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