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anybody supercharged an e39 auto-box

Discussion in 'Forced Induction' started by Eric Reed, Apr 9, 2008.

    Eric Reed guest

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    Just curious if the auto could take the extra power? I've got a 2000 528iT/ 5-speed Steptronic that could use some more power, but I don't want to be buying new trannys every year or two either.

    Thanks,

    Eric

    e396spd guest

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    Partially helpful answer

    Quite a few guys have supercharged the 540 autobox, but no real word on longevity, except that numerous people have exceeded 20k miles with the supercharge autos. The thing that really gave me pause when I relied on an auto (I have moved to a 6 speed 540 for my commute), is looking at the torque ratings on the transmissions. ZF rates the 5hp24 transmission in the 540 only about 15 lb-ft higher than the stock torque rating. All the supercharged 540s improve torque by a lot more than 15 lb-ft, so no way I would have done that. But some of the '97 540s had the 5hp30 transmission from the 750iL, which with tall gearing made the car slower, but was rated to handle an extra 100 or so lb-ft.

    Given that the '98+ 540's auto transmission was not rated for handling much extra torque, I'd get the specs on your transmission before making a choice.

    I think all the e39 manuals are capable of a lot of extra torque, certainly the 6 speed (also used in the M5) is capable.

    e396spd guest

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    One additional thought

    BMW-approved Dinan supercharges the automatic 540s in spite of the transmission's torque rating, so it must actually be good for more than its rating. The same could be true for the 528.
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    xelasmada

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    ESStuning has a twin screw s/c for the E39. It's 7 psi.
    Given that option, don't get a centrifugal s/c.

    Eric Reed guest

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    centrifugal versus twin screw

    Thanks for the info. What are the advantages of twin screw over centrifugal, if you don't mind me asking? The ESS setup certainly looks nice. I was also looking at the VF Engineering s/c.

    Thanks again,

    Eric
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    xelasmada

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    No car manufacturer uses centrifugal blowers, and for good reason.

    The difference, in a nutshell, is one is a compressor, and the other is a fan.

    Compressing the air and feeding it to the intake allows more power almost immediately. Blowing more air into the manifold as rpm's increase builds pressure in the manifold slowly, and thus power comes on equally slow.

    One gives power now at 2000 rpm, the other, later at 6000 rpm.

    People buy HP, but drive torque.

    Hope that helps.
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    JimLev

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    I think if you look at a few dyno plots you will see the that your "fan" blower boost comes on a lot earlier than 6000 RPM. Most start at or near 3000 RPM.
    I prefer the compressor vane type myself, but none are made for a 540.
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    xelasmada

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    That's true, however, max boost for a centrifugal (fan type) supercharger is always at redline. Additionally, it does not increase arithmetically, so there is very little boost at lower rpm's ever, with boost doubling, and the doubling again in the final few thousand rpms before redline.

    In my understanding and seat of the pants experience, it's not unfair to approximate it as @ 1 psi at 3k, 2 psi at 4k, 4 psi at 5k, and 8 psi at 6k.
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    JimLev

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    Correct on max boost at red line.
    Looking at some dynos of a few of my friends cars, their HP and torque boost starts taking off at 2750 and keeps building all the way to 6500.
    I'm running a dual stage progerssive nitrous oxide system, instant boost, no waiting.

    Bimmerdude3 guest

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    Yes its been done. You wont blow the tranny if you never go WOT. Most people blow there **** cause there retards and just slam the pedal to the floor with like 350-400 hp and wonder why **** breaks. If you smoothly engage the power and never slam the pedal I think youll be good.

    And you will only be buying one tranny after this, a good one! Not a ZF either and aftermarket high performance one and youll be good. Its part of the FI package. A turbos have the battle prepping the car is what everyone forgets about.
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    JC5

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    Supercharged my 03 530 in 2005. She's still going strong.

    The ESS kit is nice, and so is the Active Autowerk kit. The big difference is really price and the budget first.

    cwbiii guest

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    intercooler...

    I would think that figuring how to integrate the inter-cooler would probably present the biggest challenge. No supercharger/blower is going to work well without cooling the air after it has compressed it. A well though out kit should have done all of this work for you.

    Chuck
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    CRKrieger

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    [IMG]

    Didn't happen to notice this is a 2½-year-old thread you resurrected, did ya, Bimmerdude?

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