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Old Wed, Jan-15-2014, 03:36:20 PM   #1
p0lar
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Default Dyno Rev Limit Delete Howto

The E46 M3 and E39 M5 are equipped with a protection mechanism to prevent the engine from free-revving past 5800 RPM or 6300 RPM on the E46 M3 and 5700 RPM or 5800 RPM on the E39 M5 while the front wheels are static. In order to properly dyno-test the chassis, that limit must be increased via the DME, or a cumbersome procedure must be executed (not covered here). This howto will show the prospective DIY motorsports enthusiast how to make the necessary change in the MSS52/MSS54/MSS54HP.

As usual, the first step is to identify the program version of DME. Once the DME's version has been identified, reference the following table and examine the byte at the proper offset.

VersionDME VariantOffsetOEM Limit
211321000502MSS520x725800 RPM
211321000901MSS520x705700 RPM
211321001301MSS520x705700 RPM
211321001401MSS520x705700 RPM
211321001501MSS520x705700 RPM
211321001601MSS520x705700 RPM
211321001701MSS520x705700 RPM
211322000701MSS540x745800 RPM
211322000901MSS540x746300 RPM
211322001101MSS540x746300 RPM
211322001301MSS540x726300 RPM
211322001501MSS540x766300 RPM
211322001701MSS540x766300 RPM
211322002101MSS540x766300 RPM
211322002401MSS540x766300 RPM
211322002601MSS540x766300 RPM
211322002801MSS540x766300 RPM
211323001601MSS54HP0xA06300 RPM
211323001801MSS54HP0xA06300 RPM
211323001901MSS54HP0xA06300 RPM
211323002001MSS54HP0xA06300 RPM
211323002501MSS54HP0xA06300 RPM
211323002701MSS54HP0xA06300 RPM
211325000301MSS54HP {csl}0xA06300 RPM
211325000401MSS54HP {csl}0xA06300 RPM

You should see a two-byte (word) value like this:
Code:
18 9C
This is a hexadecimal RPM value, 6300 RPM. You may see others, as outlined below, based on your DME's program version:

Hex ValueDecimal RPM
16 445700 RPM
16 A85800 RPM
18 9C6300 RPM

----- BEHAVIOUR MODIFICATION -----

To increase the dyno rev limit, simply modify this value to whatever you like. The following is an 8450 RPM rev limit example, others are listed in the table below:

Code:
21 02
Decimal RPMHex Value  Decimal RPMHex Value  Decimal RPMHex Value
6000 RPM0x1770  7000 RPM0x1B58  8000 RPM0x1F40
6100 RPM0x17D4  7100 RPM0x1BBC  8100 RPM0x1FA4
6200 RPM0x1838  7200 RPM0x1C20  8200 RPM0x2008
6300 RPM0x189C  7300 RPM0x1C84  8300 RPM0x206C
6400 RPM0x1900  7400 RPM0x1CE8  8400 RPM0x20D0
6500 RPM0x1964  7500 RPM0x1D4C  8500 RPM0x2134
6600 RPM0x19C8  7600 RPM0x1DB0  8600 RPM0x2198
6700 RPM0x1A2C  7700 RPM0x1E14  8700 RPM0x21FC
6800 RPM0x1A90  7800 RPM0x1E78  8800 RPM0x2260
6900 RPM0x1AF4  7900 RPM0x1EDC  8900 RPM0x22C4

----- ERRATA -----

The dyno rev limit must still adhere to the per-gear rev limits; thus, even if you increase the static rev limit to 9000 RPM, it will not spin higher than the rev limit in the selected gear.

Last edited by p0lar; Wed, Feb-05-2014 at 09:57:35 PM.
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Old Sat, Jan-18-2014, 07:08:45 PM   #2
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Default Re: Dyno Rev Limit Delete Howto

why not just change the dynomode parameter to 01 or 02?
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Old Sun, Jan-19-2014, 02:37:29 AM   #3
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Default Re: Dyno Rev Limit Delete Howto

Quote:
Originally Posted by chris325ix View Post
why not just change the dynomode parameter to 01 or 02?
That's also an option, but insofar as I know, we don't know what else that bit affects while NOT on a dyno. Agreed otherwise!
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Old Tue, Jan-21-2014, 03:38:16 AM   #4
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Default Re: Dyno Rev Limit Delete Howto

So could this possibly be used as a means of setting an rpm in a launch control style and then use the dynomode parameter to still be able to rev to 8000rpm on a dyno?
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Old Thu, Jan-23-2014, 03:44:15 AM   #5
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Default Re: Dyno Rev Limit Delete Howto

Quote:
Originally Posted by p0lar View Post
That's also an option, but insofar as I know, we don't know what else that bit affects while NOT on a dyno. Agreed otherwise!
This is a legitimate concern. Clearly a few of those bytes were intended to be used during development, so it is possible some other important features won't work quite right. Perhaps even DSC since it is problematic for dyno use.
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Old Mon, Feb-24-2014, 03:01:00 AM   #6
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Default Re: Dyno Rev Limit Delete Howto

Is there a variable name for this parameter?
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Discussing Dyno Rev Limit Delete Howto in the Coding and Tuning Forum - Discuss all avenues of coding and tuning here! at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)