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Old Tue, Dec-17-2013, 11:55:45 AM   #1
p0lar
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Default Rev limits per gear modifications

Since the topic was recently discussed in another thread, and mentioned (more than once) how difficult it is to find information in the megathread, here's a quick howto on modifying the rev limits per gear on the MSS5x DME.

The first thing to understand is where to find the configuration values for these variables within your DME. To do this, you MUST know what version your DME is. Please see this thread about how to make that determination.

VersionDME TypeOffset
211321000502MSS520x03B0
211321000901MSS520x03B0
211321001301MSS520x03B0
211321001401MSS520x03B0
211321001501MSS520x03B0
211321001601MSS520x03B0
211321001701MSS520x03B0
211322000701MSS540x03B4
211322000901MSS540x03B4
211322001101MSS540x03B4
211322001301MSS540x03B2
211322001501MSS540x03B8
211322001701MSS540x03B8
211322002101MSS540x03B8
211322002401MSS540x03B8
211322002601MSS540x03B8
211322002801MSS540x03B8
211323001601MSS54HP0x03E2
211323001801MSS54HP0x040A
211323001901MSS54HP0x040A
211323002001MSS54HP0x040A
211323002301MSS54HP0x040A
211323002501MSS54HP0x040A
211323002701MSS54HP0x040A
211325000301MSS54HP {csl}0x03E2
211325000401MSS54HP {csl}0x03E2

A typical map would look as follows:
Code:
08 00 00 00 00 01 00 02 00 03 00 04 00 05 00 06
00 07 1F 40 1F 40 1F 40 1F 40 1F 40 1F 40 1F 40
1F 40
To simplify the meaning of this, let's look at it in a more organized fashion:
Code:
08 00 
00 00 00 01 00 02 00 03 00 04 00 05 00 06 00 07 
1F 40 1F 40 1F 40 1F 40 1F 40 1F 40 1F 40 1F 40
The first '08 00' denotes the size of the table, meaning it has 8 "x" components and 0 "y" components. Don't worry about this bit, it won't change and is used internally by the DME.

The second '00 00 00 01 00 02 00 03 00 04 00 05 00 06 00 07' string denotes the gear in question and the third '1F 40 1F 40 1F 40 1F 40 1F 40 1F 40 1F 40 1F 40' string represents the speed (RPM) in hexadecimal representative to the gear above. To convert this to a more reasonable format:

GearRPM
00 00 (neutral)1F 40 (8000)
00 01 (1st)1F 40 (8000)
00 02 (2nd)1F 40 (8000)
00 03 (3rd)1F 40 (8000)
00 04 (4th)1F 40 (8000)
00 05 (5th)1F 40 (8000)
00 06 (6th)1F 40 (8000)
00 07 (reverse)1F 40 (8000)

So, to modify a particular gear's engine speed limit in RPM, simply convert the desired RPM to hexadecimal and substitute in the string above. Here's an example to convert from the OEM 8000 RPM rev limit to 8100 RPM:

Code:
8100 RPM = 0x1FA4 = 1F A4
Just in case this seems abstract, here's a quick few screen shots of a calculator performing the function:


--->


So, if you wanted to raise the rev limit to 8100 RPM in every gear, including neutral, you would recreate the original string as such:

Code:
08 00 00 00 00 01 00 02 00 03 00 04 00 05 00 06
00 07 1F A4 1F A4 1F A4 1F A4 1F A4 1F A4 1F A4
1F A4
Let's say you wanted neutral to be rev limited at 4500 RPM, 1st gear limited to 8200 RPM, and 2nd -> 5th gears limited to 8300 RPM, 6th gear limited to 8100 RPM, and reverse limited to 5000 RPM for a more complex example (all disclaimers apply). First, calculate the necessary hex RPM values from your desired decimal RPM values:

Code:
4500 RPM = 0x1194 = 11 94
5000 RPM = 0x1388 = 13 88
8100 RPM = 0x1FA4 = 1F A4
8200 RPM = 0x2008 = 20 08
8300 RPM = 0x206C = 20 6C
So let's line it up and recreate the desired string:

Code:
08 00
00 00 00 01 00 02 00 03 00 04 00 05 00 06 00 07
11 94 20 08 20 6C 20 6C 20 6C 20 6C 1F A4 13 88
The following is a table provided for those who don't want to calculate the hex values for the most common rev limits from 7900 to 9000 RPM (you're on your own if you spin your engine at 9k RPM!):

RPM (decimal)RPM (hexadecimal)  RPM (decimal)RPM (hexadecimal)  RPM (decimal)RPM (hexadecimal)  RPM (decimal)RPM (hexadecimal)  RPM (decimal)RPM (hexadecimal)  RPM (decimal)RPM (hexadecimal)
79001E DC  81001F A4  830020 6C  850021 34  870021 FC  890022 C4
79251E F5  81251F BD  832520 85  852521 4D  872522 15  892522 DD
79501F 0E  81501F D6  835020 9E  855021 66  875022 2E  895022 F6
79751F 27  81751F EF  837520 B7  857521 7F  877522 47  897523 0F
80001F 40  820020 08  840020 D0  860021 98  880022 60  900023 28
80251F 59  822520 21  842520 E9  862521 B1  882522 79    
80501F 72  825020 3A  845021 02  865021 CA  885022 92    
80751F 8B  827520 53  847521 1B  867521 E3  887522 AB    
Attached Images
File Type: png calc_dec.png (299.8 KB, 785 views)
File Type: png calc_hex.png (298.1 KB, 780 views)

Last edited by p0lar; Fri, Aug-22-2014 at 05:31:51 PM.
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Old Tue, Dec-17-2013, 01:27:12 PM   #2
M3CARBON1
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Default Re: Rev limits per gear modifications

Polar,

I think the main points, I.E the above should all be broken down from the mega thread.

Just an idea!
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Old Tue, Dec-17-2013, 01:51:46 PM   #3
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Default Re: Rev limits per gear modifications

Quote:
Originally Posted by M3CARBON1 View Post
Polar,

I think the main points, I.E the above should all be broken down from the mega thread.

Just an idea!
We're working to segregate it into threads as opposed to picking posts from the megathread. I suspect it'll be preserved for posterity and reference, but this will allow us to keep discussion on topic and in an easily-indexed position. Did I leave something out in the information I posted above? It's easy to overlook these things once you've seen so many of them. It helps when the same question is asked several times to remind some of us that we're skipping some steps that are critical to overall comprehension. We just need to be reminded every now and then!

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Old Thu, Feb-06-2014, 03:12:14 AM   #4
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Default Re: Rev limits per gear modifications

Alright I just ran into an issue on the interstate. I just flashed a bin with rev limit and CSL and while about 4500 rpm I attempted to downshift and it wouldn't let me and then when I got off and downshifted into 3 it said redline at 4500. I m not sure if its on the rev limit behalf or the CSL I'm about to change the rev limit back to stock values and then see what happens I'll report back

Edit: changed the rev values back to stock and works like a dream. I am going to test some different combinations and see how they work

Edit 2: link to .bin

https://docs.google.com/file/d/0Bx7y...p=docslist_api

Sent from my SCH-I605 using Tapatalk

Last edited by rjskalet; Thu, Feb-06-2014 at 04:06:00 AM.
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Old Fri, Feb-07-2014, 02:55:25 AM   #5
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Default Re: Rev limits per gear modifications

Quote:
Originally Posted by rjskalet View Post
Alright I just ran into an issue on the interstate. I just flashed a bin with rev limit and CSL and while about 4500 rpm I attempted to downshift and it wouldn't let me and then when I got off and downshifted into 3 it said redline at 4500. I m not sure if its on the rev limit behalf or the CSL I'm about to change the rev limit back to stock values and then see what happens I'll report back

Edit: changed the rev values back to stock and works like a dream. I am going to test some different combinations and see how they work

Edit 2: link to .bin

https://docs.google.com/file/d/0Bx7y...p=docslist_api

Sent from my SCH-I605 using Tapatalk
I believe the stock rpm limits are supposed to be the same for all gears. But the values I see in your binary are:

neutral 4500
1st 8100
2nd 8100
3rd 8100
4th 8100
5th 8100
6th 8100
reverse 5000

Not sure if you entered those on purpose or not, but based on this my guess is it exceeded 4500 in neutral while downshifting.
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Old Fri, Feb-07-2014, 02:57:39 AM   #6
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Default Re: Rev limits per gear modifications

Yeah I did enter them that way on purpose and I had thought that may have been the issue. I was going to change it again this weekend to see if it would fix it. I need to do whatever needs to he done for unlimited flashes

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Old Sat, Feb-08-2014, 09:55:52 AM   #7
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Default Re: Rev limits per gear modifications

^ there's no trick for unlimited flashes. What most of us do is reset the counter with a BDM interface or eeprom programmer
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Old Mon, Apr-21-2014, 09:09:08 PM   #8
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Default Re: Rev limits per gear modifications

Just curious, if OEM neutral rev limit is 8000, what is the logic behind setting it @ 4500? Pro's or con's?
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Old Sun, May-18-2014, 06:52:16 PM   #9
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Default Re: Rev limits per gear modifications

Is there a way to use the neutral rev limit like a launch control?

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Old Sun, Jun-29-2014, 05:35:28 PM   #10
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Default Re: Rev limits per gear modifications

I'm curious whether anyone has an idea about the function/meaning of the OEM rev limit hex value matchings at--well there are many matching locations--but some of those nearby to the rev limit table (for MSS54HP software ...2701):

0x044E
0x090A
0x0B7C
0x17EE
0x1930
etc.

I'm guessing these mark the last x-value of an RPM-dependent curve or map. My question relates more to what happens when the rev limit is increased and the engine operates up to this limit but the dependent values in the maps and curves are not correspondingly increased? Will the maps/curves be extrapolated or will the nearest valid value be used?

Sorry if this has maybe been addressed already elsewhere.
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