Datamaster RPM limit?
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
Datamaster RPM limit?
My datamaster will not register rpm above 6375. Is there a fix for this? I cant find anything in the help menu. Thanks for your help
Edit to say I have version 4.0.1
Edit to say I have version 4.0.1
Last edited by 93 ragtop; Oct 19, 2013 at 11:39 AM.
Burning Brakes
Joined: Mar 2005
Posts: 1,082
Likes: 115
From: Richmond Hill Ontario
Seems that RPM16 value would be used if you have to go beyond 6375 Rpm
This is directly from the Help menu in Datamaster:
RPM
This displays the current engine RPM. Note that sometimes during initial engine starting this value will be shown as extremely high as the PCM attempts to sync-up with the engine. If the RPM value falls below 500 RPM, the label will turn yellow to indicate a pending stall condition. Note that the GM datastream limits this value to 6375 RPM maximum.
RPM16
This displays the current engine RPM as calculated from the Distributor Reference Pulse (DRP) rate. This allows displaying RPM Values well above the 8-bit datastream limit of 6375 RPM.
This is directly from the Help menu in Datamaster:
RPM
This displays the current engine RPM. Note that sometimes during initial engine starting this value will be shown as extremely high as the PCM attempts to sync-up with the engine. If the RPM value falls below 500 RPM, the label will turn yellow to indicate a pending stall condition. Note that the GM datastream limits this value to 6375 RPM maximum.
RPM16
This displays the current engine RPM as calculated from the Distributor Reference Pulse (DRP) rate. This allows displaying RPM Values well above the 8-bit datastream limit of 6375 RPM.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
It's a limit of the hexadecimal numbering system. The highest number that can be represented is $FF or 1111 1111 in binary. That equals 255 in decimal.
RPM is represented in two formats in the ECM: RPM/12.5 and RPM/25.
The 6375 comes from the RPM/25 thusly: 255 * 25 = 6375
RPM is represented in two formats in the ECM: RPM/12.5 and RPM/25.
The 6375 comes from the RPM/25 thusly: 255 * 25 = 6375
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
I really feel stupid on this one. I actually have 2 computers. One is very old and has datamaster 3.4.1 This one does not show the rpm16 like the 4.0.1 does. I had logged a friends car that we knew was going well past 6375 rpms, which made me bring up the question in this post. Again, I am sorry for the confusion. I will move the datalogs over to my newer computer.
