3800 series II swap, please read :)

[TK]

No, the 92 3800 doesn't have this. There is a byte that specifies the IP
divisor and a Road Speed Constant. Nothing like what you are describing.

Terry
-----Original Message-----
From: Ludis Langens <ludis at cruzers.com>
To: gmecm at efi332.eng.ohio-state.edu <gmecm at efi332.eng.ohio-state.edu>
Date: Monday, July 12, 1999 4:06 AM
Subject: Re: 3800 series II swap, please read :)


>Kevin Margitta wrote:
>>
>> Does this mean that the selector code can be
>> modified in the prom by changing the 3 bit selector code?
>
>Yes - however, GM does this in an ad hoc manner.  There may or may not
>be a PROM location dedicated to specifying the divisor.  Worst case,
>program code might have to be patched.
>
>> would the same IC
>> be used with a different divisor in the original ecm that I still have...
>
>Yes, that's possible.
>
>> possible IC swap here?
>
>No, the IC is programmed via software.  All you need to do is reprogram
>the EPROM.
>
>
>Terry Kelly wrote:
>>
>> That is exactly what the ECM has. However, when I change those bytes, the
4k
>> and 2k outputs don't seem to change only the ECM view of NMPH.
>
>Bytes?  There are only three bits to select the hardware divisor.  In
>the SyTy, these bits are specified by PROM location 0xc0f2 (aka 0x00f2).
>
>> I think it
>> affects the IPC stream too for the dashboard. Guess I could try it again.
I
>> tried it a few times after the swap was first completed.
>
>The selector bits are different than the constants the ECM uses to
>convert the VSS into MPH.  The ECM software gets to read the VSS before
>the divisor controlled by the three bits.  The output of that divisor
>drives only the 2k&4k VSS outputs.
>
>> Anything cosmic in the divisors? (Why those values).
>
>Don't ask me! ;-)  I suspect it has something to do with a gear driven
>DC motor vs. a reluctor type VSS pickup and the number of teeth possible
>on the reluctor.
>
>--
>Ludis Langens                               ludis (at) cruzers (dot) com
>Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/
>
>