[Gmecm] $6B, $8B, $A8 for 1228707 or 1228708 to control Cadillac Northstar

Thu Nov 18 22:08:32 UTC 2010

LOL... That sounds like the Lotus we know and love.

What's the difference between the 8707 and the 8708?
Did the Lotus code include boost control, or was boost mechanically
controlled externally and the only software change scaling the VE tables
for 2 (3?) bar MAP?

IOW, is it a normal Q4 code mask recalibrated for boosted operation, or is
it something special that Lotus wrote for their app?
Can those calibrations be switched to 8 cylinder operation?

I thought that the '749 could drive either loZ or hiZ injectors? Is there
a software switch or jumper that must match the injector type?

7200 RPM VE tables certainly sound useful. Is the processor limitation one
of table addressing? via 8 bit registers?

Thanks!

William

> William:
> The code mask I'm using isn't actually correct.
> I'm working with the Lotus Esprit, 2.2L 4 cylinder turbo.  Used the
> 1228707 for two years, then the 1228708 on the inter cooled models. Same
> ECM used on the Quad 4 (Since Lotus designed the Quad 4 it's no
> coincidence they have the same ECM)
>
> Lotus engineering kind of rushed things out the door, so the code mask is
> the same across several different variations of the code, and the
> checksums don't even match on several of them, the "engineering bypass" is
> set to skip the checksum on power up.
>
> Due to the limit of the processor the fuel and ignition tables are
> actually divided into two parts a "low" and "high"  If I remember
> correctly thelow table is from 1000 to 3600 and the high is from 3700-7200
> with a code routine that switches between them.
>
> As for running saturated injectors with a peak-and-hold drivers, I suppose
> in a pinch you could, but I think your going to get some erratic response
> at low pulse widths, might be able to play with the battery offset to
> help, but I'm not confident, someone else may know more about this.
>
>
> I think it would be easier to use the 7730 (or the 727) and just change
> the code to read the A/D addresses of it.
>
>
> John
>
>
>
>>-----Original Message-----
>>>From: William Lucke <william.lucke at highspeedlink.net>
>>>Sent: Nov 16, 2010 7:03 PM
>>>To: squelch at ix.netcom.com, gmecm at diy-efi.org
>>>Subject: Re: [Gmecm] $6B, $8B,     	$A8 for 1228707 or 1228708 to
>>> control Cadillac Northstar
>>>
>>>Thanks for the info!
>>>What code mask were you using?
>>>What's the max RPM for the VE table?
>>>
>>>The peak/hold drivers can still drive HiZ injectors, right?
>>>
>>>
>>>
>>>William
>>>
>>>
>>>> I've done quite a bit with the 1228708, not so much with the 7730 but
>>>> this
>>>> is what I remember.
>>>>
>>>> The 707 and 708 were both designed to interface with an ignition
>>>> "module"
>>>> it could be a  distributer, or the ignition module/coil pack setup.
>>>> The crank signals go to the ignition module and are interpreted and
>>>> sent
>>>> to the ECM.
>>>>
>>>> The quad 4 code RPM limits are well suited for the Northstar, but the
>>>> 707/708 hardware injector drivers in these ECM's have 2 outputs for
>>>> peak
>>>> and hold, great for a 4 cylinder car, not so great for the V8, it also
>>>> has
>>>> slightly different A/D addressing.
>>>>
>>>>
>>>> One thing that might work would be to use the Quad4 code in the 7730,
>>>> and
>>>> change the A/D addressing for the 7730 hardware.
>>>>
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>>>From: William Lucke <william.lucke at highspeedlink.net>
>>>>>Sent: Nov 16, 2010 11:12 AM
>>>>>To: gmecm at diy-efi.org
>>>>>Subject: [Gmecm] $6B, $8B,	$A8 for 1228707 or 1228708 to control
>>>>> Cadillac
>>>>> Northstar
>>>>>
>>>>>This question also applies to:
>>>>>$5C for 1227749
>>>>>$CE for 16156450
>>>>>$E8 for 16173278
>>>>>
>>>>>I've worked with a guy (who may be subscribed to this list) to adapt
>>>>> $A1
>>>>>in a 7730 (originally '91 3.1 DIS) to run a '93-'99 Cadillac Northstar
>>>>>with 8 cylinder DIS.
>>>>>
>>>>>There are a number of ways in which the $A1 is not appropriate to this
>>>>> task:
>>>>>-VE tables go to ~4500 RPM while the Northstar revs to 6700
>>>>>-Primitive BLM layout only has "idle" and "off-idle" BLM cells
>>>>>-RPM/25 datastream location can only report 6375 RPM
>>>>>-Others I'm probably forgetting right now.
>>>>>
>>>>>To overcome the last, he implemented an RPM/35 variable and dropped it
>>>>>into the datastream in the location occupied by EGR position. This
>>>>> allows
>>>>>RPM reporting up to 8925.
>>>>>
>>>>>The Quad 4 was GM's roughest and tumbliest engine of the late '80's
>>>>> and
>>>>>early '90's, being roughly equivalent in state of tune to the 195 HP
>>>>> 2.3
>>>>>litre S14 used in BMW's E30 M3 from '87 to '91ish.
>>>>>The code masks and ECM's listed above and in the subject line were
>>>>> used
>>>>>with Q4's, according to Tunercat.
>>>>>
>>>>>What's the ending RPM for the VE tables in these masks?
>>>>>What's the BLM structure? (IE, 16 cell like $8D or 2 cell like $A1 or
>>>>>somewhere in between?)
>>>>>
>>>>>What sort of extra I/O do the 8707 and 8708 have?
>>>>>How does the triggering of the Q4 ECM work? Does it read the crank
>>>>> sensor
>>>>>signal directly, or is there an ignition module which reads the crank
>>>>>sensor and outputs a 0-5V signal as with the V6 engines?
>>>>>I @$$ume the 8707 only has a single ignition output and the ignition
>>>>>module takes care of ignition distribution.
>>>>>
>>>>>Starting with a code mask that has VE tables that already go to a
>>>>> pretty
>>>>>high RPM would help out a lot with tuning a Northstar, as would a 16
>>>>> (or
>>>>>more) cell BLM structure.
>>>>>
>>>>>Thanks!
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>_______________________________________________
>>>>>Gmecm mailing list
>>>>>Gmecm at diy-efi.org
>>>>>http://lists.diy-efi.org/mailman/listinfo/gmecm
>>>>
>>>>
>>>
>>>
>
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