[Supras] ECU year interchangability

[Supras Ireland Admin]

ts not unusual to find PCBs with dormant components. The cost of making
separate PCBs for different models far out weighs the cost of componets so
they just fit them anyway then configure PCBs for different applications via
software.

As for the idle up being omitted. I would suggest this is because the Amp
Hour output from batteries has incresed by a large amount over the years.
Because of this its quite possible the idle up to cope with load on those
particular items was no longer required, this would also have the advantage
of mildly decreasing fuel consumption
Marty
SSi
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----- Original Message -----
From: <berniek at technicaldevelop.com>
To: <Supras at supras.com>
Sent: Sunday, July 22, 2007 3:23 AM
Subject: [Supras] ECU year interchangability


> Hi list.
>
> Anyone on the list into electronics, who has gotten inside turbo engine
> ECUs?  I opened up a couple of spares to try to determine
> interchangeability factors.  Certainly there must be small software
> differences regarding fuel and ignition mapping, but the hardware
> appears to be slightly different between '89 and 90-up years.
>
> I have both an '89  and a 91 5 speed ECU as spares.  The main and
> processor boards are the same, but board stuffing of two diodes and one
> 100 ohm resistor differ between the two.  Specifics are as follows:
>
> 1:  100 ohm resistor inputting "ECT" (from ECT computer) is not stuffed
> in the '89, so no signal from the transmission ECU is used in the engine
> ECU.  It is stuffed in the '91.  Seems strange that the resistor would
> be stuffed in any event since the ECU is intended for a 5 speed
transmission
>
> 2:  A 1N4001-like diode is stuffed in the '89 with the cathode connected
> to the "LP" pin, which is connected to the headlight relay.  It is not
> stuffed in the '91.  Presumably it is to increase idle speed slightly
> when the headlights are on, but the '91 omits it.
>
> 3.  The same type of diode is used in the '89 for "DFG", a connection to
> the defogger relay.  It is not stuffed in the '91.  Reason for inclusion
> in the '89 would again appear to increase idle speed when the defogger
> is used.
>
> The '91 I bought last month is not running at the moment, but I did
> start up the '90 with a BHG for a few minutes.  Sure enough, the idle
> speed drops when the lights or particularly the defogger is turned on.
> Has anyone got any ideas about why Toyota deleted those components after
> '89?  Alternator part numbers from the fiche are all the same, all 80A
> except for a 70A version used in some N/A cars.  Any comments about ECU
> interchangeability in general would be appreciated as well.
>
> Thanks.
>
>     BernieK
>
>
>
>
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