[Diy_efi] info on 6800 motorolla

[Mos]

Hi Remy and Alexei,

Overclocking of the 4AGE ECU has been done before, but not without its
share of problems. Obviously it messes up all the timings so your injector
opening times are too short for the actual engine requirements - it
wouldn't surprise me the engine was unresponsive...
So you'll have to do more than just overclock it to get a decent result...

A poster some time ago involved in x-raying factory ecu micros suggested
that few of the micros are actually off the shelf items and are customised
to the point where replacement is far from trivial. (There is a lot more
to it, and I might not be summarising it accurately enough, but it should
be in the archives and time is scarce...).

HTH.
Mos.

-- 
84 AE86, 90 ST185GrpA, 91 MX83Gr, Sydney, Oz.


On Fri, 9 Jul 2004, Alexis PAVLOV wrote:

> Hi Remy,
>
> I'm sorry to reply so, but I'm afraid you completely missunderstand
> how an engine control unit (ECU) works. I don't think you'll
> be able to find the solution by yourself as your request shows
> you don't know much about microcontrollers.
> Don't overclock the chip. It's not an Intel 666 processor, you
> may damage it.
> The 6800 knows nothing about engines, it's a generic microprocessor,
> which needs additional external parts to get engine related infos.
> The injection cut-off isn't just a switch, it's a software code
> which compares the current RPM with some defined value from EPROM.
> I'll need disassembling the EPROM code to find where the comparison
> is done.
>
> If you modify the input RPM related signal, the ECU won't be able
> anymore to correctly manage the injection.
>
> Alexei
>
>
> > Remy Sabale wrote:
> >
> > Hi ,
> >      My engine is a toyota 4age  (tvis). i have check the ECU and it
> > uses the 6800 series motorolla microprocessers.  My objective is to
> > make the rev limitter or fuel cut off  a  litle bit much higher   ,
> > because i'm using this car for autocross. i know someone that have
> > done this but he would not share his secret.   the details only he
> > give to me is that i must  intercept the signal going to the
> > processors so that it will think that the engine is not reving high.
> >
> > some one suggested to overclock it.
> > i try to replace the crystal clock to over clock the processor, but
> > i'm not satisfied with it. i find the engine not to responsive.
> >
> > is there any other way to remove this cut-off?
> >
> > what is the input pin of the 6800 for the distributor  signal( crank
> > angle sensor)?
> > any suggestion?
> >
> > what component should i replace to remove the cut-off?
> >
> > thanks,
> > Remy
> >
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