[Diy_efi] info on 6800 motorolla

Remy Sabale remy.sabale at gatepacific.com
Mon Jul 12 01:39:50 GMT 2004


nice info,, thanks

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]
On Behalf Of Bevan Weiss
Sent: Monday, July 12, 2004 9:13 AM
To: 'A list for Do-It-Yourself EFI'
Subject: RE: [Diy_efi] info on 6800 motorolla


He said that overclocking has it's share of problems.
It's just not worth doing, it messes up the pulsewidth timing for the
injectors as well as the ignition etc.  Don't bother.

You should look into a replacement EMS if you're really serious about
increasing the performance of your car by changing the engine control.
If you can't reprogram the control program then you really only have
replacing the entire unit.

If you're just trying to remove a rev limiter, then you'd need to
understand how the ECU sees the rev signal.  It most likely uses a
frequency to voltage converter.  Hence the ECU actually sees a voltage
that depends on the speed of the engine.  It may even obtain this signal
from the tachometer.  If that's the case then a simple zener diode
voltage regulator would stop the ECU from ever seeing more revs than the
current cutoff.  And before you ask, no I'm not going to design it for
you.

Most older ECU's don't have the processing power to calculate the actual
frequency of a pulse.  So they use the F2V method.  Then it's just an
A2D to get a digital representation of the frequency.
 

Bevan

> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org
> [mailto:diy_efi-bounces at diy-efi.org] On Behalf Of Remy Sabale
> Sent: Monday, July 12, 2004 12:41 PM
> To: 'A list for Do-It-Yourself EFI'
> Subject: RE: [Diy_efi] info on 6800 motorolla
> 
> thanks for your reply,
> 
> Mos,
>   You said that i can over clock the processor, What the
> addiitonal must I do to get a decent result?
>  will i replace my injector witrh a bigger one ?
> 
> what is your suggestion?
> 
> thanks,
> remy
> 
> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]
> On Behalf Of Mos
> Sent: Friday, July 09, 2004 11:23 PM
> To: A list for Do-It-Yourself EFI
> Subject: Re: [Diy_efi] info on 6800 motorolla
> 
> 
> 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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