DIY_EFI Digest V4 #614

Mon Nov 1 00:09:14 GMT 1999

looks super!

DIY_EFI Digest wrote:

> DIY_EFI Digest        Sunday, October 31 1999        Volume 04 : Number 614
>
> In this issue:
>
>         Re: DIY_EFI Digest V4 #613
>         Limp home mode on GM systems
>         Dallas 80C550
>         Re: DIY_EFI Digest V4 #613....AE Transients
>
> See the end of the digest for information on subscribing to the
> DIY_EFI or DIY_EFI-Digest mailing lists.
>
> ----------------------------------------------------------------------
>
> Date: Sun, 31 Oct 1999 08:23:28 -0600
> From: nacelp at jvlnet.com (CSH-HQ)
> Subject: Re: DIY_EFI Digest V4 #613
>
> Just hook it all up per the factory.  The "tough"part is the VSS and just
> read the archives for that.
>   All the sensors?. TPS, CTS, VSS, MAP, how much simplier do you want?.
> The ecm powers the fuel pump for about 2 sec when you turn the key on to
> prime the system, from then on it's the oil pressure switch that powers it.
> In a roll over it serves as a saftey item, since inverted there is no oil
> pressure.
>   Don't try just running in limp home mode, or just start it that way, do it
> right once, and limp home mode will probably get ya home if needed.
> Grumpy
>
> >
> >From: Mike Comai <comai at expert.cc.purdue.edu>
> >Subject: Limp home mode on GM systems
> >I'm putting a GM '747 system into a 1979 CJ5.  I was curious if anyone new
> >what sensors/systems the ECM uses when it enters limp home mode.  I
> >noticed that on the schematics it looks like the fuel pump is running all
> >the time when the oil pressure switch is closed(i.e. bypasses the relay)
> >and the only reason I can think for that would be if the ECM fails or
> >enters L.H.M., or the relay fails.  I just wanted to make sure that I
> >think of all the angles when I do the install, and I'd appreciate any
> >more info on L.H.M. or any other odities that aren't easy to see.  Thanks,
> >Mike Comai
>
> ------------------------------
>
> Date: Sun, 31 Oct 1999 09:40:13 -0800
> From: "John Dammeyer" <johnd at autoartisans.com>
> Subject: Limp home mode on GM systems
>
> Hi,
>
> First I guess we have to decide what consitutes LHM.  For instance,  my water
> temperature gauge input is used to determine when the engine is warm enough to
> remove cold start enhancement.  At 150 degrees all enhancements are gone and up
> to 150, the difference in engine temperature and 150 is used as a gain
> enrichment factor.  If the gauge fails open it reports 240 degrees so I force it
> to read 220 and remove enrichment.  If it fails short or stops responding I do
> nothing.  I should probably add some sort of warmup timer that sets the
> temperature to +150 if the temperature sender hasn't changed.
>
> If the MAT fails open it reports -60 so the mixture is rich.  I haven't tried
> the engine at -40 in winter so I do not know if I should consider -60 a problem.
> In either case,  if it does fail this way,  it just enriches the mixture.  Not a
> real problem.
>
> TPS is only used for acceleration and WOT enrichment so if it fails the engine
> stumbles under acceleration but does run.
>
> O2 sensor only impacts the mixture a little bit so can be discarded if it fails.
> ie: if it reports the wrong values the engine just runs a tinly bit rich or lean
> but still runs fairly well.
>
> MAP sensor This is the biggy.  If it fails such that it reports  low pressure
> the mixture will be lean and the engine will have a major drivability problem.
> If it fails with a high pressure reading the mixture will be excessively rich.
> In all cases when the MAP sensor is disconnected,  the engine stalls.
>
> The Barometer sensor is also somewhat critical if it fails with a low pressure
> reading as the mixture will become very lean.  A failure with a high pressure
> reading defaults to just below sea level (Amsterdam?) so becomes unimportant
> other than enrichening the mixture somewhat.
>
> I currently do not sense if the injectors are functioning or what the CD
> capacitor voltage is so I can't determine a LHM from that.  If the RPM sensors
> fail,  so does the timing and therefore so does the engine.  Fuel Pump is
> determined from presense of pulses and I wouldn't subvert that because of fire
> hazzard if the ECU thinks LHM is there when vehicle has crashed.
>
> Cheers,
> John Dammeyer
>
> >Date: Sat, 30 Oct 1999 22:09:58 -0500 (EST)
> >From: Mike Comai <comai at expert.cc.purdue.edu>
> >Subject: Limp home mode on GM systems
> >
> >I'm putting a GM '747 system into a 1979 CJ5.  I was curious if anyone new
> >what sensors/systems the ECM uses when it enters limp home mode.  I
> >noticed that on the schematics it looks like the fuel pump is running all
> >the time when the oil pressure switch is closed(i.e. bypasses the relay)
> >and the only reason I can think for that would be if the ECM fails or
> >enters L.H.M., or the relay fails.  I just wanted to make sure that I
> >think of all the angles when I do the install, and I'd appreciate any
> >more info on L.H.M. or any other odities that aren't easy to see.  Thanks,
> >
>
> ------------------------------
>
> Date: Sun, 31 Oct 1999 09:22:23 -0800
> From: "John Dammeyer" <johnd at autoartisans.com>
> Subject: Dallas 80C550
>
> Hi Nick,
>
> I've struggled with this one too.   What I currently do is increase the pulse
> width to a maximum value of 13ms for n seconds.  I determine this from a change
> in throttle position (dTPS) where the amount of change above a minimum change is
> multiplied by a gain factor and then added to the current pulse width.
>
> If the TPS goes above a certain value like 75% then I just apply a richer
> mixture (11:1).
>
> The tests are done with a large multi-bladed fan on a 2.4:1 reduction belt drive
> so the load on the engine varies with the fan speed.  From idle to WOT I get a
> stumble that I haven't been able to get rid of yet.  From 3500RPM to WOT the
> engine just quickly increases speed to 5100RPM.  The Fan loads the engine such
> that the engines maximum speed is at the peak torque value which for a propellor
> is just perfect.
>
> Can you tell me how you are doing the timing for the sequential injection?  ie:
> at idle where are you starting/ ending the injection pulse and where at max
> power?  How are you determining RPM?  I'm using the 80C592 and 95% of the code
> is in Tasking C.
>
> Regards,
>
> John
>
> >Date: Sun, 31 Oct 1999 11:40:06 +1300
> >From: "Nicholas Parker" <nrparker at xtra.co.nz>
> >Subject: Re: DIY_EFI Digest V4 #611
> >
> >Hi List,
> >
> >I have written an ecu in assembler for 80c552, but I now have a Dallas
> >80c550 (8x faster or so).  Its for a 4 cyl, two coil, sequential injection
> >etc. I haven't implemented 'acceleration enrichment' yet.  Can somebody
> >please give me some guidelines,  ie:  The car I designed the ecu  for is a
> >supercharged Toyota MR2 mk1. so It kind of operates in both modes...that is
> >both forced induction, and natural aspiration bue to an electromagnetic
> >supercharger clutch, and a supercharger bypass.
> >
> >Thanks,  Nick Parker.
> >
>
> ------------------------------
>
> Date: Sun, 31 Oct 1999 14:26:49 EST
> From: EFISYSTEMS at aol.com
> Subject: Re: DIY_EFI Digest V4 #613....AE Transients
>
> Hi,
>      You didn't state whether this is speed density or MAF....Man, there is
> no quick and dirty "good" way to do AE......It's a pretty good example of
> what to do, look at the Gm stuff as shown on the ftp site or ecm guys
> hacks....you'll have to stroll down through the code to find the AE stuff but
> is usually all in one spot....also watch for the IAT(Intake Air Temp)
> equation also....sorry for the vagueness but AE is alot tougher than steady
> state.....hth's
> - -Carl Summers
>
> In a message dated 10/31/99 2:19:50 AM Pacific Standard Time,
> DIY_EFI-Digest-Owner at efi332.eng.ohio-state.edu writes:
>
> <<
>  Date: Sun, 31 Oct 1999 11:40:06 +1300
>  From: "Nicholas Parker" <nrparker at xtra.co.nz>
>  Subject: Re: DIY_EFI Digest V4 #611
>
>  Hi List,
>
>  I have written an ecu in assembler for 80c552, but I now have a Dallas
>  80c550 (8x faster or so).  Its for a 4 cyl, two coil, sequential injection
>  etc. I haven't implemented 'acceleration enrichment' yet.  Can somebody
>  please give me some guidelines,  ie:  The car I designed the ecu  for is a
>  supercharged Toyota MR2 mk1. so It kind of operates in both modes...that is
>  both forced induction, and natural aspiration bue to an electromagnetic
>  supercharger clutch, and a supercharger bypass.
>
>  Thanks,  Nick Parker.
>
>  ------------------------------
>   >>
>
> ------------------------------
>
> End of DIY_EFI Digest V4 #614
> *****************************
>
> To subscribe to DIY_EFI-Digest, send the command:
>
>     subscribe diy_efi-digest
>
> in the body of a message to "Majordomo at efi332.eng.ohio-state.edu".
>
> A non-digest (direct mail) version of this list is also available; to
> subscribe to that instead, replace "diy_efi-digest" in the command
>  above with "diy_efi".